JohnAJohnson
Cleared for Takeoff
- Joined
- Aug 14, 2006
- Messages
- 1,323
- Location
- Orange Beach, AL
- Display Name
Display name:
JohnAJohnson
cross post from red...
During takeoff, got an abnormally high EGT on the #4 cylinder. CHT was OK as were the other numbers. The graph below shows the spike on the #4 EGT (blue line). The spreadsheet below it also shows the rapid EGT climb. During all other phases of flight, including the runup, all EGTs behaved normally. Later in the flight at 3000' AGL, I did a few simulated approaches and go arounds to duplicate takeoffs. Again, all EGTs behaved normally.
- Engine is an O-360-A1F6D in my 74 Cardinal with Marvel MA-4-5 carb.
- SB388C (valve wobble test) was done during annual last month, no problems. This is the second flight out of annual and the first flight showed no abnormalities. Leak-downs were all mid to high 70s.
- Yesterday (day before the flight), the idle mixture was adjusted a bit (1/8 of a turn in) to reduce cutoff RPM rise from 200 down to 60, and idle screw was turned in 1/4 turn to drop the idle from 800 (with mixture full rich) to 700 (with mixture full rich). This low, the idle is not smooth and every 10 seconds or so it sounds like it'll shake the engine off the mount. Adjusting the mixture for best RPM (approximately 760) helps some, but doesn't get rid of the misses. It smooths out at 900 RPM or so.
- Carb was overhauled two years ago, doesn't leak, and all screws/bolts are tight. Carb heat is working as it should.
Questions...
Idle mixture: Can the idle circuit have this large of an impact on the high speed circuit?
Exhaust Valve leaking: Is this possible, with the crud finally blowing out and allowing the valve to start sealing again?
Intake leak?
Spark Plug: These are two year old Fine Wire Champions. If one of the #4 plugs were dropped at annual, could it intermittently fail causing this indication?
Thanks and any input or ideas would be appreciated.
During takeoff, got an abnormally high EGT on the #4 cylinder. CHT was OK as were the other numbers. The graph below shows the spike on the #4 EGT (blue line). The spreadsheet below it also shows the rapid EGT climb. During all other phases of flight, including the runup, all EGTs behaved normally. Later in the flight at 3000' AGL, I did a few simulated approaches and go arounds to duplicate takeoffs. Again, all EGTs behaved normally.
- Engine is an O-360-A1F6D in my 74 Cardinal with Marvel MA-4-5 carb.
- SB388C (valve wobble test) was done during annual last month, no problems. This is the second flight out of annual and the first flight showed no abnormalities. Leak-downs were all mid to high 70s.
- Yesterday (day before the flight), the idle mixture was adjusted a bit (1/8 of a turn in) to reduce cutoff RPM rise from 200 down to 60, and idle screw was turned in 1/4 turn to drop the idle from 800 (with mixture full rich) to 700 (with mixture full rich). This low, the idle is not smooth and every 10 seconds or so it sounds like it'll shake the engine off the mount. Adjusting the mixture for best RPM (approximately 760) helps some, but doesn't get rid of the misses. It smooths out at 900 RPM or so.
- Carb was overhauled two years ago, doesn't leak, and all screws/bolts are tight. Carb heat is working as it should.
Questions...
Idle mixture: Can the idle circuit have this large of an impact on the high speed circuit?
Exhaust Valve leaking: Is this possible, with the crud finally blowing out and allowing the valve to start sealing again?
Intake leak?
Spark Plug: These are two year old Fine Wire Champions. If one of the #4 plugs were dropped at annual, could it intermittently fail causing this indication?
Thanks and any input or ideas would be appreciated.
