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Old 06-27-2001, 03:26 AM   #1
WRXwannbe
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Default benifits of increasing intake plenum size

Is it worth the money and effort to increase the plenum and intake runs size? On the EJ22 it's very small, I would venture a guess that the engine would love a larger itake system.
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Old 06-27-2001, 08:18 AM   #2
LUME
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Larger intake volume will increase low end torque, but your high end power may suffer (unless you add some sort of boost controller).

--Roy
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Old 06-27-2001, 08:47 AM   #3
roninscar
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Default I think you might have that backwards

It is my understanding that increasing plenum volume, presumably by increasing the diameter of the runners would have a detrimental effect on the lower end. Increasing the volume will decrease the velocity of the intake charge at lower revs, hurting power. However, having the larger capacity will help higher rpm breathing by increasing potential throughput.

This is why some high performance applications, like the SHO I used to own had 2 sets of runners, longer ones used exclusively up until 3k or so, and then a butterfly valve would open up a very short runner increasing flow considerably. If you looked at the dyno, there were actually 2 torque peaks in the graph, coolness.

Cheers,
scotto
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Old 06-27-2001, 09:23 AM   #4
ColinL
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the runners in a port injected manifold aren't the plenum!

leave the plenum alone and fabricate a secondary airbox of as large a volume as you can fit in the engine bay and under the hood. the stock torque chamber (black box, sits on top of throttle body) is the right idea but too small.
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Old 06-27-2001, 10:15 AM   #5
mhj
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not exactly an answer, but if you want to see a custom intake manifold being fabricated, take a look at this:
http://www.sdsefi.com/rv4.htm
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Old 06-27-2001, 12:42 PM   #6
RageHardIntoTheBendies
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thats cool, could have teh TB facing foward for a FMIC too, would that clear the hood?
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Old 06-27-2001, 09:33 PM   #7
WRXwannbe
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The only reason I ask is because the plenum is very small (about the thickness of two sandwhiches.

Could someone explain, why larger intake volume would hurt air flow? To me, at present state, there just seems to be not enought air, or rather a blockage of air.

hmm...
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