"Tri-power TBI's

[Greg Hermann]

><SNIP>
>
>> Run the center unit injectors as the primaries, run the end
>> units as the
>> secondaries, and use the drive by wire actuator which
>> normally operates the
>> secondary throttle on the Vette to operate the end TBI unit throttles.
>> After all, none of the stock tri-powers were mechanical
>> linkage throttles
>> anyway!
>
>Yikes! Think about this one for a second... If the ECM opens the rear
>throttle bodies (i.e. the secondary ports in the ZR1), what is going to
>control acceleration? Recall, in the ZR1 engine, the secondary valve is
>downstream of the throttle body, so while you increased the overall flow
>potential through the head (while not adversely affecting velocity at lowe
>RPM), you still had the gross control of the throttle body, which is
>controlled by you :)

Yo--I agree with you won this--I have not had my hands dirty enough on any
of the drive by wire stuff which is now on the market to have a clue what
kind of safeties are used (if any??) to close the throttles (or shut off
the fuel in the case of diesels). For a tri-power TBI,  I would think a
linear actuator of some sort for opening the secondaries would be the way
to go, and it would not be too hard to devise a positive mechanical
over-ride for closing them for sure when foot lifted.  The stuff used on a
Holley 4150 G carb for the governor to close the throttles no matter what
your foot is doing comes to mind. Maybe a simpler approach would just to
put an ecu operated solenoid valve into the existing vacuum line to the
existing throttle opening diaphram----

And yeah, I do have an ulterior motive in all this talk--I have this .58
W-300 Dog (hey--so two letters fell off) with a 440 6-pack under its
bonnet----(not at all a case of all bark, no bite with this particular Dog)
:-)

Regards, Greg

If you used the ECM to open up the back TB's, hold on!
>Now, if you controlled the opening to correspond to say, a 50%-100% curve of
>the primary throttle body, while maintaining a POSITIVE shut off
>mechanism...that would be cool :) Only bad thing I can think of with this
>though, is that the secondary valve control is an on-off switch, not a
>stepper motor control (i.e. IAC valve)....but I could be wrong.
>
>>
>> Doesn't have to be a Vette computer--just something that could be
>> programmed that way and with the right sort of I/O capabilities to get
>> there.
>>
>> You could even use the "valet key" feature--lock out the end
>> units until
>> enabled.
>>
><SNIP>
>
>TTYL!
>
>Larry