Pros / Cons of twinscroll & divided flange

[Nebraska_e28]

I've been doing some light reading online & thought to look here for some additional insight. From what I understand, using a twinscroll gives a wider range of power. Particularly at low rpm. Does this remove some ability to make boost at higher rpm since it essentially moves the exhaust pulses that would be otherwise used at this higher rpm?

Teach me.

[Shadow]

It's better in every way.

[GI jonas]

What he said. I refuse to believe my holset would spool as soon as it does if i did not utilize the twin scroll feature. Top end is not compromised, not sure why you get that idea.

[Nebraska_e28]

Top end is not compromised, not sure why you get that idea.

Honestly, I know nothing when it comes to twin scroll. Just looking to learn a little something.

[Brad D.]

One of the biggest benefits is not spool, but to prevent manifold crosstalk between cylinders with adjacent valve openings. This is why on a 4 cylinder 1 and 4 and 2 and 3 are paired. Reversion causes trapped residuals in the cylinders which cause other issues with combustion stability and phasing. It can also lower the knock threshold. The increased spool is a bonus.

[DangerWillRbnsn]

One of the biggest benefits is not spool, but to prevent manifold crosstalk between cylinders with adjacent valve openings. This is why on a 4 cylinder 1 and 4 and 2 and 3 are paired. Reversion causes trapped residuals in the cylinders which cause other issues with combustion stability and phasing. It can also lower the knock threshold. The increased spool is a bonus.

Cool bit of info there, Brad. Even I did not know that...

[Good & Tight]

With a twinscroll you can run a larger turbo without the penalty of lag. My BWSX300 is a much larger turbo and spools faster than the smaller HX40 I was running.

[Nebraska_e28]

How come twinscroll aren't more popular if they are all that? Cost?

[Shadow]

Yes basically.

It's easier to make 1 big open 6 branch collector
then a nice split, and figure out how to do the wastegate.

You have to make 4 collectors for a split.
then you have to make something like this for the wg.

[Nebraska_e28]

Yes basically.

It's easier to make 1 big open 6 branch collector
then a nice split, and figure out how to do the wastegate.

You have to make 4 collectors for a split.
then you have to make something like this for the wg.

Thanks for the pic. Good info to marinate on.

[Murfinator]

Another option is to run two wastegates: one for cylinders 1-2-3 and the second for 4-5-6. Plumb the wastegates into each merge. Note the pulses remain isolated all the way to the turbine. Packaging isn't overly difficult.