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EGT spike during decent & landing

B

birddog486

Well Known Member
New engine and plane with about 4 hrs on it running a slick and a Pmag. The EGT spread got my attention while landing and decided to give this program a try.

I'm thinking maybe something caught in the injectors?

#3 hit 1575 which was about 300 hotter than the lowest cylinder

any thoughts on this

 
Intake retorque

Like Michael pointed out, I had something similar, and it came to intake leaks. I was amazed what it took to retorque after six hours or so, exhaust and intake flanges, clamps for drain back and intake hoses. Touch them all. After doing so, I’ve had no problems or repeated issues. BR Rick
 
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I think a temporarily fouled spark plug could do similar. Might clean them or at a minimum swap top to bottom.
 
Checked all the intake tubes and all of them were still at final torque. I removed the flange on #3 which had the spike and theres no trace of leakage. I pulled a couple plugs and they look great. Maybe I'll try swapping the plugs

This is on a new IO-360
 
Out of curiosity, how is your P-mag timed and is your IO-360 an angle or parallel valve engine?
 
The first thing I would check is the idle mixture setting. Be sure the rpm rises a little as the mix is pulled on shutdown.

Do you have popping on final in the exhaust too?

Why mixture?? Because at idle on final, you can have a misfire due to mixture variance. You won't feel it as the power level is so low. Burn rate in the cylinder is very dependent on mix and if it is at one end or the other (A/F wise) it can burn really really slow. In that, case the flame is still burning when the valve opens and yields a high EGT. Even in engines running under load, it is known in a test cell that the flame may not completely burn until 18" down the exhaust pipe.

BTW - we LOOK for trouble in the first few hours and can see ordinary things that seem out of expectations. It may be nothing. Let us know what you find.
 
BillL said:
The first thing I would check is the idle mixture setting. Be sure the rpm rises a little as the mix is pulled on shutdown.

Do you have popping on final in the exhaust too?

Why mixture?? Because at idle on final, you can have a misfire due to mixture variance. You won't feel it as the power level is so low. Burn rate in the cylinder is very dependent on mix and if it is at one end or the other (A/F wise) it can burn really really slow. In that, case the flame is still burning when the valve opens and yields a high EGT. Even in engines running under load, it is known in a test cell that the flame may not completely burn until 18" down the exhaust pipe.

BTW - we LOOK for trouble in the first few hours and can see ordinary things that seem out of expectations. It may be nothing. Let us know what you find.
Click to expand...

It's a parallel valve engine and I've heard a few pops but very few. It was about a 75 RPM rise on shutdown yesterday so I'll give it a couple clicks lean on the injector.

I was assuming if it was a rich mixture causing the spike it would affect all the cylinders but Ill update once I make the adjustment.

Thanks
 
N941WR said:
Out of curiosity, how is your P-mag timed and is your IO-360 an angle or parallel valve engine?
Click to expand...

Its a Parallel engine and the Pmag is timed at 23-24 degrees (same as the slick)

I clocked it 1.5-2 degrees ATDC trying to keep break in temps down
 
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