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Old 07-04-2004, 12:16 AM   #1
railguy
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Default Twinscroll

After going over and checking out impreza's sti swap, I have a couple of questions about it.....first, how does it even work? I mean reaching boost so quickly....Are their any downsides? I know I could seach and find the answers but my main question is can a company make any turbo twinscroll? I mean if you twinscrolled a td-04 their would be pretty much no lag at all. And lastly what is the difference in lag between the sti stock turbo and the stock wrx turbo. Thanx for the imput.
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Old 07-04-2004, 01:49 AM   #2
ButtDyno
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Downsides: no boxer rumble.. not many turbo options.. having idiots like me drooling on your car

The STi has a lot less *percieved* lag because it's got the extra displacement...the VF39 is still a bigger turbo than the 13G...

john
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Old 07-04-2004, 03:23 AM   #3
ImprezaRSfan!
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doug-e-fresh will answer this thread soon, i can feel it .

Basicly, the exhaust pulses are working together instead of at different intervals, like a row team rowing all at once instead of out of sync. The stock twinscroll manifold is nice.

I havent felt it yet, but supposidly it has much better throttle responce and actually pulls in the top end instead of losing the torque.

I know you cant read japanese, but you can look at the pictures. Altavista translate it if u want.http://www.subaru.co.jp/impreza/wrx/.../09/index.html
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Old 07-04-2004, 11:04 AM   #4
iamptam
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twinscroll is nothing new people. My 1987 rx7 has a twin scroll turbo as well as an active twin scroll actuator, which was a bad idea. But this is not a new concept.
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Old 07-04-2004, 11:09 AM   #5
railguy
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Can you send a turbo away and they rebuild it to a twinscroll? Also, can you port and polish one?
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Old 07-04-2004, 11:45 AM   #6
iamptam
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you can polish them, it'sjust like any other turbo. t's jsut a devided exhaust housing
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Old 07-04-2004, 12:25 PM   #7
railguy
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Do you have any websites that can explain it better? I guess I need a visual...I cant read japanese david....Can buy a devided exhaust housing and install it in your own turbo? Kinda like upgrading the internals of the turbo?
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Old 07-04-2004, 12:49 PM   #8
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Also, if I got just the turbo with the headers and all the things needed for it to bolt up to the block. Could I use the utec or would I have to get a jap spec utec like ImprezaRSfan? Also, I would need upgraded injectors and fuel pump right?
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Old 07-04-2004, 01:09 PM   #9
KONKILR
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RSfan has a japan spec ECU, no UTEC.

jake
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Old 07-04-2004, 01:19 PM   #10
iamptam
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It's just the flow design, all you'd need is the exhaust manifold and the turbo exhaust housing. I doubt there is a twin scroll housing made for your turbo but you could search around.

twin scroll turbine housing uses dual side by side passages into the housing. When coupled with a pulse converter manifold that separates exhaust pulses as many crank degrees in the firing order as possible, a twin scroll or divided housing works to reduce lag, decrease exhaust manifold backpressure on the top end, reduce the potential for reversion, and increase fuel economy. The twin scroll is based off the same reasoning a tri-Y header uses: keep spent exhaust gases out of an adjacent cylinder drawing in fresh air. At high rpm on a turbo car, exhaust backpressure is usually significantly higher than atmospheric pressure, and often higher than intake manifold pressure as well. A divider between each of the two volutes allows the cylinders to expel the exhaust gases without it interfering with the fresh air for combustion. Since there are two openings, each a smaller overall volume than a single scroll design, the exhaust velocity of each pulse can be maintained. This also spins the impeller more easily because lag is a function of the scroll area. A single turbine housing opening isn't as efficient since cylinders on the exhaust stroke of the 4 stroke cycle contaminate the cylinders that are on overlap with exhaust gas. A conventional turbine housing is not as effective in using exhaust pulse energy to help spin the turbine up to speed as it does not exploit the energy contained in the pulses as well.


http://www.nissanperformancemag.com/...h/images/2.gif

again, this is nothing new. The majority of subaru "car guys" baffle me.
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Old 07-04-2004, 01:22 PM   #11
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Quote:
Originally posted by KONKILR
RSfan has a japan spec ECU, no UTEC.

jake
Yeah but if he wanted to get a utec he would have to get a jap spec utec.....
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Old 07-04-2004, 01:27 PM   #12
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iamptam, if this is nothing new then how come they didnt make all new turbos twinscroll? So, all I have to do is find a twinscroll housing that will fit my td-04? Gotcha! thanx for the info.
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Old 07-04-2004, 01:28 PM   #13
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Do you know the size of the exaust housing for a td-04? Also, what company makes the stock wrx turbos? I am clueless....mitsubishi?? Also, what is the exact number td-04-15 or td-04-18?

Last edited by railguy; 07-04-2004 at 02:01 PM.
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Old 07-04-2004, 02:49 PM   #14
iamptam
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it costs more money to make a twinscroll turbo. Car company's are run by bean counters. Bean counters limit what an engineer can do. They have to pick and choose to meet their cost goals.

Stock WRX turbos are made by Mitsubishi, they're the IHI style turbos. I said before, good luck finding a twin scroll for your turbo. You're most likely going to need to get a different turbo. To do a twin scroll system correctly you need to have a manifold specifically designed for the turbo. There is a difference between having a twin scroll exhaust housing and having a real deal twin s roll system for your car. IT costs a significant amount of money to design it perfectly.

however you still will nostice some gains even with a poorly designed system. I don't see any gain in using a twin scroll housing witout any divide in the exhaust manifold collector.
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Old 07-04-2004, 04:07 PM   #15
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gotcha......
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Old 07-05-2004, 01:30 AM   #16
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TD-0413G
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Old 07-05-2004, 08:50 AM   #17
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Ok, cool....well it looks like my quest to have the quickest spooling turbo with power will have to be the stock p&p td-04.....thanx all.....unless the rx7 twinscroll will fit and I dont even know if that tihing could fit in the car.
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Old 07-05-2004, 10:19 AM   #18
iamptam
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rx7 twin scroll housing is about twice the size of yours. you won't spool till 5.5k if you're lucky
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Old 07-05-2004, 12:44 PM   #19
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lol
well then looks like stock turbo...... will suite me fine.

Last edited by railguy; 07-05-2004 at 12:51 PM.
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