low end torque

[trdragons44]

I don't know if any body might know the answer to this question but here goes, i have 1997 expy and i want to do a cat back exhaust but i don't want to lose the off-the-line low end. I tow alot and i like have having the low end torque but if i can't keep the low-end-torque i might not do a cat back.

 

[green03]

Which cat back are you planning on going with? I put on a magnaflow muffler with the stock pipe and then put on a 3 inch pipe later and the low end and part throttle was better with just the better muffler on the stock 2.75" pipe.

Matt R

 

[trdragons44]

i was going to leave the stock pipe before the muffler and put a flowmaster 942543. and then 2.5 pipe back to where the factory pipe exits.

 

[green03]

the flowmaster will give you good low end because it will give you just a bit of backpressure.

What size is your stock pipe? 2.5 is smaller than stock isn't it?

 

[trdragons44]

i measured the pipe around the outside and then used the circmference to diameter formula then subtracted for the thickness of the pipe and got 2.5 inches. If your's is bigger than ford must have changed the pipe size after 97 because mine is 2.5

 

[green03]

I was referring to the outer diameter of the pipe. 2.5 inch pipe is the outside dimensions. My 03 was 2.75 OD on the tailpipe.

Matt R

 

[wrangler45337]

What size is the cat-back piping? Shorty headers will help with the low end torque. If you open things up to make the engine breath better and flow better you can still gain some low end torque as well as more mid to upper horsepower, but if are after torque, shorties and a good aftermarket muffler is the way to go. Some exhaust restriction is good for your torque numbers but will kill high RPM horsepower numbers. If you are towing, I would do some shorty headers and a Flowmaster for the backpressure. :shootout:

 

[ELVATO]

I've heard that shorties don't do much, and aren't an improvement over stock.

As far as I've read, long tube>shorties.