Hey guy's I have 91 D250 and want to put a larger exhaust on. I have a 4" down pipe from my old powerstroke do you know if the flange will match up to the turbo? I know I have to cut the pipe and turn it then weld it so it will work that way, I was just wondering if the flang would match up.

Thank you.

 

if the turbo is stock it only has a 3 inch exhaust outlet.

 

Thank you. Is there an adapter or something that I can get to change that to 4" ?

 

I have seen a downpipe that was fab'd 3 " flange to 4 " pipe, but i don't really see the point. It's only as good as the exhaust housing...3" You could change the housing to one with a 4 inch flange. Or just upgrade the turbo to a HX40
In other words, there won't be much of a performance upgrade unless you have a bigger exhaust housing flange. What are you trying to do? Fill out your sig so we know a little about your truck..

 

Piers diesel makes an adapter. They made my 4" downpipe too.

 

So, am I understanding this correctly? I won't see any performance gain from replacing the stock 3" exhaust with 4"? Unless I get a new 4" housing?
I need to know this because I'm fixin to have new exhaust put on my truck.Thanks

 

Where would I get a HX40 turbo and how much do they run.
I have a 91.5 single cab 2 wheel drive. I put a k$n air cleaner on and my buddy is going to turn up the pump this weekend. I want to go 4" from the turbo to a 8" miter single stack.
This is my first Dodge I have always had Powerstrokes but Im selling that and I got a good deal on the 91.5.

 

(IMO) I think you will see a little gain performance wise but not alot, your EGT's should come down a little because the exhaust is bigger and because the stock exhaust is crushed at the bends and not mandrel bent. 4inch mandrel bent should flow much better. Plus it will also sound better.

 

I didn't notice any seat of the pants HP gain with the 4" exhaust. Deeper louder sound( I LIKE THAT) I'm sure it probably flows a Little better, But nothing you'll notice driving it. Do you have a high flow air filter? Won't get air out if it's not getting more in.... Kinda have to do those together.

If you have stock 3 " exhaust, do a muffler delete, you'll see just as much difference as putting on 4 Inch exhaust.

When you upgrade your turbo would be the time to upgrade to 4 inch...IMO
I think i pretty much wasted 400 bucks on mine until i go with a bigger turbo.

 

the sound is nice...The problem is the 3 inch flange on the turbo housing
is restricting it still. You'll reduce backpressure by going up to 4" at the muffler, but doing a delete will do the same. And it will sound good too,and only cost you a couple clamps and a piece of pipe. my 2cents

 

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this is my 4" down pipe. we just cut a flat 3/8" steel plate 4" round with a 3" hole in the middle, cut the flange off the stock DP and welded it together. Between that and the rest of my 4" stright pipe i could feel a difference driving and now you can really hear the turbo