[aardvarcus]

I normally don’t try to advertise when I do something stupid, but this is important for everyone to know so I will put my pride aside to maybe help others.

Well I finished my belly pan on the back half of my car. I have had the front half on for some time. I had originally intended to do the back piece as two separate pieces before and after the muffler, but at the last minute I changed my plan and just made one piece to cover the whole area, and spaced the pan away from the muffler. Additionally the entire pan and frame is all made of aluminum so I knew the pan could withstand some heat without issue.

I drove it to work and back, but something just didn’t seem right and I didn’t see the fuel savings I was expecting show up on my gauge. I thought that my departure angle was too aggressive, and began to dream up ways to adjust it. Then, to compound my confusion, my fuel indicator on the dash started to move quicker than usual.

Well, when I got home from work the second I got out of my car I could smell gas. I had trapped too much heat from the exhaust components above the belly pan, which is also where my gas tank is. Notice I had appropriate clearances between all components and the pan was still open on the sides allowing some air flow, but just the fact that I stagnated the majority of the the warm air above the pan was enough that as I drove the heat soak slowly began to warm up everything on the underside of my car, including the fuel in the fuel tank. As the gas began to warm, it expanded and evaporated and began to leak fumes out of the fuel cap.

Getting out of my car and seeing the gas vapor stream out from my fuel cover and hearing the sound of the pressurized gas escape scared me worse than any horror movie I have ever seen. I quickly got myself and my dogs away from the car waited five minutes. When the car didn’t explode I got brave, went back outside and took a water hose and started spraying off everything I could get to with the water hose. I then wheeled the car away from everything into the yard. The gas vapor was everywhere, so using only hand tools (nothing electric- risk of sparks) I removed the back belly pan to investigate.

After removing the pan, I put my hand on the fuel tank. I don’t want to say it was hot- but it was definitely very warm. Notice this was 30 minutes later and after vigorous water hose spraying. The exhaust components were cool to the touch at this point. I wanted to get my non-contact thermometer but I knew better than to have anything electric or battery operated anywhere near the car given the amount of fumes. I filled up the car the next morning, and based on my car’s average fuel economy and the amount I had to add to fill it up, I estimate that I evaporated 0.58 gallons of gas in my two hour one hundred mile drive to and from work. This is very serious and very dangerous.

I beg anyone who has a belly pan under their entire car to please next time you drive it on a trip to take one minute and at least touch their gas tank after the trip and make sure that it isn’t getting warm.

I took the removed pan far away and uphill from the car, and used my electric saw to cut the back belly pan piece after the muffler off. This was all past where the fuel tank and muffler are. I then readjusted my rear frame and reinstalled this piece using only hand tools, since it isn’t related to the gas heating issue. Currently I have left the portion of the car belly from 60% back through 85% back exposed.

I drove the car to work in this fashion this morning. Upon arriving I touched the fuel tank and it was cold to the touch, so I can safely say that this was the problem.

Well, I would like to put part of this missing belly pan back and obviously I need to allow for airflow and heat to escape, but I already have a build thread in the aerodynamics section so I would like to keep that discussion together. I have included some before and after pictures to illustrate, the first two are the complete pan and the second two are with the offending piece removed and only the very back section re-added. Notice you can see the exhaust pipe, the gas tank, and the muffler from these photos.

Has anyone else experienced heating issues with belly pans around exhaust components? I know I have ready many threads about heating, but they were all focused about the heat affecting the belly pan (note the reason I used aluminum) not the trapped heat affecting the car.