Bubbling gas at track

The boiling point of gasoline is around 400 deg F, or 205 deg C. That BP would be for high octane (i assume you're running 93) gasoline. It seems like a hot exhaust could definately achieve such a temperature.

Also, boiling points are pressure dependent (PV = nRT, where P is pressure, V is volume, n is number of moles, R is the gas constant, and T is kelvin temperature). Your tank is pressure sealed to keep vapors from pouring out, primarily for environmental and safety reasons. If your ECU detects a pressure drop (try opening your gas cap with the car idling for a while) it will turn the CEL light on and mess with fuel settings to compensate.

If your tank is pressurized and heated it may not boil, but when you open the tank, the pressure drops and it boils in a frenzy to lower the temperature of the gas. It's kinda intuitive that this is dangerous as all hell, things could catch fire, explode, etc.

Look for threads about tracking your car and exhaust heat. I saw one a while ago about the insulation around the stock exhaust causing things to get insanely hot, and loosening screws. I think someone mentioned something about using ceramic as a heat shield around the pipes or something, but you should look into this. The op posted it as WARNING: blah blah exhaust blah...

Edit:
here it is: http://www.lotustalk.com/forums/f154/warning-track-guys-check-your-exhaust-systems-58233/

U4IA187 said:

I plan on opening up the bottom end of the car to check ut the exhaust system, make sure there arent any brackets loose or anything else noted n the warnig thread.

I aslo plan on giving plenty of time between track, cool down, and refueling.

Your inputs are greatly appreciated, maybe i should just sit back and calmly smoke a cigarette.

Click to expand...

I'm not an overly cautious person, but I can't help thinking that your situation is a lot like a can of creamed corn in a camp fire. Sure, your tank is pressurized, but who knows what pressure you're generating by heating up your gas above its STP (std. temp and pressure) boiling point. I have no idea how the pressure system works and if it can vent, if it'll blow ur gas cap off, if itl kill ur fuel pump, if it'll compromise your fuel tank, etc... Either way, I don't think your gas should ever boil, GET IT FIXED. anic:

At a bare minimum, monitor your fuel temperature, even if you have to use a dipstick thermometer every 10 minutes. Also, if your exhaust is getting that hot, you risk a fire elsewhere.

I'm not even suggesting that you spend a load of money getting people to check it out, but, for the love of god and all that is holy: find a way to monitor the temperature of your fuel and the temperature in the engine bay around the heat shields.

Without knowing your temperatures, all the tightening of bolts and fiberglass wrapping or removing is like trying to catch a bat in a cave without a headlamp.

I wonder if you can get a thermometer long enough to poke in there if it happens again... It would remove all doubt. It seems like it would be very possible to boil fuel, especially when you first open the cap. The B.P. of gas varies widely in range depending on octane and composition, but could be as low as 200 F. Given that other post about exhaust temperatures, and the fact that a few elises have lit up, I would check on it if it was me. I'm not saying there aren't other possibilities, but it seems like it's worth checking with a thermometer. I have not looked to see how shielded everything is in the back of the car, I've only had my front clam off, not the back.

Btw: did you actually SEE it bubbling out of the tank, big time? Was the smell of gas completely overpowering? Or did you just hear a hissing noise, like someone else suggested. I'd think if it was past the STP boiling point, you'd hear a pop or loud hiss the moment you opened the cap, and then smell lots of gas fumes and hear lots of bubbling.