REFLECTOR: Running LOP

[Dave Philipsen]

If all of your EGT probes are strapped to the outside of the exhaust it 
is probably ok even if your EGTs seem low.  The preferable way is to 
drill a tiny hole in the exhaust pipe just big enough for the EGT probe 
to enter.  Most probes have a shoulder that will allow them to stop at a 
preset depth.  You can then use a hose clamp with a similar sized hole 
drilled in it and slipped over the top side of the shoulder to secure 
the probe to the pipe.  Each of the holes in the exhaust pipes should be 
as close as practical to the exhaust port but all equidistant from their 
respective ports.  I think around a half-inch to an inch is probably 
about right.  But, the absolute EGT is not what is important.  You will 
be watching for when the EGT peaks on each cylinder (which will be a 
little more difficult with your "one at a time" system since you'll have 
to constantly switch to and record each EGT as you lean).  As you lean, 
and after each cylinder has peaked, then you just continue to lean until 
the last cylinder (to peak) is about 60 degrees cooler than where it 
peaked.  That means the other cylinders will be more than 60 degrees 
cooler than where they peaked.

The whole process apparently works best on fuel-injected engines because 
the variation in fuel flow from one cylinder to another is fairly 
uniform.  A carbureted engine is more difficult because the fuel is all 
coming from one source and takes different paths to get to each cylinder 
which causes more of a difference between cylinders.  But, Deakin 
explains that some carbureted engines have successfully evened the fuel 
flow by simply using carb heat.

Your overall fuel flow (which you have instrumentation for) will help 
you see the benefits of running LOP.  You could show a 15-20% decrease 
in fuel flow with only a 5-10% decrease in speed.

Deakin is also a proponent of flying WOT (wide open throttle) all of the 
time.  Instead of using the throttle to regulate power (and thus speed), 
you can use the mixture.  The farther LOP you go, the less power 
produced.  He even says it's possible to land the plane with the 
throttle wide open and just pulling the mixture back to reduce power!



aminetech at bluefrog.com wrote:
> Thanks Scott and Dave.  I've got all the cylinder readouts, but
> just one at a time, so I'll have to work at it.  My EGT probes are
> strapped to the outside of the exhaust and my readings seem
> low.  What's the procedure for putting them inside?
> I have the fuel flow.  Also, it's a carburetor, not injected.
>
> John
>   

-- 
Dave Philipsen
Velocity STD-FG
N83DP