[ Twin Scroll Turbo, oh yeah ]

[MadSideways]

This is just a fyi, perhaps sticky, for people talking about twin scroll turbo's.

This turbo setup is oem in us-spec volvo s40's, and Japanese STI/EVO's. This technology is revolutionizing the future of turbo applications.

Twin-Scroll Turbine Housing

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.

Taken from:

http://www.egarrett.com/technology/tech ... d=2&l3id=2

If somebody could develop a dual ball-bearing twin-scroll turbo setup for the sr20det, that would be essentially the perfect turbo setup, (not only would it negate bottem end lag, but it would strengthen high-rpm efficiency).

From what I am reading here, it seems as though it would only take the turbo itself, and a properly designed split & equal length turbo manifold.

[Siddhartha]

Twin scroll technology has been used by Mazda before. in the mid-80s Turbo II RX-7s came with twin scroll turbos.

Admittedly, this was a primitive setup. I can't wait to get my hands on whatever new **** garrett is cookin up!

[Eswift]

now that honeywell owns garrett, we will be seeing some nice turbos. (honeywell has paid lots of money to get their hands on VGT technology)

[Dori Dori]

You'd also need a custom manifold get the most out of a twin-scroll turbo.

But as someone else already stated, twin scroll has been around for a while...I think IHI started but I don't really know.

[Dori Dori]

Here's a picture of the JDM STi's manifold...notice the turbo flange in the middle.



Oh BTW, if you ever wondered why subaru's spool so slow, notice the length of the manifold!

[Dori Dori]

Notice the turbine section is split in two...cool huh. :-p

[Jonny 290]

<diehard ka-t fan sneaks into the forum>

that looks really sweet. i can definitely see how it works.

<runs out with his lip zipped>

[voddka]

The MR2's/ST185+ Celicas also utilized the twin-entry technology IIRC. Its far from new.

[GraySilvia]

Twin scroll isn't the future of turbocharging. Variable area turbine nozzles and air bearings and other cool s*** are. Have any of ya'll heard of the aerocharger? I still think two aerochargers on an SR would be an ideal setup.

[GTS4-R]

Here's a picture of the JDM STi's manifold...notice the turbo flange in the middle.



Oh BTW, if you ever wondered why subaru's spool so slow, notice the length of the manifold!

ACtually the turbo flange is up top to the left right where the turbo is located on a wrx or sti......remember its a boxer4 motor so there is 2 cyl to the left and 2 to the right.....thats why that setup is like that......BTW not too much of a good idea on those WRX's.....all the extra exhaust piping.....so they try to save on IC piping by putting the IC in probably the HOTTEST place possible to save piping and to add a FMIC its a nother mile and a half of IC piping.......sorry i'm just not much on wrx's.....i guess they're okay if u wanna leave em bone stock.....otherwise get a EVO8....just my 2 cents

[Movingviolation240]

divided entry turbine's are overrated IMHO, at least if you want to make big HP numbers. They are not very effecient at high boost levels (just ask Derek Greaser). I ran a turbo like that on my CA19 and it did help spool a little bit (maybe a few hundred RPM's at most) but it also took a little bit of the edge off my top end.

And that was with a properly designed HKS tubo manifold (seperated runners) If you just stick it on a stock manifold or a 'normal' aftermarket mani you will not see any of the benifits.

There's a reason you don't see more of those.... they don't work. It's technology from the 60's.

Paul

[Dori Dori]

ACtually the turbo flange is up top to the left right where the turbo is located on a wrx or sti......remember its a boxer4 motor so there is 2 cyl to the left and 2 to the right

I just typed without thinking. I used to own a WRX, so it's pretty sorry I even did that. Thanks for pointing it out though. I'll edit.