My 99 5.4 orp has two 2.5 inch pipes(it still has the cats)with 4 inch tips. I am sure that this question has been asked a 1000 times, but I was still wondering. Did I add or lose any horsepower by doing this. Any replies would be appreciate. I'm sorry, it has no mufflers.

 

Flats man went from an after market "Y Pipe" to 2 1/2" into a muffler with dual 2 1/2" pipes coming out of it, to true-dual 2 1/2" pipes and lost 17 RWHP!!! I think the best way to go, for me anyway, is single 2 1/2" straight pipe.

-AR

 

17 HP is a LOT! I never thought we would lose that much if the truck is N/A, but I know that Flatsman's truck is N/A! Does anyone know what causes the trucks to lose HP like that going to duals? I know the backpressure thing, but I didn't think it would cause THAT much!

 

if you have "true dual" exhaust, you essentially have 2 separate 4 bangers exhaust systems. You NEED and H-pipe or preferably and X-pipe so that the scavenging effect will occur between the 2 exhaust banks.

X-pipe info

 

Then why not just add a crossover tube?? Hp isnt the only thing to look at for a 4x4. Especially if you are going to be towing or offroading. low end torque is actually a little more important. Also the way new cars and trucks are, all the parts are tuned (picked) to harmonize and work together. Therefore if you change something on one side, you should change something on the other. For instance, exhaust- intake. Just what I've learned. I hear the best bet is just changing the muffler to a high flow unit or using a Gibson or similar cat back.