REFLECTOR: Running LOP

[Chuck Jensen]

John,
Just leaning til is sputters will get you close.  The purpose of the
EGTs is to make sure that the last cylinder gets 50 LOP before the first
cylinder to lean gets so lean that it causes the noticeable loss of
power or stumble.  If your injectors aren't balanced, the first cylinder
to go way lean of peak and cause sputter, may leave two or three other
cylinder right at the peak temps.  In sum, as long as the fuel flow
spread across all cylinder for peak EGT is <0.5 gph, the lean-to-sputter
will get you there pretty reliably.

Chuck Jensen
 


-----Original Message-----
From: reflector-bounces at tvbf.org [mailto:reflector-bounces at tvbf.org] On
Behalf Of John Dibble
Sent: Thursday, December 14, 2006 1:06 PM
To: velocity at davebiz.com; Velocity Aircraft Owners and Builders list
Subject: Re: REFLECTOR: Running LOP


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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