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Van's Air Force
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Fuel pressure, Vapor lock?
- Thread starter Redbud
- Start date
Dad's RV-10
Well Known Member
You'll likely have to upload your movie file to Youtube and then post the link.
Pilot135pd
Well Known Member
Pilot135pd
Well Known Member
Is that kind of banging noise halfway through the video, wind? The times I've had vapor lock on the ground due to heat it sounded like a race car, like this until it cleared out and got good cool fuel to the engine
https://www.facebook.com/reel/368993005055285
https://www.facebook.com/reel/368993005055285
Vapor Lock
Yes. My 9A (IO320, CS prop, dual Pmag electronic ignition, Dynon Skyview engine instrumentation) had this problem for the first 3 years. I tried everything to cool the fuel firewall-forward - fuel pump shroud with a blast tube, reflective kevlar fuel line sleeves, routing fuel lines away from exhaust - and had no luck. Fuel flow still cycled up and down, making lean of peak impossible and causing the engine to hesitate or stop in flight above 12,000 feet msl. Then, I looked up vapor pressure of 100LL and found that some components have a vapor pressure very close to ambient atmospheric pressure at 15,000 feet - where the 9A loves to cruise. Added to that is the fuel system architecture that requires the fuel to be pulled up (negative pressure in the fuel line) about 12" to the mechanical fuel pump.
So, what finally fixed it was installing a 6 psi facet pump, from the Van's catalog, just downstream of the high pressure electric fuel pump to boost the fuel up to the mechanical fuel pump. After installing the facet pump, I climbed up to 17,700 feet, wide open throttle and lean of peak, and loitered there for a half hour. The fuel pressure was rock solid at 29 psi and the fuel flow was steady. I've flown it for 7 years since and have never had another vapor lock problem.
This may not be the only solution but it worked for my 9A build.
Yes. My 9A (IO320, CS prop, dual Pmag electronic ignition, Dynon Skyview engine instrumentation) had this problem for the first 3 years. I tried everything to cool the fuel firewall-forward - fuel pump shroud with a blast tube, reflective kevlar fuel line sleeves, routing fuel lines away from exhaust - and had no luck. Fuel flow still cycled up and down, making lean of peak impossible and causing the engine to hesitate or stop in flight above 12,000 feet msl. Then, I looked up vapor pressure of 100LL and found that some components have a vapor pressure very close to ambient atmospheric pressure at 15,000 feet - where the 9A loves to cruise. Added to that is the fuel system architecture that requires the fuel to be pulled up (negative pressure in the fuel line) about 12" to the mechanical fuel pump.
So, what finally fixed it was installing a 6 psi facet pump, from the Van's catalog, just downstream of the high pressure electric fuel pump to boost the fuel up to the mechanical fuel pump. After installing the facet pump, I climbed up to 17,700 feet, wide open throttle and lean of peak, and loitered there for a half hour. The fuel pressure was rock solid at 29 psi and the fuel flow was steady. I've flown it for 7 years since and have never had another vapor lock problem.
This may not be the only solution but it worked for my 9A build.
