REFLECTOR: Running LOP

[Gary T. Ciampa]

A technique that I use to optimize leaning is to essentially use shoot 
for a maximum RPM at any given throttle setting.

For example, at a given RPM setting (fixed pitch prop), say 2450, I'll 
lean until a feel a slight decrease in RPM/engine smoothness, and then 
richen the mixture a tick; Finally, I'll tweak the mixture until I get 
the highest RPM, say 2470 for that throttle setting. My *theory* is that 
at this mixture setting, I'm at the optimum effectiveness for all 
cylinders, given the potential variances due to fuel/air mixtures across 
each cylinder. My cht's are all w/in limits and the egt's are generally 
just ROP;

Thoughts?!?



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>Today's Topics:
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>   1. Re:  Running LOP (John Dibble)
>
>----------------------------------------------------------------------
>
>Message: 1
>Date: Thu, 14 Dec 2006 12:05:48 -0600
>From: John Dibble <aminetech at bluefrog.com>
>Subject: Re: REFLECTOR: Running LOP
>To: velocity at davebiz.com,	Velocity Aircraft Owners and Builders list
>	<reflector at tvbf.org>
>Message-ID: <4581927C.97F79BA9 at bluefrog.com>
>Content-Type: text/plain; charset=us-ascii
>
>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
>>
>>    
>>