minifold pipe
Thread Starter
|
Posting Guru
Joined: Jun 2004
Posts: 1,808
Likes: 0
From: Cincinnati Ohio
minifold pipe
I have 3.5 exhaust from under the cab to the back and I want to get 3.5 from the motor to where the 3.5 begins. Where can I get the 3.5 pipe? or should I take it off and take it to a muffler shop and get it made?
Post Fiend
Joined: Nov 2003
Posts: 21,285
Likes: 15
From: Nutter Fort, WV
You can get away with about 3" then start increasing the size.
You want to step up in stages so the exhaust can expand evenly.
Another thing is the way the drivers side dumps in the passenger side pipe.
The stock pipe is close to a 90 degree intersection.
With a little work that can be changed so it is more like a 45 degree intersection.
Better flow if the angle is less.
You want to step up in stages so the exhaust can expand evenly.
Another thing is the way the drivers side dumps in the passenger side pipe.
The stock pipe is close to a 90 degree intersection.
With a little work that can be changed so it is more like a 45 degree intersection.
Better flow if the angle is less.
Posting Guru
Joined: Aug 2006
Posts: 2,175
Likes: 0
From: Kent WA
Take a look in my gallery at the improved Y-pipe I made for my old NA truck. I made mine using the crossover pipe from an ATS turbo kit, but you could just as easily do the same thing using the two stock pipes from the manifolds and adding a couple of 90* degree elbows and maybe one 45* elbow from NAPA.
Where your major restriction is with the stock system is at the Y where the two pipes from the manifolds join. Like Dave said, with the stock setup the two 2.25" pipes meet as a T-joint and dump into one 2.5" pipe - which pretty much sucks in terms of flow.
You could easily start the 3.5" at the Y. Make a Y pipe similar to the one in my gallery with the two stock 2.25" pipes dumping into one 3.5" pipe. FWIW, I've read that they did some flow testing and determined that for an NA truck, increasing the exhaust up to 3" made significant gains, but that above 3" the gains dropped off. For turbo trucks the point where the gains started dropping off fast was 4" pipe.
Based on that, I can say from building mine, that if you re-work the Y to make it a smooth transition for both of the stock pipes into one 3.5" piece of pipe, you'll be very pleased with the results.
With a less restrictive intake and a reworked Y-pipe if you turn up your pump about 1 flat, my butt-dyno says you'll get about 10-15 ponies out of it. That is a significant improvement for an NA truck.
Where your major restriction is with the stock system is at the Y where the two pipes from the manifolds join. Like Dave said, with the stock setup the two 2.25" pipes meet as a T-joint and dump into one 2.5" pipe - which pretty much sucks in terms of flow.
You could easily start the 3.5" at the Y. Make a Y pipe similar to the one in my gallery with the two stock 2.25" pipes dumping into one 3.5" pipe. FWIW, I've read that they did some flow testing and determined that for an NA truck, increasing the exhaust up to 3" made significant gains, but that above 3" the gains dropped off. For turbo trucks the point where the gains started dropping off fast was 4" pipe.
Based on that, I can say from building mine, that if you re-work the Y to make it a smooth transition for both of the stock pipes into one 3.5" piece of pipe, you'll be very pleased with the results.
With a less restrictive intake and a reworked Y-pipe if you turn up your pump about 1 flat, my butt-dyno says you'll get about 10-15 ponies out of it. That is a significant improvement for an NA truck.
