Spark Tuning

[Dave Zug]

Hi Mark thanks for the info ant time...

The car has ALUM heads.. admittedly the intake runners in the heads 
are far too large for the stock TPI setup and I've lost some of my 
monster torque I used to have. (200cc intake riunners on the heads, 
2.02 intake, 1.60 exh) the car is an automatic w. 2.73 or 2.77 or 
whatever  (the really bad gears). the factory correct cal is AUJL. 
the differences are mainly the TCC stuff. I thought the supercharger 
would make up for the TPI setup a bit and give me a decent setup but 
it looks like I'll be going for more boost and an intercooler and 
intake runners  and probably headers to compensate.

Now 4th gear at 600 rpm.. in an automatic may be tough, I wonder if 
I can unhook the TV cable and lock the tcc manually or something to 
get close.

with the stock vette cal ARAP I get 1 knock count every 1-2 shift so 
I see I have a ways to go before the engine is unhappy.  what 
generally can I expect from the alum verses iron heads in the 
way of advance toleration for a given octane?


> From:          "Mark Romans" <romans at pacbell.net>
> To:            <gmecm at efi332.eng.ohio-state.edu>
> Subject:       Re: Spark Tuning
> Date:          Sat, 31 Jul 1999 15:00:06 -0700
> Reply-to:      gmecm at efi332.eng.ohio-state.edu

> 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
> 
> 
> 
> 
~~~
Dave Z. www.delanet.com/~tgp