REFLECTOR: More leaning learning.

[Terry Miles]

Bernard, 

Thanks for the thoughts.  I was indeed sweet spot oriented.  

Someone posted that power point that was provided at OSH.  Slide six of that
presentation might be one to consider so we are all on the same page with
the same data.  

In my Ly IO-540, there is a 60 degree spread from the coolest to the hotest
cylinder, and about a 60 to 80 degree spread in peaks temps when leaning.
Here is a question for the group.  You look at your engine analizer and see
this:  -61, -91, -36, -71, -31, -61.   I didn't make this up.  It is out of
my engine log.  Taking cylinder #5 another 19 degrees cooler and will have
the power stroke on cylinder #2 signifcantly out of the balance.  Look at
that PP presentation and look how power drops off when a given cyl is past
100 LOP.  

I understand what Scott is saying.  Believe me.  I would never ignore you,
man.  Every fool and his dog is making presentations on this LOP issue like
it is some new discovery, with the usual crap about OWT that were sound
advice for carburated engines.  Several of write ups--due maybe to editoral
demands for not too much detail--do not provide "big picture" explanations,
let alone adress EGT spreads within a single power plant and how they should
be addressed in practice.  As Scott has mentioned when you are at altitude,
when full throttle is below 65% the concern with "over pressure" within the
given cylinders is greatly reduced. 

When it sounds and feels the best to me in this airplane with this engine,
#2 is about -60 LOP and #3 and #5 are right near peak.  If I pull #3 and #5
to -50 LOP and let it sit and then enrich again it is clear the mixture was
too lean.  This is sitting in a cruise situation on a 3 hour cross country
at a constant speed making small adjustments and waiting for things to
stabilize.  

Terry



-----Original Message-----
From: reflector-bounces at tvbf.org [mailto:reflector-bounces at tvbf.org] On
Behalf Of Scott Derrick
Sent: Sunday, August 30, 2009 21:58
To: Velocity Aircraft Owners and Builders list
Subject: Re: REFLECTOR: Fuel Consumption Performance

But Bernard, to have all the cylinders Lean of 50 LOP, you have to lean to
the "Last to Peak", not the first.  The first is the leanest cylinder, all
the rest are richer.

You use the "First to Peak" for ROP operations.

Scott


Bernard Despins wrote:
> I think Terry may be arriving at the same "sweet spot of leaning" as 
> you are Scott.  He is just making all of his cylinders leaner than the
> sweet spot, and adding fuel until the FIRST cylinder reaches it.   The
> rest of the cylinders are cooler than the sweet spot.   The only
> problem with this is that when all the cylinders go leaner than the 
> "sweet spot"  (lets say 50 LOP) you may go a little too far on the 
> lean side and the engine could run a little rough depending on how
> well balance the injectors are.   No harm done.
>
> Scott just skips the step of making all the cylinders leaner than the 
> sweet spot and leans starting on the ROP side of things until the LAST 
> cylinder gets to 50 LOP.  The rest of the cylinders are cooler than 
> the sweet spot.  Just like Terry's method.  The only problem would be 
> leaning too slow and lingering in the "danger zone".  But once you get 
> use to the "big pull", it is absolutely not a problem.
>
> Hope this helps.
>
> Bernard Despins
>
>
>
> Terry Miles wrote:
>>
>> Al,
>>
>> Here is my cruz engine log to include this last IN to CO trip. 
>> Westbound was full power.  10,000 will get me mid 180 Kts TAS and 
>> 12,000 gets mid 190 kts TAS.  That runs about 11.5 at full throttle 
>> and leaning 50 LOP.  Thanks to Scott I did it right and pulled the 
>> mixture out until they were all LOP and enriched back on the first to 
>> peak so to get 50 LOP.
>>
>
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