CorvAircraft> Avweb article about operating Rich of Peak EGT

[Dave Morris "BigD"]

I asked Walter what he would recommend for those of us with 
non-injected engines who want to run anywhere near peak EGT, because 
I personally cannot get close to peak before my O-360 starts running 
rough.  He said that you can try adding a tiny bit of carb heat and 
see if it smooths out.  Sometimes that will change the mixture just 
enough that you can get a smoother run.  In fact, he would do several 
iterations.  Try some carb heat, see if it smooths out.  Lean the 
mixture a tiny bit more until it runs rougher, try a little more carb 
heat.  And so on.

Remember we're doing this at a high enough altitude and/or low enough 
power settings that will not get us into detonation.  But he also 
dispells the myth of detonation being the cause of exploding engines, 
with a discussion of how preignition is probably what we've been 
seeing all along.  Definitely worth reading that article and the 
others that group have produced.  You can Google around and find 
discussions he has had with the RV group and others.

Walter, John Deakin, and George Braly also run a seminar in Ada 
Oklahome, I think it may be in the $900 range, that would probably be 
worth attending if you really wanted to become an expert on engines.

The scary thing is that most of us were taught to run at 50 degrees 
rich of peak, and that is precisely the worst possible place in the 
world to run the engine, because the intracylinder pressures and CHTs 
are the highest there.

Dave Morris

At 04:49 PM 2/19/2007, you wrote:
>  Dave,
>         This is interesting statement. I have tried many times in the
>past year to run my corvair at LOP. I agree and in fact think it is no
>mans land. Every time that I get to peak and try to lean any more at all
>causes the engine to stumble and even to the point of I was afraid that
>it might quit. I have my exhaust temps within 30 to 40 deg of each other
>when I have it leaned to 1340 deg. on the highest exhaust. I can lean to
>as much as 1370 deg. but the span increases also. So I personally have
>settled on the 1340 deg indication as my goal for a leaned and smooth
>running engine that leaves a clean exhaust pipe. I have a fuel flow
>sensor also and can see the drop in floe at that setting. I also have
>sensors on all cylinders and exhausts so I do know what it is doing not
>guessing from one or two probes. Another thing that may or may not be
>relevant is the mixture gauge. I can not run leaned  on the mixture meter
>either with always one or two green lights on.
>Joe Horton, Coopersburg, Pa.
>joe.kr2s.builder at juno.com
>
>  This
> > particular article is full of good stuff, but one thing as Corvair
> > drivers you need to realize is that trying to run lean of peak is
> > difficult with a carbureted engine.  Most of the LOP operation is
> > going to require injection, and balanced injectors at that.  On the
> >
> > other hand, since you are building the engine yourself, you may be
> > able to achieve a more balanced fuel-air ratio than Lycoming does
> > when it cranks out another engine on the assembly line.
> >
> >
>
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