Spark Tuning

[Mark Romans]

Hi Dave:   I have a friend that has an 89 TPI engine is his 79 Camaro, he
also has installed a 95 6spd and a Vortech.  He has recently been having
ignition problems.  I have done a series of chips for him to address a
number of driveability problems.  He called me and just pulled off the MSD
boost timing controller.  His ign problems are gone and he can't believe how
well the car is running.  He has run it with diacom and recorded some runs
and says detonation is minimal,  ie: the ecm is pulling some timing out, but
not much and not near what the max is.  I have it set to pull out as much as
15 degrees and it is not pulling out more the 6-8.  The weather has been a
bit cooler than normal for Northern CA so it may still detonate a bit more
if it gets over 100 out, so we'll have to wait and see.

The way we tuned the car was to make sure it had plenty of fuel,  02 above
900 mv and load the engine in 4th down to about 600 rpm and go to wot and
record the run to redline with the diacom.  This puts the engine under max
load.  If the ecm is not pulling out more than a few degrees of timing,
perfect.  I have tried for zero knock retard and the car slows down.  Also
in lower gears since the rpm's climb faster the engine likes a few more
degrees of timing.

Are you running aluminum or iron heads?  Is this an automatic or manual
trans?

Mark
-----Original Message-----
From: Dave Zug <dzug at delanet.com>
To: gmecm at efi332.eng.ohio-state.edu <gmecm at efi332.eng.ohio-state.edu>
Date: Friday, July 30, 1999 12:40 PM
Subject: Spark Tuning


Don't think I've seen this subject and thought I'd get a head start
on it...

Background:  1989 5.7l TPI, 165 ECM, ARAP (vette 350) BIN,
Supercharger, alum 200cc intake runner heads, stock compression,
13.50 quarter mile on 5 psi boost w/ stock chip.

What I plan on doing is subtracting 8 or 9 degrees from the stock
main spark table.. going for a few runs, checking the data... then
bumping all the load / rpm values that did NOT knock up a degree, and
all the ones that DID knock down a degree (lower --> toward 0 btdc).

Now WOT spark advance I see is available to me as well. that's not
what I'm doing right now. and I know I gotta get the fueling right
to be able to start the sparking stuff, correct?

If I can get a large range represented in the 1 run of recorded data,
then I may be able to feed it into a (this is getting old I know)
utility that will spit out a new table (just looks at rpm, lv8, knock
and decides +1 , 0 , or -1, pretty easy)

I've thrown out my guess on procedure here.. if anyone has the "real"
way please educate us! thanks.
~~~
Dave Z. www.delanet.com/~tgp