REFLECTOR: More leaning learning.

Bernard Despins bdespins at telusplanet.net
Tue Sep 1 08:51:02 CDT 2009


Just to continue to get everyone on the same page, the actual numbers 
you are seeing on the engine monitor for EGT - in other words the EGT 
spread at peak is not important.  What is important is the fuel flow 
occuring when the individual cylinders are peaking.  So we should be 
talking fuel flow spread not temperature spread.  As a ball park figure, 
a difference of 0.5 GPH between the richest and leanest cylinder would 
probably allow you to run to 100 LOP.  Google "Gami lean test" for more 
info.

Bernard Despins



Scott Derrick wrote:
> Oh,
>
>     Sorry Terry.  Didn't realize you already were running an EI.   That
> explains why you can almost run LOP.  Most IO540's  have horrible peak
> egt spreads.
>
>     I think Ken's recommendation of using Airflow's injector
> restrictor's  would be the ticket.  Though a quick injector swap may be
> very enlightening.  Just note down who you swap so you can undo it later
> if needed.
>
> Scott
>
>
>
> Terry Miles wrote:
>   
>> What about shutting off the mag and running only on my Jeff Rose?  I just
>> didn't want to do that, but it might be a step in the direction of a more
>> even across-the-cyl combustion picture.  
>>
>> -----Original Message-----
>> From: reflector-bounces at tvbf.org [mailto:reflector-bounces at tvbf.org] On
>> Behalf Of Scott Derrick
>> Sent: Monday, August 31, 2009 21:05
>> To: Velocity Aircraft Owners and Builders list
>> Subject: Re: REFLECTOR: More leaning learning.
>>
>> Terry,
>>
>> Glad to hear you are cognizant of the issues.  Sounds like you are tuned in
>> to LOP.
>>
>> as long as you lean as you described below, above 8,000 ft, that should be
>> perfectly acceptable.  Because the engine is making less than 75% power at
>> full throttle, and leaned to your described settings probably closer to 50%
>> power.
>>
>> But that is not leaning to LOP, that is leaning to best run.  I did that all
>> the time in my Bonanza above 8,000 ft because my engine like yours couldn't
>> run LOP, the mixture spread was to poor.  It was carburated.
>>
>> I believe you have three alternatives to being able to truly run LOP. At low
>> altitude, even in a cruise climb.
>>
>> 1.)  Expensive but guaranteed to work is to order  GAMIjectors from GAMI
>> http://www.gami.com/   Looks like it would be $800 
>>
>> 2.) Play swap the injectors.  Swap the leanest cylinder(first to peak) with
>> the richest cylinder(last to peak).  See if it improves.
>> Re-evaluate.  Sometimes you have to do a few swaps with different cyls. 
>> It all trial and error.  Cheap, relatively easy and perfectly legal in
>> an experimental.   Sometimes it works sometimes not. It didn't for my IO360.
>>
>> 3.) My Io360 would not run LOP, even after playing swap the injectors. I
>> then installed a Lightspeed Ignition system.   It improved the fuel burn
>> so much I could then just barely lean to 50-60 LOP.   I couldn't get
>> below 10-20 LOP before the Lightspeed.
>>
>> Maybe somebody else knows of another method to improve your fuel spread.
>>
>> Scott
>>
>>
>> Terry Miles wrote:
>>   
>>     
>>> 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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>>>       
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>
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