You might remember me from my previous engine problem thread: http://www.vansairforce.com/community/showthread.php?t=153150
Have a O-360 with Rotec TBI. With the flow straightener, was able to fly with all winter/spring. However once summer rolled around have been having problems. It would run up fine at the hangar, but after taxiing out to the run up area (about 1/2 mile away) it wouldn't run at full power. Lower power settings work fine. Taxi back to the hangar no problem. Back at hangar, no full throttle available. Anything over about 2100 RPM and it just quits.
At first, I suspect it is something related to the TBI mixture problem I was having before. I never was quite happy with the way that I had to advance the throttle and mixture together, didn't feel safe for a go around.
Based on this previous thread: http://www.vansairforce.com/community/showpost.php?p=910868&postcount=68
Take off the TBI, drill out five holes at the full throttle end to #79 (they were already bigger than #80). Put it back on, spend a morning resetting the idle mixture setting. As I'm doing it alone this means lots of short runs with the cowling off. Oil temps get high (but in the green - around 190F) but everything else is fine. Really like how it runs with the bigger holes, the same mixture setting will run the engine from idle to full. Everything running great.
So, put the cowling on the now hot engine, do a preflight and go to fly. No full throttle available. Fuel pressure looks fine (5 psi). Start thinking about vapor lock with that hot engine. It ran fine when uncowled so the TBI was in full air blast, but now cowled up runs poorly. Mess with the mixture trying to get it to run. It just keeps getting worse. Eventually can't get it to run over 1500 RPM or so. After shutdown fuel pressure goes high (up to 15 or so).
Try again another morning, when it should be cooler, and the enigne has cooled down. Not quite as early as I had planned, ATIS as 84F. This time, run up in the run up area just fine. Actually take off. About the time I hit pattern altitude the RPMS come down just a little. Once around the pattern and land. Taxi back to the hangar and no full throttle available. Oil temp about 170F.
Ran an air blast tube from the reat of the baffle to the TBI. Tried test runups this evening. Outside air temperature was 90F per the ATIS. Trying to make vapor lock happen do a long low thottle setting runs with occasional full throttle (can't run full for long as CHTs get high). I don't have the forest of sensors that the glass panel guys run, so using oil temperature as my guess for under cowl temps. Runs great up to 140f. At 140F get a little stutter if I advance the trottle quickly, but fine if I run slow. At 180F oil temperature the problem is back. Max RPM available 2100. At 190F max it will run is 1900.
Highest in-flight oil temp I've seen so far is only 160, but don't consider this fix enough.
So, my question. Does this sound like vapor lock? I want to make sure I've got the right diagnosis before I do anything else.
Have a O-360 with Rotec TBI. With the flow straightener, was able to fly with all winter/spring. However once summer rolled around have been having problems. It would run up fine at the hangar, but after taxiing out to the run up area (about 1/2 mile away) it wouldn't run at full power. Lower power settings work fine. Taxi back to the hangar no problem. Back at hangar, no full throttle available. Anything over about 2100 RPM and it just quits.
At first, I suspect it is something related to the TBI mixture problem I was having before. I never was quite happy with the way that I had to advance the throttle and mixture together, didn't feel safe for a go around.
Based on this previous thread: http://www.vansairforce.com/community/showpost.php?p=910868&postcount=68
Take off the TBI, drill out five holes at the full throttle end to #79 (they were already bigger than #80). Put it back on, spend a morning resetting the idle mixture setting. As I'm doing it alone this means lots of short runs with the cowling off. Oil temps get high (but in the green - around 190F) but everything else is fine. Really like how it runs with the bigger holes, the same mixture setting will run the engine from idle to full. Everything running great.
So, put the cowling on the now hot engine, do a preflight and go to fly. No full throttle available. Fuel pressure looks fine (5 psi). Start thinking about vapor lock with that hot engine. It ran fine when uncowled so the TBI was in full air blast, but now cowled up runs poorly. Mess with the mixture trying to get it to run. It just keeps getting worse. Eventually can't get it to run over 1500 RPM or so. After shutdown fuel pressure goes high (up to 15 or so).
Try again another morning, when it should be cooler, and the enigne has cooled down. Not quite as early as I had planned, ATIS as 84F. This time, run up in the run up area just fine. Actually take off. About the time I hit pattern altitude the RPMS come down just a little. Once around the pattern and land. Taxi back to the hangar and no full throttle available. Oil temp about 170F.
Ran an air blast tube from the reat of the baffle to the TBI. Tried test runups this evening. Outside air temperature was 90F per the ATIS. Trying to make vapor lock happen do a long low thottle setting runs with occasional full throttle (can't run full for long as CHTs get high). I don't have the forest of sensors that the glass panel guys run, so using oil temperature as my guess for under cowl temps. Runs great up to 140f. At 140F get a little stutter if I advance the trottle quickly, but fine if I run slow. At 180F oil temperature the problem is back. Max RPM available 2100. At 190F max it will run is 1900.
Highest in-flight oil temp I've seen so far is only 160, but don't consider this fix enough.
So, my question. Does this sound like vapor lock? I want to make sure I've got the right diagnosis before I do anything else.