[Yukon]

Going Down Under

Now, John that made me laugh.
Pete.

PS. Unfortunately my ancestors came here during the Gold Rush, not earlier as convicts. I say, unfortunately, for 'convict' heritage in Australia affords a certain desirable status. Fit's in with the Aussie refusal to respect autority just because it's there, without it earning respect.
P.

"Autority" is that one of those funny English words, or is it the beer talking?
I'll say it for you a little more slowly, because George tends to type a little fast. DONT..................LEAN.....................YOUR....................CARBED
LYCOMING..............BELOW .......................5000'....................................

It's got nothing to do with respecting authority (US spelling). It's done because the designer and manufacturer tells you to do so. Just as VAN tells an intelligent person the max weight to fly at, or GRT tells you how to recover from a software fault..........

You know Pete, if you guys exported anything mechanized, say besides beer and alligator movies, these concepts might not be so foreign to you.

Good Day Mate

 

[gmcjetpilot]

Mel and Beer

You know Pete, if you guys exported anything mechanized, say besides beer and alligator movies, these concepts might not be so foreign to you. Good Day Mate

Don't forget we GOT Mel Gibson. Hey I spent 3 months in South East Australia once doing training, and you got to love the drive thru liquor stores. However they like "meat pies" and the meat (organs of some kind) bite back. Not sure what the crunchy bits where.

Pete PS, I agree when you are down to about 80% power you can tweak mixture, but guess what, that is about 5,000 feet DA! If you crack the throttle (to activate the bleed valve in the Carb) it will do 90% of the leaning below 5,000 foot for you.

PSS: In the latest "Kit Plane" they talk about ECI's new fuel injection for Lycs. They just copied it from the Continental FI design, so it is also a non mass-air flow controlled fuel injection. It uses a gear driven fuel pump on the accessory case which measures RPM, like a prop gov. Other than RPM and throttle position, it does not care if you are 0 feet or 100,000 feet, so no wounder they lean on climb out. Of couse they program for a normal or reasonable range of altitudes. The Lyc (Precision/Bendix, Airflow Perf) systems are (better) mass-air control and lean out as you climb without pilot action. So there's leaning going on that you are not aware of, but it's automatic. I am not sure if the Lyc FI cares if the throttle is wide open or not in regards to "auto lean"? It may boost the fuel a little at WOT.

 

[fodrv7]

Not a dinky die Aussie.

Actually, we don't claim Mel.
He was born in NY.

You are quite right George.
Though I have FI (not a carby) what you say is true, it is measuring Mass Airflow and so you won't see much change in EGT. So, as I said earlier, after take-off I select my GRT Engine Monitor to NORMAL and it displays 'Degrees CHANGE' above the EGT. When it reads 20?C (less) or so I lean it back to 0?C change..... which of course happens around 5000'

What you say about the Lycoming Fuel Flow Graph with the dogleg in it above 80% power is interesting, as if it is merley measuring Mass Air Flow why would the mixture become richer above 80%. Maybe it has a compensation system like your carby when mass air flow is higher than that required to produce 80% power. I dunno.

John. I must say I am inpressed with your knowledge if Aussie history. But, contrary to your implication, we do export the odd manufactured article. Not just wool and Fosters. Which I wouldn't touch.
Pete.

 

[Yukon]

No implications here, Peter. We American's import anything and everything, and pay cash for the privilige! Can't say that I've ever flown, driven or navigated anything Australian! What exactly do you guy's do for a living down there, anyway?????? (Pass me another Foster's honey).

 

[Yukon]

Three Pete's to the wind!

Call me cynical, but I'd say Peter has passed out by now!

 

[fodrv7]

Still Sober

Nah! Still sober.
Just composing an email for a Yankee RV owner on how to find the Philippines QB factory.
Get back to you later.
Pete.

 

[Ironflight]

After that interlude....

....back on topic?

Going back to George's post, I wanted to comment on the "automatic enrichment at full throttle" part. I have always been taught that this is true, and that if you are using full throttle in cruise, you are wasting fuel - even when you lean. Well, I have always believed that, because I had no reason not to - but I also never had an accurate fuel flow meter before either.

Now that I do, I have done a little experimenting - after leveling off, with full throttle and 75% power, I have teased th throttle off the wide open stop, looking for a decrease in fuel flow. What I have observed is that the fuel flow stays constant (to within 0.1 gph, which is the granularity of the display) until the % power (as shown on the EFIS) starts to drop, If, as I have been taught, the enrichment is purely a function of the full throttle position, then I would expect the fuel flow to drop off a bit as you come off the stop.

I must admit that I am not an expert on the exact way this automatic enrichment is supposed to work, and have not found a really detailed description of how the carb is built to make this happen.

It could be that this only actually works at higher percent pow, which, of course, could also explain the "kink in the curve". Maybe tomorrow I'll try this little experiment at lower altitudes and higher power settings, and will record and plot some data to see if I can detect the automatic enrichment.

Paul

 

[fodrv7]

And FI

Paul,
Next time I fly I'll do the same with my FI and report back.
Pete.

 

[Yukon]

Peguin's Back

[ed. All of this text deleted by the forum owner, Doug Reeves. Way, way way over the line. User 'Yukon' has been banned from the forums for 30 days....the first time I've had to take this drastic of a step.

I'm very serious about these forums remaining perfectly civil.

dr]

 

[gvgoff99]

One last stop on detonation.....

BINGO!!
** NOTE **
(Detonation: Can you tell if you are detonating? No. Yes EGT goes down and CHT goes up during detonation, but than it's a little late, and are you sharp enough to notice? You may get distracted. Water cooled little bore engines are not big bore air cooled engines, so cars can tolerated detonation better and besides you can hear it. Walter talks about combustion pressure probes, which will indicate a detonation by a pressure spike, but we don't have this info. I doubt pressure probes will ever be practical for daily flying. The longevity of these probes is in question. One big issue is there's no room for a pressure probe in the cylinder head. Pressure probes that piggy back on spark plug are custom and are inaccurate. Car's use piezo microphones to listen for the "PING", but they don't work on aircraft due to noise. So what is the DATA? Let's be conservative and follow good practice based on 100,000's hours test cell and flight test the manufacture did to protect ourselves. The RULES of operation is what gives you the protection. 75% power is key. Is 79% OK? May be on a good day. May be is not good enough for me.)

George, Thanks for the carburetor info. I guess it really is destruction of a cylinder or two that is the first fully recognizable sign of detonation given our inability to monitor cylinder head pressure. It is pretty obvious that monitoring EGT/CHT is of little use even though "EGT goes down and CHT goes up during detonation" since "EGT goes down and CHT goes up" on virtually every climb out per my observations and the discussion on this thread. Bummer.........I'll keep doing the things that I have always done which to date has prevented detonation due to too lean a mixture. Unfortunately, there is no way to detect detonation due to an improperly timed mag or EI. Nor is it possible to detect an uncommanded timing advance from an ignition system that has just decided to slide up the BTDC numbers on its own due to some malfunction!
George

 

[gmcjetpilot]

Mad Scientist at Work

....back on topic? Going back to George's post, I wanted to comment on the "automatic enrichment at full throttle" part. Paul

Paul I love it you mad scientest. That is the way to do it. I am no expert either, BUT! Here is a quote from the manual:

FOR the O-360

"e. MECHANICAL AIRBLEED ENRICHMENT SYSTEM, (Large MA-4-5, HA-6 Carburetors, Ref. appropriate figure for a particular model).?When we increase the air velocity through the main venturi, we get an increased pressure drop that enriches the mixture, and to prevent this enrichment, an air bleed of a very precise size is used between the float bowl and the discharge nozzle. If we increase the size of this air bleed, we lean the mixture, and if we decrease it, more fuel is pulled from the discharge nozzle and the mixture becomes richer. The air for the air bleed comes from the float chamber and passes through the air bleed metering valve. The needle for this valve is held off of its seat by a spring and is closed by an operating lever attached to the throttle shaft. When the throttle is wide open, the lever closes the air bleed valve and enriches the fuel ? air mixture. "

FOR THE O-320's

"f. BACK-SUCTION TYPE ENRICHMENT SYSTEM, (Small MA-3, MA-4 (spa) Carburetors, Ref. appropriate figure for a particular model). ? The back-suction mixture control varies the pressure in the float chamber between atmospheric pressure and a pressure slightly below atmospheric. This pressure variation is accomplished by using a control valve located in the float chamber vent line. The float chamber is vented to the low-pressure area near the venturi through a back suction channel. This lowers the pressure in the float bowl. When then mixture control is in the rich position, the vent valve is open and the pressure in the float bowl is raised to essentially the atmospheric pressure, and a differential pressure exists across the main metering jet. This causes fuel to flow out of the discharge nozzle. When the mixture control is moved to lean, it closes the vent valve, and pressure in the float chamber is decreased to a pressure that is essentially the same as that of the discharge nozzle. This decreased pressure differential decreases the flow of fuel."


Clearly the "economizer" works on a pressure differential scheme. My guess is the "economizer" is more effective at lower altitudes (higher ambient pressure). At altitude there is only so much differential pressure available. Also if you have manually leaned it with the main metering valve, which has more authority than the "economizer", especially at altitude, it is not surprising you did not see a big change.

In my opinion the bleed-air economizers main function is to lean in climb, especially where there is the greatest pressure change, the first part of the climb after take off. There is only so much they can do with differential pressure. I don't think they make any claim it will lean in cruise at higher altitudes. I think it works best in climb at lower altitudes and is not a substitute for the mixture knob, especially at altitude.


This is a FREE ALERT (to all cheap skates), here is an on line manual as I mentioned before. I must admit I forgot about all the fuel delivery "circuits" in a carburetor, special features for idle, acceleration and cruise. I have a new found respect for the lowly Carb.

Here is the manual. There's no direct link so you have to navigate thru to get to the manuals:

http://www.precisionairmotive.com/
Select:

Support
Product Specific Support: MSA Float Carburetors
MSA Float Carburetor Handbook
Read the book.
-OR-
troubleshooting charts​

 

[Ironflight]

Good Reference George

I hadn't reviewed that for awhile!

Carb circuits always make my head hurt....the little diaphragm carbs on my jet skis have five different circuits, depending on where you're at on the throttle curve, and if any one of them plugs up, you're looking at toasting a piston due to a lean seizure.....

With this reference, we see that their is actually a mechanical linkage that acts at the end of travel of the throttle linkage, so there is no doubt there is something that is happening.

I went out to fly some test points this morning, but only did so at altitude - and (as expected) couldn't find anything in the fuel flows as I backed off the throttle. As conservative as I am , I just can't figure out a way to test at the higher power settings that satisfy me as being safe for the engine, but I bet if I could, I'd see something in the fuel flows.

What this also implies is that you want to avoid "slightly partial throttle" climbs at low altitude - take the throttle off the stop, and you are possibly cutting out the automatic enrichment.

I think I am satisfied that, at least as far as RV's are concerned, leaning below 5K is at best an academic argument, because you just aren't down there very long. I built a little spreadsheet to compute total fuel used in climbs at different fuel flows, and in a climb to 8,000', you probably spilled more at the gas pump before the flight.

A lot of good information here however!

Paul

(Oh, and I'm not a Scientist George - I'm an Engineer! We have Practical reasons for breaking things....)

 

[Walter Atkinson]

Gentlemen:

1) I only know of one pilot who has claimed to have heard detonation from the cockpit. He is reliable and I believe him. During a lot of detonation testing, I have never heard it on an aviation engine. I suspect it is essentially very difficult if not impossible to hear or feel in an aviartion engine.

2) The trouble-shooting guides of JPI, EI, and GEM notwithstanding, detonation does not result in EGTs going down while CHT's go up. If EGT's move at all, it is so little that you wouldn't notice it. After watching many hours of detonation testing, I am comfortable in telling you that EGTs stay pretty steady and CHT's go up moderately quickly. BTDT. During Pre-ignition, EGT's fall rapidly, followed by CHT's rising rapidly, and the engine may crater in short order. There is time to notice this and stop it.

3) Detonation, contrary to many years of incorrect assumption, is not very damaging to an engine as long as it is not allowed to progress to the point that it becomes pre-ignition. We have watched many, many hours of light and medium and even a little bit of heavy detonation and have even had the engine torn down by third parties to assess any damage. NONE. That is the reality, and it does fly in the face of many years of assumptions and reports to the contrary. Keep pre-ignition out of the picture and the engine seems to survive detonation pretty well--hangar-flying expert opinions notwithstanding.

4) Leaning by Target EGT is clearly the optimal way to go. Some engines and fuel set-ups do this for you automatically. Others require more pilot input. The result is the same.

5) Leaning an engine set WOT, does, indeed, override the fuel enrichment in the design. There is no need to bring the throttle back out of the auto-enrichment range.

6) Altering timing without a full ICP map of the effects is a risky business. Detonation margin erodes quickly. It could quickly result in detonation and/or pre-ignition. So far, I am unaware that any of the electronic ignition companies have actually done these tests. I only know of one place in the US where these tests could be run and it hasn't been done there. If you are using altered timing maps, you are a TEST PILOT. Be aware, significant risks are there. To each his own. I have SEEN these effects with my own eyes on a live running engine and I am impressed with the negative effects.

Nothing substitues for real, live engine testing on a very advanced, computerized test stand where you can WATCH this for yourself. I've found out just how wrong the conventional wisdom that I used to believe was. (Crow tastes a lot like Spotted Owl!)

If I can answer any other specific questions on this subject, feel free to let me know.

Walter Atkinson
Advanced Pilot Seminars

 

[Kevin Horton]

Walter - Interesting info about detonation. Thank you very much.

It is encouraging to learn that detonation isn't as harmful as generally assumed. But, there is still pre-ignition to worry about, which apparently would probably not be noted by the pilot, with the first obvious symptom being engine failure.

In the past I worried about detonation. Now I have the same type of worry, but I have just replaced the word "detonation" with "pre-ignition".

You mention ignition timing being too far advanced as one possible cause of pre-ignition. This could be caused by maintenance error, a failure of the ignition system, or an after market ignition system that has a too aggressive timing curve. Given that it seems that no one has actually done instrumented bench testing of their after market ignition system, the best we can do is look for ones that have a long and good service history, and not make any other mods that could degrade the pre-ignition margin (don't further increase the compression, or run fuel with lower octane, etc).

What other possible causes of pre-ignition should we be aware of, and what can we do to mitigate each of these risks?

 

[fodrv7]

IMC

Paul,
No flight testing possible today. Met. man (He IS a scientist) changed the forescast from 'Fog then Sunny' to 'Drizzle' at the last moment. Actually, about the time it started.
Try again tomorrow.
Pete.

 

[N91CZ]

JetA + Avgas

Walter,
If you add a small amount of JetA to Avgas, do you get detonation or preiginition? I had an engine ruined by a ~3% blend of JetA and I never knew a thing was wrong until the FBO informed everyone of the problem.
The top of the pistons were stripped of all carbon deposits, the babbit of the connecting rod bearings was smeared against the crankshaft and the exhaust valve seats had turned blue.

Chris

 

[gvgoff99]

Walter, YES!!

That is a five star answer and the one I have been hoping to see. Thank you very much!

My understanding of preignition is that it is an uncommanded event independent of the ignition system installed in the plane. I.e. a combustion event or series of events caused by something in the cylinder being hot enough to ignite the fuel prior to the spark (or Jet A being part of the fuel). I guess it really does not matter if the event is detonation or preignition if it happens enough before TDC to really clobber the piston, rod, journals, crank & bearings, cylinder heads etc. I assume that damage will result if the events are too premature and violent enough. It is somewhat comforting to know that "normal" detonation will probably do no harm because, in reality, none of us know if we are having detonation or not. All of us will continue to take precautions, as you re-emphasized.

Your answer on detonation makes sense because with all the planes that are flying I am sure that there are quite a few every year that experience detonation without incident. I had sort of come to this conclusion because I did an NTSB search from 1/1/01 to 6/5/06 using "detonation" as the search criteria. There were 34 reports that turned up. Most mentioned "detonation" in the report saying that the engine "revealed no evidence of detonation." One mentioned that detonation was probably the result of Marvel Mystery Oil being used in the fuel. Another was the result of "old" auto fuel being used and another turbo-normalized Bonanza conversion on an engine that was not recommended for turbo-normalization. There were about three that mentioned detonation but it was unclear how much it figured into the accident and another couple where detonation seemed to play a role but the planes involved did not seem to be the best maintained.

I fully agree with you about being a test pilot when using one of the experimental EI systems and at this point would probably recommend a conventional mag with the experimental EI so that the EI might be turned off in the event things do not seem to be going right with the engine. If "test" results reveal good performance in the next few years then converting to all EI may be prudent at that time.

I speak from experience now that I am grounded in Fayetteville, NC because something was not right with my setup.

 

[dan]

I speak from experience now that I am grounded in Fayetteville, NC because something was not right with my setup.

George, hope you don't mind me asking what the scoop was with your setup. You mentioned P-mags in a previous post...not sure if that's what you have, single or dual.

 

[Joey]

Thanks for a great post, Walter.

 

[avpro56]

Leaning at WOT

Gentlemen:

1) I only know of one pilot who has claimed to have heard detonation from the cockpit. He is reliable and I believe him. During a lot of detonation testing, I have never heard it on an aviation engine. I suspect it is essentially very difficult if not impossible to hear or feel in an aviartion engine.

2) The trouble-shooting guides of JPI, EI, and GEM notwithstanding, detonation does not result in EGTs going down while CHT's go up. If EGT's move at all, it is so little that you wouldn't notice it. After watching many hours of detonation testing, I am comfortable in telling you that EGTs stay pretty steady and CHT's go up moderately quickly. BTDT. During Pre-ignition, EGT's fall rapidly, followed by CHT's rising rapidly, and the engine may crater in short order. There is time to notice this and stop it.

3) Detonation, contrary to many years of incorrect assumption, is not very damaging to an engine as long as it is not allowed to progress to the point that it becomes pre-ignition. We have watched many, many hours of light and medium and even a little bit of heavy detonation and have even had the engine torn down by third parties to assess any damage. NONE. That is the reality, and it does fly in the face of many years of assumptions and reports to the contrary. Keep pre-ignition out of the picture and the engine seems to survive detonation pretty well--hangar-flying expert opinions notwithstanding.

4) Leaning by Target EGT is clearly the optimal way to go. Some engines and fuel set-ups do this for you automatically. Others require more pilot input. The result is the same.

5) Leaning an engine set WOT, does, indeed, override the fuel enrichment in the design. There is no need to bring the throttle back out of the auto-enrichment range.

6) Altering timing without a full ICP map of the effects is a risky business. Detonation margin erodes quickly. It could quickly result in detonation and/or pre-ignition. So far, I am unaware that any of the electronic ignition companies have actually done these tests. I only know of one place in the US where these tests could be run and it hasn't been done there. If you are using altered timing maps, you are a TEST PILOT. Be aware, significant risks are there. To each his own. I have SEEN these effects with my own eyes on a live running engine and I am impressed with the negative effects.

Nothing substitues for real, live engine testing on a very advanced, computerized test stand where you can WATCH this for yourself. I've found out just how wrong the conventional wisdom that I used to believe was. (Crow tastes a lot like Spotted Owl!)

If I can answer any other specific questions on this subject, feel free to let me know.

Walter Atkinson
Advanced Pilot Seminars

Walter:

Good information, thank you.

I'd like to explore more about leaning at WOT with an electronic ignition system and fuel injection. My RV-8 is equipped with a single electronic ignition system, a regular mag and Airflow Performance fuel injection. The ignition system includes a cockpit indicator that tells me the current timing setting. Running at full power (O-360 A1A) I see the timing is set within a degree or so of the fixed magneto timing at 25 degrees. This is resonable, so I don't think I'm eroding margins that may have been established long ago.

The Airflow Performance fuel injection system is capable of running very rich. So it's necessary to lean at high power settings. I guess the question is how much?

 

[Walter Atkinson]

To further clarify and answer the questions above:

Detonation occurs after the planned spark event and all of it's effects are noted AFTER TDC as the piston is going down. It is the explosive burning of the end gasses AHEAD of the flame front. It creates a shockwave in the combustion chamber which bounces back and forth at the local speed of sound. This scrubs the thermal boundary layer and results in increasing CHTs by increasing BTU transfer into the combustion chamber walls. This can actually clean deposits from the chamber! It has little to no effect on EGTs.

Detonation causes include, high CHT, low Octane (Jet A contaminated? Auto fuel?), improper mixtures ROP (detonation doesn't occur LOP because the ICPs are not high enough), timing too far advanced.

Dangers of detonation include shock to the bearings and other engine parts when allowed to progress to heavy detonation and the PRIMARY danger is the destruction of the spark plug ceramic integrity which leads to pre-ignition. Some Lycoming engines experience light detonation on almost every takeoff. As long as it is a conforming engine on conforming fuel, it is VERY difficult to get a TCM engine to detonate. We've been unsuccessful in many instances of trying--even in turbo'd TCM engines.

EGTs will remain fairly steady and the CHTs will rise steadily. To stop detonation one must reduce ICPs and CHTs. Going full rich or leaning further LOP will stop the event. The most detonation-prone mixture is 40-50dF ROP.

It is virtually impossible to get detonation in a naturally aspirated conforming engine being operated on conforming fuel. Advance the timing or use other than the proper fuel as designed to be used and all bets are off. Mixture mis-management can result in detyonation in Lycomings.

Pre-ignition is the initiation of the flame front PRIOR to the designed degrees before TDC. It is VERY destructive as ICPs and Temperatures rise rapidly beyond the design capability of the materials. The most common cause of pre-ignition is a damaged spark plug. The commonly sited cause, a glowing ember of carbon deposit, is unlikely and has never actually been demonstrated. The most common cause of the failed spark plug ceramic is dropping during maintenence or detonation. If you drop a plug more than 1", hit it with a hammer and throw it away (this keeps cheap airline pilots from using it after you toss it! <g>) Using advanced timing is the same as having pre-ignition. Having a timing map showing the resulting ICPS of the timing changes' effects on ICPs is critical. I know of NO testing on EIs which provide this--or even know about this.

Since the common cause is spark plug failures, I do in-flight mag checks routinely to test the plugs.

During Pre-ignition EGTs fall rapidly and CHTs rise rapidly. We know of several pilots who are graduates of the APS class who have recognized pre-ignition events and have properly acted to stop the event and have saved their engines. Switching to one mag, going full rich, or leaning further when LOP are all positive actions to stop the event.

Further questions?

Walter

 

[Walter Atkinson]

Chris:

**If you add a small amount of JetA to Avgas, do you get detonation or preiginition?**

The probable scenario was detonation leading to a failed spark plug ceramic which lead to the destructive pre-ignition.

Walter

 

[gvgoff99]

EGR Valve

Edge, You are correct. I should have mentioned that I started my auto experience in a '41 Ford (which was older than I ). It has been a long time since I have heard detonation. It will be nice when our aircraft engines have some of this automatic detonation prevention stuff. People will look at these posts like we look at '41 Fords, antiques!
Walter has raised the bar on our knowledge of this subject from when the post was started. George

 

[Mel]

Current knock sensors don't work on aircraft engines. It's been tried. These engines are just too noisy.

 

[gmcjetpilot]

Electronic ignition and leaning

Gentlemen:

1) I only know of one pilot who has claimed to have heard detonation from the cockpit.

2) The trouble-shooting guides of JPI, EI, and GEM notwithstanding, detonation does not result in EGTs going down while CHT's go up. If EGT's move at all, it is so little that you wouldn't notice it.

3) Detonation, contrary to many years of incorrect assumption, is not very damaging to an engine as long as it is not allowed to progress to the point that it becomes pre-ignition. Keep pre-ignition out of the picture and the engine seems to survive detonation pretty well--hangar-flying expert opinions not withstanding. We have watched many, many hours of light and medium and even a little bit of heavy detonation and have even had the engine torn down by third parties to assess any damage. NONE.

4) Leaning by Target EGT is clearly the optimal way to go. Some engines and fuel set-ups do this for you automatically. Others require more pilot input. The result is the same.

5) Leaning an engine set WOT, does, indeed, override the fuel enrichment in the design. There is no need to bring the throttle back out of the auto-enrichment range.

6) Altering timing without a full ICP map of the effects is a risky business. Detonation margin erodes quickly. It could quickly result in detonation and/or pre-ignition. So far, I am unaware that any of the electronic ignition companies have actually done these tests. I only know of one place in the US where these tests could be run and it hasn't been done there. If you are using altered timing maps, you are a TEST PILOT. Be aware, significant risks are there. To each his own. I have SEEN these effects with my own eyes on a live running engine and I am impressed with the negative effects.

Nothing substitutes for real, live engine testing on a very advanced, computerized test stand where you can WATCH this for yourself.
If I can answer any other specific questions on this subject, feel free to let me know.

Walter Atkinson Advanced Pilot Seminars

To summarize points 1) and 2), you can't tell if you are detonating useless you have hearing like a dog. I agree, EGT and CHT is not a reliable indicator of detonation and its too late for pre-ignition. Thanks for the input.

Item 3), I don't know what light, medium detonation means? Regardless I can't recognize detonation, therefore I follow procedures to prevent it, like not leaning above 75% power. How can I use the concept that detonation is not that bad? Detonation, even "light" can crack plugs, which will than lead to pre-iginiton. Before I disregard the manufacture and accept another experts opinion, I would like more data than "we have watched IT for many hours". What engine? Tell me how do I know I'm detonating again? Your comments are vague and nonspecific, sorry. I guess we can agree to disagree.


Item 4) Agree 100%. Lycoming drivers find EGT drop is small in climb. Therefore the Target EGT method has less benefit. Carbs and fuel injection used on Lycs do lean with out pilot action during climb, unlike the fuel injection on most Contenentals, which are pure mechanical units working on RPM and throttle position only. The AvWeb article was written for the TCM (Continental) not the Lyc. Leaning below 5,000 feet or above 75% pwr is not a good idea IMHO. Each to his own. Above 5,000 or below 75% target EGT away. I talked to Lycoming, they say don't do it, and they do have data to back it up, that you don't have. What expert to believe?


Item 5), I don't know what you mean? You got it backwards. Leaving the throttle WOT overides the auto lean on MA carbs used on Lycs. Not sure why you want to change the procedures for carburated Lycs. Yes you can override the bleed air valve (economizer) with wide OPEN throttle and lean in climb using the target EGT. Why and to what advantage I'm not sure. Clearly a big advantage for a TCM engine. Are we changing for change sake or trying to fly our Lycs like TCM engines? AFM?s for Lyc powered aircraft recommend a slight power reduction after takeoff for climb for a reason, not arbitrary.


Item 6) You have alluded to this "computerized test stand" data showing electronic ignition is dangerous! I speak for many, please tell us more. I know you're proud of the "ery advanced, computerized " ?GAMI?s Carl Goulet Memorial Engine Test Facility?. Don't scare us and give no data. What ignition curve and what engine? Why keep it secret.

Personal EI experience has been positive. Engine runs smoother, making more power with better spacific fuel consumption. I never heard of any EI induced detonation or engine damage. I think the experience of 1000's of pilots with EI speaks well comparied to your one test?

True experimental EI systems may not be "Dyno-ed", but the LASAR has. LASAR worked direct with Lycoming and of course the FAA in their certification efforts. Lyc has advanced computerized test equip BTW.

EI offered on the market are safe, here's why:

My references are:

Unison engineering and LASAR ignition,
Klaus Savier at Light Speed Engineering,
Jeff Rose at ElectoAir when he was running the show.
Aerosance/Lyc engineering certified & experimental FADEC systems.​

LASAR - used "computerized test stand" data from Lycoming no one else is privy to, including you. They feel their system provides safe timing adv. Considering it has been on the market for +5 years, with many units flown countless hours, what is the problem? LASAR is a FAA certified system. I assume Lycoming, Unison and the FAA know something about doing this safely.

Klaus @ LightSpeed - has sold his Plasma EI units for over 10 years successfully with no detonation or engine damage.

Jeff Rose's ElectroAir - I talked to him and he's very smart and convinced me that the method he used in the timing curve is safe. Again apparently no one has damaged an engine.

ElectroAir's fixed RPM/MAP curve is below.

Here is the ElectroAir timing formula and curves:
EIS Spark Advance (Timing) = Installed Adv (0) + RPM Advance + Vacuum Advance

Ideal or perfect? No. Safe conservative timing curve scheme? Yes. Way better than a fixed 25 degrees? Yes (NOTE: Vac advance starts at 24", which is about 5,000 feet, hummm. LASAR starts at 27"!)

Aerosance - Their FADEC includes electronic ignition and electronic port fuel injection. They don't use combustion pressure. What timing advance curve do they use? It's certified. It's even certified on your beloved TCM engines which are now available with Aerosance FADEC. It's a Lyc option for a little over $7,000. What is the "PRISM" going to cost?

Conclusion all the EI: Light speed, ElectroAir, and E-mag have a conservative scheme to advance timing that's less aggressive than the certified and tested LASAR, e.g., LASAR starts adv over 25 deg at 27" MAP where ElectroAir starts at 24". They are all extensively field proven.


Walter I know your GAMI buddies are working on the "PRISM electronic ignition" which will utilize "ICP map" combustion pressure input to advance timing. Knowing combustion pressure is SUPER, but making a practical, reliable, production inflight instrument to measure combustion pressure will be a challenge. Good luck; keep us posted. RPM/MAP has worked exceedingly well. (Note: ICP - Integrated Circuit Piezoelectric, tm name of PCB Piezotrinics, Inc.)


Walter, tell us more specifics of the data showing EI adv is not safe? You put this BIG CLOUD over our experimental EI, with out stating the data to support your claim. Why worry folks if it does not apply. If there's a problem, please tell us what EI? What timing curve? Was it tested leaned?

 

[BOBM]

Item 5), I don't know what you mean? You got it backwards. Leaving the throttle WOT overides the auto lean on MA carbs used on Lycs. Not sure why you want to change the procedures for carburated Lycs. Yes you can override the bleed air valve (economizer) with wide OPEN throttle and lean in climb using the target EGT. Why and to what advantage I'm not sure. Clearly a big advantage for a TCM engine. Are we changing for change sake or trying to fly our Lycs like TCM engines? AFM?s for Lyc powered aircraft recommend a slight power reduction after takeoff for climb for a reason, not arbitrary.

If you have an O320, you have an MA4 carb which has no economizer valve.

 

[gmcjetpilot]

Thanks Correct, O-320 Carb is different than O-360 Carb

If you have an O320, you have an MA4 carb which has no economizer valve.

Thanks Bob. Not all MA carbs have the bleed air valve feature, yes that is true. However I believe the MA-4 Carb (O-320) does have a fuel enrichment scheme, but it's different.

Check out the Precision Airmotive manual. MA-4's apparently has fuel enrichment. The manual shows MA-4's and MA-3's have a "BACK-SUCTION" type enrichment system (or at least some them). They do not have a bleed-air valve, but the result is the same, to boost or lower bowl pressure to increase or decrease fuel flow.

It does work differently. It works with mixture control postion not throttle. When you start to lean and "pull the mixture off" off of full rich, it closes a passage and drops the bowl pressue. This reduces the fuel flow. So it is more enrichment system than leaning, however this has impact in the Target EGT method.

In regards to leaning during climb with your O-320, aka Target EGT, I am not sure you want to pull the mixture back off of full rich, even just a little right after takeoff, since it will switch the carb into a lean mode. If the O-320 has a rich mixture mode it may need it (you think?). It may be wise not to move the lever until you really are ready to lean, i.e., below 75% power? It may make little differnce, so try it and see. I am all for experimenting (with your engine).

At least if you try the Target EGT method with your O-320, you might wait until you've climbed to about 3,000 feet before moving the mixture, since you might get a large initial drop in mixture with just a small movement of the mixture control.

Last although the MA-4 (O-320) carb does not have a bleed air valve it does work like a Carb and gets leaner as you climb. The amount of fuel the is sucked out of the bowl is based on the pressure in the Ventuir. Guess what, as you climb the pressure drops and do does fuel flow. It is in a sense a mass-air flow system. Again the system on the Teledyne Continental Motors don't work this way. So if you do nothing in climb with your O-320 Lyc it will lean.

The throttle does not affect the fuel enrichment feature on the MA-4 carb apparently, so if you want to fly WOT climbs, it should be OK, but coming OFF rich too early, at low altitude, high power and WOT, might get more EGT rise than you desired. Call me chicken. Fear is good and goes with respect. Respect the AFM or engine manufactures procedures, don't hold them in contempt. There are reasons behind the procedures and because others say they are "OUT DATED" does not make it so.

This question can definitely be answered for your Carb model with a call Precision Airmotive during business hours, 360-651-8282. Be sure to have model and part number. Usually they answer the phone right away. They are Pacific time.

Good point though, the O-360 carb is quite a bit different than a typical O-320 carb. This illustrates an important point, every engine and fuel system is different, and you can't make "best" broad bush techniques for all engines. That's why there are many different procedures. One size does not fit all. G

 

[Ironflight]

A Little more Data

I had an old engineering professor who once told me that if you are having trouble coming up with an answer, then you probably have not fully (or properly) framed the question. By Corollary, if you completely and fully define your question answers usually become almost self evident.

After all these pages of posts, and all the information and data that has been presented, I was tooling along a little while ago at 1500', and I suddenly realized what had generated my question in the first place! It all stems back to the Lycoming graph that Peter posted several days ago...

This is directly from the O-360 operator's manual, and I interpret this to mean that no matter what the engine is actually doing (it doesn't know if it is climbing or in level flight), Lycoming wants you to feed it at least this amount of fuel.

I guess that my question all along has really been this - can we take this chart at face value, and lean to these fuel flows - even in the climb? Lycoming does NOT make any qualifying statements, such as "except in climb"....

So as I was flying along, I quickly set up a little data run. I went full rich on the mixture, and set percent power to 70%. I let the fuel flows stabilize, and then got the value. I then went to 80, 85, 90, and full throttle - which was 95%, letting flows stabilize and writing down the value each time. Here is what I got: (Pressure Altitude about 1500', Temperature was stinkin' hot...)

Percent HP/Fuel Flow
75/ 12.4
80/ 14.6
85/ 16.3
90/ 17.0
95/ 17.8

As you can see if you plot these on graph, these values are all considerably above the minimum recommended fuel flows.

So.....This leads us to my real question (which I am just now beginning to understand) ....is it safe to lean down to the graph values if you know the percent power precisely? This is only a meaningful question in these days of digital instrumentation and EFIS/EIS displays which compute the real-time percent HP value for the pilot in the cockpit. Before we had this, it was too tough to compute, and you had to use the rules of thumb. Again, as I wrote a few posts back, this is still largely academic, as you spend so little time climbing below 5,000' anyway. But if you have leveled off down low to stay clear of airspace, and leaned while you are there, perhaps you don't need to go full rich when you resume the climb - but only need to enrichen to this line. (Again, keeping CHT's under control).

Again, I might very well be all wet with this idea....but why would Lycoming publish this plot if it was not safe to run the engine at these values?

Or....Maybe my mixture is just set way to rich at the rich stop....

 

[aadamson]

Might be acedemic but do you have this data?

Paul,

Just curious. If you just use the chart as and example and repeat the test, only this time lean to the lyc min FF's. Where is each Percent Power as it relates to Lean. In other words, if you set 75% power and a FF of 9.5 (exactly on the line), then determine how much that setting is ROP, Peak, or LOP (doubt any will be there). Where does each PP and min FF leave you?

Im not sure really, the value of doing the above, but it might be an interesting test to know what influenced Lycs data. For example, would it be that their line is always 50 ROP for any give PP, or does it vary widely. Plotting your data along side the Lyc data would show you similarities in the curves to see if there in linearity to the science.

Just a thot, YMMV

 

[Ironflight]

Paul,

Just curious. If you just use the chart as and example and repeat the test, only this time lean to the lyc min FF's. Where is each Percent Power as it relates to Lean. In other words, if you set 75% power and a FF of 9.5 (exactly on the line), then determine how much that setting is ROP, Peak, or LOP (doubt any will be there). Where does each PP and min FF leave you?

Im not sure really, the value of doing the above, but it might be an interesting test to know what influenced Lycs data. For example, would it be that their line is always 50 ROP for any give PP, or does it vary widely. Plotting your data along side the Lyc data would show you similarities in the curves to see if there in linearity to the science.

Just a thot, YMMV

Alan -

Good thought! I have played with that a bit in the past when I was BELOW 75%, and as best I can tell, that line is about 50 ROP. I may sneak up in the higher power values, but I'm goign to be very conservative!

Paul

 

[Walter Atkinson]

**nt knock sensors don't work on aircraft engines. It's been tried. These engines are just too noisy.**

The Carl Goulet Memorial Engine Test Facility is using pressure transducers that work quite well on aircraft engines to detect knock. They are being developed for production.

Walter

 

[Walter Atkinson]

George:

Let me respond in text.

**To summarize points 1) and 2), you can't tell if you are detonating useless you have hearing like a dog. I agree, EGT and CHT is not a reliable indicator of detonation and its too late for pre-ignition.**

No, either CAN be recognized on the current engine monitors--easily, if one knows what they are looking for. I have described that. PLease go back and read it again.

**Item 3), I don't know what light, medium detonation means?**

I'm referring to the standardized definitions used by the FAA. As you point out, one unfamiliar with those defnitions might not be capable of appreciating my comments. That does not make those comments incorrect.

**Regardless I can't recognize detonation, therefore I follow procedures to prevent it, like not leaning above 75% power.**

If you're a ROP operator, that is a good idea. If you operate LOP, then that concern is not valid.

**How can I use the concept that detonation is not that bad? Detonation, even "light" can crack plugs, which will than lead to pre-iginiton.**

I did not say that. Light detonation is essentially harmless.

**Before I disregard the manufacture and accept another experts opinion, I would like more data than "we have watched IT for many hours". What engine? Tell me how do I know I'm detonating again? Your comments are vague and nonspecific, sorry. I guess we can agree to disagree. **

I have reams of data that you can look at that cannot be posted here due to the bandwidth issues. How many times do I need to post how you can identify detonation? You can disagree all you wish, but the data is still what it is. Unfamiliarity with it could be the problem.

**the Lyc. Leaning below 5,000 feet or above 75% pwr is not a good idea IMHO. Each to his own. Above 5,000 or below 75% target EGT away. I talked to Lycoming, they say don't do it, and they do have data to back it up, that you don't have. What expert to believe? **

You have missed the point--badly. If the fuel system setup leans for the pilot or the pilot is doing it manually, the result is the same... it is being leaned in the climb. The TCM aneroid fuel pump does this with NO input from the pilot. I have chosen not to believe Lycoming. They have repeatedly made statements that are not in harmony with their own data. I find that unsettling. I really would prefer to rely on the hard data rather anyone's opinion. And, BTW, I HAVE seen their data. The Lycoming HARD data supports my position quite well.

**Item 6) You have alluded to this "computerized test stand" data showing electronic ignition is dangerous! I speak for many, please tell us more.**

It is not up to ME to give you ICP data on EIs. It's up to the manufacturer of the system. They do not do that. They should. I have seen the results. That data is propriatory and not for internet publication. I simply suggested that that data is not made available to the customer of the EI systems--and it should be. Unfortunately, the EI manufacturers don't provide that data. It's not up to me to provide it. I only reported my first-hand experience. Take it or leave it.

**I never heard of any EI induced detonation or engine damage. I think the experience of 1000's of pilots with EI speaks well comparied to your one test? **

You can bet your engine and your life on it. Our experiences are quite different. I AM aware of EI problems. You may disregard that if you wish.

**Lyc has advanced computerized test equip BTW.**

I wouldn't bet on it's state of the art. You might be shocked to find out just how little some who *should* know, do actually know about this very subject. I found it astounding.

**LASAR - used "computerized test stand" data from Lycoming no one else is privy to, including you. They feel their system provides safe timing adv. Considering it has been on the market for +5 years, with many units flown countless hours, what is the problem? LASAR is a FAA certified system. I assume Lycoming, Unison and the FAA know something about doing this safely.**

Are you sure? Where is their ICP data? No one's SEEN it. Why? Are oyu sure you are makiing a valid assumption? I far less confident than you about their level of understanding.

**Klaus @ LightSpeed - has sold his Plasma EI units for over 10 years successfully with no detonation or engine damage. **

Interesting claim. Are you sure?

**Jeff Rose's ElectroAir - I talked to him and he's very smart and convinced me that the method he used in the timing curve is safe. Again apparently no one has damaged an engine. **

Where are his ICP data curves?

**ElectroAir's fixed RPM/MAP curve is below. **

Yes, and NOWHERE on it is ICP data, which is the ONLY measure for detonation margin.

**Here is the ElectroAir timing formula and curves:
EIS Spark Advance (Timing) = Installed Adv (0) + RPM Advance + Vacuum Advance**

My point EXACTLY. No ICP data at all.

**Ideal or perfect? No. Safe conservative timing curve scheme? Yes. Way better than a fixed 25 degrees? Yes (NOTE: Vac advance starts at 24", which is about 5,000 feet, hummm. LASAR starts at 27"!) **

Not so. Incomplete.

**Aerosance - Their FADEC includes electronic ignition and electronic port fuel injection. They don't use combustion pressure. What timing advance curve do they use? It's certified. It's even certified on your beloved TCM engines which are now available with Aerosance FADEC. It's a Lyc option for a little over $7,000. What is the "PRISM" going to cost? **

Aerosance is calculating what they cannot measure. That's not a positive thing. I do not work for GAMI. I have no informationon the cost of PRISM. The one FADEC I do KNOW about was about $20,000 installed.

**Conclusion all the EI: Light speed, ElectroAir, and E-mag have a conservative scheme to advance timing that's less aggressive than the certified and tested LASAR, e.g., LASAR starts adv over 25 deg at 27" MAP where ElectroAir starts at 24". They are all extensively field proven.**

We do not share that conclusion.

**Knowing combustion pressure is SUPER, but making a practical, reliable, production inflight instrument to measure combustion pressure will be a challenge. **

That challenge has been solved.

**RPM/MAP has worked exceedingly well.**

An assumption borne of not seeing the ICP data from such.

** (Note: ICP - Integrated Circuit Piezoelectric, tm name of PCB Piezotrinics, Inc.) **

????? ICP = Internal Cylinder Pressure. I appologize. I made an error in assuming you knew what ICP was in the context of this discussion. That is my fault. I should have defined it earlier on.

** tell us more specifics of the data showing EI adv is not safe? **

The reality is that there are very few who have looked at the ICP data from those systems. Those who have (which does not apparantly include the manufacturers of same) are astounded at the negative aspects. It is not up to me to solve others' problems and all I am telling you is that based on the propriatory data I have seen, *I* would not put an EI as currently available on MY airplane. Others may do as they choose.

**You put this BIG CLOUD over our experimental EI**

Yep. A big cloud may well be appropriate. Certainly, anyone who is considering such a system should know what he does not know----because it is not being provided by the manufacturers.

It is always frustrating to realize that one has made a big investment in something that when looked upon with a critical eye may not be the end-all answer nor provide the intended result. The law of unintended consequences is alive and well in EI systems.

Again, based on what I have seen with my own eyes on Lycoming and TCM engines where timing alterations are concerned, *I* will not be putting any alterable timing apparatus on my engine for which there is no ICP data provided.

YMMV.

Walter

 

[Walter Atkinson]

** that line is about 50 ROP.**

FYI, based on all of the data from all sources, 50df ROP is the MOST detonation-prone mixture setting there is. If the object is to run the engine at the highest possible internal cylinder pressures and the highest possible CHTs for any given MP/RPM, that's your mixture--50dF ROP.

Walter

 

[gmcjetpilot]

Detonation

Walter: No, either CAN be recognized on the current engine monitors--easily, if one knows what they are looking for. I have described that. Please go back and read it again.

G: Yes I got that detonation = Rising CHT; Pre-ignition = Fast Rising CHT and EGT drop. However its a hot day, climbing out and CHT is climbing (while you are leaning), is it because its just hot or you have detonation? It is not that I am dumb I just don't agree. Engine monitor or not, if you are guessing your hot CHT shows detonation you're not doing it right. With pre-ignition, in my opinon, if you see a CHT spike, it's too late. Good standard operating procedures make either of these an issues moot. The timing advance issue is interesting, addressed below.



Walter: Light detonation is essentially harmless.

G: My main question was how do you know from the COCKPIT you have light or moderate detonation? High CHT - again or hot day? What engine was tested? TCM? Do you think it applies to a Lycoming? Did you test a Lyc? What model? Who tore it down?



Walter: How many times do I need to post how you can identify detonation? You can disagree all you wish, but the data is still what it is. Unfamiliarity with it could be the problem.

G: I found the "Pellican Perch #43 article, May 2001 by Deakin, "Detonation Myths" which explains a lot but raises more questions.

"The problem is how to detect it, and prevent it from becoming worse, because "light" can progress rather quickly into "medium" and worse. It is a "positive feedback" process, with a very negative result!"​

I agree with that, but they don't answer the solution to the problem. I tried to plow thru it but bottom line is light detonation is not bad. OK. That is cool, I did think ANY detonation was bad, but still it is not something you want to play wiith. My favorite Par is:

"A few years back, some of the research done by General Aviation Modifications Inc. (GAMI) in Ada, Okla., began to raise further questions in my mind about detonation. George Braly, the founding genius and chief engineer, started running a highly instrumented engine deep into detonation, and recording data that no one had ever seen before." ​

I love the part about Founding genius and chief engineer. WOW, if there is a doubt that Deakin is in love with Braly of GAMI, there isn't any more. I do think that its pretty neat neat stuff. I would like it of they did the Lycoming which they apparently did not. I don't think you can make assumptions they will detonate the same. I also like this Par:

"IO-470, and an IO-520 trying to destroy the engines. They still run pretty well (Well, sorta pretty well!), but you really wouldn't want those engines in your airplane."​

This confirms it, I still don't want to detonate my engine, even if it cleans the carbon off my piston. It's a good article and I see where you get the "proposed" detonation definitions. My issue is I can't really use it as a pilot in the cockpit, but it's interesting. It also says light detonation is not harmful, but it can progress quickly to med or heavy detonation. That confirms my "operational" phylosopy, follow the book.


Walter: You have missed the point--badly. I have chosen not to believe Lycoming. They have repeatedly made statements that are not in harmony with their own data. I find that unsettling. I really would prefer to rely on the hard data rather any one's opinion. And, BTW, I HAVE seen their data. The Lycoming HARD data supports my position quite well.

G: Would not be the first time I missed the point. I talked to Lycoming and you came up. They say they have data YOU have not seen. Of course you say the same thing about them. I don't want to get in the middle of the urination match between you and Lycoming, but you apparently have an invitation to visit them but have not taken them up on it? I'm just the messenger.

 

[gmcjetpilot]

Electronic Ignition Timing Advance is dangerous

Walter: It's not up to ME to give you ICP data on EIs. It's up to the manufacturer of the system. They do not do that. They should. Take it or leave it.

G: I hear you, but can't you characterize the data you have seen a little? You really have said nothing but "ITS BAD", so there is not much to take or leave?


Walter: You can bet your engine and your life on it. Our experiences are quite different. I AM aware of EI problems. You may disregard that if you wish.

G: Disregard, no, especially when you imply I will die ; you have my attention. Inquiring minds want to know. We all want to hear about the EI problem you are talking about, in detail. Rumor and hearsay does not count. No offense, but facts please. What plane/engine came to grief due to timing advance? What happened?


Walter: I wouldn't bet on it's state of the art. You might be shocked to find out just how little some who *should* know, do actually know about this very subject. I found it astounding.

G: Clearly you have some "issue" with OLD Lycoming, and frankly they have issues with GAMI and advance seminar group. I don't want to be in the middle. I respect both sides of the argument. We all can decide what to believe. You say they contradict themselves. I do it all the time, is that bad? I've talked to very sharp people at Lycoming and they are not clueless. I am sure there is the "new hire" answering the phone issue, but its a corporation. They do have key core technical people that are "brilliant geniuses".


Walter: Are you sure? Where is their ICP data? No one's SEEN it. Why? Are you sure you are making a valid assumption? I far less confident than you about their level of understanding.

G: I talked to Unison LASAR. All I can say is repeat that they worked with Lycoming and they produced reams of test and flight test data, including detonation margins. I respect your skepticism, you want to see it. I want to see the GAMI data; however being that they are certified by the FAA and have 10,'s of thousands of hours of safe operations, what can I say, we disagree. Since GAMI is not putting out the data; I'm skeptical.


Walter: Interesting claim. Are you sure?

G: Unless you are saying Klaus is lying, yes he is sure. I talked to him and that is what he said. There where early issues with early Plasma control boxes (e.g., no spark) 10 years ago but no engine damage according to Klaus. I've not heard of anything. Even mags can cross spark and cause pre-ignition damage. If you HAVE spacific case data, beyond rumor and urban legend, we would all love to hear it.


Walter: Where are his ICP data curves?

G: HOW MANY TIMES DO I HAVE TO TELL YOU. I am kidding. To answer you question, no I have not seen any combustion pressure curves. However to be fair you have not shown me any data either.


**ElectroAir's fixed RPM/MAP curve is below. **
Walter: Not so. Incomplete.

G: This is the "SOLUTION", the final RPM/MAP mapping, not the method to get the curve. What is left out? This is a timing curve. LOOK AT IT. Less than 25 degrees until you're less than say 80% power. Not much adv at all. I suspect the GAMI EI test was done with a critically lean mixture. I can't imagine the mild advance at these lower power settings would cause a problem.


Walter: Aerosance is calculating what they cannot measure. That's not a positive thing.

G: They made it clear this is TOP Secret data no else has, like your GAMI info is proprietary. Do you think the FAA wanted detonation margins before certifying their Continental Bonanza/C-210 installations? Is measuring ICP hard? It's not that exotic. Don't you think they can afford test equip?



**Conclusion all the EI: Light speed, ElectroAir, and E-mag have a conservative scheme to advance timing that's less aggressive than the certified and tested LASAR, e.g., LASAR starts adv over 25 deg at 27" MAP where ElectroAir starts at 24". They are all extensively field proven.**

Walter: We do not share that conclusion.

G: Fair enough, but the fact the data, like excellent field service history contradicts your comments that somehow the small timing advance at low power that EI achieve is risky business. Yes EI timing advance does produce less detonation margin, that is why the timing advance only occurs at lower power. You do have to be careful with how you lean and combining high compression pistons, but this is well understood.


**RPM/MAP has worked exceedingly well.**
Walter: An assumption borne of not seeing the ICP data from such.

G: I agree if you want to run at the edge of detonation, which is most efficent, ICP is the way to go. However a conservative (timing) solution is well understood. Not excotic or mysterious.



** tell us more specifics of the data showing EI adv is not safe? **
Walter: The reality is that there are very few who have looked at the ICP data from those systems. Those who have (which does not apparently include the manufacturers of same) are astounded at the negative aspects. It is not up to me to solve others' problems and all I am telling you is that based on the proprietary data I have seen, *I* would not put an EI as currently available on MY airplane. Others may do as they choose.

G: I don't know what to say about TOP secret data, fascinating but I hope you can tell us more in the future. It would be of benefit to the RV community. May be I'll buy a data logger to measure my own ICP http://www.tfxengine.com/hardware3.html, here is a plot:

**You put this BIG CLOUD over our experimental EI**
Walter: Yep. A big cloud may well be appropriate. Certainly, anyone who is considering such a system should know what he does not know----because it is not being provided by the manufacturers.

G: How do you propose we get the knowledge? I don't think ICP measurment is that rare or exotic. However a fact is 20 years of years of combined EI experience in the experimental community, one of which is certified. I guess by "flight testing" all these years we provided the knowledge. You can't argue with success.


Walter: It is always frustrating to realize that one has made a big investment in something that when looked upon with a critical eye may not be the end-all answer nor provide the intended result. The law of unintended consequences is alive and well in EI systems.

G: Well first I love my electronic ignition and so do 99% of the other EI owners. They do what they are advertise to do, and no one is frustrated. Again no reported detonation damage.



Walter: Again, based on what I have seen with my own eyes on Lycoming and TCM engines where timing alterations are concerned, *I* will not be putting any alterable timing apparatus on my engine for which there is no ICP data provided.

G: I don't know what data you've seen and you are not talking. I am not trying to sell you on the idea of EI but consider this. You agree 25 degrees is OK and is designed for 100% power. Now refrence the ElectroAir charts; you have to get down to 83% percent power to see the timing move 1 degree. Seems safe to me? From the charts, at 75% power the advance is about 7-8 degrees. This is not radical stuff. You need to be at 50% power to see the max advance, about +18 degrees over 25. The main benifit Walter is the hotter and longer duration spark. The small advance is just frosting on the cake. BTW all the manufactures will BURN in a new timing curve at your request. If you want to maintain a fixed 25 degrees you can do that as well.

Clearly you feel that without ICP there is NO safe way to advance the timing.

IT was a pleasure. Take care. G

 

[osxuser]

A company called Aerosparks makes a fixed-timeing EI that I setup at 23? BTDC on one of my customers RV-6's, it orginally was set to 25 degrees, but Aerosparks recommended 23 when he put 10:1 pistons in.

http://www.aerosparks.com/index.html

 

[Walter Atkinson]

George:

**However its a hot day, climbing out and CHT is climbing (while you are leaning), is it because its just hot or you have detonation?**

The two CHT rises are different. One levels off at the higher value simply because of the higher OAT, the other continues--even when it's not hot. <g>

**With pre-ignition, in my opinon, if you see a CHT spike, it's too late. **

We have several examples of confirmed pre-ignition events whereby the pilot recognized the event and stopped it BEFORE any damage was done. We have the actual monitor data as confirmation of the event and the borescope examination as confirmation of the lack of damage.

**My main question was how do you know from the COCKPIT you have light or moderate detonation? **

From my experience, light detonation doesn't really affect CHTs or cause harm. You wouldn't know it. You really wouldn't care, either... see below.

**What engine was tested?**

Lycoming TIO-540J2BD, as well as others, including TCM models. The VAST amount of detonation testing has been done on the Lycomings. Why? They suffer from detonation much more readily than do the TCM engines. The tear-down was done by a very reputable shop.

** I found the "Pellican Perch #43 article, May 2001 by Deakin**

Yes, and in the ensuing 5 years since John wrote that we have learned a WHOLE LOT more.

**I do think that its pretty neat neat stuff. I would like it of they did the Lycoming which they apparently did not. I don't think you can make assumptions they will detonate the same. **

Well, ya oughta be happy then, 99% of the detonation research done there has been on the Lycoming model referenced above.

**I see where you get the "proposed" detonation definitions. My issue is I can't really use it as a pilot in the cockpit, but it's interesting. It also says light detonation is not harmful, but it can progress quickly to med or heavy detonation. That confirms my "operational" phylosopy, follow the book.**

Those definitions are not "proposed" but operational. You might be surprised to find that we discovered that the big Lycomings can and do experience light detonation on takeof as a matter of routine if they are set up according to Lycoming. We also KNOW from experience that using the OEM FF recommendations in the POHs, that some of these engines routinely erode the detonation margin. There is some opinion that if they had to certify that engine today, it would NOT pass the detonation testing. That opinion is shared by multiple individuals both in and out of the FAA.

**you apparently have an invitation to visit them but have not taken them up on it? **

That's news to me. I've never recieved such an invitation. Had I, would have been there post haste. They have recieved an OFFICIAL invitation from us, delivered in person during a meeting I had with the new president and VP of engineering, to come see this stuff with their own eyes, which as of yet they have not accepted. TCM did accept our invitation and followed up. It was a learning experience.

BTW, labeling George as a genius is not adulation, it is factual.

Walter

 

[Walter Atkinson]

George:

**G: I hear you, but can't you characterize the data you have seen a little? You really have said nothing but "ITS BAD", so there is not much to take or leave? **

Yes, I can. It requires showing you recordings of a LIVE engine run where these data are collected. I cannot do that on this forum. The files are HUGE. I am willing to do that. You'll have to contact me off-forum.

**Rumor and hearsay does not count. No offense, but facts please. **

That's immenently fair and reasonable. What you might see in the ICP data would convince you. It won;t play here. Some of the information is propriatory and I cannot show it publically. It doesn't belong to me. There are hamonic effects which are scary. There are ICPs which erode detonation margin which are noteworthy and significant.

**Clearly you have some "issue" with OLD Lycoming, and frankly they have issues with GAMI and advance seminar group.**

That's their problem. I have NO issue whatsoever with anyone. The DATA has an issue with what Lycoming is says publicly... their OWN data is at odds with soem of what they say. 'Tis a puzzlement.

Our data is available for review. It has been peer-reviewed by industry experts across the board and the FAA sent folks fomr the small engine directorate to take our course and review it. NONE who have seen it have intimated that there is anytihng wrong with it, much less pointed out any errors in the data. These experts include, but are not limited to TCM, Beech, Cirrus, Columbia, the FAA, the Autralian FAA counter part, and auto engineers fomr Detroit. I ask you, who is conspicuosly absent that list?

**HOW MANY TIMES DO I HAVE TO TELL YOU. I am kidding. To answer you question, no I have not seen any combustion pressure curves. However to be fair you have not shown me any data either. **

I AM willing to show them as stated above. If I were selling an EI system, they would be PRINTED in the accompaning paper-work... if they existed.


** I can't imagine the mild advance at these lower power settings would cause a problem.**

Reasonable, but unless tested, reasonableness isn't much help.

**Is measuring ICP hard? It's not that exotic. Don't you think they can afford test equip? **

It's tougher than one might think.



**Conclusion all the EI: Light speed, ElectroAir, and E-mag have a conservative scheme to advance timing that's less aggressive than the certified and tested LASAR, e.g., LASAR starts adv over 25 deg at 27" MAP where ElectroAir starts at 24". They are all extensively field proven.**

** Yes EI timing advance does produce less detonation margin, that is why the timing advance only occurs at lower power. You do have to be careful with how you lean and combining high compression pistons, but this is well understood. **

That is true.

G: How do you propose we get the knowledge? I don't think ICP measurment is that rare or exotic. However a fact is 20 years of years of combined EI experience in the experimental community, one of which is certified. I guess by "flight testing" all these years we provided the knowledge. You can't argue with success.

George, remeber that one timing at full rich is quite a different matter than the same timing at a less rich mixture. Actual power being produced is only part of the equation. This where the ICP data is so helpful. We do agree that the effects are far less serious at lower powers.

Best regards,

Walter

 

[Walter Atkinson]

George:

Could you help clarify something for me? On the chart you posted, it shows CP (I am assuming that is combustion pressure??) as 1600+ at the peak pressure. Something's weird. The TCM and Lycoming engines tested show peak pressures in the 1000 psi range or lower on takeoff at the designed full rich mixture. If one were to takeoff at a lower FF than designed those pressures can quickly get above 1100psi.

We know from imperical evidence that spark plugs begin to be blown out of the cylinders at about 1200 psi. (don't ask me how we know! ARRGH.)

This reality is difficult to reconcile with the graph you posted. What am I missing? What are the units?

We have learned that keeping max peak pressures under about 800 psi in cruise is in in harmony with longevity concerns and is in line with what we see from TCM. That's a little lower than we see on the Lycoming engines. They operate under sligthly higher ICPs at takeoff than do the TCM engines and is a major reason they detonate easier.

Thanks,

Walter

 

[chuck]

George:

Could you help clarify something for me? On the chart you posted, it shows CP (I am assuming that is combustion pressure??) as 1600+ at the peak pressure. Something's weird. The TCM and Lycoming engines tested show peak pressures in the 1000 psi range or lower on takeoff at the designed full rich mixture. If one were to takeoff at a lower FF than designed those pressures can quickly get above 1100psi.

Walter:

Georges image was pasted from the web site that sells the ICP sensor. The typical application is for hot-rods, dragster cars etc.

This is the page:
http://www.tfxengine.com/software7.html

Chuck

 

[osxuser]

**What engine was tested?**

Lycoming TIO-540J2BD, as well as others, including TCM models. The VAST amount of detonation testing has been done on the Lycomings. Why? They suffer from detonation much more readily than do the TCM engines. The tear-down was done by a very reputable shop.
Walter

The TIO-540 J2BD is significantly different in design and operation than the Lycomings that we fly in our RV's (even the rockets and the -10s). First off, it's turbo'd, which raises induction temperatures significantly, second, it uses a completely different cylinder design than any that we use, third it employs updraft cooling exclusively, due to the exhaust exiting the top of the cylinders. It is also putting out 350HP, which is .64HP/ci as opposed to .50hp/ci on an O-360 or .55hp/ci on an Angle Valve 360.

Given inductions temperatures are higher, that already has decreased your detonations margins. Given the high HP output per ci and the high IAT I'm not surprised to see light detonation on takeoff. These engines have a reputation for making 2000hr TBO's with proper maintainence and operation as well, so it probably isn't that big of a deal.

To acheive the same HP/ci with a 360, it would be outputting 230HP. This is not particularly realistic with a stock setup (without going to a high-boost turbo or extreme compression ratio). So say we get around 220HP out of an angle valve with porting, ram air (COLD) and EI. Considering it is still putting lower HP/ci output than the stock configuration of the engine you tested, shouldn't the detonation margins be greater? I'm not an engineer, so that isn't meant to be retorical, I'm just thinking out loud.

Using the same HP/ci ratio of .64, that would mean that an IO-390 could possibly made to put out 250HP who needs a Rocket? I'm waiting for some crossflow IO-390 cylinders .

 

[gmcjetpilot]

Thanks for the reply

Thanks a million Walter. Great stuff and I need to take time to read it and digest. Good stuff.

The one question about the outrageous combustion pressure is off a drag racer (blower). It's just a screen shot off the companies web site that sells the equipment yo measure ICP. I enjoy the "world of (ICP) internal combustion pressure measurement" and the work the Geroge at GAMI has done is very interesting. I wish he would treat it like a university or NASA and print reports, but it is commercial enterprise and the data is proprietary.


IS IT DETONATION?
Flying CHT/ EGT subtleties to identify or run near detonation in my opinion is OK for testing, but not practical for daily flying and a true preventive indicator. Many engine monitors do have RATE OF CHANGE of CHANGE alarms, helping the pilot monitor the CHT/EGT. 10-15 years ago you where lucky to have one analog CHT or EGT. Today most have everything monitored except torque and ICP. Add those as well we will be flying test cells.

I am not sure we'll ever have production instrumentation to read ICP in the cockpit for every day general aviation planes. Is it needed to safely fly? With FADEC the topic of LOP and Target EGT is MOOT. You have no control the computer does it. We flew for years with NO engine instruments other than oil temp. I do love having the engine monitors, let's use them to our advantage other than filling the panel.


FLYING ON THE EDGE
The extream gas milage we get from cars today is in part because they run on the edge of detonation, which is ideal from the stand point of getting the most power out of the fuel. I know that WET running of aircraft engines is not efficient and wastes fuel. However that may be a necessary evil for an air-cooled engine, but pilots can always do better in the leaning area.

Topics of ICP and detonation you bring up, increase the knowledge of all the RV pilot community. I am sure that's why advanced pilot seminars are popular and you get all the student endorsements. I know I've learned a lot. We all like learning new stuff. The Target EGT is interesting in that it started a great conversation. I've been lazy leaning above 5,000 feet, and will be more aggressive leaning. However the EI issue came up. Do you want to lean in climb with timing advance, even if the advance is small? Needs to be looked into. How much benifit is leaning in climb to us? Is there secondary effects? Does having EI affect they way you operate?


EI TIMING ADVANCE
I'll look into EI advance problem because it's a safety thing, not just an "operational technique" you can choose to do or not. This controversy is not new. Many home builders don't use EI, staying with mags. For one mags are realitively cheap, especially if you already own them, and they work. The main claim to fame of EI is the longer and hotter FAT spark. The adv timing does not start to really kick in unless you are at 9,000 feet.

Back about 8 years ago when EI was new, before LASAR, there where concerns. The worry went away after they flew successfully with no ill effects for several years, BUT as Walter points out no one he knows of has measured ICP, a key parameter, with the EI. It should be done. I agree with that.

As Walter points out CHT is a secondary indicator of detonation (ICP being the main or critical parameter). I know that Klaus (lightspeed engineering) flys his equipment extensively (and wins lots of races) and has "flight tested" differnet timing curves using what he does know: CHT/EGT/RPM/MAP/FF. It is not like there has been no testing. Also they have been around for +10 years. From what I know, the E-mag has an even more mild timing advance.


Take care. George

 

[Fitz]

FLYING ON THE EDGE
The extream gas milage we get from cars today is in part because they run on the edge of detonation, which is ideal from the stand point of getting the most power out of the fuel. I know that WET running of aircraft engines is not efficient and wastes fuel. However that may be a necessary evil for an air-cooled engine, but pilots can always do better in the leaning area.

I'm sorry, I have to disagree with that somewhat. The reason that modern cars do not run lean of peak for fuel economy is primarily polution. Cars spend much of their time idling at 'peak' because that helps the most with emissions. If the sole objective was fuel economy cars would idle leaner.

Knocking and pinging when we stomp on the gas also does not mean that we are riding the ragged edge of disaster at higher power. It just means that low RPMs on a high compression engine, especially one idling at peak, have lots of time in each cyl where the conditions are ideal to form easily auto-ignitable compounds from the longer hydrocarbon chains. So, when we stomp on the gas and more fuel is fed into the chamber, we tend to hear the knock of detonation until RPMs go up. At that point the 'window' for compound formation has dramatically shrunk and the ECU has set the engine to best power (say an AFR of 11 or 12 to 1) instead of the leaner 14.7:1 it was idling at - giving a much greater margin from detonation.

I also am not sure that I agree that EGT and CHT are a practical indicator of detonation in an aircraft. Audible sensors do not work, but Saab did quite a bit of experimentation with ionic sensing in ignition systems. The research papers are well worth reading for many reasons, but one thing that really stands out is how bad detonation needs to get before EGT drop is significant. You can read some of the earliest Saab work on ion sensing here: http://www.fs.isy.liu.se/~larer/Projects/main.html

-jjf

 

[Walter Atkinson]

**Considering it is still putting lower HP/ci output than the stock configuration of the engine you tested, shouldn't the detonation margins be greater? **

That is quite logiocal, but it turns out may not be accurate.

Why does everytrhing have to be so complicated? <g>

Walter

 

[Walter Atkinson]

George:

Excellent points.

**Flying CHT/ EGT subtleties to identify or run near detonation in my opinion is OK for testing, but not practical for daily flying and a true preventive indicator. **

Absolutely agreed. 100%. That's why I have expressed some of the concerns I have expressed.

**I am not sure we'll ever have production instrumentation to read ICP in the cockpit for every day general aviation planes.**

It may be available soon. I've seen it. I'm involved in the devlopement of the monitor side of that effort and who it will be displayed in the cockpit.

FLYING ON THE EDGE
The extream gas milage we get from cars today is in part because they run on the edge of detonation, which is ideal from the stand point of getting the most power out of the fuel.**

Yes, and they can do that with water cooled heads and very ehavy construction, neither of which we enjoy.

**I know that WET running of aircraft engines is not efficient and wastes fuel. **

Yeah, like the Admiral once said, "Water cooling an aircraft engine makes about as much sense as air cooling a submarine!"

<gg>

**Do you want to lean in climb with timing advance, even if the advance is small? Needs to be looked into. How much benifit is leaning in climb to us? Is there secondary effects? Does having EI affect they way you operate? **

All of these are very sifggnificant questions. Some have answers, others do not yet have data collected to be clear what the answer is. What is important is having the EFFECTIVE timing occur at approximately 16dATDC. That is the ultimate goal. The combinations of MP, RPM, timing, and mixture are the affecting variables. There are times and conditions whereby advancing the timing is VERY good. There are other times where retarding the itming will result in greater power to the prop. Without hard data collected, these remain unknowns, only "guessed at." Guessing is sometimes fun... and every once in a while it can be serundipitously correct.

**The main claim to fame of EI is the longer and hotter FAT spark. **

Yes, and that alone advances the EFFECTIVE timing--which could be positive or negative, depending on the other factors I listed above.

Regards,

Walter

 

[Walter Atkinson]

** Knocking and pinging when we stomp on the gas also does not mean that we are riding the ragged edge of disaster at higher power. **

Comparing auto and aircraft applications can be a slipery slope. The robust nature of the auto engine's construction is a plus we do not enjoy in aircraft applications. What passes as benign, limited knock in an auto engine may not do so in a lighter, hotter-running aircraft engine.

Walter

 

[Fitz]

** Knocking and pinging when we stomp on the gas also does not mean that we are riding the ragged edge of disaster at higher power. **

Comparing auto and aircraft applications can be a slipery slope. The robust nature of the auto engine's construction is a plus we do not enjoy in aircraft applications. What passes as benign, limited knock in an auto engine may not do so in a lighter, hotter-running aircraft engine.

Walter

I wasn't comparing auto to aircraft, I was questioning a point made about auto engines themselves.

My only points related to aviation were A) that trusting CHT and EGT for detonation detection is very, very, dubious and B) LOP operation is not inherently closer to detonation and is not even the mechanism normally employed by cars (they run closed loop at stoichiometric at low power for emissions reasons).

I'm not sure I get all your points about aircraft engines. Overall, existing designs are surprisingly well suited to GA applications. Simple, moderately efficient. In my 25 years of using them my biggest complaint is that the overall quality of the manufacturing has remained poor. Auto manufacturers have the economics of scale, but I suspect that their providing a meaningful warrantee has driven improved quality control and manufacturing tolerances as much as anything.

-jjf

 

[Walter Atkinson]

I have a question.

How does one reconcile these two Lycoming recommendations?

1) Do not lean above 75% power.

2) Lean for high DA takeoffs.

The answer to that may solve the whole darned thread. <g>

Walter

 

[Tandem46]

Simple answer

Walter,

The following is right off of the Lycoming.textron.com website:

First we must know that cruise power for Lycoming normally aspirated engines is generally considered to be 55% to 75% of the maximum power for which the engine is rated. At these power settings, the engine may be leaned at any altitude. There has been confusion about the reference to not leaning below 5000-feet density altitude. Remember that this reference only applies to those power settings above the cruise range ? those normally used for takeoff and climb. Once cruise power has been set, leaning to best economy should be standard procedure as damage to the engine will not occur from leaning at cruise power settings.


At high DA's, you won't have 75% power available, so the two statesments can coexist. Of course I think the target egt leaning method is right on target.

 

[Fitz]

I have a question.

How does one reconcile these two Lycoming recommendations?

1) Do not lean above 75% power.

2) Lean for high DA takeoffs.

The answer to that may solve the whole darned thread. <g>

Walter

As stated above, when you go up in DA, the NA engine can no longer generate more than 75% anyway so...

I'm not sure why so many pilots struggle with this. Of course, 'Recommended leans', just rich of peak and vague FAA warnings about 'too lean' without any real explanation of in-reference-to-what and why, don't help.

-jjf

Edit: I also agree that the constant EGT method works, but I think that pilots should really understand what is going on. So I have question:

When we go up, the air gets 'thinner' - IE, fewer molecules per volume. So mixture must get leaner to maintain the same air/fuel ratio. If we are burning less fuel, then there is less energy being released.

A smaller release of energy over the same interval of time is the same as saying we have less 'power' available. We see this at the crankshaft at higher DAs.

But, if we accept that the total energy available is now smaller, why does constant EGT work? In other words, if the total pie we are measuring gets smaller, why does keeping the 'thermal slice' the same size work well?