REFLECTOR: Running LOP

[John Dibble]

Yes, some EGTs are very low and the highest and lowest are over 200C (360F)
different.  My probes are just two wires fused together.  At least that's how they
used to be until 2 years ago when they corroded apart.  I cut the corroded ends off
and just crimped them together with crimps from the hardware store.  Seems to be
working as well as before.  I think I will keep them on the outside of the pipes as
long as the data is useful.
If high CHTs are the key indicator of conditions to avoid, then perhaps I don't need
to be concerned with where I am on the curve.  My highest CHTs on takeoff are 160C
(320F) and 140C at cruise.  So maybe I can just use the old fashion approach and lean
until the engine sputters and then back off a little.  What do you think?

John

Dave Philipsen wrote:

> 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
>
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