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  #11  
Old 11-23-2018, 04:49 PM
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rv6ejguy rv6ejguy is offline
 
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This engine has a standard Lycoming sump with vertical induction. Ralph has about 5 hours of flight time on the plane now and has found a total of 12% trim is required on 2 cylinders. 0, 0, -5 and +7. EGTs align nicely with this setting at 2500 rpm cruise but as you change rpm, the trim amounts change as other people have noted as well.
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Ross Farnham, Calgary, Alberta
Turbo Subaru EJ22, SDS EFI, Marcotte M-300, IVO, RV6A C-GVZX flying from CYBW since 2003- 427.8 hrs. on the Hobbs,
RV10 95% built- Sold 2016
http://www.sdsefi.com/aircraft.html
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  #12  
Old 11-23-2018, 05:30 PM
jump4way jump4way is offline
 
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Location: Coolidge, AZ
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This brings up a question for me. Which is the best way to utilize the trimming function, trim for EGT or CHT?

It seems CHT might be a better indication of engine balance. There is no sensor variance as the CHT probes are all installed in the same location where as EGT could be prone to variances from the install process.

Any thoughts on how that might effect engine performance?
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  #13  
Old 11-23-2018, 06:25 PM
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rv6ejguy rv6ejguy is offline
 
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The thought is that there is no way to know whether the cooling airflow is equal to each jug so there is not much point in balancing to equal CHTs initially.

Equal numerical value EGTs may not indicate equal AFRs, the only way we can tell that is if they all peak at the same time as this indicates near stoich on all. So IMO, the best way to trim is to get all cylinder to peak at the same time. Then we can look at CHTs and start trying to get those more equal with baffle and deflector changes.

Note though that if the cylinders are trimmed differently, this means unequal airflow in and/or perhaps differences in exhaust scavenging and likely that each cylinder is producing a different amount of hp and therefore heat. Different primary exhaust tube lengths or intake runner lengths can explain some of this. Ralph did notice that trim amounts changed with a change in rpm and this is expected with big differences in intake and exhaust tube lengths as the pressure waves take longer or shorter times to reach each end.

Therefore the best you can do with what you have is to trim so all cylinders peak simultaneously and then go after getting the CHTs equal with lots of tries at baffling alterations followed by more testing.
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Ross Farnham, Calgary, Alberta
Turbo Subaru EJ22, SDS EFI, Marcotte M-300, IVO, RV6A C-GVZX flying from CYBW since 2003- 427.8 hrs. on the Hobbs,
RV10 95% built- Sold 2016
http://www.sdsefi.com/aircraft.html
http://sdsefi.com/cpi.htm



Last edited by rv6ejguy : 11-23-2018 at 09:11 PM.
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  #14  
Old 11-23-2018, 07:45 PM
jump4way jump4way is offline
 
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Interesting point about the peak of EGT. I guess the actual numerical value of the EGT is useless as long as they cylinders reach peak temperature together. Ill give that a shot. Thanks.
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  #15  
Old 12-03-2018, 07:13 PM
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rv6ejguy rv6ejguy is offline
 
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Ralph is past the halfway point on the 25 hour flyoff. Hopefully soon we'll be able to shoot some more videos when we get some decent weather.
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Ross Farnham, Calgary, Alberta
Turbo Subaru EJ22, SDS EFI, Marcotte M-300, IVO, RV6A C-GVZX flying from CYBW since 2003- 427.8 hrs. on the Hobbs,
RV10 95% built- Sold 2016
http://www.sdsefi.com/aircraft.html
http://sdsefi.com/cpi.htm


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