Twin Scroll Turbo

[Lukefraizer]

So I have been looking around a bit and it seems like twin scroll is the way everything is going now. So who all is going with these and how is it working? Any good numbers or can you not really see the difference.

 

[4thStroke]

There are twin scrolls of all shapes and sizes, what exactly are you after? There's the twin scroll Mitsu housing (not for GVR4/DSM), T3 housing, and T4 housing.

 

[Lukefraizer]

Well I'm not really looking to buy one. I'm very happy with my evo3 turbo. It seems like they are popping up everywhere though. Just wanted some more info on them. I have been doing some research and they are very smart matching the pulses and everything but how much better are they and how do they actually help?

 

[4thStroke]

They help the turbo spool up considerably, but they don't breathe as well up top. It really depends on where you want the power. The twin scroll can be nice to help a larger turbo spool up since our motors are relatively small and still have the ability to keep pulling in the higher RPM range.

 

[cheekychimp]

Are there any small frame T3 or T4 twin scroll turbos say in the range of a 16G-20G?

 

[RedTwo]

Switzer/Borg Warner (I think they're the same) does a T3 and T4 twinscroll S200 and I think the 'Disco Potato' GT28somethingsomething can be had in twinscroll T3.

 

[WaRrIoRs16]

Quoting 4thStroke:
They help the turbo spool up considerably, but they don't breathe as well up top. It really depends on where you want the power. The twin scroll can be nice to help a larger turbo spool up since our motors are relatively small and still have the ability to keep pulling in the higher RPM range.



My understanding was the TS offered the best of both worlds, faster spool without sacrificing anything up top.

 

[Lukefraizer]

I had read that they didn't loose any uptop. I would like to hear from some people running them to see how much of a difference it really makes though. Supposed to do and actually do can be two completely separate things!

 

[GVR-4]

From a design standpoint, I don't see how they flow less that a single volute.

 

[littleb]

If anything, I think a twin scroll would flow better up top. There's less backpressure at higher RPM's so the air would flow through easier which would help it breathe better.

 

[4thStroke]

It kinda depends on how you look t it. If you have a .82 A/R housing and throw a divider in there, you effectively turn that .82 A/R housing smaller, thus moving the powerband.

If you have an open .82 and a divided .82, then you will pick up bottom end, while comparable up top.

There are other variables. Something to think about, the highest HP Evo with an FP black had the twin scroll divider cut out.

 

[littleb]

But when you're comparing divided to undivided exhaust housings you usually go up on size for the fact that you have better spool. And when you to that, you get better top end along with it. So I can see where you're coming from but most people won't go with the same a/r for a divided and undivided housing.

 

[belize1334]

Toyota made a twin-scroll ct-26 for the 2nd generation Celica Alltrac. Flows about like a t25 but with better spool.

 

[RedTwo]

I might have to keep these on the clipboard as they're quite handy...

Extract from a Mazda technical paper on single vs twin scroll turbos, comparing two otherwise identical turbos:

 

[Lukefraizer]

red! that was the most helpful piece of information I have seen thus far!!!! thanks much for the information!

 

[littleb]

Thanks for that. I was never completely sure if the decreased back pressure would actually help the turbo breathe any better with results