Paul 5r4
Well Known Member
I've been through every thread I can find regarding high EGT on a single cylinder. Here's the facts. Just completed 8th annual condition inspection. Changed from champion plugs to tempest... same size and heat rating. That's the only thing different. On cylinder three the temps have jumped by 150 deg or so and at times 200 especially at higher power settings. At cruise or less, cylinder 3's EGT are a little more reasonably in line with the other three. An interesting note... The engine never did idle well. I always had to keep a little rpm on it for smooth running. With no throttle carb adjustments made, with the new tempest plugs it idles perfectly smooth. Also the champion plugs that were removed with the exception on one, failed the ohm test horribly.
What I've done/confirmed
1. Changed air intake gaskets
2. rechecked compression on cylinder 3, (75/80), incase of carbon or speck of trash on the exhaust valve seat
3. all plug wires checked with cable tester and all check good
4. swapped out probes with cylinder 1. Still indicates the high EGT are on cylinder 3
5. although all plugs are new, I Just swapped out plugs with another cylinder to see if that moves the problem. Haven't test flown yet.
6. mags are timed correctly at 25 BTDC, (rechecked).
7. at run up mag checks are good. About 80 rpm drop on each and EGT rising in all cylinders with each side then back down when placed on both
8. All four CHT temps are good in all flight modes, even cylinder 3.
9. Engine running smooth as silk at all times. No valve sticking symptoms
If swapping the plugs with another cylinder doesn't change anything then it seems the only thing left is to pull the plugs from cylinder 3 and put a couple of the champions back in and test fly it, (for a single test flight only CAN I DO THAT one cylinder with champion and the other three running tempest)?
The only thing that changed was the new plugs! If I can do it and it brings the EGT back in line with the others at all settings, I'm going to change back to champion and will have 8 new tempest plugs for sale.
Discussion: I've watched Mike Busch's online video regarding CHT and EGT and understand his points however..... It IS different and it puzzles and concerns me.
Any thoughts???
What I've done/confirmed
1. Changed air intake gaskets
2. rechecked compression on cylinder 3, (75/80), incase of carbon or speck of trash on the exhaust valve seat
3. all plug wires checked with cable tester and all check good
4. swapped out probes with cylinder 1. Still indicates the high EGT are on cylinder 3
5. although all plugs are new, I Just swapped out plugs with another cylinder to see if that moves the problem. Haven't test flown yet.
6. mags are timed correctly at 25 BTDC, (rechecked).
7. at run up mag checks are good. About 80 rpm drop on each and EGT rising in all cylinders with each side then back down when placed on both
8. All four CHT temps are good in all flight modes, even cylinder 3.
9. Engine running smooth as silk at all times. No valve sticking symptoms
If swapping the plugs with another cylinder doesn't change anything then it seems the only thing left is to pull the plugs from cylinder 3 and put a couple of the champions back in and test fly it, (for a single test flight only CAN I DO THAT one cylinder with champion and the other three running tempest)?
The only thing that changed was the new plugs! If I can do it and it brings the EGT back in line with the others at all settings, I'm going to change back to champion and will have 8 new tempest plugs for sale.
Discussion: I've watched Mike Busch's online video regarding CHT and EGT and understand his points however..... It IS different and it puzzles and concerns me.
Any thoughts???