Cummins Diesel Forum banner

I want to straight pipe but...

6K views 15 replies 13 participants last post by  dshupe24 
#1 ·
i want to put a 4" MBRP straight pipe on my 5.9 12v cummins but will it hurt my truck or is it better with the muffler i dont really care about noise i just dont want it to hurt my truck id prefer straight pipe but like i said i dont want it to hurt im almost at 300k too. and i get 20MPG
 
#2 ·
It won't hurt anything. You don't need a muffler either. The turbo creates enough back pressure for the engine and most aftermarket mufflers are strait threw anyways. It defiantly won't hurt your truck. If it still has the factory muffler and resonator on it then more than likely it will help it. I would also consider drilling a few 1" holes into the lower half of your air box to increase air flow to the filter.
 
#3 ·
yeah it still does everything is stock on the truck. and thanks for responding
 
#4 ·
The only thing straight pipe will hurt are your ears and the relations with your neighbors.
 
  • Like
Reactions: Chevy12Valver
#5 ·
I have my 96 straight piped with 4" and I don't think its too loud... sounds awesome going under an overpass! lol
 
#11 ·
My exhaust is stock until where the cat used to be. I took off the cat and everything back, then cut up the pipe and welded it back together into a side-dump that ends halfway between the passenger door and the wheel well on my long box, pointed to the rear at about a 45* angle. It's all 3.5" I believe (whatever stock diameter is) until the last foot which is 4". No drone, a bit louder than stock inside and no drone or anything. You hear the turbo real well, especially when against a wall or jersey barrier. Outside, at idle, the turbo makes it sound like a 747 taxiing for takeoff, and under throttle it's real loud. The rearward angle is nice for blasting Prius's at your 4 or 5 o'clock.

I drove it around for a couple weeks with the exhaust behind the cat removed, and the empty cat shell still installed dumping under the bed. Cab drone with that was horrible, at 1k and 2k you couldn't hear anything but a skull-crushing hum.

IMO, straight pipes are the way to go on a diesel.
 
#12 ·
Did you notice any performance or mileage improvements with the CAT being removed? Just curious as I removed my original CAT a few days ago and will be putting a pipe section in its place. Rest of exhaust and muffler is stock.
 
#14 ·
I went to a 5" diamond eye with resonator and it's still really bad with the drone. Choose wisely on your exhaust.
 
#16 ·
I've had strait pipes on all of my Cummins trucks, as I've gotten older though I got sick of the noise. If you have passengers in the back seat and pull a trailer at the same time they tend to go deaf. I now run a 4 inch turbo back with a strait through muffler, still sound good but not so loud while towing. As far as gains go, I never could tell a difference.
 
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top