2 Questions about GM-TBI

[Brandon L. Walters]

On Wed, 27 Dec 1995 FIScot at aol.com wrote:

>     That being done, I still have two questions.  Will the stock peak-and
>     -hold injector drivers like having double the load if I parallel the

If the stock drivers are set to peak at Ip/ hold Ih, and were already
really doing that as O.E., It seems like the parallel setup causes the
same current to be divided between the to injectors. My guess is the
drivers live, but now you go back and adjust something because you have
two solenoids, but lower current in each. 

I am going to find out what the impedance of my injectors are. If the 
driver was actually using some "load-line", and you parallel them, you 
may get toast.

>     Also, the firing order.  The intake is an Offy 360.  It is similar to
>     an open plenum with a divider in the middle.  This puts cylinder #7
>     just 90 crank degrees after cylinder #5, with another 630 crank degrees
>     until cylinder #5 fires again.  Will this set-up have a big mixture
>     distribution problem? That is, will cylinder #5 receive most of the
>     fuel that is injected?

I'll buy that - because our firing order is 1,8,4,3,6,5,7,2 - maybe with
supercharging it's OK. To me it looks like each side of that manifold will
see pulses at 0,270,450,and 540 degrees (reverse for the right side). 

Seems like for a normally aspirated 350, it'd be nice to combine the
intake pulses of 1,4,6,7 on one hole - and 8,3,5,2 on the other. (Chevy
cyl. numbering). I wonder if I'm not describing the "Crossfire" setup. I
am trying to lookup a picture of one to be sure.

>     TPI has long runners.  This makes great mid-range torque.  Great for
>     gas mileage, and I imagine a great tow-motor in a truck.

I wanted to see just how accurate you could get with TBI before it quits
being any fun. I like the ruggedness of it, and the low fuel rail
pressure. 

Seems like any old car with dual SU's would do as well with dual GM 2.5
liter TBI's, and a dirt-simple ECU.

Happy New Year,
Brandon Walters