REFLECTOR: Running LOP

Thu Dec 14 21:35:08 CST 2006

For LOP operation on a carburated engine try closing
the throttle until you see a slight change in mp.  Run
it with a small amount of carb heat.  The combination
of the two will allow many lyc's to rum LOP.
--- Dave Philipsen <velocity at davebiz.com> wrote:

> I think Chuck's answer is right on the money. 
> Simply leaning until 
> sputtering may not insure that the all cylinders are
> lean of peak.  You 
> could have one cylinder running lean and the others
> in the "red box".  
> It's entirely possible that your carbureted engine
> won't run well LOP 
> because of variation in fuel flow to the individual
> cylinders.
> 
> 
> John Dibble wrote:
> > 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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> 
> -- 
> Dave Philipsen
> Velocity STD-FG
> N83DP
> 
> 
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