Re: P&H Injector Interface

[garwillis@msn.com (Garfield Willis)]

On Tue, 23 May 2000 23:12:38 -0700, "Walter Sherwin" <wsherwin@home.com>
wrote:

>Just wanted to confirm the scenario of 4  (2 groups of 2) TBI injectors,
>which would be slighlty different than couplings of the TPI flavour P&H's.

How so slightly different, Walt? We've seen repeated examples of where a
driver capable of driving 2 P&H TPIs also could drive 1 TBI. Are you
saying that's not quite so? I'd be interested in hearing any even slight
differences.

>You drew a distinction between TPI and TBI P&H injectors earlier, and I just
>wanted to remind you that many of us still tinker with multiple TBI type
>injectors, be it with a 4BBL Holley or a couple of Rochester TBI's.  That
>translates to 4/1 amps per injector.

Yup, understood, this case we covered previously as well; the TBI's are
4A-peak/1A-hold, and have nominal specs of (1.2ohm, 2.0mH). The TPIs or
rather just "PI"  (Port Injectors), are nominally 2A-peak/0.5A-hold
devices with a nominal spec of (2.4ohm, 4.0mH). Several of us spent the
last two days going over this to confirm what I had understood (or at
least thot I did) from prior list discussions, that the GM ECMs
alternately drive either 2 "PI" P&H drivers per pin, or 1 "TBI" P&H per
pin (or 4 SAT injectors...per pin).

>Who says that 4 of such injectors is even the practical limit?...

Huh? Practical limit how? Do you mean in terms of what people are using
in their P&H conversions today, or the practical limit as to how many
can be driven? Everyone seems to say that at present, driving two of
those humongous TBIs is about as far as anyone cares to go, in terms of
a single injector driver load. We have to pick some reasonable
expectations on how many will be driven in common conversion
applications, don't you agree? What then would you say was a "practical
limit" such a P&H interface should be designed to meet?

Currently, the problem is two-fold: we have guys with ECMs batch-firing
SATs who want to convert to P&Hs of the normal PI variety. I haven't
heard anyone say they wanted to drive twice that capacity. (Heh, if they
did, wull they would just need TWO interface modules :). We also have
guys with sequential ECMs whose drivers are only capable of driving
individual SAT injectors, and they also want to upgrade to P&Hs. Lastly,
we have people who want to use their ECMs to drive twice the number of
P&H TBI injectors than those ECMs are built to drive (yours and Bruce's
Holley case I take it). This is the case where someone wants to drive 2
TBIs per driver, or (2 groups of 2) TBI injectors, as you describe it
above. ALL of these common cases we have already covered with the Batch
interface design scenario we've been discussing.

>The "VIC" is simply a 2-8 signal (1-4 plus 1-4) batch firing device with BPW
>compensation on each of its outputs.  Very simple and effective, based upon
>its intended market.............

It sounds like you're more familiar with it than I. Is it then NOT able
to fire 8 individual & separate P&H injectors to support SEFI? Perhaps
then it falls into the category you mentioned earlier, of being a
"specialty box that attempts to cater to too small a market segment"?
And dang, it's already $400+. Imagine that! It appears from your
description above, that sans the "PW compensation" fluff, it's
equivalent to the proposal on the table at present, to provide a module
for Batch firing, that can fire two banks of 2, 3, or 4 P&H injectors.
Why then do you consider that Accel device "simple and effective, based
upon it's intended market"? where as you thot a box that did everything
BUT the PW-compensation (the proposal on the table) was too narrow? I
don't understand, unless you DO think the Accel device is too
specialized OR you think the PW-fiddling is an essential feature. I'm
kinda puzzled.

Gar


----------------------------------------------------------------------------
To unsubscribe from gmecm, send "unsubscribe gmecm" (without the quotes)
in the body of a message (not the subject) to majordomo@lists.diy-efi.org