747 Timing Connector and misc questions

[Bruce Plecan]

-----Original Message-----
From: Jason Weir <jweir at worldnet.att.net>
Subject: Re: 747 Timing Connector and misc questions


>Bruce Plecan wrote:
>> No, no, no
>> The ESC is for retarding the timing due to knock.   It sends a signal
>> to the ecm when knock is detected.  The ecm then retards the timing.
>> the ESC is the thin black box about 2"x2".  All it does is listen to
>> the knock sensor.  When it hears the right noise it tells the ecm hey
>> we got knock.  Trouble with this system is that certain sounds sound
>> like knock, and can falsely trigger it.
>>
>> With the timing connector disconnected (tan/blk wire) the ecm has
>> no control over the timing.  The only timing is what is inherit with
>> the actual design of the electronics.
>
>inherit in what electronics, ECM, ESC? That doesn't make sense to me, If
>you look at the graphs I posted  

The reluctor+pickup generate an A/C signal,  As you spin it faster it 
makes more voltage, earlirer, so the timing advances.
  The ESC just listens for a noise/sound/vibration period.  It sends a
signal to the ecm for retarding the timing only..
>
>http://home.att.net/~jweir/graph.html
>
>the curves follow each other really close. if what you say is true that
>with the bypass disconnected the ECM had no control over the timing
>curve then why do they follow each other so closely? coincidence?

More coincidence then anything.  
>
>> When you rev a ecm timing controlled car in neutral (gm ie 747) the
>> timing curve you see with a timing light has nothing to do with what
>> you have in gear, or when driving the car.  The timing curves you
>> have posted have notthing to do when the car is in gear, or when
>> a vss is present.
>
>I have VSS disabled, so that doesn't play a part in this equation, in
>the timing table the timing curve is based on RPM?

Did you turn the malfunction flag off?.  Or are you running around with 
a SES light on?.

 I understand that
>there is a WOT spark add, is there also a TPS transition spark add as
>well, and maybe a MAP spark add (vacuum advance)?

There is a hot spark bias adder, cold spark bias adder, then there is
a WOT/PE sparker adder, then the MAP/RPM spark table, those are
for openers, and there may be more on the 747.
>
>thanks for giving us ignorant folks a helping hand,

I don't mean to sound like I'm talking down to anyone if that is what is
meant in that last comment.  I'm just trying to explain things.

If you look in the archives there are a bunch of timing tables, and
descriptions of things.  Ain't no one ignorant around here.  

 Jason Weir

Cheers
Bruce