glider_rider
Active Member
I hava an IO-390EXP119 with 400h on hobbs flying on RV14. One Pmag, one magneto, airflow performance injection system. The engine runs smooth, Cyl #1 is always the first to peak, spread between the first and the last one to peak is 50 deg. In cruise the engine runs rather cool, CHTs are all 320 +- 10 deg.
I’ve recently finished an oil change and took that opportunity to boroscope the cylinders. The only surprise was the exhaust valve on cylinder #1. It was all whitish. The exhaust valves in other cylinders are nice, brownish like.
I’ve checked the contact surface of the offending valve and didn’t notice any problems, it’s smooth. Had a look inside, at the valve guide, again all looks normal.
I run the engine WOT few degrees LOP, certainly don't lean aggressively.
Why would a valve face become white? I’ve read somewhere that a white exhaust valve is caused by high combustion temperatures. But the EGTs and CHTs look normal, don’t they?
Is it possible that a valve would overheat and the CHT indicate 321 deg?
Something related to fuel distribution? Again EGTs would be different?
Is the cylinder #1 running too lean? Should I get a custom injector nozzle?
The pistons are all covered with dark residue, that indicates there was no detonation of any kind.
I’ve run out of ideas.
Please have a look at the photos and the temperature log from the last flight before oil change
I’ve recently finished an oil change and took that opportunity to boroscope the cylinders. The only surprise was the exhaust valve on cylinder #1. It was all whitish. The exhaust valves in other cylinders are nice, brownish like.
I’ve checked the contact surface of the offending valve and didn’t notice any problems, it’s smooth. Had a look inside, at the valve guide, again all looks normal.
I run the engine WOT few degrees LOP, certainly don't lean aggressively.
Why would a valve face become white? I’ve read somewhere that a white exhaust valve is caused by high combustion temperatures. But the EGTs and CHTs look normal, don’t they?
Is it possible that a valve would overheat and the CHT indicate 321 deg?
Something related to fuel distribution? Again EGTs would be different?
Is the cylinder #1 running too lean? Should I get a custom injector nozzle?
The pistons are all covered with dark residue, that indicates there was no detonation of any kind.
I’ve run out of ideas.
Please have a look at the photos and the temperature log from the last flight before oil change
