slackl
Member
Guys.
I'm constantly battling with my #6 cylinder, which is:
- either permanently going MUCH colder than others
- or constantly getting extremely rich mix
My problem is ONLY with #6 cylinder - all others are performing fine.
Engine is around 180 SMOH with new ECI cylinders back in 2011.
Compressions (both cold and warm) in upper 70's.
Symptoms are:
- on start - cylinder is working fine.
- while warming up and on idle - spontaneous misses, CHT not more than 200F, dropping EGT. If I'll lean the engine 1/2" out - goes fine, CHT and EGT goes in-line with other cylinders.
- on take-off: temps are OK, but observers from the ground state darker smoke from my left side exhaust
- in cruise - as soon as I drop MP below 25" and/or RPM less than 2500 - CHT/EGT on that cylinder drops to around 220-240F CHT/ 900-1100F EGT. Leaning does not help a lot.
What was done and what was found during several approaches:
- front cross-tube was insulated to avoid fuel condensation. Helped a BIT - less leaning needed to normalize cylinder performance at idle.
- cylinder removed:
1. found torn intake valve oil seal. Replaced.
2. exhaust hydraulic lifter SEEMED to be "softy". Replaced both (intake and exhaust) with new.
3. heat signature on valves is even
4. piston rings - gaps OK, side clearance ok, no visible damage or worn areas on cylinder walls, cylinder honing is ok.
5. Noticeable amount of unburned fuel deposits in the top of the cylinder and on the piston (I'm running mogas, so this is surely not lead deposits from 100LL)
- No intake or exhaust leaks on that cylinder
- checked valve springs, comparing them to the ones from the next cylinder. Dimensions and compression forces are the same.
- cylinder and piston geometry well within service limits.
Cleaned the cylinder and piston, reassembled the engine, flew for ~20 hours, from which first 7-8 hours where problem free. Maybe because of the hot weather and short flights around the patch.
Last 10 hours everything returned back as it was stated.
For those sceptics, who want to tell me that all that deposits in the cylinder are from oil.
My current oil consumption is around 1quart of oil for 25-28 hours....
So, obviously, the reason for all above either:
- cylinder is either cooling way better than others (wrong baffling ?)
- something is wrong with the (your idea here. I've run out of them, that's because I'm writing this poem)
- I do exclude carb as a source - because all other cylinders work OK.
- I do exclude leaky fuel primer lines due to the fact that fuel primer is not connected to 2 frontmost cylinders on my engine.
I do kindly ask 14-19-2, 14-19-3 owners and any other users of O-470 to photo their cooling baffles around frontmost cylinders of their engine.
Or give me any working idea I'll believe or able to check.
I'm constantly battling with my #6 cylinder, which is:
- either permanently going MUCH colder than others
- or constantly getting extremely rich mix
My problem is ONLY with #6 cylinder - all others are performing fine.
Engine is around 180 SMOH with new ECI cylinders back in 2011.
Compressions (both cold and warm) in upper 70's.
Symptoms are:
- on start - cylinder is working fine.
- while warming up and on idle - spontaneous misses, CHT not more than 200F, dropping EGT. If I'll lean the engine 1/2" out - goes fine, CHT and EGT goes in-line with other cylinders.
- on take-off: temps are OK, but observers from the ground state darker smoke from my left side exhaust
- in cruise - as soon as I drop MP below 25" and/or RPM less than 2500 - CHT/EGT on that cylinder drops to around 220-240F CHT/ 900-1100F EGT. Leaning does not help a lot.
What was done and what was found during several approaches:
- front cross-tube was insulated to avoid fuel condensation. Helped a BIT - less leaning needed to normalize cylinder performance at idle.
- cylinder removed:
1. found torn intake valve oil seal. Replaced.
2. exhaust hydraulic lifter SEEMED to be "softy". Replaced both (intake and exhaust) with new.
3. heat signature on valves is even
4. piston rings - gaps OK, side clearance ok, no visible damage or worn areas on cylinder walls, cylinder honing is ok.
5. Noticeable amount of unburned fuel deposits in the top of the cylinder and on the piston (I'm running mogas, so this is surely not lead deposits from 100LL)
- No intake or exhaust leaks on that cylinder
- checked valve springs, comparing them to the ones from the next cylinder. Dimensions and compression forces are the same.
- cylinder and piston geometry well within service limits.
Cleaned the cylinder and piston, reassembled the engine, flew for ~20 hours, from which first 7-8 hours where problem free. Maybe because of the hot weather and short flights around the patch.
Last 10 hours everything returned back as it was stated.
For those sceptics, who want to tell me that all that deposits in the cylinder are from oil.
My current oil consumption is around 1quart of oil for 25-28 hours....
So, obviously, the reason for all above either:
- cylinder is either cooling way better than others (wrong baffling ?)
- something is wrong with the (your idea here. I've run out of them, that's because I'm writing this poem)
- I do exclude carb as a source - because all other cylinders work OK.
- I do exclude leaky fuel primer lines due to the fact that fuel primer is not connected to 2 frontmost cylinders on my engine.
I do kindly ask 14-19-2, 14-19-3 owners and any other users of O-470 to photo their cooling baffles around frontmost cylinders of their engine.
Or give me any working idea I'll believe or able to check.
