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Driveline, Engine & DME Tuning
Talk about driveline improvements, NA tuning and DME tuning your E46 BMW here. This includes diffs, intakes, exhausts, chips, software and OBD tuning.

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Old 03-03-2016, 05:25 AM   #1
jcsbanks
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Throttle/rev hang - idle speed control valve and negative throttle retard testers rqd

We find when throttle steering that a throttle lift whilst in gear doesn't reduce engine torque fast enough. Whether this is due to air, fuel or spark is to be debated and fixed.

I have only tried this at idle, but noticed that whilst the main throttle is closing fast, the idle speed control valve is remaining open as per the attached standard table, so I copied the 1408 RPM column all the way across to high RPM.

I would like to test this some more, but cannot soon as my car is away at the track. Altering this table with throttle blips at idle did reduce the MAF and engine load to zero quickly. However, RPM still dropped at 1400 RPM/second, no faster than standard. I haven't tried it when driving because my car is a track car only.

I would like to experiment with ignition retard on negative throttle as well as the above idle speed control valve table and leave fuel adjustments alone for now.

This is where I could do with some input from you guys for ideas, experience and testing. Reading MS42 functional description and MS41 info on RomRaider http://www.romraider.com/forum/viewt...t=deceleration I have been trying to look at what tables I would need to alter to get more ignition retard on partial and gradual accelerator pedal lifts as well as fast lifts. What I am struggling with is working out the gradient limitations as the tables don't quite match between MS41, 42, 43 and disassembling these complex routines would take a lot of time.

So from the pops and bangs people, without influencing fuelling, which tables control the gradient limitation as I want a similar time of ignition retard before fuel is cut off, but I want it to be deeper and faster to reduce engine torque faster. Are there any others you know of apart from those shown that influence gradient of ignition retard?
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Last edited by jcsbanks; 03-03-2016 at 05:30 AM.
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Old 03-03-2016, 05:33 AM   #2
daniel_f.
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Take a look at c_n_grd_*

0x40082 Measurement_n_grd
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Old 03-03-2016, 05:37 AM   #3
jcsbanks
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Noticed then forgot about those lol. They are global ignition gradient limiters mentioned in MS42. Any others that are load and engine speed related like MS41?

Last edited by jcsbanks; 03-03-2016 at 05:48 AM.
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Old 03-03-2016, 05:47 AM   #4
daniel_f.
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Probably not, maybe its something like ip_iga_lgrd_ris__n_grd

ris means "restart" function going into idlespeed.
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Old 03-03-2016, 07:12 AM   #5
jcsbanks
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c_isapwm_slow_pu_dec looks like idle speed actuator decay when throttle closed slowly.
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Old 03-03-2016, 07:33 AM   #6
jcsbanks
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ip_iga_accin_puc__n__tco if anyone hadn't realised is fast negative throttle with aircon.

Wondering if these aircon tables work just depending on the button or whether your aircon is actually working (ours are removed for track cars).

Last edited by jcsbanks; 03-03-2016 at 07:52 AM.
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Old 03-03-2016, 08:37 AM   #7
jcsbanks
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Over 272mg/stroke c_iga_lgrd_3 is used which is 2.65 degrees per segment.
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Old 03-03-2016, 08:59 AM   #8
jcsbanks
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Noticed you said c_n_grd which is engine speed gradients, could be interesting. Looks to be related to detection of deceleration. But that is a bit late to sort out rev hang - chicken/egg.

I was looking at ignition limiting gradients because of this: "The gradient limitation used for ignition angle correction (IGA_PU_PUC) in trailing throttle (LV_PU) or trailing throttle fuel cut-off (LV_PUC) must be lower than the general gradient limitation used for the nominal ignition angle out of start (IGA_BAS)"

Last edited by jcsbanks; 03-03-2016 at 09:03 AM.
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Old 03-03-2016, 11:30 AM   #9
jcsbanks
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Thinking of this.
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Old 03-17-2016, 01:07 PM   #10
jcsbanks
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On brief testing it seems to work with a more obvious drop in torque on lifting the accelerator pedal.
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Old 04-04-2016, 12:34 PM   #11
RapDoug
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Would you like another test car for this? Just let me know which maps, maybe a screenshot of before and after.

I'm on MS43.
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Old 04-04-2016, 06:01 PM   #12
jcsbanks
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It worked as shown above. Let us know how you get on.
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Old 04-04-2016, 06:02 PM   #13
jcsbanks
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It works as above. Let us know how you get on.
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Old 04-04-2016, 06:29 PM   #14
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Just copied over the maps from the attachment. Flashing it in a couple mins for a test drive. Will report back very soon.
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Old 04-04-2016, 07:39 PM   #15
RapDoug
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Test drive done.

So, I do notice it engine brakes harder especially at slower speeds.

Also noticed crackle pop is now more quiet and doesn't start popping until around 3000rpm and below. No more pops above that.

Free revs in neutral don't have a noticable difference in engine speed accel or decel.

Overall, not a drastic difference, but you can feel it.
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