I think this has been discussed before but its called divided something.

I was talking to a STi guy and he was telling me about them. Is anyone using these? Any more info on these? I got some info off this site: http://www.forcedperformance.net/faq.aspx

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.

 

hmm, i am also curious, as my tII had a twin-scroll solenoid, i assume it had a twin-scroll turbo as well. It was a turd!

 

I believe it uses the firing order to direct the exhuast in alternating sequence through the turbine housing. If the firing order was 1-3-4-2, cyl. 1 and 4 would go to one side, and cyl 2 and 3 to the other. The exhuast pulses wont back up on each other. I think. Ive heard it called tangital divide too. Although I could be wrong cause Im a carpenter not a nerd.