Question = Which is better: Single Scroll Turbo or Twin Scroll Turbo???

[Blackraven]

Any automotive engineers here? I ask this because I've read up on this and I've found that there are two different power train versions available:

Subaru Impreza WRX STI - Wikipedia, the free encyclopedia

Specs
Japanese Version
Turbo
twin-scroll turbo
Displacement
1997 cc
Power
308 PS (304 hp/227 kW)
RPM
6,400
Torque
422 N·m (311 lb·ft)
RPM
4,400

versus

Specs
Non-Japanese
Turbo
single-scroll turbo
Displacement
2500 cc
Power
309 PS (305 hp/227 kW)
RPM
6,000
Torque
393 N·m (290 lb·ft)
RPM
4,000

So what do you think is better then? What is worse? In what aspects is it better/worse? Thanks

[dickrazor]

A twin-scroll turbo reduces turbo lag, slightly improves fuel economy, and according to the facts there it gives more torques and horsepowers (improved efficiency). The last item(s) on my list is the most important, followed closely by the first.

[Blackraven]

Originally Posted by deathrazor

A twin-scroll turbo reduces turbo lag, slightly improves fuel economy, and according to the facts there it gives more torques and horsepowers (improved efficiency). The last item(s) on my list is the most important, followed closely by the first.

You have a point there........though apparently I'm also thinking of something else. I'm having the notion that a probable reason as to why it is not being sold outside Japan is because it might call for uber high-quality fuel.

You know something like unleaded fuel with an octane rating north of 100. I've noticed this as well in cars like the Legacy where the JDM spec have rev limit that is up to 9k (while overseas versions only up to 8k RPM).

Any other opinions or ideas?

[dickrazor]

Emissions is the biggest part, followed by octane ratings of fuels.

[Blackraven]

Originally Posted by deathrazor

Emissions is the biggest part, followed by octane ratings of fuels.

Yup you do have a point there. I think this is the same case when we compared power output ratings between the JDM of the Accord versus the one sold in Europe as well as the one sold Stateside (as an Acura TSX) and there are differences in performance.......even if they all come from the same factory in Tochigi, Japan.

Surprisingly, the engine also tends to have a higher rev limit though I'm thinking that @ same RPM, there shouldn't be much of a difference I think. Just probably the ECU mapping as well as the engine management controls have to slightly differ but I think everything else is the same.

Two cents

[dickrazor]

Now if we had global emissions guidelines... but that would never happen.