Lean O' Peak & engine ops

[captain_john]

I have been sold on the lean of peak method of engine ops since I read the artilces on AVWeb.com.

Just this past month AOPA Pilot had a piece under www.aopa.org/frugalflier column discussing the benefits of the method.

I can't wait to try it in the RV when (and IF) I get it done!

Q. Is anyone out there employing it in their plane?

They say that it is very difficult to harm your engine below 65% power.

Q2. Where does this figure come from? ie. how do they arrive at it?

My primary reason for going with high horsepower (about 200hp) in the RV is so that when I bring back power to 65% I will still have 130 hp or so left.

I wonder what that will produce for airspeed at say, 8000'?

Any thoughts of yours to be added?

Are you gonna do it too?

CJ

[smithhb]

CJ,

My RV-9 runs great at LOP and on my ECI IO-360 I just have to be sure I am less than 75% power. I am also running the dual AFS 3500s (until they can ship me my 4500's) that displays %HP and have a way cool Peak EGT feature.

I typically climb full power at 110 kts to my desired altitude with conservative leaning. At altitude I trim and reduce power until I am at or below 75% HP. I then begin leaning slowly until all cylinders peak and then pull to 10-15 LOP. This will reduce fuel flow from 15 gph (full power/full rich) down to around 7.0 gph. I find that if I richen to 10-20 ROP to engine runs smoother and my fuel flow increases to 9.0 gph.

Either way, it helps (correction: is IMPERATIVE) to have the instrumentation to measure CHT and EGT on all 4 cylinders.

[smithhb]

Oh CJ,

I forgot to mention that in order to get airspeed you will need to install a prop.

[4kilo]

CJ,

I am somewhat conservative in my engine operations; the simple version is:

75% to 100% - Full rich
65% to 75% - Traditional rich of peak leaning
0% to 65% - Lean of peak

Percent power is figured using standard engine performance chart info plugged into my GRT EFIS engine pages.

When I go for long cross countries, I typically use the mid to upper teens, and I get about 160 to 165 KTAS on 6 to 6.5 gallons per hour. This is on an IO-360 180 hp using wide open throttle and about 2250 rpm.

At low altitude, I can still get about 6 gallons per hour, but the speed drops off to around 145 to 150 KTAS. 8000 MSL gets me about 155 KTAS. These altitudes require throttling the engine to obtain less than 65%, which probably accounts for some of the reduced efficiency, while simple aerodynamics at the higher air density accounts for the rest.

On formation and acro flights, I set up about 75%, lean well rich of peak, and leave it.

So far I have had no problems, and the engine performs fantastically. Lean of peak at 65% the CHT's usually run at very near 300 degrees, and the oil temp rarely goes above 180.

Hope this helps,

Pat

[captain_john]

That is great insight guys!

Bret, I hear that LOP is usually 25 to 50 degrees LOP. Why are you so shy of it?

Pat, you are doing it during formation? Aren't you worried about all those power setting variables being a mixture problem or do you mean loose, commuting formation?

CJ

[smithhb]

CJ,

I am having to compensate for my #3 cylinder which is running richer than my other cylinders. Since it is the last to peak, I use it as my "control" and keep it at 10-15 LOP. The other cylinders are usually 25 - 35 LOP.

I need to schedule time to fly over to SC and let Don Rivera at AFP balance my fuel flow.

[captain_john]

Yah you do.

I plan on using his system too for the same reason, I can drop in and see him with questions!

Have you been there to see him yet?

When yo see him, ask him about Andair's new fuel pump and compatibility with his system. I hear that it shouldn't be any problems interfacing with things.

CJ

[4kilo]

CJ,

Second to the last paragraph of my previous post:

On formation and acro flights, I set up about 75%, lean well rich of peak, and leave it.

If you call the 37 ship at Osh "loose, commuting formation" then that is what I do. I was number 8 in the Osh formation (slot in the second four ship of the front diamond).

Pat

[captain_john]

hahaha...

SORRY if I offended you Pat!



I missed the RICH of peak part. I read just the LEAN part.

Yah, that makes sense.

CJ

[4kilo]

No offence taken CJ.

Pat

[captain_john]

Good video on LOP operations:

http://www.youtube.com/watch?v=3lGYWadl ... r_embedded#!

CJ