i have a single super 40 flow right now and i was wondering if my gas mileage will go up or down after i put on a straight pipe?

 

Probably down. It needs SOME back pressure. I'd buy a DynoMax Ultra flow muffler and be done with it. They flow WAY better than a super 40 hands down.

 

flowmaster sounds good, but flows horrible. believe me, ive got two of em on my truck. lol.

 

I used to think they needed back pressure. Dyno results on a more open exhaust proved me wrong. A mustang with 3" exhaust made more torque and more HP than the aftermarket H/X pipe. I just think that straight pipes sound like ***.. Thats just my .02

 

Its not about the power, it's about burning exhaust valves.

 

It burns exhaust valves if there is no header or manifold, because it sucks in cold air.

 

The burning of Exhaust Valves and seats with a straight exhaust is a myth. As the resident A-hole states this can only happen if cold out side air can get a direct shot at the valves. The name of the game is better air flow. The less restriction there is the better the power. What is also important is the cross scavenging that happens when one exhaust pulse moves down the exhaust pipe will help to pull the exhaust gases out of the next cylinder in the exhaust stroke. This is why a true dual exhaust is not really the way to go, the X cross over being the best for power and torque.

 

Was this on the high end I assume?

 

Okay, I dont care really. Its not my motor.

 

All the way across the graph bottom to top. You do not lose any low end tq.
Look at it like this. If straight pipes burned valves then drag cars would run full exhaust.