I was looking into getting a larger downpipe for my 95, but is it worth it with the stock turbo??? I believe the turbine exducer is only 2.25" and the downpipe on the truck is 3" OD. It doesn't seem like going to a larger downpipe with have any benefit at all. The reason I'm asking is because I'm planning on installing a electronically controlled exhaust cutout before the cat, and I want to know if I should go to a larger downpipe. The truck will have the following mods: cold air kit, 3000rpm GSK, #8 plate, then bump up the boost and tune it on the dyno

 

Naw, there's no benefit on a stock truck. Anything larger than 3.5" to 4" is going to hurt performance by slowing down your turbo spool time.

 

The truck won't be completely stock. I am going to be installing a cold air kit, 3000rpm GSK, #8 plate, then bump up the boost and tune it on the dyno. Will there be any benefit with a larger downpipe??
The diesel world is new to me. On turbo powered gasoline engines a 3inch exhaust would be more then enough when the turbine has a 2.25inch exducer. Are these diesels any different??

 

are you just going to a larger DP or a whole larger exhaust system? just the down pipe wont do you any good, but if you steped up to a complete 4" system you should recieve a drop in egt's

 

I'm going to install a exhaust cut-out before the cat so there won't be any back pressure from those items.

 

A 4" exhaust is good for up to 500 hp. A full exhaust will give you a drop in egt's. Not that you'd reach critical temps. with your mods anyway. You might benefit a little by going with a 3.5" downpipe (as far as lowering your egt's a tiny bit), but anything bigger is pointless. Might as well save your money.

BTW: with the cutout, your truck is going to be loud!

 

Why does the larger exhaust slow spool time?

Jim

 

I guess it has to do with the velocity of the exhaust gasses. The larger the diameter of the pipe, the slower the exhaust gas moves out, the more time it takes to get the turbine wheel spinning.