Henning! You might be able to answer my question.

Theboys

Theboys

Line Up and Wait
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Theboys
Was wondering why one cylinder is running high EGT at high altitudes. I'm having heck of time with number 3 on tsio550. It seems like it's getting worse also. My cht. Seems to be running normal. I would say maybe bad probe or burnt exhaust valve but when I drop to lower altitudes it go's to more normal like rest. Seems bad over fl210 but gets normal in the low teens.
 
Theboys said:
Was wondering why one cylinder is running high EGT at high altitudes. I'm having heck of time with number 3 on tsio550. It seems like it's getting worse also. My cht. Seems to be running normal. I would say maybe bad probe or burnt exhaust valve but when I drop to lower altitudes it go's to more normal like rest. Seems bad over fl210 but gets normal in the low teens.
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Next time it happens, do a mag check and see what happens. If cylinder goes cold on one, most likely one is dropping out at altitude, just looking at the plugs may indicate which as well. What is likely the issue is that you have a carbon trace in the distributor section of one of your mags that at low atmospheric pressure provides a path of lesser resistance to ground than the spark plug. If you have Champion plugs, this very likely indicates you have a bad resistor in that plug and it needs to be replaced. You should also likely have your mags cleaned and serviced.
 
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I was kind of leaning to the bad exhaust valve. Thinking my turbos were blowing hot gas out when they were working so hard, but like your ideas better. I was having a hard time keeping it below 1640 which ironically, is what my tit was also
 
Theboys said:
I was kind of leaning to the bad exhaust valve. Thinking my turbos were blowing hot gas out when they were working so hard, but like your ideas better. I was having a hard time keeping it below 1640 which ironically, is what my tit was also
Click to expand...

Typical when you run these engines on one mag. If it was an exhaust valve, the problem wouldn't be altitude dependent.
 
A plugged or slightly plugged injector will cause that cylinder to run leaner. If you are ROP, then the EGT will be higher. Could be something as simple as a piece of lint in there. Check that before panicking about a burnt valve.
 
It idles fine and I run it very lean of peak. I was running it at 31 inches of mp and around 16 gal. I was running 140 to 180 degrees difference on that cylinder. Within 20 on the rest. It runs fine seems like. Normally though I can run around 13 gal with same settings but it was around -20f to plus 20f during the flight. Same altitude.
 
small intake leak to that cylinder
 
it's either spark (ignition, plugs, leads), fuel mixture (injectors).....for the #3 cylinder.

another trick to get your TITs lower is verify your timing is correct....and accurate....and not retarded beyond the limits. Adjustment towards the advanced limit will cool the TIT in cruise but reduce available takeoff power.
 
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