Edelbrock TBI Conversion 101

[Dennis Bell]

Ludis,

The following information is from a partial circuit trace on the 7747/8746.
I believe it is correct but it may be incomplete.

23263 (U12) - 7  ->  U21 - 5
23263 (U12) - 8  ->  U21 - 6

U19 - 1  ->  U21 - 1,2,3,4
U20 - 1  ->  U21 - 14

23264 (U13) - 12  ->  U19 - 1
23264 (U13) - 13  ->  U12 - 8, U21 - 6

HTH,

BTW, thanks for providing us all with your great web site, very helpful.

Dennis

Ludis Langens wrote:

> Shannen Durphey wrote:
> >
> > I know that early 2.8 engines are double batch
> > fire, 2 banks of 3 injectors.  These systems alternate banks with each
> > reference pulse, front then rear.
>
> Nope, both banks fire at the same time.  The injectors are fired every
> third (on the V6) reference pulse.  The firing duration can be multiple
> reference pulses long.  The position of the motor determines which
> "third" pulse is used for firing.
>
> Take a look at the '7170 schematics on my web pages.  The '6870 uses the
> same PCB/circuit (different limp home chip and different harness
> connections though.)  From the schematics, you'll be able to see that
> both banks must fire at the same time.  You can also see how the ECM
> counts reference pulses, and how you can switch the hardware between 4,
> 6, and 8 cylinder engines.
>
> As to the dual injector TBI systems - I think even they fire both
> injectors at the same time (with each reference pulse.)  The engine
> control chip just doesn't quite have enough features to do anything
> else.  Could someone with a '7747 handy check what pins 7 & 8 of the
> 16023263 (or just 23263) chip connect to?  Also check where pins 12 & 13
> of the 16023264 chip connect.  And also, pin 1 of the two little 8 pin
> P+H controllers (probably 3640).
>
> --
> Ludis Langens                               ludis (at) cruzers (dot) com
> Mac, Fiero, & engine controller goodies:  http://www.cruzers.com/~ludis/