1227165 Tuning Advice

[David A. Cooley]

At 01:36 PM 4/22/99 +0200, you wrote:
>Hi,
>
>Presently, I am trying to optimize the ECM tuning. The application is a MAF
>87 TPI Camaro with a moderately modified 355 CI (aluminum heads) motor.
>
>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??
>

Is this at idle or in all blm cells?
If it's all, then dropping the FP to 37-38 psi Idle may be a good place...
110 is low, but not out of range for the ECM.

>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. 

A "tickle" to the knock sensor with no audible knock means you are running
the max for your fuel/engine combo...  What you really need to look at is
knock retard degrees and see what it says.  Knock counts on my 95 lesabre
start at 0 when the key is turned on, but the engaging of the starter to
the ring gear causes 10-15 knock counts as you crank...  If Knock retard is
less than 2 degrees at WOT, your timing is just fine.
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           David Cooley N5XMT           Internet: N5XMT at bellsouth.net
     Packet: N5XMT at KQ4LO.#INT.NC.USA.NA   T.A.P.R. Member #7068
   Sponges grow in the ocean... Wonder how deep it would be if they didn't?!
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