I'm in the final stages of picking out my fuel system for my io-540 powered bearhawk.
Due to the fuel system not really flowing more than 50GPH, and my desire to not add header tanks and such, I'm thinking I want to stay with mechanical injection. A returnless system won't ever overrun the factory fuel plumbing, while an EFI system returning 50-75GPH to the tank with the engine at idle could suck air. This combined with the dependence on electricity has me thinking that AFP is the right tool for the job.
The issue with mechanical injection of course is the limitation of 100LL due to vapor lock. Not that running 100LL is the end of the world, and it will surely see a lot of it when I'm traveling, but at my home airport there isn't any fuel, and there is a source of eth free mogas 2 miles away, and I have a 72Gal fuel transfer tank in the bed of my truck, so mogas is WAY easier to get most of the time.
I have read very post I can, and in this thread:
http://www.vansairforce.com/community/showthread.php?t=87674
N427EF talks about putting a vapor return line in and using an .020 orifice to bleed some fuel back to the tank for the purpose of cooling the mechanical pump and giving vapor a place to go.
This sounds a lot like what the continental engines do, and probably why they get STC's to run mogas. If a T'd in orifice, cooler around the mechanical pump, and a return line through a duplex valve is all that's needed to reliably run mogas, then that sounds great.
Has any one else done this? I messaged N427EF but he didn't respond.
Another question is if this would also make it more reasonable to run the FM-200A system without the purge valve given that there is a place for the vapor to go. It would be nice to not have another knob on the dash.
Any thoughts for those running injection and mogas would be welcomed!
schu
Due to the fuel system not really flowing more than 50GPH, and my desire to not add header tanks and such, I'm thinking I want to stay with mechanical injection. A returnless system won't ever overrun the factory fuel plumbing, while an EFI system returning 50-75GPH to the tank with the engine at idle could suck air. This combined with the dependence on electricity has me thinking that AFP is the right tool for the job.
The issue with mechanical injection of course is the limitation of 100LL due to vapor lock. Not that running 100LL is the end of the world, and it will surely see a lot of it when I'm traveling, but at my home airport there isn't any fuel, and there is a source of eth free mogas 2 miles away, and I have a 72Gal fuel transfer tank in the bed of my truck, so mogas is WAY easier to get most of the time.
I have read very post I can, and in this thread:
http://www.vansairforce.com/community/showthread.php?t=87674
N427EF talks about putting a vapor return line in and using an .020 orifice to bleed some fuel back to the tank for the purpose of cooling the mechanical pump and giving vapor a place to go.
This sounds a lot like what the continental engines do, and probably why they get STC's to run mogas. If a T'd in orifice, cooler around the mechanical pump, and a return line through a duplex valve is all that's needed to reliably run mogas, then that sounds great.
Has any one else done this? I messaged N427EF but he didn't respond.
Another question is if this would also make it more reasonable to run the FM-200A system without the purge valve given that there is a place for the vapor to go. It would be nice to not have another knob on the dash.
Any thoughts for those running injection and mogas would be welcomed!
schu