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914World.com _ 914World Garage _ What's the consensus about individual throttle bodies?

Posted by: daveyboybadion Aug 25 2009, 10:10 AM

I am building a 2056 with aftermarket itb's and ecu and a crank fired ignition. I'm getting ready to order a cam from Jake Raby and wondered if anyone has any hard info on which set up produces the most torque: Injector bungs mounted closer to the valves in the manifolds, or farther away with the injectors integral to the throttle body? thanks...daveyboy

Posted by: underthetire Aug 25 2009, 10:34 AM

Must be a reason all the OEM's went away from throttle body injection and went to multi-port as close to the valves as possible.

Posted by: zymurgist Aug 25 2009, 12:09 PM

Here's what Porsche did with MFI... one throttle body per cylinder...

IPB Image

Posted by: gothspeed Aug 25 2009, 12:20 PM

Here is the ultra high RPM method ......

http://www.youtube.com/watch?v=oFm0m6sbOi8&feature=related

Posted by: Jake Raby Aug 25 2009, 07:30 PM

On an engine so mild you won't see any benefits of one over the other location wise..
I have tested them low in the manifold, in the TB and high atop the velocity stack with results that were nil.

Install them where they are easiest to service and keep the fuel coolest...

Posted by: tomeric914 Aug 25 2009, 09:36 PM

What a coincidence, Cupomeat and I were discussing this earlier tonight. Jake is right, you won't notice a difference on a mild motor. But with something more aggressive, individual TBs close to the valve should allow for a faster throttle response. My beef with individual TBs is the additional linkage and synchronization of both. Much easier to have a single TB into 4 runners with injectors at the heads, IMHO.

Posted by: CliffBraun Aug 26 2009, 12:46 AM

Another reason OEM's do it is because it helps with cold start, you get less fuel stuck on the walls of the intake tract and the valve gets hot first so the fuel vaporizes better.

Edit: There's actually a whole video about wall wetting compensation, I can't find it at the moment online, but I have it here and I could host it if anyone is interested and can't find it.