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      09-09-2019, 04:19 PM   #1
FZ36
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Bootmod3 - Need some help

Car: 2018 440xi GC, B58, non-MPPSK, automatic
Tune: BM3 Stage 2 91 oct
Mods: ER Catless DP

BM3 has been fantastic so far but there’s this odd scenario I keep encountering at highway speeds in sport mode, or city driving in 5th gear +. When the car is in Sport mode (by pressing the button, NOT by pulling the shifter to the left) and sitting in 5th gear at around 100-110km/h and I hit the accelerator, the car gives off what I can only describe as a droning sound and hangs in 5th for a second. it’s almost like it doesn’t want to leave 5th unless I WOT and then it’ll get to 6th but at a higher RPM. It doesn’t do this always but frequently enough that I’ve noticed it.

Kinda similar in city driving as well. Comfort mode is keen in keeping the RPMs low and gear changes frequent. 5th gear at around 65km/h has what I can only describe as drone and the car rocks when I try to get it to 6th gear at around 70-75km/h. It’s like it can’t decide which gear to be in so it tries to keep me in 5th with this very subtle rocking of the RPMs.

Has anyone had a similar experience? I’m not sure if I should do some data logs. I’m knew to tuning so if I should do some logs please let me know what gear(s) I should log cause I see conflicting information.
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      09-09-2019, 05:32 PM   #2
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Get logs and contact bm3. Otherwise we are just speculating.
***Just enable the log at any given point. Bm3 will know what to look for.
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      09-09-2019, 06:48 PM   #3
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Sounds like you are lugging the engine. Not sure about the F30 automatics, but my E90 doesn't down shift unless you hit the kick down switch (basically you push it to wide open throttle). I feel a click when I hit the kick down switch. Otherwise you are lugging the engine, something the factory tune won't let you do because it doesn't wanna put the strain on the drive train. Welcome to tune life. Boot mod3 doesn't alter the transmissions calibrations, so it's essentially a mismatch in some sense.
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      09-09-2019, 07:34 PM   #4
marcthedark
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Quote:
Originally Posted by zinner View Post
Sounds like you are lugging the engine. Not sure about the F30 automatics, but my E90 doesn't down shift unless you hit the kick down switch (basically you push it to wide open throttle). I feel a click when I hit the kick down switch. Otherwise you are lugging the engine, something the factory tune won't let you do because it doesn't wanna put the strain on the drive train. Welcome to tune life. Boot mod3 doesn't alter the transmissions calibrations, so it's essentially a mismatch in some sense.
How do you do that in Sport mode? Or even Comfort ... the ZF will keep the engine in the happy rpm range. Why would a tune change the engine behavior at the same rpm from normal operation to lugging as the size of the turbo, cam tuning etc doesn’t change.
And I think it is impossible to “lug” the engine with the ZF8 as lugging indicates an “unhealthy” rpm range and the ZF downshifts if that happens.
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      09-09-2019, 07:38 PM   #5
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Do you have a transmission tune? Did you chose the BM3 Stage 2 with reduced torque so that the ZF stock limit is not triggered? Wild guess you chose the not torque limited option and open throttle at low rpm produces a torque spike hitting the ZF factory limits and the transmission and the ECU panic
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      09-09-2019, 09:02 PM   #6
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Quote:
Originally Posted by marcthedark View Post
How do you do that in Sport mode? Or even Comfort ... the ZF will keep the engine in the happy rpm range. Why would a tune change the engine behavior at the same rpm from normal operation to lugging as the size of the turbo, cam tuning etc doesn’t change.
And I think it is impossible to “lug” the engine with the ZF8 as lugging indicates an “unhealthy” rpm range and the ZF downshifts if that happens.
The aftermarket calibration gives you more boost/tq down low, just take a look at a dyno graph, it's a huge uptick in boost/power down low. Given the initial post it looks like the engine is spinning around 2600 rpm if you do the math. If you take the PTF provided dynos that around 90-100+ tq over stock. It is ~25% more tq than stock at a low RPM it's just lugging the motor with not a lot of gearing advantage (1:1 in 5th gear). The stock tune won't let you do that because well it's not good for the powertrain. Just take a look at a stock vs tuned dyno, the tq increase with a tune is 25% more over stock about 1/2 the rpm window stock takes to develop less tq. Is it good to have that huge hit of TQ down low? Sure. Is it good in 5th gear @ 60mph to exercise that extra power no.

BMW has that kick down switch automatic transmissions thing they do, I dunno why probably something lame like MPG or emissions. Just click down a gear or two or just pedal to the metal and let the transmission shift.

https://www.roadandtrack.com/car-cul...ad-for-engine/
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      09-09-2019, 09:06 PM   #7
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This thread is pointless without logs. But yes, I agree you should log and file a support ticket with PTF. They'll be able to tell you what's up. Also some of us here can read logs and can give you a general idea of what's going on.
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      09-09-2019, 09:20 PM   #8
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Quote:
Originally Posted by zinner View Post
Sounds like you are lugging the engine. Not sure about the F30 automatics, but my E90 doesn't down shift unless you hit the kick down switch (basically you push it to wide open throttle). I feel a click when I hit the kick down switch. Otherwise you are lugging the engine, something the factory tune won't let you do because it doesn't wanna put the strain on the drive train. Welcome to tune life. Boot mod3 doesn't alter the transmissions calibrations, so it's essentially a mismatch in some sense.
F30 will down shift before the kick , even in comfort mode.
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      09-10-2019, 07:00 AM   #9
marcthedark
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Quote:
Originally Posted by zinner View Post
The aftermarket calibration gives you more boost/tq down low, just take a look at a dyno graph, it's a huge uptick in boost/power down low. Given the initial post it looks like the engine is spinning around 2600 rpm if you do the math. If you take the PTF provided dynos that around 90-100+ tq over stock. It is ~25% more tq than stock at a low RPM it's just lugging the motor with not a lot of gearing advantage (1:1 in 5th gear). The stock tune won't let you do that because well it's not good for the powertrain. Just take a look at a stock vs tuned dyno, the tq increase with a tune is 25% more over stock about 1/2 the rpm window stock takes to develop less tq. Is it good to have that huge hit of TQ down low? Sure. Is it good in 5th gear @ 60mph to exercise that extra power no.

BMW has that kick down switch automatic transmissions thing they do, I dunno why probably something lame like MPG or emissions. Just click down a gear or two or just pedal to the metal and let the transmission shift.

https://www.roadandtrack.com/car-cul...ad-for-engine/
What you are describing is the torque after tune being higher than the transmission limits (which a transmission tune would raise). Has nothing to do with lugging .... unless you drive stick or overwrite the auto to fully manual control (which the OP didn’t do) you can not lug an engine (as the auto would downshift if the rpm is getting too low)
And torque at low rpm being a problem? Look at a Diesel engine and how it develops torque and you see that the same transmission in the same car with a Diesel engine has to “suffer” higher torque stock.
The problem is again mostly with stick or fully manual auto as in case of WOT the trans wouldn’t downshift but stay in the rpm range which has the highest torque .....

Last edited by marcthedark; 09-10-2019 at 07:05 AM..
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