'7747

[Shannen Durphey]

Ken Kelly wrote:
> 
> >>Are you interested in using a 7747, or an 8746, or???
> The information for both ecms is available.  Are you planning a swap from
> one ecm
> to the other?
> 
> I'm interested in the '7747 as a retrofit to the '5550; I have an '82
> Corvette. I'm trying to get all the wiring down; it has the two A.I.R.
> valves, which concerned me.
Well in that case, you probably don't want to spend any time looking at the pinouts
for a different ecm.  


> 
> > 1. C8;PSPS - what the heck is this? (Power steering?) What does it do? How
> > does it work? (It's labelled as an input..)
> closes when power steering system is pressurized.  Consider it a load sensor
> to
> help prevent stalling.
> 
> Hmm.. could this be wired to something else that tends to load down the
> engine? I assume it just bumps up idle by X amount..? If so, where is that
> amount determined (or is it preset, not in the PROM?) Or does it just bring
> idle up to where it should be, if this switch is set?
Doesn't matter if you're using a 7747.  It's not an input to that ecm.

> 
> > 2. A2;A2OUT - listed elsewhere as "A/C Control" .. how is this wired in
> with
> > the A/C? What does it do? Are you supposed to wire your A/C switch into
> the
> > ECM, and the ECM to the compressor (so the ECM controls the compressor?)
> I'm
> > only assuming that it cuts the compressor off at higher throttle settings
> so
> > you get more power? (y/n?)
> 
> >>It's not used in all applications.  If you're installing a 7747 in a
> system with
> "self contained" a/c, it's not necessary to connect this.  Although it might
> be a
> nice touch to make a "professional" job out of it.
> 
> Okay, so I could wire it in as I described (switch to ECM, ECM controls
> compressor) and it would cut off the A/C .... at what point? Is it
> determined by load, or by throttle position? I like the sound of that, so I
> don't have to shut my A/C off if I punch it.. (I know, sounds like I'm
> lazy!) BTW, what do you mean by "self-contained A/C" ?

Doesn't matter if you're using a 7747.  It's not an output from that ecm.
Self contained?  Sorry, I was kinda tired.  I was thinking of a situation where the
a/c system was designed to operate without an ecm, like in an efi retrofit or an
early factory efi car.

Simply connecting a wire to the ecm does not necessarily cause the desired input or
output function of that pin to start working.  If the calibration data and/or code
is not written to use that pin, you won't have the desired results.  I don't
believe thes pins will do the same job in a 7747 that they do in the 8746.

There may be a drawing floating around of the pins used in that swap.  Try a
subject heading with more description to see what shows up.  There have been list
members in the past that have done that swap.

I know the hood solenoid and AIR valves were issues in the conversion.  I wonder if
the hood solenoid could be connected to the 7747 egr or canister purge valve pin
and the tables reworked.  The AIR valves could take more research.  Either convert
to older vacuum operated AIR valves, or start searching for a 7747 application
which controlled an AIR pump.  I don't know of any offhand, but I'd start with the
first year for tbi in a pickup and I'd also look at v6 applications. 
> 
> Thanks again VERY much for the reply; just these little tidbits have helped
> tremendously.

Just wait.  The 7747 will help your car tremendously.  The first thing you'll
notice is that the cold morning rich misfire will be gone.  I've got a 7747 powered
crossfire 302 in a 57 pickup, and the ecm swap was the best move I could make.

Would the real Ken Kelly please stand up?  

Shannen
> 
> Ken
> 
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