Throttle(s) before or after plenum chamber?

[Todd Knighton]

Egil Kvaleberg wrote:
> 
> What would happen if I replaced this with one large throttle before the
> plenum chamber? I am imagining that it wouldn't matter as far as max.
> power output (under WOT) is concerned, but would there be other disadvantages
> with such a layout? Theoretically slightly slower throttle response, perhaps,
> but would it be noticeable?

	Emissions will change a bit, throttle response will change a bit.  Your
idle compensator routines, if you have them, will change a bit.  Max
power should go up if you do a good job on smoothing the port areas up.

> 
> (I would imagine that changes to the fuel curve would be required, but I'm
> going to have to alter that anyway due to other changes)
> 
> Also, I am having this feeling that the inlet runners are far too short
> for such a low RPM engine. They are currently approx. 9.5 inches - to move
> the 2nd harmonic point down to a usable point for this engine would
> require runners over twice the current length. Any experience or
> referrences in this area?

	don't forget to add in the port length as well.  The book "Scientific
Design of Intake and Exhaust" goes into great depth on this subject. 
Definately a reader.

Todd Knighton
Protomotive Engineering