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Old 06-23-2010, 11:53 PM   #1
Scooby Specialist
Member#: 136282
Join Date: Dec 2006
Chapter/Region: MAIC
Location: Gaithersburg, MD
2002 WRB WRX
2010 Infiniti G37xS

Default Uppipe Question for Exhaust Nuts/Engineers

I'm not sure if I'm completely off base or not, but I'd like to hear everyone's thoughts on this.

Here are some basic assumptions on my part so if any one of these is wrong I doubt this will work at all

1. A small diameter uppipe will decrease spool time significantly
2. The reason no one runs a small diameter uppipe is because it will limit total flow during full boost.

Could a system be designed relatively similar in nature to this, but for the uppipe?

Basically there would be the primary smaller pipe that would run around the main pipe so spool would be fast then the main uppipe would open during load.

Here's a Paint rendering LOl

Would this even be worth the trouble? How would the wastegate or valve to the bigger pipe be controlled? Could it be a purely mechanical design? What could be used to prevent backflow into the big pipe?
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Old 06-26-2010, 12:18 AM   #2
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Join Date: Nov 2003
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XP class Impreza L


This would not be worth the trouble.

You would not gain much in spool or top end due to the large discontinuity in the flow path to the turbo. You are much better off going with a well designed set of headers and uppipe.

To make your idea really work well you'd need 2 flowpaths from the head to just before the turbo. You would also need a way of having the valve(s) sealed in the pipe which would be very difficult at the temperatures that exhaust runs at next to the head. Back at the muffler the exhaust is much cooler.
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Old 07-11-2010, 03:25 AM   #3
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Location: Salt Lake City, UT

spracing is way ahead of you. havent seen it in this particular application but is what your looking for.

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