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kyepan

ITBS with plenum over it... why?

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kyepan

Have a friend with a BMW 2002, its in having throttle bodies fitted, and both his mechanic and the rolling road are recommending fitting some kind of plenum. 

He's running a fairly wild schrick cam, more compression, and what looks like quite short trumpets..

 

They're saying -  you'll get colder air, more low end torque, and it's because of the cam. 

 

 

 

I thought:

ITBS idle better with lairy cams because the pulses don't interfere with other cylinders, like they would with a plenum

Top end you have less restriction?

And where the torque is is more a function of the tract length than anything else, as dave walker proved with his article where he did multiple runs with different inlet lengths. 

Plenum will dial down the glorious induction hammer.

 

His rolling road date is next week, and i'm saying to him that if i wanted to move the torque around i would be experimenting with different trumpet lengths. 

There is LOADS of space in front of the trumpets, like a foot, and the trumpets look about 60mm. 

 

@Sandy?

 

cheers

Justin

 

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opticaltrigger

Hi Justin,

Just seen this was there any updates on it as yet. Very interested.....

 

All the best,

O.T.

 

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blandy

I fitted air box to mine. 

 

On dyno 60mm trumpets made 3hp more than 90mms at same lbft

 

with the airbox fitted it made a additional 2hp that with the box off and open trumpets which surprised both myself and tuner as I was prepared to loose a hp or 2 as I went for a airbox to knock some noise off as very loud on drive by so wanted to keep within trackday limits. Can still hear the itbs though just takes some of the edge off. 

 

Sure theres a lot more science to it but seemed to work ok 

Edited by blandy

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Gaz7612

Brandy, 

Who did the mapping for you with the airbox fitted?

 

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blandy

was done at Northampton Motorsport - intake is in the l/h headlight  

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