Timing Jump on 165/TPI System

[Mark Romans]

I don't know how to change the base fuel map in the idle area, so I may
raise the fuel pressure a bit. I think with the maf modified by removing the
screens and heat sink it may make the engine lean a small%, it makes up a
higher % of total air flow at idle, so fuel pressure should help.  What do
you think?  Any other suggestions?
Mark
-----Original Message-----
From: Bruce Plecan <nacelp at bright.net>
To: gmecm at efi332.eng.ohio-state.edu <gmecm at efi332.eng.ohio-state.edu>
Date: Sunday, January 09, 2000 6:51 PM
Subject: Re: Timing Jump on 165/TPI System


>
>It usually makes the engine surge wildly, when it applies, on modified
>engines, even mild surge on stockers.
>  The mechanics are opening IAC, and adding fuel.  If bad enough I think it
>might move the timing.
>Grumpy
>  You might just for grins try uping the BL to a higher number for the idle
>stall thing.
>
>
>| I just rechecked and 700 rpm's for both GDF files, stall1 and stall2.  I
>| wonder if that has something to do with stall saver rpm's?
>| Next question, what specifically does stall saver do?
>| Mark
>
>| From: Bruce Plecan <nacelp at bright.net>
>| Subject: Re: Timing Jump on 165/TPI System
>| >| Hey Bruce: If I disconnect my est connector, should I see the advance
>at
>| >| 2500 rpm?
>| >Yes
>| >| I am wondering if this is why I have the idle problem.  Remember how
>the
>| >| signal goes to zero advance?
>| >As I recall it did that during the stall and it was right at 400 rpm,
>which
>| >is when the ecm drops out of bypass, and it would read 0 as I understand
>| >things.
>| >The only failure I've personnally had or diagnosed with a gm module is
>hot
>| >stalling, and progressing to where the engine needs to cool before it
>would
>| >restart.
>| >BTW, is yours a large or small cap Dissy
>| >Bruce
>| >| Mark
>| >| From: John T. Martin <gmman at eskimo.com>
>| >| Subject: Re: Timing Jump on 165/TPI System
>| >| >My  $.02
>| >| >That is a normal condition, also a test for P/U coil signal strength.
>| The
>| >| >advance is triggered by the P/U coil signal amplitude, not RPM. It is
>a
>| >| back
>| >| >up as I understand it, but a good test if you suspect a weak magnet
in
>| >the
>| >| >dist. We had a run of K engines with shaft problems a while back and
>in
>| >| >bypass (est disconnected), 2500 rpm the advance was not triggered.
>Also
>| >the
>| >| >weak pick-up signal affects idle quality.
>| >| >Subject: Timing Jump on 165/TPI System
>| >| >A question:
>| >| >With timing control connector disconnected (ie. setting timing on a
>| >| >165-based TPI motor), timing should sit still, which it does for me
at
>| >low
>| >| >RPM. However, when I idle it on up to say 2000 or 2500, it seems to
>| >advance
>| >| >like 12 degrees or so, instantaneously, and hold up there until I
idle
>| it
>| >| >back down. Then it jump-returns to the previous value. This is all
>| >| >timing-light based. Any thoughts on what is being seen? There's about
>a
>| >1-3
>| >| >degree drift on idle-up, probably from timing chain stretch, but
>that's
>| >not
>| >| >huge.
>| >| >Anyways, fishing for thoughts. It's not problematic, just would like
>to
>| >| >understand what's happening and why.
>| >| >Sincerely,
>| >| >Craig
>
>