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  #1  
Old 05-31-2017, 11:46 AM
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Jesse Jesse is offline
 
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Default EGT Spike

I have a fuel injected engine that runs a little rough at full power and the EGT on cylinder 4 spikes. The data log shows 1560 on that EGT with no significant change in CHT, up or down. When I pull power back, things seem to smooth out, and the data log shows that EGT coming down to roughly inline with the others.

I have looked at the nozzle and it doesn't appear to have any obstructions in it. I have done a flow test on the injector line, and it flows like the others. I have tested the plugs and they fire fine and wires are good.

Any other things to check before flying again for more data?

Thanks.
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  #2  
Old 05-31-2017, 11:52 AM
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istrumit istrumit is offline
 
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Dunno what kind of mags you have...I have one LS and one mechanical. Mine was running poorly and spiking on #6.

The plug was fouled. I cleaned it. Problem came back.

It was the mechanical mag. Rebuilt it and problem went away.

Might also be an intake gasket, but that seems kinda unlikely.

Scott
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  #3  
Old 05-31-2017, 02:56 PM
BobTurner BobTurner is offline
 
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If by spikes you meant the egt goes up 50 F or so, I'd suspect one of the plugs won't fire at high cylinder pressures. A mag check at that power should tell you which one it is. Then you need to see if it's the plug or the mag, but since it's only one cylinder I'd guess plug.
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  #4  
Old 05-31-2017, 04:28 PM
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Jesse Jesse is offline
 
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I removed and tested the plug and it tested fine, although it's still a little fouly at full rich. I swapped out the injector as well. Problem seems to have gone away.

It was spiking about 200F at this event. That's a lot more than the 50F I have seen mentioned in my google searches for similar events. We'll see how things go with this new nozzle.
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RV Hotel (hangar, room, car) at X35 in north FL

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  #5  
Old 05-31-2017, 06:27 PM
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Lenny Iszak Lenny Iszak is offline
 
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Jessie, try a LOP mag check. If you have an ignition system problem it is more likely to show up while LOP.

Lenny
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  #6  
Old 06-01-2017, 10:05 AM
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daddyman daddyman is offline
 
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Jesse,
Sounds like a dirty fuel int any that cylinder. If it is not fully functioning, the decrease in fuel need paradoxically causes heat, as fuel cools.

Daddyman
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  #7  
Old 06-01-2017, 10:57 AM
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hawkeyestof hawkeyestof is offline
 
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Jesse: Except for the "runs a little rough at full power", I would suspect the EGT probe - especially if using the Dynon supplied probes. You may recall that I replaced all my probes - after several failures - with EI probes. No problem after few hundred hours. Jerry
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  #8  
Old 06-01-2017, 12:08 PM
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Jesse Jesse is offline
 
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It is a G3X with those probes. The injector seems. Have fixed the problem. No issues after 4+ flight hours after changing the injector.
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RV Hotel (hangar, room, car) at X35 in north FL

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  #9  
Old 07-16-2017, 09:36 AM
schaplerrh schaplerrh is offline
 
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Jesse, I'm seeing excessively high EGT but normal CHT on all four cylinders when I trying going LOP. Engine roughness hasn't been a problem while leaning at cruise -- may because temps climb so fast I quickly richen the mixture to cool things down. I have the GRT engine monitor remotely mounted with AFS EFIS displays. Any ideas? Forgot to mention: IO-360 with MT CS acro prop and properly timed, good old fashion mags.

Robert

Last edited by schaplerrh : 07-16-2017 at 09:38 AM.
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  #10  
Old 07-16-2017, 02:34 PM
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Jesse Jesse is offline
 
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How's high is excessive? If you are not above 65% power and CHT's are fine, then I wouldn't worry about it.
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Jesse Saint (Saint Aviation, Inc. - VAF Advertiser)
352-427-0285
jesse@saintaviation.com
RV Hotel (hangar, room, car) at X35 in north FL

Commercial ASEL/S A&P/IA EAA Technical Counselor

Dynamic Prop Balancing, Prebuy Inspections, Condition Inspections, Repairs and Mods, Injector Tuning, Airframe, Engine, Panel Upgrades, Ferrying, etc.
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