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Technical Topics B48 4-Cylinder Turbo Engine / Drivetrain / Exhaust Modifications G20 Throttle Input While Downshifting

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      12-21-2019, 09:13 PM   #1
Nichols623
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G20 Throttle Input While Downshifting

Hello G20 Forum. Iím new to BMW and I wanted to ask fellow G20 owners of this symptom is normal. During breaking, around 3rd 2nd and 1st gear, there is a slight throttle input when the transmission is downshifting. Requires the driver to adjust breaking pressure to accommodate so not to jerk, just slightly. While I donít expect BMW transmissions to act like Honda or anything, just wondering if this was normal, perhaps due to dual clutch tech. Not sure.
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      12-21-2019, 09:54 PM   #2
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My G20 330i behaves exactly like you said. 1300 miles and I still can’t modulate the brakes perfectly for a jolt free stop in Sport mode. Sucks. Same issue in another 330i I test drove. Btw our cars have the zf8 tranny, not dual clutch.
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      12-22-2019, 01:59 PM   #3
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Quote:
Originally Posted by VipinLJ View Post
My G20 330i behaves exactly like you said. 1300 miles and I still canít modulate the brakes perfectly for a jolt free stop in Sport mode. Sucks. Same issue in another 330i I test drove. Btw our cars have the zf8 tranny, not dual clutch.
I am on Stage 1 93 tune by BMS and I no longer have this issue. Because of emissions requirements they probably restricted performance in 330i and since the engine is not operating at the optimum output level because of emissions regulations and requirements, the 4-cyl engine doesnít make enough power and therefore causes jerkiness while braking..
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      12-23-2019, 12:23 AM   #4
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Not sure if it’s an emission thing or not. My B9 A4 made the same power and the brakes were strong and grabby on that. But it had the same stopping power till the car came to a complete halt and the brake pedal didn’t need to be modulated as much for a smooth stop. In the Bimmer, towards the end of the stop, it feels like the brakes grab more, making me ease up a wee bit on the brake pedal in order to reduce the jolt. Not sure if it’s the actual brake or engine braking causing it.
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      12-24-2019, 02:00 AM   #5
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Originally Posted by VipinLJ View Post
Not sure if itís an emission thing or not. My B9 A4 made the same power and the brakes were strong and grabby on that. But it had the same stopping power till the car came to a complete halt and the brake pedal didnít need to be modulated as much for a smooth stop. In the Bimmer, towards the end of the stop, it feels like the brakes grab more, making me ease up a wee bit on the brake pedal in order to reduce the jolt. Not sure if itís the actual brake or engine braking causing it.
Iím almost certain itís not the actual brake because I observed the RPM drop when you are applying the brakes, itís the engine braking that is making the car jerk. Since Iíve flashed the tune, I no longer have this problem, and the RPM drop and downshift is smoother now.
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      12-24-2019, 12:49 PM   #6
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If only I had the balls to try flashing my car again
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      01-17-2020, 08:06 AM   #7
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I also have the same "issue" feels like your manually downshifting (therefore feel small jerks) just before stopping. Didn't have that feeling in my previous DCT cars.
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      03-02-2020, 11:10 PM   #8
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Originally Posted by VipinLJ View Post
If only I had the balls to try flashing my car again
I think you should be good now to be honest... I saw your messages on a different forum and you flashed your car with the wrong engine map right? If that is the case there shouldnt be a problem now.

Do you have a JB4 currently or are you running stock?
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      03-03-2020, 09:03 AM   #9
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I think you should be good now to be honest... I saw your messages on a different forum and you flashed your car with the wrong engine map right? If that is the case there shouldnt be a problem now.

Do you have a JB4 currently or are you running stock?
It was the right map. I thought it was wrong because the map said B48. But I checked with PTF and they said itís the same for the B46 too. And it didnít work when I tried twice.

Iím running a JB+ for now. Not JB4. I didnít get the jb4 because of the hassle of install but, after seeing how easy it is, I wish I had gotten the jb4 back then. Right now, Iím waiting for a few more months for more people to flash their cars with a BM3 before I go at it again.
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      03-03-2020, 11:47 AM   #10
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Quote:
Originally Posted by VipinLJ View Post
It was the right map. I thought it was wrong because the map said B48. But I checked with PTF and they said itís the same for the B46 too. And it didnít work when I tried twice.

Iím running a JB+ for now. Not JB4. I didnít get the jb4 because of the hassle of install but, after seeing how easy it is, I wish I had gotten the jb4 back then. Right now, Iím waiting for a few more months for more people to flash their cars with a BM3 before I go at it again.
Try again when BM3 has an update for B48 maps

They still have not updated the B48 map since release, I can see them updating it soon so that it will work.
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      03-03-2020, 12:45 PM   #11
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Try again when BM3 has an update for B48 maps

They still have not updated the B48 map since release, I can see them updating it soon so that it will work.
I will. Iím in touch with a guy from India who just bought a BM3 tune but his car also has an ECU software from 03/2019 unfortunately. Waiting to see how it goes for him.
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      03-04-2020, 08:37 PM   #12
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Quote:
Originally Posted by VipinLJ View Post
Quote:
Originally Posted by g20beam View Post
Try again when BM3 has an update for B48 maps

They still have not updated the B48 map since release, I can see them updating it soon so that it will work.
I will. I’m in touch with a guy from India who just bought a BM3 tune but his car also has an ECU software from 03/2019 unfortunately. Waiting to see how it goes for him.
Let us know how it goes for that guy
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      03-04-2020, 09:51 PM   #13
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Let us know how it goes for that guy
I will! Iím guessing heíll be fine since his car is an early 2019 car and doesnít have the updated software. But yes. Waiting to find out how that goes for him.
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