can it exit in front of the rear tires
Here in California, you can dump the exhaust out anywhere you want, as long as the emissions tester can reach the pipe with his sniffer, and that's amazing, since Ca is the strictest state around when it comes to just about ANYTHING having to do with automobiles. As pointed out previously, it's not too safe to have those gasses coming out directly under the car, but it's done. The city or state YOU live in may have laws against this, I don't know. ChucklesMost pickup trucks have exhaust pipes pointing to the side from the factory. Why, I don't know. And most SUV's do also.
The pipes cannot end under the car. they must end only at the edge of the car. If they ended under the car, ait would result in exhaust entering the passenger cabin of the car. eventually poisoning the people in the car. And if the pipe exited to the side, the exhaust will blow straight into the car stopped in the next lane at a stop signal. This will cause problems to others. Therefore we have the pipe exit to the rear, as far as possible from the people in the vehicle.
Lake pipes or side pipes on cars like Corvettes or Vipers exit in front of the rear axle. The main thing is that the exhaust be directed away (down or out), so it does not heat something up too much and minimize the chance of fumes coming into your own vehicle. For a vehicle that could be driven with a rear window open (station wagon, etc.) you would not want it directly in the rear because that can get sucked into the rear window. Apparently there is nothing that says you cannot blow smoke in your neighbor's face or trucks, buses, and school buses would all have high exhaust out the top instead of blowing diesel smoke out the side or rear into your face.
