P-mags, E-mags, EI discussion

[MarkC]

Well I'm certainly not looking for an argument here, just that we have both been given opposite advice for the same symptoms and while I do not have your experience of detonation there seems to be a few things that don't add up in my mind.

When my engine was borescoped it was found to be in perfect order so the outcome may well be fine in each case.

Can't say I have experienced the scenario you describe when running LOP, as I run roughly 100F LOP all the time and don't get any signs of pinging.

I understand how you can get blowby, by which I assume you mean the charge blows out of the exhaust valves rather than pushing the piston down?...This in theory would raise the EGT's but how does that explain the high CHT's you experienced?

Secondly, I thought you said you had redline (or at least high) oil temperature?

From my Google searching on "pre-ignition" The explanation I got was that charge was lit (or lit itself) while the piston was on its way up the bore, thus putting a great deal of stress on the piston and big end bearings because the piston was trying to compress a rapidly expanding charge. The resulting pressure forced this red hot charge past the rings and heated the oil directly in the sump, presumably with quite a bit of crankase venting going on too.

With all these nasty happenings going on it was suggested that the engine could well be damaged and the borescope would reveal the tell tale signs of pitted pistons etc.

As I said I'm just trying to learn here for mine and the collective benefit of the group.

Frank

You run 100 degrees lean of peak, all of the time? Really? Well, I guess I just learned something because I have never heard of that before. We can always learn something, that's for sure! I'm pretty sure I won't be doing that with my engine though.

Pre-ignition and detonation are 2 very different things. I'm not going to explain any more here as it would appear that Google has more to offer.

Take care,

Mark

 

[Captain Avgas]

Try running about 90 degrees lean of peak over 8k feet, even with just mags at the regular 25 degrees BTDC, that is what pinging sounds like, you'll know it once you hear it. Pinging happens at the onset of detonation.
Mark

Mark, I would suggest that at over 8K feet with a normally aspirated engine you probably cannot develop more power than 75%. Therefore at 90 degrees lean of peak at that altitude there is virtually no possibility of detonation. At less than 75% power and 90 degrees LOP one would expect low internal combustion pressures, low EGTs, and low CHTs...hardly the circumstances to produce detonation.

At any rate I take this to mean that you were running ROP when this incident happened.

In reality if you had've been running LOP there is some possibility that even with the overly advanced timing the engine might not have quit. A lean mixture has a slow flame front which would have resulted in peak pressure being retarded.

 

[Pat Stewart]

PMAGS

Ok, I just returned from Vacation today and immediately got online to see whats going on with the e/pmags. First let me say that Brad and Tom are great guys and customer support has been outstanding. However with that said I am also surprised too not see them jump in to these post and try to address many pages of issues. I purchased two PMAGS and in three flights logged about an hour to one and a half hours. I had the first failure on the ground before the first flight and three more in flight before removing and returning to EMAG. Here is what I experienced.

Failure 1.

During first ground run switched off power to each mag individually to check PMAG fuction. Each PMAG provided power down to about 650RPM's. After performing test the left MAG was dead. Returned to EMAG who fixed what they said was a software problem.

Failure 2.

After 30 minutes circleing a couple of local airports with a perfectly running very smooth engine I landed very happy with my PMAGS. Before shutdown I checked each PMAG. The left PMAG was running really bad and the right was ok. Trouble shooting indicated that the left PMAG had jumped about 180 degrees out of time. This had to have happened during decent or taxi after the flight because the flight had no PMAG perfomance problem. Performed the blow timing method and both PMAGS performed well during ground runs.The next morning prior to flight during ground run I again checked both PMAGS and the left PMAG had again jumped out of time. Now I am suspecting my own wiring of the left PMAG so me and another RV friend went through the entire system and found no problems. Again returned left PMAG and they replaced it with another PMAG. Not sure if they found a problem.

Failure 3.

Several grounds runs later both PMAGS performed well and I took off and again circled the airport. After two times around I elected to fly toward another airport within 4 miles. Half way there the left PMAG jumed out of time again. I pulled back to idle and glided back to my home airport (altitude is your friend). This time Brad asked me to bring in both PMAGS because there was a new software update available and he wanted to update the right PMAG as well. The right PMAG was updated and they replaced the circuit board in the left.

Failure 4.

After very successful ground runs I again took to the air (not for long). Of course I executed a maximum rate of climb takeoff feeling like this was indeed a test flight. About 900 feet AGL at maximum climb angle takeoff my left PMAG failed again (significant RPM drop). I must say I had no time to look at RPMS, CHTs or anything else other than airspeed. I pushed the nose over and pulled back the throttle, made an instant turn to cross and downwind and the landing was a non event. On taxi I switched the MAGS and determined that it was indeed the left again however this time even the right was not as smooth however about the same as my Slicks. Troubleshooting again showed the left PMAG had jumped significantly out of time and this time the right PMAG was also out 20 to 30 degrees.


I returned both PMAGS and recieved a full refund. Brad and Tom were great. I did request that the call me and tell me what they found. It seems a known bad board was accidentally put in the left PMAG. I understand they are still looking at the Right PMAG.

That was my situation before VC and next weekend I will be re-installing my Slicks.

With that said I must also say that one of my hangar friends has dual PMAGS and did also have the same failure number 1 however since the software fix he has many fantastic flying hours on his PMAGS with no problem. I also have other friends flying both E and PMAGS with great results.

I may not have cleared anything up however I did want to say that my experience has not been about timing advance issues, (im not sure how you would tell) it has been about the soft timing issue and how they jump out of time.

Pat

 

[frankh]

Hmm

Well the soft timing issue and Jumping out of time could well end up as an advanced mag issue.

For me the units were runing great and then without warning the the CHTs and oil temps maxed....While in IMC of course! My reading on the matter (plus advice from Mahlon) pointed towards pre-ignition.

Did you by any chance intall the Pmags NOT using the blow in the tube method? I am still wondering if the units lose their modified timing and revert back to factory default.

My Pmag is installed with the factory timing and the Emag has the blown tube method. I'm not sure how I would get it back to its original setting in any case.

To be honest my biggest fear is this has done some long term damage to the bottom end of the engine, while the borescope showed no signs of preigntion and there were no chunks in the oil filter there is still a nagging unknown.

As I am coming up on 100 hours I will send an oil sample for analysis to see if there any abnormal signs.

If that comes back ok then I may choose to resurect the premium autogas experiment with timing retarded to 26 degrees. This time however it will be done with one tank of 100LL and one of autogas...This gives me an out in the event of similar symptoms.

Frank

 

[Yukon]

Big bal*s, Frank! To save what ....... a dollar a gallon on auto fuel????

 

[frankh]

Dollar a gallon adds up

to roughly the cost of a rebuild over the standard TBO.

Having said that, the autofuel experiment has been shelved until I get through my Instrument rating, i.e its not a priority at the moment.

But there is a beligerant (and admittedly less than logical sometimes) part of me that says "these engines are advertised as being OK to run on mogas so I should jolly well be able to". Our Sooby bretherin love to point out that autofule is an advantage for them, I'd like to show that it isn't....besides if the new gas tax comes our way it may make more sense.

Frank

 

[grantcarruthers]

2.50 a gallon vs 4.00 at 10 gallons/hour at 200 hours/year = $3000/year


times 2000 hour TBO = $30,000 = free factory engine!!!!!!!


Works for me


Plus I can have fuel delivered to my home (known quality, volume discount) and a transfer tank in the back of my picup truck so I can refuel on arrival to field without taxi to pumps.

 

[Ron Lee]

Dual P-mags

In all this discussion has this group determined a reasonable isolation process if they have symptoms discussed here?

Would it not be simplest to switch in order to a single mag (left or right) to determine if the engine runs fine on only one mag IF one mag is causing the problem?

Knowing what to do before such a problem occurs may prevent a forced landing.

 

[frankh]

Exactly

And I wish I had done this.

1) Reduce power...a lot!
2) Go full rich or full lean (probably easier to go rich)
3) Simply switch one off and watch the temps for a minute
4) repeat on other E/Pmag if nothing changes.

Oh and switch to the tank with the 100LL in it...


Frank

 

[Jekyll]

E-mag snuck in under the wire

E-mag has a new Mandatory Service Bulletin on thier web site, released 2/12/07:

http://www.emagair.com/E-MAG Service Bulletin1.pdf

It addresses the inadvertant loss of timing due to intended and unintended features of "guick-set" timing. Part is operator error and part is E-mag's fault. They have released Firmware update #24 to fix their part of the problem and provide some operating guidance to help with our side.

I urge all users to go to the site and read the bulletin.

I guess they don't monitor this site. Could have ended a week's worth of speculation by addressing the thread.....

Jekyll

 

[Bob Brown]

Recent ignitions only

Although I haven't had any performance problems with my P-Mags, I spoke with Brad about this SB to see if it applied to mine. He indicated it was only for recent ignitions (firmware loaded December 2006 thru February 11, 2007) and that the SB did not apply to my ignitions.

I agree it would be nice if Emagair would monitor this site and answer questions from time to time. I don't get the feeling they are trying to hide anything, they have been very reachable when I've ever had a question, including Brad giving me his cell phone number when he was going on vacation and I had some install questions last year. On the other hand, I think if they wanted to, they could answer the same questions 500 times a day ad infinitum...

 

[Davepar]

Reading the service bulletin, I'm glad I set up my ignition toggle switches the way I did. My P-mags will never go into set up mode unless I specifically hook up a jumper.

 

[Yukon]

2.50 a gallon vs 4.00 at 10 gallons/hour at 200 hours/year = $3000/year


times 2000 hour TBO = $30,000 = free factory engine!!!!!!!


Works for me


Plus I can have fuel delivered to my home (known quality, volume discount) and a transfer tank in the back of my picup truck so I can refuel on arrival to field without taxi to pumps.

How about these numbers.......

Total engine failure during first run on auto fuel.........$25,000
Realization that auto fuel is for cars..........................priceless!

 

[Ron Lee]

P-mag service bulletin

Before this came out there were posts made here that provided enough info that loss of timing was a credible reality.

 

[walter]

Reading the service bulletin, I'm glad I set up my ignition toggle switches the way I did. My P-mags will never go into set up mode unless I specifically hook up a jumper.

I agree with this method and it's how I've had mine wired since day one. No
chance to screw it up in flight.

Ok, here comes the confession part. I was an early adopter of a dual P-Mag
setup. I traded out a LASAR system at 25 hours trying to cure a high CHT
issue. The LASAR system can advance to 45 degrees BTDC in certain situations. Thinking that I could lower advance with P-mags and believing that
they were the wave of the future were two of a few reasons for trading.
I eventually solved the CHT issues, it wasn't the ignition system.

The first set of P-Mags ran well for 20 hours. I opted to send them in for an
optional firmwear update. When they came back one of the units was failed.
I sent them back, twice. Brad indicated that a magnet had moved. I got
them back and they worked as advertised for another 45 hours when I sent
them back for another optional firmware update. This was the famous blow in
the tube update.

I could get only one P-mag to set timing correctly with the blow method,
one went to blinking red and the other to green. I sent them back.

When they came back I could get neither to go to green led with the blow
method. Instead I manually set the timing and they seem to work well
on the ground. I had not tried this on the first attempt. I have yet to fly
with them after the latest update since I've been down for paint prep work. I
expect to fly in 1.5 weeks after a small vacation.

At this point I don't feel confident that the blow method works. I highly
recommend you set the timing mechanically.

I have been a supporter of emagair and continue to be so. Although, I did
tell Brad the last time I spoke that if they didn't work this time I would look
for an alternative and send them back until there were more, many more
successful hours in the field. I still may do so if they don't perform as
expected. I don't mind that the blow method doesn't work as I don't intend
to use that method until it's proven tested.

I guess I don't mind being a beta tester. I haven't had any failures in
flight. I *routinely* check the P-mags in flight, on almost every flight.
I have included the power-off procedure in my POH in case of roughness
or failure in flight.

I still think this is the future. I can't say it's the present just yet but I am
willing to fly with them as long as I have two of them.

 

[rv8180]

Switch Set Up

Reading the service bulletin, I'm glad I set up my ignition toggle switches the way I did. My P-mags will never go into set up mode unless I specifically hook up a jumper.

Dave,

Would you describe how you set your toggles up?

How do you do the run up checks? Can you check for operation without ship's power?

I'm using toggles also and would like to compare. I'm just about to start wiring.

Thanks!

 

[N941WR]

Roy,

Here is how I wired mine up:



BTW, one minor change I made after I drew this up was to replace the ground service switch with an 1/8" mono jack and plug. That way, there would be no possible way to put it in ground service mode in flight.

 

[grantcarruthers]

How about these numbers.......

Total engine failure during first run on auto fuel.........$25,000
Realization that auto fuel is for cars..........................priceless!

Oh Pahleez!!!!!!!

True example with a monitored engine and an awake pilot or exageration for the sake of the argument????

 

[Davepar]

I did mine the same way as Bill, except I didn't do the ground maintenance switch/plug at all. I use a jumper wire with some alligator clips to wire the P-mag power lead to +12v for setup. Had I known I'd be messing with the P-mags so often, I would have put the switch in.

From Walter's post and others, it seems like the firmware updates are a large part of the problem. When I talked to Brad a few weeks ago to ask a question, he suggested I send mine back for another update. He said they had cleaned up the firmware code. Hopefully that's a good thing.

 

[walter]

In order to put them into setup mode I disconnect the ground lead and p-lead
wires from each switch and connect them together. Do this on both switches
with a little male-male faston connector I made. Simple and cheap. On the
tipup I have good access to the backs of the switches so it only takes a minute.

 

[NeilMcLeod]

Just to throw in my data point. I had an early emag. Running one emag and one Slick. New engine from Bart in my just completed 7. The emag developed an oil seal leak and soaked the electronics causing a gradual failure within 5 hours of initial flight test. During this time I am also having high cht problems but manageable with full rich, limited climbs, higher speeds, throttling back etc. Thinking, new engine, break in and all that. Get a new emag in exchange. Seems to work but still high cht's, go crazy checking baffles, cowling, numerous phone calls and re-timing, setting the emag with and with out MAP sensing, limiting it to 25 deg advance etc. Nothing helps. Now the new emag starts to quit when it gets hot and... hmmm the cht's come down when it quits. Back it goes to the factory. Now I'm tired of messing with this thing and want to get on with flight test and fly my new plane so I ordered another Slick. Have been happily flying ever since with no CHT problems. Got the emag back after a lengthy time in the shop with no explanation. Never got around to calling and asking to see what if anything they found. To busy enjoying my plane. It remains in the box...

Neil McLeod

Neil

 

[Yukon]

Oh Pahleez!!!!!!!

True example with a monitored engine and an awake pilot or exageration for the sake of the argument????

I really have no idea what you are trying to say Grant...... much too cryptic for me. What I'm saying is Frank Hinde came really close to wadding up his new RV on his first flight on auto fuel. This with a specially engineered fuel system for auto gas.

Time to face facts guys, car gas is risky. Car gas with 40 degrees of advance is very risky.

 

[airguy]

Time to face facts guys, car gas is risky. Car gas with 40 degrees of advance is very risky.

Ahhh - and there's the rub, the advance. I disagree with the first part, wholeheartedly agree with the second. If car gas were risky we wouldn't run it in cars. You don't see cars running 40 degrees at WOT, either.

Running autofuel gives you a large percentage gain in miles/dollar over 100LL, and running conservative timing advances will cost you a very small percentage in miles/dollar due to slightly lower efficiency. I can see running 92UL with mags on a conservative timing schedule, but that's about it. You'll still come out far ahead on the distance per dollar and not risk your engine.

 

[frankh]

I did?

I really have no idea what you are trying to say Grant...... much too cryptic for me. What I'm saying is Frank Hinde came really close to wadding up his new RV on his first flight on auto fuel. This with a specially engineered fuel system for auto gas.

Time to face facts guys, car gas is risky. Car gas with 40 degrees of advance is very risky.

Thats news to me...But I admit the pucker factor was significant..

Here a few facts about my incident.

1) I had been running autofuel for two tankfuls before the "incident"

2) The engine ran fine after the incident for a few hours then it happened again. At this point I had discounted the autofuel as the cause because if it was the fuel it would have shown the same symptoms on every flight right?

3) I was running (in theory) 34 degrees, not 39. Even so if I go back this way after my IFR checkride I will retard (not me the engine) to 26deg max.

4) The E/Pmags will only show max advance at very low manifold pressure.

5) The engine never quit, apart from abnormal readings it ran normally until I cleared the runway....

6) No signs of detonation or preignition were found inside the cylinders of my engine. After running 6 or 7 hours I was told it should be detectable if it was detonating the mixture...Thats comforting..

It should be noted the latest incident happened on 100LL.

I honestly do not believe (beyond the small risk of vapour lock) that premium autogas is a problem in these motors. Do you think Superior and others would give us their blessing to use 91 octane and risk their reputation by doing so?

I could be wrong on the above of course but there are a lot of engines out there that see nothing but autofuel. I have a found a few of them?and guess what? Few of these guys will post on public forums due to the hostile response they receive form the ?autofuel is dangerous? crowd. So, rather than gathering useful data that maybe helpful to all of us they stay in the shadows and none of us learn from their experiences. This I gathered from a number of conversations with autofuel converts.

Note my fuel system (one electric fuel pump in each wing root) cannot vapour lock.

Frank

 

[Yukon]

Frank,

I can talk until I'm blue in the face about the dangers of autogas in airplanes, but there is no more compelling evidence against it than first hand accounts (Like Yours) of how it took someone out of the sky. Search the web, there are plenty of stories.

Stories about auto gas AND random ignition timing are also very compelling.
Guys don't post because they aren't confident in the wisdom of what they are doing.

 

[Geico266]

There are more aircraft flying on Mogas than any other fuel. Rotax has more engines in the air at any one time than any other piston engine in the world. The fuel of choice for the 912 / 914 is unleaded 92 O.

I'm no expert, but to say that mogas is dangerous seems to be a stretch.

 

[frankh]

Dangers of Mogas

The other issue for me (like Geico said) Is that Rotax motors rarely see anything but mogas and my Subaru install on my previous airplane ran 400hours on it with no ill effects whatsoever.

So the question becomes is not the "dangers" generally so much of contaminated mogas, or as was pointed out there would be dead cars littered all over the highways and my Sooby would have had a few engine outs.

The question really is the compatibility of aircooled motors, (specifically large displacement slow turning lycs) and mogas. The evidence I was able to gather and the recommendation of the engine suppliers told me that swapping to premium mogas was an acceptable risk. I grant you it IS a risk because there are a few unknowns and we know the detonation margins must be less with a lower octane fuel.

But once again we are making assumptions that my engine issue had something to do with mogas...Maybe but now we find a number of Pmags with slipped timing and mine was one of the suspect batch...Aaand the issue did not occur on every flight.

Starting to look like Mogas had absolutly nothing to do with my engine issue.

As to folks keeping quiet who have used mogas, I have had two witnesses who have used it for several years with no isues, one of those intended to even break in his new engine on it based on 20 years of field experience. He told me point blank that he would never report his findings to a group like like because of the emotional response it will generate.

Hence we never learn and we stick to the same group think that has plagued the A/C industry forever. Not saying there is not wisdon in sticking with what works but John Deakin's articles for example are littered with what he calls OWT's

We still get similar responses over running LOP...Isn't it time to move on and examine real data rather than what we think we know?

If we KNOW mogas is dangerous then post the facts and the corroberating evidence, nothing wrong with that. But so far I haven't seen anything but regurgitation of what SOUND LIKE OWT's

Frank

 

[Yukon]

See Frank, listen to Geico. He thinks that because Rotax's run on auto gas, Lycomings should too. Absolutely no recognition of the fact that the Rotax is a small bore, fast revving motor, with none of the detonation or flame-front issues of the tractor-sized Lycoming pistons. And watercooled too, making it more tolerant to the savages of pre-ignition and detonation.

This is for you Geico.....when you firewall a fixed-pitch Lycoming on takeoff, it is like starting a car out in 3rd gear. The engine is bogged down to about 2200 rpm, but without the knock sensors and variable timing of a car. That's why we have to have a large detonation margin with the fuel we use.

With a few exceptions, Rotaxs are used on low-performance, low-altitude aircraft, making vapor lock at altitude a non-issue. Besides, Rotax recommends car gas because their spark plugs fowl on aviation gas, and for no other reason.

Frank, why should I take the time to catalog the issues of auto gas when you yourself have stopped using it, but continue to trumpet it's virtues?
And the same goes for Emag.......Mark has plenty of evidence, not only from his engine failure, but from the huge number of other posted problems, but has chosen to re-install another set of them! Judgement is suspect here.

I'll tell you, Frank, all of this is just incomprehensible to me.

 

[kentb]

Geico266, in two different threads you have made this statement.

There are more aircraft flying on Mogas than any other fuel. Rotax has more engines in the air at any one time than any other piston engine in the world.

What is the basis for this? I can believe that there are a lot of Rotax engines flying in ultra light planes, but it seems that you would need to know the number of hours of operation on all the Rotax per year and compare that to the number of hour of operation on all Lycoming engines.

What is the source for your statement?

Kent

 

[Geico266]

Yukon, Good points one & all.

I have 280 hours flying a 50/50 blend of mogas & avgas in a 0-360 Lycoming without a hickup. My greatest concern and confusion is why water is seperating in my 100 gal storage tank after mixing the two togeather.

I read somewhere there are 30,000 STC's for mogas issued to certified aircraft (most by Perterson Aviation) accepted by the FAA I don't see this as a huge problem causing planes to fly out of the sky. I see this as a subject to be discussed, thought about, and discussed some more.

Lets try to keep the emotions out of this so everyone with good, pertinent information to share can and will come forward.

 

[Yukon]

Yukon, Good points one & all.

I have 280 hours flying a 50/50 blend of mogas & avgas in a 0-360 Lycoming without a hickup. My greatest concern and confusion is why water is seperating in my 100 gal storage tank.

So you are saving 50 cents a gallon, before the costs of transporting, pumping and storing the auto fuel. I would assume the water is precipitating out in your tank because alchohol holds water in suspension,
where gasoline won't. Imagine what happens when you fly high and the fuel
is resting against 30 degree aluminum? This is another thing that cars don't do, nor Rotaxs for that matter.

Speaking of risk factors.........how about the guys that leave off the gascolators because this is experimental.......and they can!

 

[Geico266]

What is the basis for this? I can believe that there are a lot of Rotax engines flying in ultra light planes, but it seems that you would need to know the number of hours of operation on all the Rotax per year and compare that to the number of hour of operation on all Lycoming engines.

What is the source for your statement?

Kent

Rotax is a world wide aircraft engine manufacturing company. There are simply more Rotax engines flying around the world than any other piston engine.

 

[Yukon]

Yukon, Good points one & all.

I have 280 hours flying a 50/50 blend of mogas & avgas in a 0-360 Lycoming without a hickup. My greatest concern and confusion is why water is seperating in my 100 gal storage tank after mixing the two togeather.

I read somewhere there are 30,000 STC's for mogas issued to certified aircraft (most by Perterson Aviation) accepted by the FAA I don't see this as a huge problem causing planes to fly out of the sky. I see this as a subject to be discussed, thought about, and discussed some more.

Lets try to keep the emotions out of this so everyone with good, pertinent information to share can and will come forward.

Yes, Peterson has sold many auto gas STC's..........and rejected many a plane
for certification because it would't pass their tests. Take a look at their website. Many of the planes rejected were low-wing, with tightly cowled engines. Sound familiar?

I see you are using a 50/50 mix. Can I interpret that as a defacto nod to some of my concerns?

 

[Geico266]

So you are saving 50 cents a gallon, before the costs of transporting, pumping and storing the auto fuel. I would assume the water is precipitating out in your tank because alchohol holds water in suspension,
where gasoline won't. Imagine what happens when you fly high and the fuel
is resting against 30 degree aluminum? This is another thing that cars don't do, nor Rotaxs for that matter.

Speaking of risk factors.........how about the guys that leave off the gascolators because this is experimental.......and they can!

Actually, I'm saving $1.65 a gallon.

No alcohol in the fuel, I check every tank. (EAA test kit) Avgas can hold some water in suspension, but not much, mogas can hold .5 tsps.of water per gallon, ethonol fuels 3.5 tsps. of water.

I've never found water in the gasolator, just in the bottom of the transfer tank, and a tiny bit in the wing tanks (not enough to even make a drop).

I would really like to know why it seperates. Must be due to mixing?

 

[rv6ejguy]

My hangar mate has used a 50/50 mix of 100LL and 92 RON Mogas for over 10 years in his aircraft with no issues.

Rotax has concerns with the lead in 100LL contaminating the oil with sludge. They prefer you use a full synthetic oil but don't permit this on a diet of 100LL.

With the reduction gear sharing engine oil, Mobil 1 is preferred on Mogas or a conventional blend motorcycle oil with EP additives for better redrive gear life.

The techs tell me of more issues with exhaust valve seats when these engines are operated exclusively on 100LL.

912/914 powered aircraft operate at at roughly the same altitudes as most RVs. I don't think there is inherently any danger running Mogas with properly designed fuel systems using submerged pumps and components shielded from heat sources. Rotax powered aircraft would be falling from the skies all the time otherwise.

If this Lycoming did not suffer any detonation or pre-ignition damage from the ignition system glitch, this Mogas thing is a non-issue in this case. Why the engine would actually stop from highly advanced or retarded timing is unclear. If the ignition actually signed off for some reason, that makes more sense. Many people are running atmo Lycos on Mogas with no problems.

 

[Geico266]

I see you are using a 50/50 mix. Can I interpret that as a defacto nod to some of my concerns?

Absolutely! LOL!

 

[kentb]

Again, an interesting statement.

Rotax is a world wide aircraft engine manufacturing company. There are simply more Rotax engines flying around the world than any other piston engine.

How many Rotax engines are flying around the world?
How many hour per year are put on each Rotax engine?

How many Lycoming engines are flying around the world?
How many hour per year are put on each Lycoming engine?

Kent

 

[Yukon]

OK Ross, I'll bite. Show me a normally-aspirated Rotax airplane that will climb to 20,000 and cruise at 200 mph like a 6, 7 or 8? Most Rotax are on puddle jumpers. If you want to *hit, take a look at 2 stroke Rotax failure rates!

Your guy too is using a 50/50 mix. What does that tell you?

 

[Yukon]

Actually, I'm saving $1.65 a gallon.

No alcohol in the fuel, I check every tank. (EAA test kit) Avgas can hold some water in suspension, but not much, mogas can hold .5 tsps.of water per gallon, ethonol fuels 3.5 tsps. of water.

I've never found water in the gasolator, just in the bottom of the transfer tank, and a tiny bit in the wing tanks (not enough to even make a drop).

I would really like to know why it seperates. Must be due to mixing?

You are saving 1.65 on the 50/50 mix??????

 

[tinman]

Who needs a gascolator? The Grumman that I flew did not have one. That is what a wing sump is for. When you add a gascolator, you are adding one more item that can become heat-soaked which could lead to other problems. Sump your fuel tanks before flight to remove stratified water...don't trust on a colator to do this for you once the fuel starts flying through the lines...
My boat had a gonja big fuel filter/water separator that would allow the fuel to slow down enough on its journey through the system so that water would have the time to precipitate out of solution. I have serious doubts that the dinky gascolators slow the fuel down enough to do the same...
I would love to use one of the marine filters on my aircraft, but they are so heavy...

 

[Geico266]

You are saving 1.65 on the 50/50 mix??????

Well you got me there, I guess it would be 1/2 of that or $.82 per gallon saved = $82 per tank load. Still makes it worth my time though.

(I could have said yes, I save $1.65 on the 1st 50 gallons! )

 

[rv6ejguy]

OK Ross, I'll bite. Show me a normally-aspirated Rotax airplane that will climb to 20,000 and cruise at 200 mph like a 6, 7 or 8? Most Rotax are on puddle jumpers. If you want to *hit, take a look at 2 stroke Rotax failure rates!

Your guy too is using a 50/50 mix. What does that tell you?

Most RVs are operated below 12,000 feet. The speed has nothing to do with vapor lock issues. You might be surprised what some of these puddle jumpers have accomplished like flying across the Atlantic.

Having been involved now on a 912 development project for some time including running one on a test stand at length and being privy to considerable information from the service and overhaul side on these engines, I believe that most failures, including those on 2 stroke Rotax's have been due to operator procedures or improper maintenance. I too, used to hear all the horror stories about these engines and believed them. These engines are not like Lycomings or auto engines. They have specialized tuning, maintenance and overhaul procedures and demand special tools as well. If you are what we call a "hammer mechanic"- meaning the only tools you use are a crescent wrench and 2lb ball peen hammer, you shouldn't touch these engines. It will almost certainly end in tears. The overhaul facilities have countless horror stories of their own describing what idiots have done to these engines and then are upset when they fail.

These are actually pretty nice pieces. While some things are weird on them, they do work and there are thousands flying worldwide.

 

[Yukon]

You know Geico, I too used to be an auto gas proponent. I used to fuel my Long-eze from 5 gallon cans..........until I saw pictures of a buddies plane that caught fire from a static electricity spark that jumped from the plastic can to the plastic airlpane. Who'd a thunk?

So I cleaverly went to a metal can, grounding the can to the plane to prevent such an occurance. This enabled me to continue using auto fuel just long enough to burn a piston, from dome to skirt, fully metalizing a 30 hour engine! Now there's economy!

 

[Yukon]

Most RVs are operated below 12,000 feet. The speed has nothing to do with vapor lock issues. You might be surprised what some of these puddle jumpers have accomplished like flying across the Atlantic.

Having been involved now on a 912 development project for some time including running one on a test stand at length and being privy to considerable information from the service and overhaul side on these engines, I believe that most failures, including those on 2 stroke Rotax's have been due to operator procedures or improper maintenance. I too, used to hear all the horror stories about these engines and believed them. These engines are not like Lycomings or auto engines. They have specialized tuning, maintenance and overhaul procedures and demand special tools as well. If you are what we call a "hammer mechanic"- meaning the only tools you use are a crescent wrench and 2lb ball peen hammer, you shouldn't touch these engines. It will almost certainly end in tears. The overhaul facilities have countless horror stories of their own describing what idiots have done to these engines and then are upset when they fail.

These are actually pretty nice pieces. While some things are weird on them, they do work and there are thousands flying worldwide.

I agree, Rotax is making inroads into the general aviation world. But if you think it's any kind of advantage not to be field serviceable, I think you are wrong. It will ultimately limit their market share severely (SEE APPLE COMPUTER FOR DETAILS). Yes, I do believe many of the 2 stroke problems are owner-induced. But isn't that exactly the problem we are discussing here with Lycomings and Van's aircraft?

So if auto fuel is such a no brainer, why is your buddy using a 50/50 mix?

 

[Yukon]

Ross,
Come to think about it, Rotax guys are pretty much in the same boat as you Subaru guys (well maybe not you, because you are a gearhead!). So what do you do if you are out flying on a cross-country, and your Eggy powered
RV burns a valve, or busts a head gasket? Will the Subaru dealer come to the airport to work on an airplane??? Lot's of liablility issues, huh? Will the Lycoming A&P put down his 2 pound hammer and crescent wrench to pull the head off an engine he has never seen before??

Sounds like a real problem to me. One of those problems you only discover after you've poured countless thousands into it. And there's another really great thing about Lycomings. You only have to pull off the defective cylinder, not the 1 or two sitting next to it!

 

[rv6ejguy]

My buddy uses 50/50 because he has 9.5 pistons I think.

Rotax is very serious about the worldwide market for small aero engines and trying to get more trained people out there to service them. Rotech Research up here does a booming business offering training courses on Rotax engines. A new line is about to open to keep up with the demand for these engines created by the LSA explosion. The RV12 will only add to that demand.

Cylinder/ head asemblies on the 912/914 engines are individually removeable like a Lycoming BTW.

Fortunately on Subarus, they rarely burn valves nor suffer the dreaded sudden low compression syndrome Lyconentals are sometimes prone to. 70 lbs. means you have a very serious problem on a Sube!

You are right, if something goes wrong with the Sube, you have to fix it yourself or if really bad, get a new crate motor from the dealer for $6K. It is not normal to be opening up these engines for any reason for 1000+hours. The advantages of liquid cooling, tight clearances and synthetic oils means no thermally stressed components or high wear rates.

When I mentioned the term "hammer mechanic" this was not intended to include those who service and overhaul Lyconentals, more the backyard guy on the acreage who has no idea what he is doing and performs his own "overhaul" without even the factory manuals, let alone training or special tools.

 

[fodrv7]

Chauck away the Spark Plugs!

Mark,
The sun went down, again, so I pushed "Riveting Experience" into the hangar, drove home, opened a beer and started digesting John Deakin's latest epistle (that was bought to my attention on the forum recently) and a bit relevant to your aircraft jumped out at me. Read the last sentence.
Here it is:
Also, a word about redlines. Factory redlines are intended to be "momentary only." We have a lot of recorded data where CHT has risen to the redline, usually due to an ongoing series of pre-ignition events. On those events that go beyond the factory redline, damage is inevitable. For those where the CHT is promptly controlled and brought back down, we seldom see damage to the cylinders. However, the spark plugs are often damaged, and should always be changed even if no damage is evident.

regards,
Pete.

 

[elippse]

Detonation and Pre-ignition. Detonation is "pinging" or "spark-knock", and is usually caused by advanced timing. Detonation will result in the top of the piston looking as if had it had been beat-on with a ball-peen hammer. Preignition is a whole new scary child! That's when the charge in the cylinder ignites as much as 90 deg BTDC! The piston is being pushed up against a burning/burned charge and the pressures and temperatures being generated are horrendous. Typically the piston will fail within a few revolutions. Detonation can LEAD to preigniton, but if it doesn't, you can run the engine all day with mild detonation. GM Powertrain Staff Engineer Allen W. Cline wrote an extremely informative article on these engine destroyers in Contact! magazine issue #54! www.contactmagazine.com

 

[gmcjetpilot]

Small correction

Detonation and Pre-ignition. Detonation is "pinging" or "spark-knock", and is usually caused by advanced timing.

Detonation will result in the top of the piston looking as if had it had been beat-on with a ball-peen hammer. Preignition is a whole new scary child! That's when the charge in the cylinder ignites as much as 90 deg BTDC! The piston is being pushed up against a burning/burned charge and the pressures and temperatures being generated are horrendous. Typically the piston will fail within a few revolutions. Detonation can LEAD to preigniton, but if it doesn't, you can run the engine all day with mild detonation. GM Powertrain Staff Engineer Allen W. Cline wrote an extremely informative article on these engine destroyers in Contact! magazine issue #54! www.contactmagazine.com

Well I agree with most, but you can't really support your first sentence.

Detonation can be cause by many things: poor fuel quality (octane), high compression, high combustion pressure (high power) and excessive lean mixture (which is a likely scenario for us). Actually detonation gone too long or far can result in pre-ignition (which you actually say later).

Mild detonation can be tolerated, but in aircooled engines detecting detonation from none to severe is very difficult to impossible (unless you can measure instantaneous combustion pressure). So its academic what we can tolerate; aircooled aircraft engines are a special breed; there are many differences between water cooled car engines.

 

[N941WR]

Here is a thought...

After talking with Dayton and hearing how when he leans his -4, it goes from running fine, to nothing. He is running duel P-mags, BTW.

Is it possible that these planes are being flown too lean which then triggers Detonation?

George? Others?