Throttle Body Size

[Doug Robson]

kleenair at ix.netcom.com wrote:
> 
> Jonas Hageberg wrote:
> >
> > Nice formula, but can anyone explain to me why the throttle body
> > size is important in a plenum intake EFI system? In my opinion, it just has
> > to be big
> > enough to let the required amount of air in, since you do not need a certain
> > air speed to keep the fuel atomized, and the acoustics/tuning is maintained by
> > the tubes connecting the plenum and the intake valve.
> > The only problem I can imagine with a too big throttle is unlinear throttle
> > response.
> >
> > Can anyone explain this to me?
> >
> > Regards Jonas Hageberg
> 
> Hi,
> If the throttle body is too small, obviously you will limit maximum air
> flow.  If its too big, at lower engine speeds it becomes difficult for
> the driver to control engine output (i.e. barely openning the throttle
> results in significant air flow increase).  This is especially a problem
> if you are trying to drive a high power, low weight car in rain or snow!
> 
> One inovative solution I have seen to the low throttle angle flow problem
> is a lip incorporated into 1/2 the circumference of the new GM pick-up
> engines.  Effectively, for the first 20 degrees of throttle openning, it
> limits the air passage from 1/2 of the throttle blade.
> 
> Best Regards, Mazda
All I know form this is i took my 200 bhp isuzu 8 vale twin Cam engine
from 48mm webers to 4 50mm throttle bodies and lost 30 hp, when i put
45mm throttle bodies i ended with 204, such a small change but a huge
effect. I think Taper was very important

regards
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