twin turbo 2276

[sidemarkers]

Looking for info on sizing a pair of t25 turbos for my variant. Who here has experience or info on a ballpark size? Target range 18 lbs boost for a street driven car 42/37 ported heads, 8.5 comp, 1 1/2 diameter turbo headers, injected, twin intercoolers, water injection. Thanks in advance!

[sidemarkers]

25 views and zero responses. I see that as a good sign, been looking forward to this for a while! Opting between t25 and t28 turbos...

[Clonebug]

While I have quite a selection of turbos in my garage I don't know what size I would use for mine let alone a 2276 if I were to mess with twin turbos.

It still would all come down to what your total hp goal is.
Do you want good low end and stupendous top end or are you just looking for good all around performance with a reasonable max hp.
Do you plan on two parallel turbos or two in series??????

Right now I'm getting pretty good results from just one turbo but if I wanted to go for 350 plus hp and good low end I would probably use a Holset H1C for the biggy and one of my IHI RHB5 turbos for the little one and put them is series.
That would give me an rpm range of 2500-8000 rpm but I would have to add cam, heads and better flowing intake.....Way to much plumbing for a daily driver.

[Chip Birks]

Get in contact with Evin Artleson on facebook. He's dabbled in the twins world for years. Actually just built a pretty sweet twin t25 or 28 setup for his ghia recently.

[sidemarkers]

It still would all come down to what your total hp goal is.
Do you want good low end and stupendous top end or are you just looking for good all around performance with a reasonable max hp.
Do you plan on two parallel turbos or two in series??????

Single turbos are great, been daily driving one for over 15 years. The header is showing fatigue and I bought the turbo used from a junkyard when I started this journey. Time to switch it up.

With the air cooled VW engines it's difficult to fabricate a practical design that's even remotely close to equal length. When I changed heads or reshimmed to change compression or flycut the heads etc I'd often have to cut and reweld the header to adjust for the engine size difference.

I came up with a design that is equal length, non bulky, and keeps the tubes from having to cross from one head to the other.

One header, one turbo and one intercooler per head blowing into a single throttlebody. Two lightweight t25 turbos should spool quickly and the two wastegates will be controlled by a single electronic boost controller.

Seems like it would be hella complicated but it's quite the opposite.

[sidemarkers]

Can't decide if these header merge pieces are more eye candy or engine jewelry.

Twins are gonna hang in style!

[panel]

Where did those come from ?

[sidemarkers]

From deep in my wallet...they aren't cheap.

[Chip Birks]

Burns?

[sidemarkers]

Not that deep, but close.

[petew]

So what you're essentially hunting for is a turbo for a restrictive-ish 1100-1200cc motor. I say restrictive, because compared to a lot of the sport bike turbo kits, even the best heads we have flow pretty poorly. That's a challenge. I'd be looking at ball-bearing turbos from 2 litre turbo diesel engines. They are literally tiny. I'd also think hard about which cylinders you will pair. It may well be that front and back pairs of cyls might spool better than banked pairs.

On a related note, look at what Subaru has done with twins in the past. It's all been sequential turbo setups. None of them were paired cylinders. Not saying it can't be done, but history is against you. However, I found this on line...

http://www.superstreetonline.com/featur ... s-winning/

Works well, but it's a 2.5L motor, so he's ahead of you in terms of capacity and head-flow. Dead stock Subaru 2.5l heads will flow 300hp. Obviously his Garrett GT28RS turboes will be too big for your motor without lots of revs and will lag too.

What you might well consider is slightly increasing your comp ratio. That's what all the modern 4cyl turbo guys are doing. That way you can run lower boost and spool faster.

P.s. but I see what you're doing and I get the short manifolds and the whole idea.

[sidemarkers]

T28 turbos are basically a hybrid of a t25 with a t3 compressor housing and wheel. For my purpose they are a bit large even if I drove a street subaru. Interesting article. Project is moving along nicely.

[seabeebuggy]

I don't think it will work as good as a correct single but go for it. I'd run 4 into 1 and back out to 2 so you get all 4 banging into them.

[sidemarkers]

I don't think it will work as good as a correct single but go for it. I'd run 4 into 1 and back out to 2 so you get all 4 banging into them.

If someone can show me an off-the-shelf properly designed "correct" single header, I'd love to see it.

[Wally]

There is nothing off-the-shelf, I agree, but you can consider a proper twin-scroll with twin wastegates and at least make it equal length per scroll, that would be as close to twins as possible and still give you better spool and power as opposed to sub-optimal twin diesel turbo's

Twins on a type 3 does seem more practicle though, so I see what your getting at.