REFLECTOR: Fuel Consumption Performance

[John Tvedte]

Terry,

I think Scott is saying... as you lean, the first cylinder to peak is the leanest - the last to peak is the richest... if cruising ROP, you lean by the leanest cylinder (first to peak), but if cruising LOP, you lean by the richest cylinder (last to peak) - because you are on the other side of the Red Box.

www.eaa42.org/misc/gregs_show.ppt

Note, I do not claim to have any practical experience.

John

________________________________________
From: reflector-bounces at tvbf.org [reflector-bounces at tvbf.org] On Behalf Of Terry Miles [terrence_miles at hotmail.com]
Sent: Friday, August 28, 2009 11:31 AM
To: 'Velocity Aircraft Owners and Builders list'
Subject: Re: REFLECTOR: Fuel Consumption Performance

Well I appreciate your patience.  I did read the below articles, and several
books now on related engine operations and mixture settings and we are in
full agreement on the concept.  I am not running ROP.  I am running 50
degrees LOP.  The question between us is which cylinder should be the
reference cylinder.  My choice in this is that I will use the first cylinder
to peak.
Thanks again.
Terry

-----Original Message-----
From: reflector-bounces at tvbf.org [mailto:reflector-bounces at tvbf.org] On
Behalf Of Scott Derrick
Sent: Thursday, August 27, 2009 21:01
To: Velocity Aircraft Owners and Builders list
Subject: Re: REFLECTOR: Fuel Consumption Performance

Terry,

Below is my reply of a month ago when you indicated you were leaning to 50
LOP on the first cylinder to peak.  All the rest being richer.  Which as I
stated a month ago is BAD!

Maybe I misunderstood and you are now running ROP?  Leaning until the first
cylinder reaches peak, and then enriching it until it is 50 ROP?
That would be the old school acceptable  method.  If you decide to read the
articles below, you will read that  GAMI recommends 75 ROP because 50 ROP
may be stressful to some engines  at high power settings and low altitude.

But, since you were running at 10K or above you can run at any mixture
setting and be fine, as far as detonation is concerned because the engine
cannot produce more than 75% power at full throttle.

I once again recommend the articles below by  John Deacon about how to
safely  operate these big bore aircraft engines.  They are expensive and
easy harm.

Scott


**********************************************************

Terry,

running the first cylinder LOP can put some of the richer cylinders right in
the BAD zone. Thats well... bad!  Thats why you always lean to the last
cylinder when running LOP.  Thats also why you lean to the first cylinder
when running ROP, so all the other cylinders are rich of that point.

you said

"I was afraid my coolest cyl could be 150 LOP before the last cly peaked and
that I could burn that exhaust valve."


Thats exactly backwards. Once a cylinder reaches peak EGT and goes on the
LOP side it will run cooler and cooler the leaner you run it. The absoluter
worst mixture is about 25-50 degrees ROP in terms of detonation and the
timing of peak power pulses.  If your coolest cylinder was running at 150
degrees leaner than the last cylinder to reach 75 LOP it would probably not
be firing due to the too lean mixture.

How to operate your engine is a complex topic.  Here is a great set of
articles by John Deacon, I consider a must for any recip operator, whether
you run LOP or ROP.

part 1
http://www.avweb.com/news/pelican/182179-1.html
part 2
http://www.avweb.com/news/pelican/182176-1.html
part 3
http://www.avweb.com/news/pelican/182583-1.html
part 4
http://www.avweb.com/news/pelican/183094-1.html


Here's GAMI's lean test,  a great thing for anybody to do, to see how
balanced their injectors are.

http://www.gami.com/gamijectors/leantest.php


Scott



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