ok, we all know they are implementing it on the JDM STi, and on the evo8...does anyone know the real advantages of this turbo as opposed to other ones? and the real important question...will we be able to bolt this into the USDM STi?
Originally developed for commercial diesel applications, turbochargers with a twin-scroll turbine housing have now been successfully adapted for use with passenger car engines (both gas and diesel). By utilizing dual openings, or volutes, into the turbocharger's turbine housing, exhaust energy is optimized which results in better engine performance at low speeds, decreased backpressure at high speeds, and significant gains in fuel economy.
Traditionally, passenger car turbochargers have had only one volute through which exhaust gases leaving the engine cylinders can enter the turbine housing (where they are used to create torque). Unfortunately, this single entry design can sometimes lead to combustion inefficiencies, since some cylinders are expelling burnt gases while others are inhaling fresh air for combustion. What happens is that the hot, dense exhaust gases from the first set of cylinders are drawn into the second set of cylinders, causing the combustion occurring in those second cyf the fuel it's consuming.
Several wastegate solutions were considered to counter this problem, with a twin-scroll design ultimately providing the best solution. A twin-scroll, or twin-entry, housing allows each set of cylinders to release its exhaust gases into a dedicated volute. That way, it doesn't interfere with the other set of cylinders, which is taking in fresh air at that same time. Of course, refinements were necessary to account for the divider between the two volutes, but thanks to the dedication of Garrett engineers, those challenges have been met.
As this technology is further developed, even smaller passenger car engines will be able to experience the benefits of the twin-scroll turbine housing design including those fueled by natural gas. And, as with all the products Garrett manufactures, twin-entry turbocharger technology will continue to be developed with an eye toward even greater efficiency and maximized performance.
Oops. Didn't see this post, but I just started a new thread asking the same thing. You would have to have equal length headers, so you would be buying STi or wait for the aftermarket to make one designed with dual inlets for a twin scroll turbo. I haven't seen a twin scroll for sale to the public by anybody, and I don't know how feasible it is to buy the turbo from Subaru. Theoretically, you should be able to get it as long as you can get a part number for it. It might cost you your right nut to do it though (which would suck after giving your left one just to get the car).