What'a a good GAMI spread

[GeorgePerry]

The GAMI folks say anything less than .5 G/hr is a good spread.  I was just wondering what people are actually getting.  I've got .3 g/hr.

[Cruiser]

.3 g/hr. is good.

What is the Spread and which cylinder is first to peak? Which is last to peak? Per John-Paul at GAMI, #3 is usually the first to peak and #1 is usually the last on our Lycoming IO360s. On my FREM, #3, #4 and #2 are all within .1 gph. but #1 is about .3 gph richer than the others.

 

[N57039]

I get spreads from 0 up to 0.3 gpm. Who knows what the variable is, but in any case the IO360A3B6D is sure an easy engine to operate LOP.

[GeorgePerry]

[GeorgePerry]

Quote: GeorgePerry

1 peaks first with #'s 2, 3, and 4 peaking almost simultaneously afterwards.

Also, has anyone else heard of the "rule of 46"?  I recently flew with an FAA DE with a ba-gillion hours and he was touting the benefits of LOP.  He went on to say that no matter what you do, if the sum of MP and RPM don't exceed 46 then you can operate LOP without any detonation concerns....thoughts?

[KSMooniac]

My GAMI spread is like Lance's.... typically 0.0 GPH up to 0.2 GPH on stock injectors.

George, I think the rule of 46 is used to limit your power output before leaning...nothing more, and it is quite silly.  You can run high power LOP safely so long as you lean enough!  Conversely, you must be rich enough to run high power ROP safely too.  The GAMI folks and now Cirrus have shown that using 87% power (30" MP, 2500 RPM) is a very good hi-cruise setting at 17.5 GPH on their TN-IO-550 installations.  That is 70 or 80 dF LOP, and those engines love it.  So, we could make up our own "rule of 55" if we wish too. 

Regarding detonation, it really cannot happen on our normally-aspirated engines no matter what we do, unless we get a mis-fuel or something is gravely wrong with the engine.  If you are running 100LL (on-spec of course) and everything is behaving as it should, you will not get detonation.  The Advanced Pilot Seminar course showed us this quite well.  We should be more concerned with internal cylinder pressures and CHTs to ensure longevity of the engine.

[GeorgePerry]

kinda what I figured...thanks for confirming

[Parker_Woodruff]

What's the rule of 46?

[KSMooniac]

The rule of 46 is adding your manifold pressure to your RPM/100 and making sure they do not exceed 46.  Example, 22" MP + 2400 RPM.  Just another silly old wives tale....

[GeorgePerry]

I've got a questions about LOP operations...I've been flying with Gami's and my EDM 700 for about six months and have had some good sucsess with LOP, however I don't like using LOP until I'm well above 9000 ft. 

My questios are:

1. Based on what I've read running LOP you really want to keep the power at or below 65% - is this correct

2. When people say they run 30 deg LOP I've always assumed that meant the first cylinder to peak not the last.  Is this correct.

3. What temps do most like to run?  Based on what I've read about 20-30 LOP is the norm, but some push it to 50 deg if the motors still smooth.

Thanks...All you LOP lovers out there please make me smarter. 

[Greg_D]

George, you can run LOP at any power setting.  At about 65%, you can run peak, LOP, or ROP, pretty much anywhere you want without damaging your engine.  LOP will be cleaner at all power settings.

You base LOP settings on the LAST cylinder to peak because you want to make sure all of them are running peak.  When running ROP, you'd use the first cylinder to peak.

 

Advanced Pilot Seminars has some good data on how far you need to be while LOP.  At low power settings up high, I run just past LOP, maybe 10-15 degrees.  At higher settings, I use 50-75 degrees.  I know some guys that run 87 percent power on TN engines at 80 LOP and have no problems whatsoever.

Welcome to the dark side.  Hey, did you know that Lycoming now admits LOP is a better way to run our engines?  And they claim they are going to teach us how to do it.

[GeorgePerry]

So if I understand correctly, if I want the last cyilinder to peak to run at, say 30 deg LOP, then all the others will be even more LOP...Correct? 

[etekberg]

Quote: GeorgePerry

So if I understand correctly, if I want the last cyilinder to peak to run at, say 30 deg LOP, then all the others will be even more LOP...Correct? 

[Cruiser]

It is all based in fuel consumption. The GAMI spread should be less than .5gph from (first to peak) - (last to peak). I don't know that the actual EGT temp spread is important.

[Cruiser]

I checked my JPI flight data files and found most of the EGT spreads are in the 10 - 15 dF range when setting LOP for my flights (1454 - 1468). These are with .4 or .5 gph fuel spreads. My first cylinder to peak is normally #2 sometimes #3. My cylinders #2,#3,#4 are really close (<.1gph) but #1 is ALWAYS the richest cylinder, sometimes .4gph sometimes .5gph.

When I talked with GAMI they confirmed the IO360 NA engine data shows #3 the leanest and #1 the richest cylinders.

[jlunseth]

I have a question.  A couple actually.  I have an M20K with the TSIO360-LB, GAMI's, and an EDM711.  Willmar did a lean test for me and I am within .4 gph.  I have not tried LOP yet.  So far, I have run the engine ROP. 

Someone may have asked this above, but I have read that when running the small bore sixes like mine, LOP should not be done at over 65%.  Bearing in mind that mine is a small bore six turbocharged, does anyone know if I can go higher, like 75%, without hurting the engine long term.

Also, I tried running the engine at peak once.  What I found was that although everything set up well, within a few minutes the TIT was excessive and I had to go back to 125 degrees ROP.  In fact, even when I run in the vicinity of 125 ROP the temps, both CHT's and TIT, but particularly TIT will change after a few minutes.  So I am concerned about running LOP given that.  Can anyone tell me what might be going on?

The engine is in very good shape right now,  Willmar put in new baffling, etc., etc., etc. and running at 125 ROP the cylinders are very cool.

[Cruiser]

I have heard that some Turbocharged engines have an issue with bootstrapping. If this is what you are describing, it could be problematic in that what you setup will change and may need constant attention by you.

That said, LOP is possible at 75% and higher. Because turbocharged engines can keep the power levels high, it is important to know what effect the settings have on your engine. You should take a class in LOP operations or get very familiar with the theory and be comfortable with it.

What do you mean when saying temps change? Running 125°F ROP should be near the point of highest CHT. At peak EGT (meaning the last cylinder to peak) your CHT should start to come down, and the further you go LOP the lower they should go.  

[jlunseth]

If I were more sure of what the temps were doing I would tell you.  An electrical gremlin has taken out the edm711, it is getting fixed Friday, but my experimentation with the engine settings has had to stop in the mean time.  What I can say is that after using the Lean Find feature to set the engine up at peak I flew for a few minutes and the idiot light went off indicating the TIT was at or over the 1650 redline, so I immediately leaned to 125 ROP.

Yes, I should take the class.  What worries me a little is if I set up, say, 50 LOP, and then the TIT takes off on me, it will take a little while to notice it and a little while to get it down to ROP, and in getting it down to ROP I will be actually be leaning back through peak, so I might expect the TIT to go up before it comes down.  If it is already up there, I am not sure I want that happening, although the manual does allow a temporary TIT of 1725, so probably I would be ok.

The engine wasn't bootstrapping though.  We were running at cruise for a few minutes before leaning, and there was no change to anything, altitude, MP, etc. other than just leaning the engine.