1227165 Tuning Advice

Fri Apr 23 17:48:31 GMT 1999

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??

The "Main Spark ADV vs LV8 vs RPM"  table is listed below.

RPM
400     20.0   20.0   20.0   20.0   20.0   20.0   20.0   20.0   20.0   20.0
20.0   20.0
600     22.5   20.0   20.0   20.0   20.0   20.0   20.0   20.0   20.0   20.0
20.0   22.1
800     27.1   27.1   27.1   27.1   27.1   25.3   25.0   24.3   22.1   21.1
20.7   27.8
1000   28.1   28.1   28.1   28.1   27.4   25.7   22.9   22.1   21.8   20.7
20.7   20.7
1200   29.9   29.9   29.9   29.9   27.1   22.1   19.0   18.3   17.9   17.6
17.2   27.8
1400   30.9   30.9   30.9   30.9   30.9   28.5   23.9   22.1   18.3   17.2
16.9   27.8
1600   35.9   35.9   35.5   34.5   33.8   33.0   29.9   26.0   23.9   21.1
19.3   18.3
1800   17.2   35.9   35.9   35.9   35.2   34.5   32.7   28.1   24.3   21.4
19.3   17.9
2000   17.2   35.9   35.9   35.9   35.9   34.1   32.0   28.5   23.9   20.7
19.0   17.6
2200   16.9   35.9   35.9   35.9   35.2   33.8   31.6   26.0   22.5   20.0
18.6   16.9
2400   16.2   35.9   35.9   35.9   35.9   32.7   27.8   25.0   21.8   19.0
17.2   16.2
2800   35.9   35.9   35.9   35.9   35.9   34.5   31.3   26.7   22.5   20.0
18.3   17.2
3200   16.9   35.9   35.9   35.9   34.8   33.8   32.0   27.4   22.9   20.7
19.0   17.9
3600   17.2   35.9   36.2   35.9   35.9   35.5   34.1   29.9   26.0   21.1
20.0   19.0
4000   17.9   35.9   36.2   36.2   36.2   36.2   35.2   29.9   23.9   22.5
21.8   20.7
4400   20.4   36.2   35.9   36.2   36.2   36.2   35.9   32.0   28.1   25.0
23.6   21.8
4800   21.1   36.2   35.9   36.2   35.9   36.2   36.2   34.1   30.9   25.7
24.3   22.9

LV8     32        48      64       80     96      112    128    144    160
176    192    208

>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.

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.

The BLM is 128 only at idle and at WOT. Typical part throttle data is listed
below.

RPM     LV8        Cell        BLM        INT        Comment

750        58            0           125        128        OK
975        52            1           119        136        long term rich
condition
1525      37            2           117        128        long term rich
condition
800       118           4           119        122        long term rich
condition
950       111           5           117        123        long term rich
condition
1775     41             6           111        116        short & long term
rich condition
2450     36             7           126        120        OK
1175    114            9           122        122        OK
1400    109            10         120        119        slight long & short
term rich condition
2200    167            14         123        143        short term lean
condition
2550    180            15         123        136        short term lean
condition

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??

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.

Gear = 1st
RPM = 3025
LV8 = 247
TPS = 4.55 Vdc
O2 = 0.836 V
MAT = 82° F
Coolant Temp = 176° F
MAF = 167 g/s
Injector PW = 10.4 mS
BM Cell = 15
BLM = 128
INT = 128

>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???

It is getting late so I need to sign off.

Best Regards,

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 1:39 PM
Subject: RE: 1227165 Tuning Advice

At 04:56 PM 4/22/99 +0200, you wrote:
>Thanks Dave,
>
>I looked at the diacom+ WOT data.
>
>2000 <= RPM <= 5500
>
>1st Gear: minimum retard = 5.8° , maximum retard = 9.7°
>2nd Gear: minimum retard = 4.8° , maximum retard = 10.2°
>3rd Gear: minimum retard = 7.2° , maximum retard = 12.5°
>
>I think the EPROM tables should be modified. What is your opinion??
>

Hi Bruce,
Yep... I'd pull some timing back out of the tables...  Look at the run at
each RPM point the table has and pull probably 2 degrees less than max
retard out of it...  Also, you may want to add a bit of fuel in PE (WOT)
and see if the detonation goes away or reduces substantially... could be
running lean.
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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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