efi intakes

[robert dingli]

Frank writes,

> 
> robert dingli sez:
> > Jeff, to maximise the responiveness of the complete system, you would be better
> > off placing the throttle bodies as close to the inlet ports as possible.  If
> > possible, a separate butterfly for each runner would be best. The dynamics of 
> > the inlet system are significantly faster than the reponse time of the MAF 
> > sensor during quick throttle changes and thus there would be little gain in 
> > placing it further downstream.  Ideally, the plenumn would have as small
> > a volume as possible without restricting the gas flow, if response was all that
> > you were worried about.  A MAP or TPS based speed/density system would respond
> > as fast as you desire.
> 
> OK, I had always thought this too, but why don't we see this in practice,
> especially on the Sports Prototypes (GTP) or F1 cars?  True, we see individual
> butterflies, but I have never seen multiple MAF sensors placed near the ports.
> And the plenum's always seem rather huge to me.  Any thoughts?
> 
> -frank
> -- 

I should have explained this a little better.  To maximise response (as
opposed to flow), one should aim to minimise the volume of the intake
between the throttle plate(s) and the intake ports.  In OEM efi system
where there is a throttle-plenum-intake port intake, this means using
as small a plenum as possible.  In high performance applications where
there is an air box-intake runners-individual throttle-intake ports
intake, the volume of the air box (or plenum) is less significant.
I have rarely come across racing applications which use MAF sensors.
Most are throttle position based speed density system while turbo
applications generally use MAP sensors.


Robert
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             Robert Dingli           r.dingli at ee.mu.oz.au

Power and Control Systems                 Thermodynamics Research Lab
Electrical Engineering                    Mechanical Engineering
   (+613) 9344 7966                          (+613) 9344 6728
  University of Melbourne, Parkville, 3052, Victoria, AUSTRALIA
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