Throttle Plate Control

Craig Pugsley c.pugsley at
Fri May 12 01:55:50 GMT 1995

> >    Didn't the Corvette ZR-1 use a servo-motor to control the _secondary_ set
> >of throttle plates?  
> As I recall, the ZR-1 has dual runners going to each port.  There is a
> butterfly valve in each secondary runner which is opened by a motor at
> the PCM's command for WOT operation.  If you are using the valet key,
> the secondary butterflies are not commanded open, significantly reducing
> airflow.  This is not quite the same thing as a "secondary throttle
> plate", but perhaps it's what Lou is talking about.

I'm currently designing a rev limiter that works by cutting out the
spark when the revs exceed a certain limit. I was thinking of
progressively cutting out more sparks as the revs go over a certain
level to reduce power (eg at 7000 rpm) then all the sparks (eg
7500 rpm) IE:

% of sparks being cut out 
100 |              _____ 
    |             /
    |            /
50  |           /
    |          / 
    |         / 
0   |--------- 
    +-------------------> RPM
             ^   ^  
             |   |__ Absolute max          (No power)
             |______ Start of rev limiting (Power starts reducing) 

Can/will this scheme lead to undesirable loading of the engine
components due to 'random' firing occurring? (Ie standing waves in the
crankshaft etc). The scheme I have come up with for cutting out the
spark virtually guarantees that the sparks can only occur when they
normally would, so there would be no mis-timed sparks.

I was thinking of adding a 'valet' mode to reduce power when other
people are driving the car by reducing the rev limiting to a much lower
value.. Would it be preferable to close off the secondary intake stage
like to ZR1 system mentioned above?

Thanks for any insights,

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