Throttle Plate Control

Sven-Erik Tiberg set at
Mon May 15 09:26:48 GMT 1995

Larry Harris writes;

>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.  Sending unburnt fuel out
>into the exaust system seems quite nasty.  Lots of drag racers use this
>technique with a two stage rev limiter where they sit on the line
>limiting the revs on their "launch" RPM.  Some cars will sit on the line
>backfiring through the exaust terribly.  This can only lead to thoughts
>of "There's got to be a better way".
>Has anyone out there played with cutting fuel rather than spark?  If no
>one uses this method, why not?

We did play with fuel cutoff device for a BMW 3.0SI 10y ago.
Our aim was to increase the enginebreaking by cutting of the fuel as
the trottle was close and rew. abowe 1500. We did also use the unit to cut
of the fuel at abowe 7000+ as a rewlimiter.

Used only a few devices as electronic rew.counter curcuit, 2 comparators, a
Hall-element for the trothle position and a powerstage to cut the powerline
to the injectors.

We had to install switch to disengage the enginebreak at winther as it
would break to hard on snow, specially in turns. Else it was great.

--- sven-erik --

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