1227165 Tuning Advice

[Bruce & Lisa Wilcox]

Thanks Dave,

Assuming the FP change works to eliminate the WOT knock, what would I change
to center the BLM for the closed loop condition??? There are many tables
related to the fuel control!

If I run out of FP adjustment range at WOT, do I play with the "Open Loop
A/F Pct. Chg. vs. LD Value" table or the or the "Power Enrichment A/F Pct.
Change vs. RPM table" ??? My guess is the Open loop table. Is this correct??

I looked for a WOT Spark Adder table and could not find one. Does one exist
for the 1227165 ECM's??

Thanks,

Bruce
-----Original Message-----
From: David A. Cooley <n5xmt at bellsouth.net>
To: gmecm at efi332.eng.ohio-state.edu <gmecm at efi332.eng.ohio-state.edu>
Date: Thursday, April 22, 1999 8:40 PM
Subject: Re: 1227165 Tuning Advice


At 10:48 AM 4/23/99 -0700, you wrote:
>Hi Dave and Bruce,
>
>Thanks for the help.
>
>When looking at the timing table, I need to look at the points in the table
>where the RPM and LV8 locations match the conditions of the Diacom data
>acquisition. Right??
>
<SNIP>
>
>>From looking at the Diacom data and the above table, the advance in
degrees
>looks like total advance. I am running a base timing of 10° BTDC rather
than
>the factory 6° BTDC setting. The closed loop performance is great with this
>10° adjustment. So the actual total advance is 4° greater than the table
>data would suggest.
>
>Overall, the high load/ high RPM advance does not look radical.
>
>Are there any WOT spark advance parameters??? The car runs great during
part
>throttle closed loop operation. Maybe I can adjust the spark table for WOT
>and minimally effect the part throttle response.
>

Have to look at LV8 at WOT and see what it is at each RPM point... these
will be the points the ECM is using to set spark.

>I looked at the BLM during WOT and it was set to 128. I guess this means
>that there is no WOT A/F ratio compensation via the BLM.
>

Yep


>The data is very interesting. At low rpm / low load, the A/F ratio looks
>good. At low RPM/ high load, the ECM corrected a long term rich A/F
>condition. Mid RPM / low load, the system looks ok. At mid RPM / high load,
>the system looks lean. Maybe the engine is running lean! However, I am not
>sure if a fuel pressure adjustment will work. What is your opinion??

I think at WOT the engine is running lean... I'd add 3-4 PSI FP and see
what happens... Get the O2 volts above 850 and see if the knock goes away.

>
>The knock count rate is fairly consistent w.r.t. the diacom frame rate.
>Roughly 11 knock counts are detected in 88 diacom frames. The frame rate is
>roughly 0.150 mS, so the total test run is 13 seconds (gears 1, 2, & 3).
The
>parameters when the knock count starts to increment are listed below.


>>From the above spark advance table and 10° base timing, it looks like the
>total advance is 18 +4 = 22°. Is the timing really the problem or is the
>engine slightly lean???

I'd say your a little lean... Keep the O2 above 850mv and see what
happens... As you increase FP, the idle will richen, but the ECM will drop
the BLM to compensate.
===========================================================
           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?!
===========================================================