Tried LOP....

[jetdriven]

Do he GAMI spread, and after that, level off at 2000', leave the throttle WOT, 2500 RPM, pull the fuel flow back to 8.5 GPH.  Does it run smooth? If so, next.  Now watch it for 5 minutes.  Record your CHTs also. Anything over 380,  get out.

Now, there are a few reasons it wont run smooth LOP.  Ours would not. The spark plugs were shot. The injectors were dirty.  I replaced the plugs with fine wires and cleaned the injectors with Acetone (Hoppes #9 works too).  Keep them in separate jars and keep the number of the cylinder they came from as well. The insert is also a matched item to each nozzle.  Now, swap your leanest with richest injector, IE #3 and #1..  Reinstall.  Our spread improved from .8 to .1 or zero like this.

[KSMooniac]

Quote: DaV8or

I've never heard of this. Do they have test data I can find? Are you suggesting that bore, stroke, piston crown design, cylinder head design, valve placement, ignition system, etc, etc, etc, have no bearing on the combustion in the engine? How about compression ratio? 7:1 vs. 13:1, any difference in combustion behavior?

I don't buy the one size fits all solution.

[KSMooniac]

Quote: jetdriven

Do he GAMI spread, and after that, level off at 2000', leave the throttle WOT, 2500 RPM, pull the fuel flow back to 8.5 GPH.  Does it run smooth? If so, next.  Now watch it for 5 minutes.  Record your CHTs also. Anything over 380,  get out.

Now, there are a few reasons it wont run smooth LOP.  Ours would not. The spark plugs were shot. The injectors were dirty.  I replaced the plugs with fine wires and cleaned the injectors with Acetone (Hoppes #9 works too).  Keep them in separate jars and keep the number of the cylinder they came from as well. The insert is also a matched item to each nozzle.  Now, swap your leanest with richest injector, IE #3 and #1..  Reinstall.  Our spread improved from .8 to .1 or zero like this.

[nels]

Quote: KSMooniac

I've never heard of this. Do they have test data I can find? Are you suggesting that bore, stroke, piston crown design, cylinder head design, valve placement, ignition system, etc, etc, etc, have no bearing on the combustion in the engine? How about compression ratio? 7:1 vs. 13:1, any difference in combustion behavior?

I don't buy the one size fits all solution.

[KSMooniac]

The compression ratio does not change... it is a function of the piston and cylinder geometry.  For the IO-360, this is 8.7:1.  For many other normally aspirated engines it is 8.5:1.  For many turbo engines, it is 7.5 or 7.0:1 and those are boosted to >30" MP to compensate for the lower compression.

Detonation really isn't a problem with our IO-360s so long as everything is up to spec...ie good 100LL, good spark plugs, etc.  You can't really induce detonation if you tried.  I've run ~86% power LOP for hours with cool CHTs while breaking in fresh cylinder work... no detonation.  At higher altitudes I'll run peak to 20 dF LOP depending on the temps.  If I had a turbo, I'd still run 80% or greater power LOP up high and not get detonation either.  

[74657]

What effect does the higher EGT's have on the exhaust system when running LOP?  Coming from a guy used to running "below 1400F" 1550 seems like A LOT more heat!!

 

[nels]

Quote: KSMooniac

The compression ratio does not change... it is a function of the piston and cylinder geometry.  For the IO-360, this is 8.7:1.  For many other normally aspirated engines it is 8.5:1.  For many turbo engines, it is 7.5 or 7.0:1 and those are boosted to >30" MP to compensate for the lower compression.

Detonation really isn't a problem with our IO-360s so long as everything is up to spec...ie good 100LL, good spark plugs, etc.  You can't really induce detonation if you tried.  I've run ~86% power LOP for hours with cool CHTs while breaking in fresh cylinder work... no detonation.  At higher altitudes I'll run peak to 20 dF LOP depending on the temps.  If I had a turbo, I'd still run 80% or greater power LOP up high and not get detonation either.  

[KSMooniac]

CR is constant... the amount of air available for power production for a normally aspirated engine changes with altitude.  The lower density air is still compressed 8.7:1 for our IO-360s.

[nels]

Quote: KSMooniac

CR is constant... the amount of air available for power production for a normally aspirated engine changes with altitude.  The lower density air is still compressed 8.7:1 for our IO-360s.

[carusoam]

Misplaced reply...

-a-

[74657]

Made it to Denver last evening.  We had to divert to Metro after flying around thunderstorm/hail activity that seemed to sit right on top of KAPA.  ATC was great getting me around the stuff. 

Flew LOP the whole way.  Saw fuel flows from 11.3 to 11.6 and TAS from 168 to 172 @ 10,000.  I dropped down to 8000 and saw 180 kts. on 12.8 to 13.  I'm still getting comfortable with the EDM.  My #5 cylinder seems to run about 20 degrees warmer than #6 which is the next hottest.  1-4 are about 60 degress colder than #6.  The EGT's on 5 and 6 are also the hottest, running about 1525/1500 to mid 14's for the rest.  Does this sound right?

It's a little unnerving to see the factory EGT gauge reading way hot....  I tried keeping #5 CHT at 410 (plug probes, likely 370 in "real life"). 

Is it possible to get a "false peak" using the EDM if you do not lean quickly enough?  It seemed that 20 LOP gave me the best mix of speed/fuel burn.  If I went leaner, say 40-50 I would lose 5-7 kts at a fuel savings of .3 gph.

Not a bad trip.  Made it to the Denver in 5.5, including the vectoring/airport change......  Still had 25 gallons of fuel left in the plane!!!!!