R

Rupester

Well Known Member
First off, I'm running an Aerosport Power IO-320, 160hp, with Precision Silverhawk FI; Slick mag on the left, LSEI Plasma II on the right. The engine has 32 hrs on it and runs great, using a qt about every 10 hrs. I'm approaching the end of my flyoff period and playing with LOP ops. I've read dozens of threads on running LOP, but I can't find an answer to my questions(s):
... when I lean progressively (that is, not using The BMP method), using the GRT's lean/norm functions, I clearly see when each cylinder peaks. As I continue to slowly lean more to get on the LOP side, the power falls off (as expected), but the engine runs noticeably rough - even at just 10 to 30 degrees LOP across the 4 cyl. By the time I get to that point, the RPM has dropped around 100, and the rough running is, well, unsettling. Power fall-off is obvious. The engine doesn't miss or stumble, it just runs rough and sounds awful ... like it's straining to run. When I richen until the engine sounds and runs smooth, I have moved back to the ROP side, as indicated by EGTs climbing then falling quickly again.
Nothing I've read indicates that running 10 to 40F LOP should make an engine run audibly rough or struggling. In general, most posters talk about only the slight power and A/S loss.
Should I be looking for an "issue" of some kind that prevents my 320 from running slightly LOP and smoothly?
 
Terry,

Sounds like you need to balance the fuel flow to each cylinder using the methods of either GAMI or Air Flow Performance. See the archives for descriptions of each.

Jim Berry
RV-10
 
It does sound like a fuel balance issue. I seem to do better than you with my carb and LSI.... I just notice a loss of rpm and retain a smooth running motor till it just quits.
 
The LEAN FIND function on ALL EMS systems work, but they do not work well. Especially if you travel fast in the mixture knob.

What might serve you well is to do the GAMI lean test, at high altitude do several tests slowly, very slowly at say 7500' and when doing that test take note of the MP, then drop down and do several more at 3000' but set at the same MP you had before.

This will confirm any induction leaks for a start.

Then get Don at Airflow to help you out with injector changes. Or just buy a set of Gami's.

In practise I find the most accurate method to set the "Appropriate amount" LOP is to do a BMP and sneak up until the first one peaks, not using lean find just your eyes, and it should always be the same one, and then dial it back to -10,-20,-40,-60,-80 or whatever is suitable for the power set.

The lag and delays in the engine monitor an the lean find function seem to result in you be far leaner from peak than you really think, and hence the poor result, and even bigger power/speed loss.
 
Terry,

I have roughly the same installation as yours. You will need to balance your injectors to get the smooth LOP operation that you are looking for. I used Kahuna's procedure to get the general idea of flow balancing. You can read about it here:

http://www.mstewart.net/super8/nozzles/index.htm

An autopilot helps with the data collection. Be sure that you are below 75% power when running LOP ops. Collect the stats then talk with Don at Airflow. He may want to see your data.

In my case I only had to change 1 injector nozzle to a slightly smaller size. Now I can lean until it essentially flames out. Power output is smooth across the range.
 
Joe,

Can we quit the...
Be sure that you are below 75% power when running LOP ops
Click to expand...

This is not true at all. You can run 100% power LOP safely, although I am sure you won't get there with your engine but if you could achieve it you can do it safely.

There is no limit on LOP ops, it's just a matter of how far LOP you need to be. Same applies to ROP.

:)
 
RV10inOz said:
Joe,

Can we quit the...

This is not true at all. You can run 100% power LOP safely, although I am sure you won't get there with your engine but if you could achieve it you can do it safely.

There is no limit on LOP ops, it's just a matter of how far LOP you need to be. Same applies to ROP.

:)
Click to expand...

No we cant. Especially in a test LOP for match flow. Pilots must slowly approach the red zone in order to know exactly when each peaks. Further, Lower MP are needed to keep the spider from being any factor (below 24" according to Don at AFP). While LOP can be done at any MP, High MP requires the big pull, which only really works for very experienced pilots with lots of LOP time and data to pull to a fuel flow.
Many have written on the subject. We should not be encouraging high MP when creeping to and past peak. We could certainly argue the merits of that, but the experts mostly agree on this and whats the point of going against the wisdom of the designers of these systems? There is no upside that I can see.
 
More info ....

Thanks much for the help ... I suspected this might be a flow balance issue.

Another bit of info .... my CHTs are all (and all the time) within 15 degrees, and stay very cool. My EGTs do not match for that ... cyl 2 is always 70 to 100 degrees hotter than the other four, which are very close. ( I've read where this can be sensor placement, but I measured v-e-r-y carefully when I installed them. All four are within 1/16" of the specified distance from the exhaust port.) When I'm leaning, EGT 2 peaks well before the others and remains hotter by nearly 100 degrees thruout. At high power settings it is also about 100 degrees hotter. That would seem to point to a flow imbalance resulting from too little fuel flo on #2. Looks like I should pull that injector to see if it has a speck of dirt or something in it , and then re-try.
 
Doesn't match

Rupester said:
Thanks much for the help ... I suspected this might be a flow balance issue.

Another bit of info .... my CHTs are all (and all the time) within 15 degrees, and stay very cool. My EGTs do not match for that ... cyl 2 is always 70 to 100 degrees hotter than the other four, which are very close. ( I've read where this can be sensor placement, but I measured v-e-r-y carefully when I installed them. All four are within 1/16" of the specified distance from the exhaust port.) When I'm leaning, EGT 2 peaks well before the others and remains hotter by nearly 100 degrees thruout. At high power settings it is also about 100 degrees hotter. That would seem to point to a flow imbalance resulting from too little fuel flo on #2. Looks like I should pull that injector to see if it has a speck of dirt or something in it , and then re-try.
Click to expand...


Your EGT doesn't need to match, it's not important. What matters is when they peak relative to each other when you pull the red knob, and your goal is to get them to all peak (at whatever temp), at the same fuel flow or as least within .2~.3 GPH. It sounds like #2 is getting less fuel. Find the one that peaks last and swap those two inserts. You may fix your problem or at least narrow the issue.
Also check for intake leaks, which could also be the problem.
Tim
 
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Rupester said:
Thanks much for the help ... I suspected this might be a flow balance issue.

Another bit of info .... my CHTs are all (and all the time) within 15 degrees, and stay very cool. My EGTs do not match for that ... cyl 2 is always 70 to 100 degrees hotter than the other four, which are very close. ( I've read where this can be sensor placement, but I measured v-e-r-y carefully when I installed them. All four are within 1/16" of the specified distance from the exhaust port.) When I'm leaning, EGT 2 peaks well before the others and remains hotter by nearly 100 degrees thruout. At high power settings it is also about 100 degrees hotter. That would seem to point to a flow imbalance resulting from too little fuel flo on #2. Looks like I should pull that injector to see if it has a speck of dirt or something in it , and then re-try.
Click to expand...

Terry,

Is it possible that the EGT sensor on #2 is a bit out of calibration? Have you tried switching it to another exhaust pipe to see if the temp follows the sensor or stays with the cylinder?
 
Kahuna,

With due respect, if you read again my suggestion for doing the GAMI lean test it was at say 7500', and LOP or ROP up there is a very safe place to park the engine while fiddling. Typically at this height and 2400 RPM it will be between 65-70% when ROP, depending on the ram air effect of your intake. You will note also I said drop down to a much lower level and do it again at the same MP used up high. The two results need to be collected to make the tests worthwhile. Tune your injectors with an intake leak and then fix the leak = much frustration.

I hope that satisfies your concern that I was suggesting otherwise while doing GAMI Lean Tests. That being said, doing a 15 second sweep through the red box will not harm anything on our NA engines, but it is to be avoided in a Chieftan at 42".

I must confess I did make an assumption, that is we are talking NA, and I did not modify my post to account for any TC/TN folk.

What I was protesting about was even though it was among other short statements about GAMI spread tests, a blanket statement of "Be sure that you are below 75% power when running LOP ops." is simply a statement that many folk will read and just accept as do not ever run LOP above XX% power EVER. That is how many of these myths started, and we are trying to kill them off not breed new ones. Perhaps what Joe could have said was "Be sure that you are below 75% power when performing GAMI Lean Tests." Now I think that would be a far more appropriate statement, would you agree? (Actually APS & GAMI suggest 65% but its not that critical as 75% ROP will end up 65% LOP)

The next myth that you are giving rise to is regarding higher power LOP ops.
While LOP can be done at any MP, High MP requires the big pull, which only really works for very experienced pilots with lots of LOP time and data to pull to a fuel flow.
Click to expand...

That statement is simply not true. This does not require very experienced pilots, whatever that means (maybe I should stop doing them), and as for data to pull to a fuel flow, well you either know the fuel flow you are aiming for or you don't. And if you don't, you sneak up to peak from the lean side find peak and then back off 80,60,40 or whatever is appropriate.

It is wrong to scare people off by statements such as never operate LOP over 75% or never do BMP's unless you are very experienced. Heck we teach people to do this BMP process with their eyes closed. Yes eyes closed! Why? Because it actually works better. You only need a few seconds. And you spend less time eyes down in the cockpit too doing it this way.

Anyway, I hope that clarifies a few things and I hope that the written word comes across with an educational tone not an inflammatory one as often can be the case on a forum.
 
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Rupester said:
Thanks much for the help ... I suspected this might be a flow balance issue.

Another bit of info .... my CHTs are all (and all the time) within 15 degrees, and stay very cool. My EGTs do not match for that ... cyl 2 is always 70 to 100 degrees hotter than the other four, which are very close. ( I've read where this can be sensor placement, but I measured v-e-r-y carefully when I installed them. All four are within 1/16" of the specified distance from the exhaust port.) When I'm leaning, EGT 2 peaks well before the others and remains hotter by nearly 100 degrees thruout. At high power settings it is also about 100 degrees hotter. That would seem to point to a flow imbalance resulting from too little fuel flo on #2. Looks like I should pull that injector to see if it has a speck of dirt or something in it , and then re-try.
Click to expand...

Terry,

as others have pointed out, do not worry about the difference in the raw EGT value. What you are interested in is the fuel flow between first to peak and last. It sounds like all you will need to do is call up Don at Airflow and ask him for a next size up injector, I believe he keeps them in 0.001" increments and see. Give him the GPH at each peak as he may decide on a couple of steps.

While on the topic of the RAW EGT value, there are a few times when it is worth noting, for example but not limited to;
1. Turbine Inlet Temp (TIT) usually a limit of 1650-1700
2. Target EGT for a climb or for takeoff at a high field elevation
3. observing a sudden change when starting up and taxiing, maybe a dead magneto or you are just on one not both.
4. Carby engines, when trying to run them LOP getting the max EGT difference to a minimum.

Hope that helps!
 
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My general problem with this thread now is that the OP was asking what to do with his miss on LOP. Match flow is the answer. And that being the case, we should not be encouraging folks to work their flow matching above 24" regardless. A long time is spent in the red zone to accomplish this task, a long time, as well as some manufactures indicating that there are system issues with doing this above 24". That was my point.

This thread has creeped into normal LOP operations which can be hashed in another thread or into any of the many that exist now.
 
Kahuna said:
My general problem with this thread now is that the OP was asking what to do with his miss on LOP. AgreedMatch flow is the answer.Only part of the answer, a few of us have mentioned intake leaks. And that being the case, we should not be encouraging folks to work their flow matching above 24" regardless. Nobody has, again 7500' WOT & then same MP at say 3000'A long time is spent in the red zone to accomplish this task, a long time, as well as some manufactures indicating that there are system issues with doing this above 24". That was my point. Fair enough too, but nobody is suggesting otherwise, not even me!

This thread has creeped into normal LOP operations which can be hashed in another thread or into any of the many that exist now. I do not think so, even our little debate here is not taking it down that path, besides most of the thread by volume at least is still about Terrys questions in both his posts.
Click to expand...

Maybe we are looking at the mountain from opposite sides, still the same mountain just a different view of it. :)
080215-file-7.gif


Terry, does all this make sense so far?
 
Absolutely. I have three things to check: a) possible dirt in the #2 injector nozzle, b) possible intake leak, c) possible wacko EGT sensor. Gives me plenty to keep me busy in my last 8.2 hrs heading for 40. :)

Thanks to all !
 
Rupester said:
...As I continue to slowly lean more to get on the LOP side, the power falls off (as expected), but the engine runs noticeably rough - even at just 10 to 30 degrees LOP across the 4 cyl...
Click to expand...

This was my experience with the -8 initially. It would hardly run at 30 LOP. The "game changer" in my case was simply the replacement of magnetos for a pair of PMags. With no other changes, the airplane will now go smoothly to 100+ LOP.

If you are rough across the board (all 4 cylinders), I'd take a hard look at the ignition. Since you are running electronic already, it's not as likely, but don't rule it out.
 
Toobuilder said:
This was my experience with the -8 initially. It would hardly run at 30 LOP. The "game changer" in my case was simply the replacement of magnetos for a pair of PMags. With no other changes, the airplane will now go smoothly to 100+ LOP.

If you are rough across the board (all 4 cylinders), I'd take a hard look at the ignition. Since you are running electronic already, it's not as likely, but don't rule it out.
Click to expand...

In addition to the above, plug gap 0.016-0.018" for massives, and resistance belw 5k ohms makes all the difference.

If you have auto plugs, check the gap range suggested, anecdotal reports I have seen suggest 25/26 thou as being a good start. Others here with more experience may wish to chime in.
 
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