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EGT Spike

Jesse

Well Known Member
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.
 
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
 
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.
 
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.
 
Jessie, try a LOP mag check. If you have an ignition system problem it is more likely to show up while LOP.

Lenny
 
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
 
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
 
It is a G3X with those probes. The injector seems. Have fixed the problem. No issues after 4+ flight hours after changing the injector.
 
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
 
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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.
 
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

How's high is excessive? If you are not above 65% power and CHT's are fine, then I wouldn't worry about it.
Scott and Jessie,
I had all of the symptoms you have been describing also last month. High EGT but normal CHT on #3 cyl. Going LOP would have #3 EGT bouncing around while the others were rock solid. Went through all the same troubleshooting thoughts. Spark plugs fouled? Cleaned aviation plugs and replaced auto plugs? Nope! Bad EGT probe? Swapped them around. Nope! Finally removed all fuel injectors. Closely inspected each injector but could not see anything abnormal at all. Cleaned them with ultrasonic cleaner anyway. Bingo! Runs like a top now. Even though there was nothing visual blocking the injector there must have been something in there. Everything is great now.

So if anyone is seeing erradic EGT readings you might think about fuel injector cleaning as a good place to start.

Live Long and Prosper!
 
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