Cheburator

Hi folks,

My fabricator said that he can easily make a different intake manifold for the GTS based race engine. We intend to use a design similar to Phil Threshie's single throttle body plenum. However, he needs exact dimensions for the plenum size and the length/diameter of the intake runners. Could someone point me in the right direction, where I can find more information and guidance on how to calculate the correct numbers for our application.

Thanks in advance,

Alex

Mongo

There are some people on here that have done some individual throttle body setups on their 928s on here, but have used open velocity stacks due to a change in the engine management system. They may be helpful to provide any runner lengths and diameters you are looking for. Unfortunately the factory workshop manual does not specify these specifications (DOH).

Hacker-Pschorr

If you are looking for the stock length / size they are not all equal.

mark kibort

just make them big, and have velocity stack inlets to them as they are fed from the plennum box. the key things are going to be fitting in the existing engine area, so the hood shuts. the runner length and diameter seem to be only a big concern for mid range torque. if this is going to be a race inspired design, the larger diameter is going to be fine.
having a simple aluminum box, that feeds 8 bell mouthed runners, and allows for the MAF to attach at the rear, would be something i would buy in a heart beat.

Have you seen the $7000 plennum for the PTG BMWs? They gain about 10% over the engine without it. Huge runners into a CF plenum

mk

Cheburator

The reason we got thinking about it is the write-up on the Porsche supported cup car, which was good for 330RWHP with a manifold, which had a shape very similar to Phil Threshie's single throttle body. It would still be nice to get some pointers towards a calculator though...

drnick

here is some quick and dirty theory: http://www.team-integra.net/sections...?ArticleID=466

here is one for runner length: http://www.bgsoflex.com/intakeln.html

and one for runner diameter: http://www.rbracing-rsr.com/runnertorquecalc.html

they indicate that the independant throttle bodies have a slightly different theory behind them and that taper plays a part in the calculations for these, not sure if it does for the simple runner with a bellmouth coming from a plenum. also they suggest a plenum volume of 50-60% of displacement for a 4 cylinder car.

the runner length calculator gives good numbers at about 15" i think - but i know nothing about all this!