1227165 Tuning Advice

[Bruce & Lisa Wilcox]

Hi Bruce,

The chamber size is 58 cc. What is your guess on the required total
timing???

Best Regards,

Bruce (the other one)
-----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: Thursday, April 22, 1999 1:31 PM
Subject: Re: 1227165 Tuning Advice



> 1. The heads are Air Flow Research 190's. The overall Compression Ratio is
> 10:1.

What chamber size?.  The smaller the less total timing generally needed.

> 2. This data represents the first performance baseline.
> 3. The injector pulse widths are listed below.
>     1st Gear: 8.5 - 9.6 mS
>     2nd Gear: 7.8 - 10.0 mS
>     3rd Gear: 8.5 - 11.0 mS

Performance as in time to speed, distance to time, etc.

> 4. What methods can be used to analyze the starting mode knock counts???

Looking for something that rattles whille cranking.
If applicable set min MPH for Knock detection to maybe 2 MPH.
Should erode.
>
> 5. The engine is so loud I can not hear the WOT pre-ignition or spark
knock.
> Can the knock sensor get false triggers???

Easily happens, just overtoquing it, at installation can ruin it.

What compression ratio generates
> enough noise to create false triggers???

Not about CR, usually about other things done at the same time, like
unknowingly installing solid lifters, too much piston clearance, yada yada.
>
> Thanks and Best Regards,
>
> Bruce
>
> Subject: Re: 1227165 Tuning Advice
-- Original Message -----
> > 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?.