twin scoll manifold wastegate question!

[M1L3S]

So ive been looking into twin scroll manis.

I know they obviously need 2 wastegates for the 2 separate chambers. The question I have is ive seen a few with a single waste gate attached to the piping before the collection chamber (sorry I dont know the technical term :/ )

What I was wondering, does this basically stop it from being a true twinscroll?

Or does having one waste gate not matter as long as the exhaust moving into the t3 flange is divided?

[M1L3S]

Mr peepers twin scroll is the one im talking about.

link to his mani. (Yes I know its homemade)


https://www.google.com/search?q=mr+p...iw=360&bih=615

[dsmolition]

looks like there is a runner collecting the half's of the collector in the back. I could be wrong. They should connect at the wg.

[goodhart]

To be done right it should really have 2. I know swifty ran twin scroll with 1 and it worked okay, but it still creeped.

[asshanson]

Boost creep may be from only having a single small wastegate not being able to bleed off enough exhaust gas, but I thought the main benefit of having the twin scroll is so that the exhaust pulses match up in each chamber for better spool. If you combine them with a single wastegate, some of the exhaust makes its way into the other chamber, which reduces the spool up benefits of twin scroll. At least that is my take on the issue.

[turbotalon1g]

As long as it's divided all the way to the base of the wg it will perform 90% as good as 2.

Its what I plan on doing if I switch away from a mitsu housing.

[Shane@DBPerformance]

Here is a comparison while on the dyno a couple minutes apart with true twin scroll versus single external wastegate killing the twin scroll effect.

http://dbptuning.com/dyno/graph_dyno...type=hptqboost

[turbotalon1g]

Wasn't that an evo with a single external gate?
Details?

[asshanson]

Wow, 1000rpm better spool. Would not have expected the difference to be that much. Very cool.

[Shane@DBPerformance]

FP Black Evo 9, stock ported exhaust manifold. Internal and external wastegate. External used for final boost level. Internal used to retain twin scroll until 20+ psi. Once the internal opens, the exhaust merges for a few inches to the external. The laggier run is with the internal wastegate arm unhooked and the flapper open to the external the whole time. With the factory Evo twin scroll and internal gate, the exhaust does not mix until the wastegate opens.

[turbotalon1g]

But thats not divided to the base of the wg is it?

That guy miles posted above has had perfect results by keeping both chambers divided to the base of the wg.

[Shane@DBPerformance]

No, they merge for a few inches.