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Old 03-27-2009, 10:09 PM   #1
gumby647
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Join Date: Sep 2000
Chapter/Region: South East
Location: Orlando, Fl
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2001 2.5RS-T
BRP

Default Unequal length twin scroll header

I have to build a new up pipe for my car since the current one I have is not Scottish and therefore crap. Since my car was originally N/A all the pipes are custom and none of the off the shelf stuff will work. I used to have a Borla header on the car but found the stock exhaust manifold to offer much lower boost threshold with no noticeable loss in top end power. I attribute this to the pipes being shorter and smaller diameter on the stock manifold.

My thinking was that since I'm redoing the up pipe I don't have to make it mount to the stock exhaust manifold. On the N/A cars the pipes route around the back of the motor rather than the front as on the turbo cars. Also the pipe from the right bank of cylinders makes a very tight radius 180 degree turn to mate with the pipe from the left bank at the collector. I was thinking of changing the exhaust housing on the turbo and making a twin scroll setup. When I got under the car and tried to start laying things out it seems it will be very difficult/impossible to make a proper equal length twin scroll header without making the same tight radius 180 deg bend found on the stock manifold.

My current plan is to make an unequal length header since it will be much easier, use less bends and the internal volume will be less, thus offering faster spool, the ultimate goal of running a twin scroll set up in first place. The problem is I don't have any experience with twin scroll turbo stuff. I don't know how important it is for the pipes to be equal length. I'd hate to waste the time, money and effort to build something that not only doesn't work but is worse than what I have now. I was hoping some of you guys on here might have some input.
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Old 03-28-2009, 12:25 AM   #2
BigRigger
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Default

You MUST have equal length headers and uppipe to run a Twinscroll turbo, no way around it.

First decide your power goals and how much money your willing to spend. Find the twinscroll turbo that suits your needs.

Once that is done and if you are keen on custom fab everything, I would get a set of JDM twinscroll headers and custom fab a uppipe for the turbo you choose. Keep in mind TMIC or FMIC for fitment as well as turbo flange type.

Heres a thread I started about twinscroll EWG setups.

http://forums.nasioc.com/forums/show...ght=twinscroll

In the end twinscroll setups cost alot of money.
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Old 03-28-2009, 06:50 AM   #3
gumby647
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Must seems too strong. The car won't stop running. Maybe I won't gain the maximum benefit but I would expect some. Same as with your wastegate thread, one will work but two will work better.

I don't really know how the size of my turbo plays into this. I've already made my decision on that and twin scroll exhaust housing for my existing turbo are readily available.

As stated this earlier this was originally an N/A car so the JDM twin scroll header will not fit without changing a lot of crap on the car.
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Old 03-28-2009, 10:35 AM   #4
FuJi K
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There's NOT a lot to change. All you change is the crossmember. That's just about as much WORK as doing your exhaust. AND the time you are USING to make your exhaust, you can already have taken the crossmember off and swap it with a WRX/EJ22T one. Steering rack&pinion swaps right over. Newer STi crossmembers are a bit different because of how the steering rack&pinion bolts on.

Don't make it hard on yourself. You are NOT limited to your setup in parts. There is NOT a lot of space behind there for all uppipes, EWG, and 3" down pipe. Everything will be a tight squeeze. Also think about servicing and getting the your nuts/bolt or V-bands. Gonna be a pain to get them off with so many pipes in one area.
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Old 03-28-2009, 11:09 AM   #5
seanathanq83
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now with one more gear

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yes it has to be equal length twin scroll, i have the jdm set up and like it very much, but i got a pretty good deal
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Old 03-28-2009, 11:11 AM   #6
jigga
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IIRC, I think FAT created a twin scroll setup that wasn't equal length a while back.. Some digging might find the particular thread..
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Old 03-28-2009, 12:02 PM   #7
seanathanq83
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now with one more gear

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it would not be very effiecient, you have to much mix of exhaust pules i, i mean i guess if you had two 2cylinders that go to gether the same length, then the orther two cylinders the same, but you could not have 4 differant sized pipes would defeat the point of twinscroll
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