Safe boost

[Mike Loeks <neanderthal@ardvark.com>]

I was just thinking about how to get >1.5bar boost while still  maintaining
the safety cutoff circuit. Why couldn't one construct a circuit that has the
zener diode clamp but connect the anode to the output of an open collector
comparator instead of ground.  The comparator would have a user adjustable
reference on the inverting pin, and transducer output on the non-inverting
pin.  The way the circuit would work is that while the boost pressure is in
the safe range, the zener clamp would be in effect.  When boost reached
dangerous levels, the comparator would let the output float high, which
would remove the zener clamp and the ECU would shut off the fuel pump.  Has
anyone tried this?  Is this theory valid?  If this is the way to go, I could
design and construct a circuit board that does this. On cars with a knock
sensor, is seems like the zener clamp is the way to go instead of the divider.
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               Michael Loeks
               '86 5kcstq - Red w/ Fuchs/D60A2 wheels 1.8 bar boost
               '86 5kcstq - Grey w/ stock wheels/Comp T/A HR4 1.8 bar boost
               '84 Ford F350 dually flatbed(NOW we're talking utility)
               Warren, Oregon


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