3.5 downpipe

S

sy1765

New member
for what turbo?
the stocker would do best w/ a 2.5" mandrel bent down pipe. it would spool faster with a 3" but would make less power. i believe that we have a 2.25" dp from the factory.
rule of thumb is to match dp diameter to the exhaust outlet diameter.
 
M

Methuselah

New member
sy1765 said:
for what turbo?
the stocker would do best w/ a 2.5" mandrel bent down pipe. it would spool faster with a 3" but would make less power. i believe that we have a 2.25" dp from the factory.
rule of thumb is to match dp diameter to the exhaust outlet diameter.
Click to expand...

Why would the stocker make less power with a larger (than 2.5") downpipe? Are you arguing that the velocity of the exhaust decreases and affects the peak rate of flow through the exhaust housing?
________
Buy extreme q vaporizer
 
Last edited:
S

sy1765

New member
Methuselah said:
sy1765 said:
for what turbo?
the stocker would do best w/ a 2.5" mandrel bent down pipe. it would spool faster with a 3" but would make less power. i believe that we have a 2.25" dp from the factory.
rule of thumb is to match dp diameter to the exhaust outlet diameter.
Click to expand...

Why would the stocker make less power with a larger (than 2.5") downpipe? Are you arguing that the velocity of the exhaust decreases and affects the peak rate of flow through the exhaust housing?
Click to expand...
yes, the velocity would decrease and you would not make as much horsepower. a 3.5" would be way too much and you'd never get it to fit the stock bolt holes anyway.
 
ghettosled

ghettosled

SYTY SUPERSTORE
You are incorrect.

Velocity is used to spool the turbo, and the bigger the downpipe the better. You want to get rid of the exhaust as fast as possible so the shorter and bigger, the better. The only thing you want to watch out for is turbulance. You dont want to jump from 2.5" straight to 3.5". You need to transition the air similar to the way a cylinder head works.

As for Jacks question, the PTE housing limits alot of our choices. I dont think you would have seen a noticable difference, and the fit would have been a bitch. To make 3.5" work we would have had to transition right at the outlet, and you would not have been able to access the bolt holes to attach the dp to the housing. Then you have to deal with the gap b/t the frame and bellhousing. The outlet of the housing even on the Q trim was only 2.75", so stepping it up to 3" should be enough.
 
ghettosled

ghettosled

SYTY SUPERSTORE
Its been done with custom headers and KB headers. A t4 housing with a V band flange gives you a lot more options. However i think your setup should work quite well. Atleast alot better then your old setup.
 
ghettosled

ghettosled

SYTY SUPERSTORE
its hard to say.. when they are running, they dont go to the track. And when they went back to dyno they changed other things. Jerry and his sons truck both use 3" downpipes..
 
tyndago

tyndago

New member
There are NO downpipe options for the stock turbo.

Unless you are weird like me and get one custom made....


Problem is there is no real cost effective solution that doesnt end up with another issue...

You open up the downpipe - get rid of the cat

Then you over boost......

Or you do the downpipe and external on the crossover - why stick with the stock turbo ?

Then you go with a Garrett and ATR makes a downpipe that is in the way of #6 . Or you get one of Mikes from AR....
 
nightdiver

nightdiver

Active member
I ordered a cone from 75mm to 90mm about 8 inches long
Ill make it smooth like Mike said,after all he knows better..........
The first cone i did was 3 inches long and it smells turbulance
 
canadian

canadian

sy in progress
For the stock turbo you can get one made up, or if you can find a good deal on the KB downpipe, you can cut, trim, and reweld it so that it will work with the stock turbo. That's what I've done. The wedling isn't pretty, but it fits fine.
 
tyndago

tyndago

New member
canadian said:
For the stock turbo you can get one made up, or if you can find a good deal on the KB downpipe, you can cut, trim, and reweld it so that it will work with the stock turbo. That's what I've done. The wedling isn't pretty, but it fits fine.
Click to expand...


How big is the Kenne Bell downpipe ? I have the Kenne Bell headers - I think its 2.5 maybe....Maybe 2.25... its not that big....I wouldnt go though the hassle of making that work....
 
canadian

canadian

sy in progress
for the stock turbo, i wasn't going to spend nearly $500 for the ATR setup, so choices for a better built downpipe were limited. for less than $200 i have a mandrel bent downpipe that now fits on the truck. if you can find a better deal than that i'm all over it! since i'm such a cheap bastard, this is best i could come up with on a limited budget. i'm sure you could piece together a system from exhaust parts, but that was more trouble than i was going to go through.
 
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