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BMW 3-Series and 4-Series Forum (F30 / F32) | F30POST > Technical Forums > N20, N26, B46, B48 Turbo Engine / Drivetrain / Exhaust Modifications > Stock tune N20 logs -- timing corrections
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      09-22-2020, 05:36 PM   #1
ktw
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Stock tune N20 logs -- timing corrections

Hi folks,

I collected a few logs on my N20 with stock tune since I'm planning to flash to BM3 stage 1 soon. Seems like there are timing corrections happening regularly, so I'm looking for some advice on that. Here are the car/test details:
  • Car: 2014 F31 328i xDrive
  • Odometer: ~55k mi
  • Gas: CA 91 octane
  • Ambient temp: 75 F
  • Elevation: sea level
  • Motor: N20 EWG
  • Tune: stock
  • Spark plugs: NGK SILZBR8D8S @ 0.028-0.029", ~5k mi
  • Coils: stock, ~55k mi
  • Engine mods: ER TIC and CP, BMS OCC
  • Test: 3rd gear WOT

Logs for the three pulls are here:
https://datazap.me/u/ktw/21sep2020-s...log=0&data=3-6
https://datazap.me/u/ktw/21sep2020-s...log=0&data=3-6
https://datazap.me/u/ktw/21sep2020-s...log=0&data=3-6

I'm new to interpreting logs and appreciate any feedback, but here are my takeaways:
  • Consistent results between the three runs.
  • Accelerator pedal position is incorrectly logged. If anyone knows the reason or a fix, that would be appreciated!
  • Boost is hitting target with wastegate duty cycle at a comfortable <90%. Some throttle closure when pro-throttle boost is too high, but MAP is always at target, so no problem.
  • HPFP at target throughout.
  • AFR is a smooth curve and seems to be in the normal range of what I've seen.
  • STFT doesn't vary much from 1.
  • There appear to be frequent timing corrections with timing being pulled at various times in each cylinder. Seems like this is not normal from logs I have seen. Perhaps cylinder 3 has consistently more retarded timing than the others.

The timing corrections are my main concern, and I'd certainly appreciate tips on potential causes. My suspected causes from most to least likely are:
  1. Low octane fuel. California fuel is notoriously bad, but I could try a different gas stations (this was Costco) or an octane booster as a test. My guess is that this is much more likely than the remaining hypotheses.
  2. Spark plugs. The plugs are relatively new (5k mi) and gapped slightly narrower than stock (0.028-0.029" right now). Everything I've read would suggest stock gap would be fine for stock and stage 1, but slightly narrower wouldn't cause timing issues. (I had gapped them down slightly for the Dinantronics sport tuner formerly installed.)
  3. Coils nearing end of life. Sounds like coils are typically fine for ~100k miles, so doesn't seem likely. Also, all four would have to be failing given the random corrections on each cylinder.
  4. Carbon bulid up in intake. I inspected recently and while there certainly is some carbon in the intake, my assessment comparing to pictures from various engines/mileages is that it is not bad at all right now.

Thanks in advance for any suggestions and feedback! Figure I should get this sorted before flashing BM3 stage 1.
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      09-23-2020, 12:41 AM   #2
tpoddar
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It's most likely CA fuel. Try an octane booster to see if the timing clears up but I think you'll be fine if you switch to the Bm3 91 ACN map.
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      09-23-2020, 03:58 PM   #3
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The stock map works with 91 and 93 octane. On California gas, it probably needs to correct itself to run on the lower octane we have here.

It shouldn't have any problems with CA gas but since this is a universal map for all US octane, it'll need to correct itself to run on the lower end of the octane it is designed for.
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      09-23-2020, 06:10 PM   #4
ktw
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Thanks guys! Good to have some confirmation that my thinking isn't way off since I'm still learning how to interpret all these data. I just remembered that there are a couple gas station near here that sell 100 octane, so I may try mixing it in to get to 93 and collect new logs for kicks.
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      09-25-2020, 12:30 PM   #5
JohanSun
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My N20 did sort of the same - fuel cleaning additive was the reason. New tank of EU octane 100 solved the problem.
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