REFLECTOR: Running LOP

michalk michalk at awpi.com
Wed Jan 3 10:54:49 CST 2007


I agree with your last two paragraphs, but disagree with "useless 
distraction".

The pains I am taking for accurate temperatures are for me.  It's not a 
distraction in the cockpit to know that my sensors are telling me the 
truth.  For me, if I have a sensor, I will have it calibrated so that I 
know I can trust it within a certain tolerance.

We are arguing semantics here.  This started out as a discussion on LOP 
operations.  One can have even temps and still be running 50 ROP and 50 
LOP, but they won't peak at the same time.

I do agree that having even EGT temps doesn't get you much with normal 
operations.  However, if you can trust your sensors, that will tell you 
if you have a misfiring plug, or something else like lower compression 
in a particular cylinder.

Scott Derrick wrote:
> I was talking about aircraft engines, what else is relevant to this topic??
> 
> I was also talking abut standard probes, customizing probes could be 
> done for each cylinder, but  its a waste of time for the aviator.  
> Information relevant to an  engine designer but just a distraction in 
> the cockpit.
> 
> Absolute EGT's means practically nothing,  tells you even less. Another 
> useless distraction.
> 
> What is relevant and what everybody should be paying attention to is 
> peak egts and their relationship to each other as in:  first to peak, 
> last to peak, peak spread..   This information is priceless and tells 
> you how your engine is consuming fuel and if your operating it in a safe 
> or unsafe manner.
> 
> 99% of carburated boxer aircraft engines(Lycoming, Contenental,  
> Franklin) have horrendous fuel/air mixtures, thats why they must be run 
> so rich to run smooth, pucking unburned fuel out of some of the 
> cylinders all the time.  To get precision mixtures to each cylinder the 
> best way is a carburator for each cylinder like the radials have, or 
> tuned injection like GAMI or pulsed injectors like our automotive engines.
> 
> Scott
> 
> michalk wrote:
> 
>>Well, I beg to differ.
>>In my case, I used a molten lead reference and ice bath to calibrate 
>>each probe.  Each probe also has a 0degree reference in the circuitry. 
>>When installing, I welded the probe bungs at equal distances from the 
>>exhaust port, and installed them at the same distance into the exhaust 
>>stream.  This is the assumption I was making for my statement.
>>
>>A carbureted engine does not necessarily have bad distribution.  I would 
>>bet that well tuned carbureted motorcycle engines have very good 
>>distribution.  My comment was in the theoretical, not necessarily 
>>related to aircraft engines.  There are cases where my statement does 
>>not hold true, but they are anomalies, like detonation and such.
>>
>>Scott Derrick wrote:
>>  
>>
>>>I'm talking absolute temps here.
>>>
>>>Even EGT's can mean many things, even power distribution is not one of 
>>>them.  In fact if your engine is carbureted or you do not have balanced 
>>>injectors you can bet you do not have even power distribution no matter 
>>>what your egt's are registering.
>>>
>>>Uneven EGT's, the most common reason is caused by placement and exhaust 
>>>flow, and  usually has nothing to do with mixture or power 
>>>distribution.  The only time a wild egt is connected to power in a 
>>>cylinder is if its detonating not firing at all.
>>>
>>>Scott
>>>
>>>Brian Michalk wrote:
>>>
>>>    
>>>
>>>>Well, they mean something.
>>>>Assuming the probes weren't "trimmed" to give even results and are 
>>>>reporting actual EGT's, then even EGT's mean even power across cylinders.
>>>>
>>>>Uneven EGT's can be caused my two things:  Uneven mixing of the 
>>>>air/fuel, and uneven airflow to the different cylinders.  Cylinders that 
>>>>breathe better will make more power, and thus higher EGT's.
>>>>
>>>>Different mixtures will result in peak EGT's at different temperatures.
>>>>Different airflow will result in different cylinder to cylinder EGT 
>>>>measurements.
>>>>
>>>>Chuck Jensen wrote:
>>>> 
>>>>
>>>>      
>>>>
>>>>>Joel,
>>>>>If you are using a 'normalizing' function with the VM1000, then even EGT
>>>>>bars mean nothing.  If you are not using a 'normalizing' function with
>>>>>the VM1000, then even EGT bars mean nothing.  Either way, even EGT bars
>>>>>mean nothing.  However, as you progressively lean out your engine, if
>>>>>all of your EGTS peak at the same fuel flow (well, within 0.2-0.5 GPH
>>>>>anyhow) then you are good-to-go.  In that case, you don't need GAMI, you
>>>>>need to thank your lucky stars.
>>>>>
>>>>>As Scott will advise you in spades.  The peak temperature of each
>>>>>cylinder is totally irrelevant!!  The only thing that counts is the fuel
>>>>>flow at which each cylinder reaches its peak temp, irrespective of what
>>>>>that temp is.
>>>>>
>>>>>Chuck Jensen
>>>>>
>>>>>
>>>>>
>>>>>-----Original Message-----
>>>>>From: reflector-bounces at tvbf.org [mailto:reflector-bounces at tvbf.org] On
>>>>>Behalf Of Dr. Golf
>>>>>Sent: Monday, January 01, 2007 8:58 AM
>>>>>To: Velocity Aircraft Owners and Builders list
>>>>>Subject: Re: REFLECTOR: Running LOP
>>>>>
>>>>>
>>>>>Thanks Kieth.
>>>>>If using the VM1000 engine monitor, all the cylinder
>>>>>bars are at the same level after leaning, what would
>>>>>the advantage be if I changed to the Gammi injectors?
>>>>>Joel
>>>>>
>>>>>
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>>>>>   
>>>>>
>>>>>        
>>>>>
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>>>>
>>>>
>>>> 
>>>>
>>>>      
>>>>
>>>-- 
>>>
>>>-
>>>
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>>>
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>>>
>>>
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>>
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>>
>>
>>  
>>
> 
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> 
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