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Making an airbox??

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Old 05-11-2010, 06:43 AM   #1
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Default Making an airbox??

I am going ITB, and i have 2x 4" cold air feeds from the air box to the TB or will be new air box.
The chokes are 8x 55mm, what size hole should i be looking at to make sure there are no restrictions? will make no more than around 550rwhp, there must be a calculation to work out airflow=horsepower???
At present it breathes through a NW 90mm TB as below.
It now has a FAST but its the same principle.

Click the image to open in full size.
416 Stroker in a TVR Cerbera, Flowed Dart 225, 65cc Chambers, Callies Rods, Custom cam 244/257, Dual extreme valve springs, Twin pipes, 5 speed TKO 600 Man, 3.08 Diff, Kinsler 55mm ITb's, 3D mappable ignition.532/502rwhp/lbsft. 2600lbs all up. 10.72/133.98mph. Max Speed 202mph 13/03/11 at Bruntingthorpe proving ground. Believed to be the Worlds fastest TVR.

Last edited by lstvr; 05-11-2010 at 06:50 AM.
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Old 05-11-2010, 08:51 AM   #2
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I can tell you one thing about the Harrop 55, it is a huge choke point.

I have it on my motor and we did not make anywhere near the power I expected. We did do some flow bench work and found some big restrictions in it. When mated to a TEA 245 shaped port it only flowed 270ish CFM. We ported it, port matched it and added some custom throttle shafts I designed and we picked up over 48cfm. The port matching picked up 22cfm, the porting added about another 14cfm and the throttle shafts added another 12cfm.

When I bought my intake used it came with a set of plenums that would not work for my car, but a spent a few weeks learning about fiberglass and modified them to fit my car. I use a 4" inlet like you want. Hope the pics give you some ideas.

Here is a link to a bunch of pics of the work I did this winter and the plenums.



I should have the motor up and running again shortly to see if we made any significant gains.

Good luck!

BTW I love the TVR's, such a cool car.
-1999 Formula WS6 -
Old -412ci LS2! 511rwhp thru cats
New-455ci RED's MID LS7! c/w 55mm Harrop, 705hp 663ft.lbs @ fw NA
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