What is the difference between single scroll and twin scroll?

Also what does the factory Subaru impreza wrx 2001 turbo come in?

thanks

The way I understand it and I guess nut shelled ;

A twin scroll design essentially splits the exhaust gasses going into the turbo in order to combat the exhaust gasses from opposing combustion strokes colliding with each other.

Essentially it reduces lag, increases flow into the turbo and produces better torque.

Only the JDM STI were factory fitted with them afaik.

using the Perth-WRX mobile app

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2005 WRX STI

Factory bugeye turbo is a TD04

using the Perth-WRX mobile app

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2005 WRX STI

i thought the turbine housing was split into 2 sections. one has a small A/R to get the turbo spinning. And the other section has a large A/R for more peak flow. Dunno if this is correct, just how i imagined it would work?

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Doing it for all the wagons out there

That sounds better.

My explanation was how it was explained to me a while ago. So probably not very accurate

using the Perth-WRX mobile app

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2005 WRX STI

never seen much difference in the large turbos, some of the sti spec C came with the twin scroll, but you need the correct headers to take advantage, plus change the sump if its an early model

Not worth the gains vs $$$ but Twinscroll sounds so much better imho

unless you can source all the parts cheap
sump, dip stick, header, turbo, dump

Stick with a vf34 and call it a day

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Chinese Mexican
[SIGPIC][/SIGPIC]

Totally agree with Rexxar, to how much better twinscroll sounds. When I first changed everything over I was a little bit apprehensive, but after the run in and first heard the car over 6K RPM, I wouldn't want it to sound like it used to again.

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Air is for pussies.

I will throw the cat amongst the pigeons. Whilst twin scroll is meant to promote early boost it is also meant to generate lower ultimate power compared to single scrolls.

Open to evidence on this.

i guess it's a trade off.. earlier torque for less peak power in the top end (?)