So im having an issue with my supercharged car leaning out on hot starts and missing real bad, its prevented me from getting through inspection this month so I have been going over alot of things that could be the source of the issue.
What happens is, in this hot summer heat, I can be sitting in traffic or what not, and normally the car will idle at around 13.9-14.2 AFR (which is how i have it programmed), as i sit, and the heat builds up under the hood, not really moving very fast or at all, it will slowly start to lean out...14.5..14.8...15...15.3, etc. If i punch the gas real hard, it will go back down to where it is suppose to be, in the 14's or so. I had originally thought that this was an issue with the intake air temps heating up in a stopped position after the supercharger, and the computer pulling fuel, however this is not the case, the IAT actually stays the same and the ECU does not have any programming to remove fuel based on ECT or IAT temps.
Other times I can be driving around and I will stop at a store or something for a few minutes, get back in the car, and it will be aggressively lean, 15.5 or so AFR, and have a nasty misfire.
I have replaced...
-fuel pump with a walbro 255
-fuel pressure regulator
-new maniac electric motors alternator (oem replacement, charging much better then my factory 200k one)
-upgraded ground wires from 4awg to 2awg
-heavy duty radiator and heavy duty cooling system to keep the engine cool
-new fuel filter
-reflowed solder on the main relay for dry joints being a problem
the only thing i can think of is that the gas is sucking so much heat out of the supercharger from being on top of it, that its boiling inside the rail and heatsoaking really bad, i measured 165 degrees on the outside of the fuel rail today with my tester. Im also using shell nitrogen enriched 93 octane as well, and i was wondering if that was playing a part in the boiling point being different or not. I noticed that after a hot restart and this problem is occuring that my fuel pressure will be about 3-4psi too low compared to a cold start.
I have literally gone over every logical reason why the car leans out and misses on hot starts, ive replaced a million parts, cannot figure it out, any help would be great.
I was under the assumption that gas would not boil up to 400 degrees at atmospheric but im reading now that it could be as low as 100 depending on the additives?
edit: also forgot to mention, the car is supercharged (1995 acura integra), and it runs fantastic, but it appears to be heatsoaking the fuel rail
What happens is, in this hot summer heat, I can be sitting in traffic or what not, and normally the car will idle at around 13.9-14.2 AFR (which is how i have it programmed), as i sit, and the heat builds up under the hood, not really moving very fast or at all, it will slowly start to lean out...14.5..14.8...15...15.3, etc. If i punch the gas real hard, it will go back down to where it is suppose to be, in the 14's or so. I had originally thought that this was an issue with the intake air temps heating up in a stopped position after the supercharger, and the computer pulling fuel, however this is not the case, the IAT actually stays the same and the ECU does not have any programming to remove fuel based on ECT or IAT temps.
Other times I can be driving around and I will stop at a store or something for a few minutes, get back in the car, and it will be aggressively lean, 15.5 or so AFR, and have a nasty misfire.
I have replaced...
-fuel pump with a walbro 255
-fuel pressure regulator
-new maniac electric motors alternator (oem replacement, charging much better then my factory 200k one)
-upgraded ground wires from 4awg to 2awg
-heavy duty radiator and heavy duty cooling system to keep the engine cool
-new fuel filter
-reflowed solder on the main relay for dry joints being a problem
the only thing i can think of is that the gas is sucking so much heat out of the supercharger from being on top of it, that its boiling inside the rail and heatsoaking really bad, i measured 165 degrees on the outside of the fuel rail today with my tester. Im also using shell nitrogen enriched 93 octane as well, and i was wondering if that was playing a part in the boiling point being different or not. I noticed that after a hot restart and this problem is occuring that my fuel pressure will be about 3-4psi too low compared to a cold start.
I have literally gone over every logical reason why the car leans out and misses on hot starts, ive replaced a million parts, cannot figure it out, any help would be great.
I was under the assumption that gas would not boil up to 400 degrees at atmospheric but im reading now that it could be as low as 100 depending on the additives?
edit: also forgot to mention, the car is supercharged (1995 acura integra), and it runs fantastic, but it appears to be heatsoaking the fuel rail
Last edited: