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Date: Tue, 20 Mar 2007 12:25:29 -0400
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From: Lorn H Olsen <lorn@dynacomm.ws>
Subject: Re: carbureted lean-of-peak

Bob,

I don't know where your engine came from but I would guess that you  
got it from a twin Comanche. The only fuel balancing that I have ever  
heard of on a 4 cylinder carbureted Lycoming is a spacer between the  
engine and the carburetor on the twin Comanche.

Did your engine come from a twin Comanche? What model is your engine?  
My engine came new from Lancair and the model is in my signature. Do  
you know where that spacer can be obtained? How big is the spacer?


> Lorn writes:
>
>> When I fly lean I have a lot of engine vibration because I
>> am not injected. I can see my whole right wing vibrate because
>> of the engine. I then enrich a little to stop most of the vibration.
>>
>
> "bob mackey" <n103md@yahoo.com> writes
>
> The engine is running rough (presumably) because the fuel is not
> distributed the cylinders evenly. A relatively easy way to ensure
> uniform fuel distribution is to use injectors that can be adjusted
> to match each cylinder (ala GAMI). But that's not the only way...
> carbureted engines can also run smoothly lean-of-peak (LOP).
> I don't know of any obvious way to adjust the fuel distribution
> in a carbureted engine, but adjustments to the induction path
> can have the right effect. On my O-320, there is a flow
> straightener mounted at the carb inlet in the airbox. It is
> slightly asymmetric. It can be installed in four possible
> orientations. It turns out that one of those orientations
> results in pretty good distribution, allowing the engine
> to run smoothly LOP.
>
> Has anyone else experimented with fuel-flow balancing
> on single-carburetor aircraft engines?
--
Lorn H. 'Feathers' Olsen, MAA, DynaComm, Corp.
248-345-0500, mailto:lorn@dynacomm.ws
LNC2, FB90/92, O-320-D1F, 1,300 hrs, N31161, Y47, SE Michigan