Twin Scroll?

[dsm95gsxer]

What is the difference between twin scroll turbos vs. non-twin scroll turbos?

 

[L2RTSiAWD]

It has to do with a divided exhaust housing.

If I had a picture of the turbo on an EVO VIII it would better explain.

 

[dsm95gsxer]

Is that evo specific or is it more common then that?

 

[L2RTSiAWD]

I don't beleive it's evo specific, I supposse you could build one but It might be a mitsu specific housing.

 

[dsm95gsxer]

Why would you want to run a twin scroll?

 

[psychlow]

What are twin scroll or divided inlet turbine housings? What are the benefits of using a twin scroll turbo?
A "twin scroll" or "divided inlet" means that there are two separate volutes within the turbine housing. The main reason for doing this is to isolate the pulses coming from each exhaust port and maintain more of the pulse energy from each cylinder all the way down to the turbine wheel. There are no differences between the turbine wheels used in open or single inlet turbines compared to those used in twin or divided inlet turbines.
Generally speaking, a divided inlet turbine setup will respond faster and produce boost quicker than single or open design of the same nozzle area, of course this is dependent upon proper execution. The simple fact that a divided housing is used does not guarantee these results.

While it does not cause any problems or harm to run a divided inlet turbine housing on a manifold that is an "open" design, none of the benefits of the twin inlet will be seen.

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Twin scroll turbine housing. For the exhaust manifold, picture a mirror image of this flange. For 4G63s, cylinders 1 & 2 are on one side, and 3 & 4 on the other. This allows for simultaneous exhaust pulses on each volute.

Basically, the way I understand it is that the idea is to keep about the same size opening all the way to the turbine wheel. Doing this maintains velocity, pressure and heat, all of which are desirable for faster spooling.

In contrast, regular turbos like ours go from the small exhaust port to the small runner to the LARGE opening on the exhaust manifold outlet and turbine inlet. At high RPMs/WOT this works well as the exhaust pulses are coming quickly enough to fill up the space, but at lower throttle/RPM, the exhaust pulses lose velocity, pressure and heat.

Note that I may be completely off my rocker, but again, that's how I understand it.

 

[Tallen]

These are very common, and no its not just an evo thing.

 

[dsm95gsxer]

thanks guys I always wondered

 

[psychlow]

No worries.