I think i'm experiencing vapor lock on e85
09-02-2009, 10:54 AM
#1
I think i'm experiencing vapor lock on e85 Before you jump on me, read the symptoms and the conditions of the issue. Vapor lock is very rare on an injected car due to the pressures in the fuel system.
Symptoms: Car missfires under light throttle between 1500 and 3000 rpms when hot.
When first started with a cold engine, car runs and drives fine, no issues under any driving conditions. As the engine heats up to 180ish degrees a missfire starts to happen under light throttle low load. It's not very bad but noticeable. If I stop the car for a few mins after it's over 180 degrees and restart it, it's difficult to start and when it does start it idles at 1.12 lamda vs 0.91. After a few mins of driving the idle lamda will return to 0.96. The car also develops major missfires and becomes very annoying to drive. If I take a drive on the highway an do a few quick 65-110 pulls the problem starts to lessen and after a few more minutes usually goes away. If I then park the car and let it sit for a few minutes, the problem comes back with a vengeance. The car does not have any issues under heavy loads (boost).
Last night after a drive I parked the car and let it sit for about 1.5 hours, hood down. It started hard, had the missfire after giving someone a ride. After coming back I opened the hood for 30 mins, then left and the problem was gone, but returned after about 2 mins of driving and didn't go away until after 10 mins of highway driving.
My fuel system is still a stock dead head with 95lb/hr injectors run by a megasquirt and dual in tank walbros. I'm thinking that the fuel is gassing out in the rails after heat soaking in a hot engine bay causing inconsistent flow. Seems unlikely, but it seems to fit the symptoms. The cooler the outside temperature the less problems I seem to have.
I don't know what the vapor pressure of e85 is compared to e10 gasoline but I suspect it's the problem. I'm trying to burn off the last of it and go back to 91 oct to see if the problem dissipates.
I suspected plug/wires at first and have changed the plugs, but not the wires yet and am reluctant to due to the behavior of the problem with heat. Current daytime temps are 100-110.
Symptoms: Car missfires under light throttle between 1500 and 3000 rpms when hot.
When first started with a cold engine, car runs and drives fine, no issues under any driving conditions. As the engine heats up to 180ish degrees a missfire starts to happen under light throttle low load. It's not very bad but noticeable. If I stop the car for a few mins after it's over 180 degrees and restart it, it's difficult to start and when it does start it idles at 1.12 lamda vs 0.91. After a few mins of driving the idle lamda will return to 0.96. The car also develops major missfires and becomes very annoying to drive. If I take a drive on the highway an do a few quick 65-110 pulls the problem starts to lessen and after a few more minutes usually goes away. If I then park the car and let it sit for a few minutes, the problem comes back with a vengeance. The car does not have any issues under heavy loads (boost).
Last night after a drive I parked the car and let it sit for about 1.5 hours, hood down. It started hard, had the missfire after giving someone a ride. After coming back I opened the hood for 30 mins, then left and the problem was gone, but returned after about 2 mins of driving and didn't go away until after 10 mins of highway driving.
My fuel system is still a stock dead head with 95lb/hr injectors run by a megasquirt and dual in tank walbros. I'm thinking that the fuel is gassing out in the rails after heat soaking in a hot engine bay causing inconsistent flow. Seems unlikely, but it seems to fit the symptoms. The cooler the outside temperature the less problems I seem to have.
I don't know what the vapor pressure of e85 is compared to e10 gasoline but I suspect it's the problem. I'm trying to burn off the last of it and go back to 91 oct to see if the problem dissipates.
I suspected plug/wires at first and have changed the plugs, but not the wires yet and am reluctant to due to the behavior of the problem with heat. Current daytime temps are 100-110.
09-02-2009, 09:41 PM
#2
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Join Date: Feb 2007
Location: Kissimmee
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What help does your car have, turbo, supercharger? Is it tuned for the E85? What is your base fuel pressure? How much boost are you running? Are you running a return on your fuel? More info? Vapor pressure is much higher than pump gas! Sounds like an old tune on new fuel! Retune to E85?!
09-03-2009, 12:06 AM
#4
Ok, filled up with 91 octane... Problem seems solved. No more miss firing. Looks like I'm boiling the fuel in the rail. At least that's the theory I'm going with at this point.
Aggravating, but solvable.
Aggravating, but solvable.
Last edited by Zombie; 09-03-2009 at 12:20 AM.
