Throttle Plate Control

Georg Siotis Georg.Siotis at
Mon May 15 14:07:02 GMT 1995

>> > 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:
>> In the Bosch Automotive Electronics Handbook they talk about rev 
>> limiting by chopping spark, but they use a hysteresis of 80RPM ie
>> spark disabled at 7580, and reenabled when revs drop to 7500.  This 
>> way you won't skip too many sparks so you won't get a huge backfire.
>I'm surprised that with an EFI system that people wouldn't consider 
>cutting fuel rather than spark.  Of course hysteresis as mentioned above 
>would be a must.  I would guess with too little or no hysteresis, that a 
>really lean condidtion may occur as the computer would kind of half 
>heartedly feed fuel right around the rev limit.

The most probable thing to get as a result is to increase the temperature in 
the combustion chamber. The fuel actualy acts as a coolant.

>Has anyone out there played with cutting fuel rather than spark?  If no 
>one uses this method, why not?

I think it is better to ignite later, than cutting off the fuel, in that way 
the engine is not able to raise its r.p.m, while getting sufficient cooling 
from the  incoming petrol

/Georg Siotis/

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