361
FE Technical Forum / Re: Seems like too much gas smell from the carbs.
« on: May 03, 2020, 10:47:27 AM »I didn't try to boil race gas, but it solved the problem I was having. I eventually went to a return style fuel system on the car, and re-routed the fuel lines to keep them away from the engine as much as possible, and that solved the problem. FYI the fuel was 92 octane with 10% ethanol. Race gas would certainly boil at a much higher temperature.
New cars don't need to worry too much about the boiling point of the fuel, because with direct port injection used on new vehicles, the fuel is under pressure right up to the point where it is injected into the engine. 45+ pounds of pressure raises the boiling point significantly. The problem I was having was a heat soak issue; I would stop the car, the fuel lines would get hot as the underhood temperature went up, then when I started the engine again after about 20 seconds the hot fuel would go through the needle and seat, lose pressure from the fuel system, boil, and spit out the carb vents, flooding the engine. Took me a while to figure it out, it seemed like the engine was fuel starved, not flooded, but finally one day I duplicated the conditions while the car was sitting in the driveway, and watched it happen. The amount of fuel spitting into the carb was rather remarkable...
This sounds like a great job for a GoPro camera in the engine compartment.
I know the fuel is evaporating due to heat soak, and boiling when the engine is shut off because the fuel pressure drops...This is plain science at work and there is not much I can do about it.
I never thought about the fuel boiling so violently that it would erupt out the vent tubes.
Currently I have the floats adjusted so the fuel is just barely at the bottom of the view port threads when slightly shaking the car to check levels.
I wonder if lowering the level a bit more may help. I will know, due to fuel starvation and the engine losing power, if I get the level too low.