Throttle Body Size

[Chuck Tomlinson]

> From: John Hess <JohnH at ixc-comm.net>
> 
> Ah, carburetors do like velocity, don't they.  There are several 
> problems that you might see if the throttle body on a fuel injection 
> system gets too large.
> 
> Off throttle becomes ragged.

Why?

> Wide open throttle drops the vacuum in the plenum too far and 
> adversely effects the MAP sensor.

This doesn't make sense.  Zero plenum vacuum at WOT is pretty 
desirable, IMHO.

> Cruise becomes a real problem, as you now cruise at a barely open 
> throttle position.

I don't think this is a big deal, but as Mazda pointed out earlier,
high throttle gain (angle vs. power) can cause serious problems on
slippery roads in powerful cars.  

> Torque suffers due to no velocity at low RPM.

This doesn't make sense for a plenum-mounted throttle body.

> High RPM Horsepower is normally better.

Agreed.

Also, if the torque changes dramatically with throttle angle 
(which would be true for a huge TB), the TPS resolution may 
become too low.

Just my 2c, and a few questions...
--
Chuck Tomlinson