Paulyy

from my understanding these are becoming more popular day by day in the jap world.
I do understand that it's not a popular choice here because a lot of custom work is required.

running a divided housing, you get 2 options..

a) a single turbo X-over (same as stock) with a quick spool valve
b) a twin pipe X-over (with 2 wastegates) with out a quick spool valve.

Which one will have better spool and which would have better top end.

If both would cost you $0, which one would you fit? and why?

I'm only posting this here because when i googled it, not to much info came up and a lot of it was just crap.

Much appreciated,

- Pauly.

Crackership

I have no idea, but I'm very curious - Subscribed

blown 944

having done both to a small degree I would go with the quick spool valve and a large hotside.

The reason is that using a twins scroll pipe setup would require a lot of R&D to use the proper size pipes. It has been my experience that too large of pipes will allow the gasses to expand prior to reaching the t-housing and will create a bottleneck that limits flow.

Using a QSV, you can use a large hotside that could eventually be setup to be a 1:1 PR for top end and yet still retain low end by closing off one side.

I would have went this route, however, with the larger engine I don't see a need for either. I now have plenty of power from right off idle even with a large t4 hotside. And after I build my 94mm stroker this winter I will probably be looking to go even larger on the hotside.

my .02

thingo

I have a twin scroll set up, it could be a little better, but in general it works great. I consider the QSV is a very primitive device that might make a huge housing a little driveable, but it is hardly an ideal solution.
But it depends what turbine housings you want to use, there is not a lot of choice out there.

Paulyy

Hmm interesting..

Is there any advantages if you use a divided X-over? if it was made to spec?

thingo

Even on an open housing a divided crossover will perform better, but if you are going to all that trouble...

Thom

I suppose you have been thinking about the forthcoming V-band twin-scroll turbine housings from Garrett.

If I were in your shoes I would instead swap your turbine housing with a 0.62 A/R to increase mid range, or make an aftermarket intake coupled with a more agressive camshaft so that the turbo could breathe better up top.

Paulyy

Really? i had no idea that divided crossover would work better then a single crossover on a undivided housing.

Indeed i have. They look quite interesting.

I love my top end. IMO looking at my air flow curve (MAF +ve) i get maximum power at ~6200 rpm and having redline at 6500 rpm (which is limited by my standard bottom end) a cam would be out of the picture as it would push the power-band to the right.

i was thinking of just getting a .62 TiAL housing and swap it but i'm worried that i'll loose my top end.
I doubt i will really.

Because i've got a stock-ish head (port matched & slightly larger ports) i don't really see any gains with a custom made intake manifold.

Main reason i was looking at the divided housings is that im contemplating in a quicker spool but same top end or better.

Zeff

I'm on my cell so I dunno if the vid will post correctly but there are some big single supras that run the quick spool and show an increase of useable powerband on the left side of the curve.

Thom

I'm sure you love your top end... but really, I don't think both can be reasonably achieved on a 2.5 without increasing VE, which would require head and intake work.
You might lose a little by swapping the turbine housing, but it will be more cost effective and satisfying to get a better mid range for a road car.

Paulyy

interesting, nice find! thanks.

that's why i was thinking twin scroll + QSV and gain low end.

MY midrange isn't to bad. i don't really sit under 2500 rpm and after that i've got 5-10 psi untill 3000rpm.

Then again i just wanted to know the difference between divided crossover and undivided + QSV...
as how much would you gain with a divided crossover then undivided

thingo

I was talking to guy from Garret about those v-band housings the other day, he said they would be stainless steel like the tial housings, due for release at Sema this year. Useful by the sound of it.

Paulyy

That sounds quite good. I wonder if there will be a size difference from the cast twin scroll to the v-band one

333pg333

Would still love to try one of those new BW turbos.

Paulyy

Shed some info in the BW turbos you're talking about? Link?