Injector Firing

Kevin Crain kevin at warpten.com
Mon Dec 29 20:02:37 GMT 1997


This reminds me of something I saw at a local hot rod meet, a guy had a GM
Cross Fire Injection ECM running a TPI setup.  He said he used an '82
Corvette CFI system, but didn't like the dual throttle body system so he
swapped the TBIs and intake for TPI.  According to him the only
modifications were fuel supply and return lines, and splicing the
TBIs' injector wiring to the TPI injector harness.  I had originally
dismissed this idea, since he couldn't provide any technical basis for the
compatibility between the CFI logic and Tuned Port Injection.  However,
this thread makes it sound like the guy might have had a point.

Anyone ever heard of this?  I have an '82 Z28 with CFI and would like a
low-resistance path to TPI. 

Any input greatly appreciated!

-Kevin Crain
-Knoxville, TN

On Tue, 23 Dec 1997, Shannen Durphey wrote:

> 
> 
> bruce plecan wrote:
> 
> > On a GM ECM, like what is used on the 87-89 camaros (TPI) they have the
> > injectors wired into two groups of four.  Would that mean they alternate
> > firing each group every 90 degrees?,  180 degrees?  360?.
> >
> > On the TBI's they fire in synch with the cylinders only at low fuel demand
> > periods, right?.
> >
> > Do they do the same thing with the batch fired TPI's?.
> >
> > Thanks in advance
> >   Bruce     nacelp at bright.net                    Cone shaped hat is really
> > gettin
> >
> > comfortable, and the locals aren't
> >                                                                  starring
> > as much
> 
>   In synchronous mode, both TBI and batch fire tpi alternate banks, triggering
> from the reference pulses.  So in crankshaft degrees, that would be 720/8=90
> deg.  WOT, accel or decel, and cold enrichment operation are asynchronous, so
> I'm told.
> 
> GM says I'm on a need to know basis, but they won't tell me what I need to
> know.
> 




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