1227165 Tuning Advice

[Bruce Plecan]

----- Original Message -----
From: Bruce Wilcox (EUS) <EUSBEW at am1.ericsson.se>
To: <gmecm at efi332.eng.ohio-state.edu>
Sent: Thursday, April 22, 1999 7:36 AM
Subject: 1227165 Tuning Advice


> The application is a MAF
> 87 TPI Camaro with a moderately modified 355 CI (aluminum heads) motor.

GM heads?.

> There are two minor problems.
> 1.
> The nominal BLM is consistently below 128. Depending on the exact BLM
cell,
> the nominal value approaches 110. The integrator hovers around 128 +/- 5.
> Since the BLM is low and the integrator is OK, my guess is the fuel
pressure
> is high (44 PSI @ idle, 50+ PSI @ WOT). Is this a reasonable diagnoses??

Have you run any performance base lines?..  Fuel Pressure makes a ton of
difference at WOT..  Find out where your at with WOT AND cruise, then judge
where you need to move things.  (Also, measure PW/Duty cycle).

> 2.
> The knock sensor triggers during extended WOT test runs (hard to hear any
> audible effects). Given a WOT test run through the first three gears (RPM
> range: 2000 - 5500 RPM), the knock counts go up roughly 13 - 15 counts.
Part
> throttle "closed loop" conditions perform great (no knock & excellent
> performance). I would like to eliminate the root cause of the additional
> knock counts. Since the "closed loop" part throttle performance is
> excellent, I do not want to back off the base timing ( 10° BTDC). My guess
> is the spark table needs modification. Any comments or suggestions are
> appreciated.

Again, you need some baseline info so you know what you've got, so you know
where to go.  At this stage you don't know it it's too much timing, or too
lean.
You need to be able to make a change, and guage the results...
>
> Please note: the baseline knock-counts are from the initial start routine.

Your generating knock counts while cranking?.
Bruce
>
> Thanks,
>
> Bruce E. Wilcox
> Sr. Staff Engineer
> Ericsson Inc.
>
> Bruce.Wilcox at ericsson.com
> wilcox at rtp.ericsson.se
>
> 919-472-7054 (phone)
> 919-472-1103 (fax)
>