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View Full Version : Strange Spark Retard - Need Help!


mirage
April 18th, 2011, 01:46 PM
The attached log shows an anomoly that I can't seem to sort out. The issue is with the spark advance starting at frame 62. The timing goes from about 13 degrees to 7 degrees and then back again. This causes the car to buck in the middle of the RPM range. It typically happens in 3rd and 4th gear. I've followed the spark advance modifiers, but can't quite come up with the calculation that results in the final spark advance. Does anyone know the exact formula for the final spark advance on an E38 ECM? This just started happening since it has warmed up here in Houston (~88 degrees) so I'm thinking IAT modifier?


10455
swingtan
April 18th, 2011, 01:58 PM
Any chance you have "Spark Smoothing" turned on? {B0301}, try turning that off.
mirage
April 18th, 2011, 02:26 PM
B0301 - Spark Smoothing Enable = No
JezzaB
April 18th, 2011, 04:19 PM
If an area of your VE table is very high it can raise the APCYL_DMA G/Cyl (which your spark table is scaled with) up very high and shift the commanded spark to another area of the spark table. Or if the IFR have been played around with to tune it.
mirage
April 18th, 2011, 11:59 PM
If an area of your VE table is very high it can raise the APCYL_DMA G/Cyl (which your spark table is scaled with) up very high and shift the commanded spark to another area of the spark table. Or if the IFR have been played around with to tune it.

I haven't touched the IFR since I changed the injectors. Everything was working fine until the outside temperature changed. VE is high because this is a supercharged application, but the problem is occuring outside of boost (top of stock table) at 1.32 g/cyl. How is actual spark advance calculated? Anyone know?
mirage
April 24th, 2011, 05:43 AM
Any other ideas anyone?
gmh308
April 25th, 2011, 02:38 AM
You might try re-scaling the g/cyl axis if it is going off the table with the blower?
mirage
April 25th, 2011, 03:33 AM
You might try re-scaling the g/cyl axis if it is going off the table with the blower?

I think I might have resolved this based on scaling the VE too far as a previous user stated, but I'm maxing out at 1.32 g/cyl how do you scale it for the blower? is it {B5155}?
gmh308
April 25th, 2011, 12:21 PM
I think I might have resolved this based on scaling the VE too far as a previous user stated, but I'm maxing out at 1.32 g/cyl how do you scale it for the blower? is it {B5155}?

B5101 - Spark Air Flow Axis... :)
mirage
April 25th, 2011, 01:56 PM
:rockon:- B5100 and it looks like it worked. Thanks I really appreciate the help!