730 PEAK AND HOLD

[peter paul fenske]

Hi Gene and all

Well I am not 100% sure.

But theory wise say if VGS is 3 volts lets say the drive signal
to the igfet is 4.3 volts through the diode or gate
the voltage allowed through the source resistor would be
1.3 volts. Assuming a .3 ohm resistor is used this would allow
a max current of 4 amps. More than this will decrease VGS which
will decrease the current which will increase VGS, which.... 
Putting a small cap in parallel with the resistor should give you
a bit of peak drive

Important I haven't tried this.

But the .3 ohm resistors are there.
Also the voltage across the .3 ohm resistor goes to one of
the A/D channels. This is so the ecm can sense a shorted injector.

So one way is to flag those apps, ecms which list a injector fault code.

However in the 730 I dissected the via between this .3 ohm resistor and
the A/D to plug trace is not connected. Instead they use the a/d channel
for ac or something. So maybe this explains why there are different
ecm numbers for essentially the same cct board.

later:peter

At 04:43 PM 7/6/98 -0400, you wrote:
>Are you saying that a 1227730 GM computer can drive four 1.5 ohm injectors in
>parallel?   if the wire you speak of is conected a certain way?    I have a FI
>setup that has 8   1.5 ohm inj.   could be fired in batches of four.... could
>that be done by 1227730?.....
>If so I can update my FI project I did on my Pontiac some 5 years ago...
>
>any other suggestions for updating the computer?   to go closed loop?  
>
>GENE
>
>