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Okay. The intake has 12 runners for 6 cylinders - two per. However, they only use one much of the time. The "secondary" runners are used at high RPM's, when the engine needs a ton more air flow. The "secondaries" refer to the butterflies that close off the secondary manifold runners so they don't feed the cylinders too much air when they don't need them.

The IMRC (Intake Manifold Runner Control) is the device that opens the secondary runners at the perfect instant, which is why at about 3500 RPM's, your aceleration really kicks in and the engine roars.

Does this help?
 

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It's definitely not true... I recommend this thread.
 

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ok i read that post and i'm up to speed on the secondaries and how they work. so i will feel a greater kick with an SVT UIM or will it be the same. i ask cause the SVT UIM should flow more air. so i would think more air more kick. but i'm probobly wrong! also with the dual hone will i notice a difference in rev characteristics?
 

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The SVT flows more air in the sense that it has a bigger throttle body and lets slightly more air in. You should be more concerned with getting the secondaries to open before 3500RPMS.

Mike
 

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ive just changed my imrc, so im guessing that my secondaries would be opened up by the valve (butterfly) that the imrc controlls under the throttle body what would be the result if i had it opened constantly? just wondering?
 

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Your car would idle poorly because the air flow is too great. You would also lose a lot of low-end torque, so you woulld have to do clutch dumps to get a good start.

I noticed when I replaced my stock air box with an open-element intake, I felt the secondaries opening a LOT more, due to the increased air flow. I would guess that the SVT manifold would accentuate this...
 
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