Thread: Let's talk exhaust housings for a bit

This is a .63ar comparison to the .78ar divided that ATP sells.

In my car I have found that the .78ar spools insane. But there may be some downsides that I can see with this housing...

Each pulse goes through its seperate scroll, cyl 1 and 4 are separated from cyl 2 and 3.

With the divided housing, each pulse goes through an area about 1/2 the size of the entire housing. Basically, each pulse goes though an area the diameter of a nickel in the volute, and even smaller just before the turbine blades. You can see this in the pics.

With the undivided housing, there is a lot more flow right into the turbine blades. So basically it looks like the .78ar would act like a smaller housing. Does this make sense?

I was just wondering... My testing has shown that on my VE motor, the intake cam isn't showing any VE gains like it should, and this is restricting power. There is no reversion from the divided setup, but I feel like there is a lot left on the table with volumetric gains on a bigger housing. So I have been "thinking" of getting the .82 housing and see what happens. Of course it is a lot of money to test, so it is a gamble.

The other option I have is using the VET cams for their response, it will make about 380-390whp on 16-17psi (just a guess). I could rev them higher with some valve springs and just run more boost to make big power gains.

Full race sr20DET. Built, cams, and 33psi of boost


comparing a 2871r .64ar to the 3071r with the .78ar. 19psi.


So, even though a lot of you guys have not experimented with all of these setups, I want to hear your ideas. A lot of your opinions are going to direct where I do my testing next. VET cams and high revs may actually be the best overall powerband, and is cheaper. But to sacrifice the money I spent in the twin scroll setup to use the open .82ar may be going backwards. There isn't many people experimenting with twin scroll setups, but I would encourage it because although I don't make the power I was hoping for, the car feels incredibly faster.

Your thoughts!

do you think that maybe having the car completely retuned with the new housing and your other mods you may see the gains you are looking for? maybe the power is there but the fuel and igintion maps need to be tweaked to make the new mods as efficent as the old mods, just a thought

as far as the twin scroll i have heard alot of good things about them,i can see having the divided flange would give the flow of air more of a direction verses a non divided flange

Are you in a position to put the .63 housing back on and re-dyno? That'll take the cams & mani out of the equation...

I still think the .82 gt housing is would be a higher flower good alternitive .....

I would say if you have the chance just test the .63 housing back and see if the power comes back just from the housing change if it does then you know if you go bigger on the open housing (.82) you know the power will increase with the housing change... I think all the TS setups works but only if you use an extraordinary bigger housing (1.02) like (JP) or a TS TO4 housing matched with a big turbine wheel (Stage V or larger) ... But on smaller wheels like the GT30 with the limited available sizes on the housings open housing will flow better to make more top end power its just my .02 cents

Twin scroll designs are best for response. For example, my friends T-28 twin scroll MR2 spools A HELLUVA lot faster than my T-25 did. Almost 300rpm faster. Big difference considering a T25 to T28 comparison.

If you're looking for more power, you should have just gone with a .82 A/R exhaust housing. Larger housing = more lag, but more power.

With your setup, I would have gone for a 40R with divided housings.

I am actually thinking of getting a GT37 turbo. They have a lot of divided setups available. Or I can just go borg warner and see how that goes.

I still have the .63 housing, but I would have to make a new dp for it. Just a bit of a pita. I am looking into getting a larger housing as we speak. I have heard of a 1.06 housing around, but it may just be a rumor. I would love to try that out though!

The .78 will make power, but it will require a lot more boost to do so.

Well the gt37 is from what I heard just a 67mm ....if you do that look at a SC6262, or SC6265, or a PTE67 Billet wheel , all above turbos will spool better then a gt37 , but then again you are talking about turbos that should be able to make over 600whp .....I think a SC6062 ( or the 60mm billet wheel and a twin scroll ) whould be where it is at , I still want one with a t3 .82 housing , the spool is supposed to be gt30ish , and power around a 35R I think it is the best of both worlds

Here are some #s and pics from another forum ......on all the newer billet wheels ...
http://forums.vwvortex.com/zerothread?id=4320080

i agree with the larger turbos the twin scroll will yeild you better response and faster spool, which is nice if you are running 30r/35r/40r giving you a slightly better rpm power band

ok, its the going through that thin area is one of the reasons it gives so much response as it picks up air speed just before hitting the turbine. So the air hit the turbine faster than an undivided set up. However it is still deeper, so in a way it can flow more air, but the surface area before the turbine is less, so that is a restriction.

To me its kind of like comparing a 3 inch full zorst with a 2 1/4 inch tip to a full 2 1/2 inch, if this makes sense.

I would love to see a flow chart for a gt30 with a .63 and a .78


However i would put the .63 back on and see if that acts the same. If it does, i would be looking elseware for a problem. Are you sure the cams are switching? How is the tune? Is it just the ve cams that have no benifit once switched, or vet ones too?