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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, 10:13 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, 10:54 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, 02:59 PM   #3
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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, 01:23 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, 03:00 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, 01:49 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, 09:06 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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      03-03-2020, 12:10 AM   #8
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Quote:
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, 10:03 AM   #9
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Originally Posted by Beam330 View Post
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, 12:47 PM   #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, 01:45 PM   #11
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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. 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, 09:37 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, 10:51 PM   #13
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Originally Posted by hamzag20 View Post
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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      11-11-2020, 01:04 PM   #14
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Quote:
Originally Posted by g20beam View Post
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..
Could you tell what "Stage 1 93 tune by BMS" is, please?

Do you guys know whether the jb+ will solve the issue?
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      11-16-2020, 03:09 PM   #15
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Could you tell what "Stage 1 93 tune by BMS" is, please?

Do you guys know whether the jb+ will solve the issue?
My bad. I meant BM3.

Update: The jerkiness is still there, does not matter what tune or mods you do, it persists after you let the tune run for a few cycles. No clue what it is, but looks like everyone is having this problem. I can confirm it happens when you are downshifting and letting go of throttle, the engine will input throttle slightly right after the downshift, typically around 2-3k RPM. Not sure what is going on but I'm pretty sure it is normal.

There is 1 culprit I can think of, and that is the cruising function which is built in to the car, after you downshift, the car wants to stay cruising instead of slowing down, so it automatically inputs throttle so the car will stay cruising. I know that with Bimmercode that cruising can be disabled. I'm not sure this will fix the problem though, however.
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      11-16-2020, 05:27 PM   #16
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it happens to me, not very often, but when occurs its very noticable for me (im used to manual transmission, having all control on engone behaviour). Very annoying having to modulate breaking pressure, and mu impression is that occurs more in eco pro than in confort.
In my case, never use cruise control.
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      11-16-2020, 08:35 PM   #17
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Yup. It's still there after all this while (a little over a year since I've had the car). You kinda get used to it but coming to a smooth stop is still a wee bit difficult with the 330i. Either the car feels jerky when you brake normally, or it feels like you braked too hard when you apply a little excess brake pedal pressure to try and prevent the car from being jerky.
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      11-17-2020, 06:29 PM   #18
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hear hear guys. Even in sport individual when engine does not stop and everything is not eco friendly. There is some input required to stop the car smoothly. I do not know if this is related to high torque of this engine or some software issue. The M brakes are great and crisp when pressure applied =)
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      11-17-2020, 11:05 PM   #19
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Quote:
Originally Posted by BmwDriverStockholm View Post
hear hear guys. Even in sport individual when engine does not stop and everything is not eco friendly. There is some input required to stop the car smoothly. I do not know if this is related to high torque of this engine or some software issue. The M brakes are great and crisp when pressure applied =)
Not sure if it's because of torque. My B9 A4 was more powerful even in stock form (even though it is rated less on paper). That car had AMAZING stopping power. Hell. At the end of the lease, after lots and lots of hard driving with braking, launch control etc, that car had better brakes (stopping power) than my brand new 330i (even now). So yes. I think it's a tuning issue?
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      11-20-2020, 06:09 AM   #20
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I noticed that sometimes I have normal driving in the range of 0-30 km/h but sometimes it's so jerky with constant engine breaking that makes the whole driving experience a disaster. I also found that right after being in a traffic jam when the car is being jerky it then accelerates much slower, say to a 100, as if not all the cylinders contribute or the turbine is not performing properly.
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      11-20-2020, 08:58 AM   #21
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Quote:
Originally Posted by sid.hse View Post
I noticed that sometimes I have normal driving in the range of 0-30 km/h but sometimes it's so jerky with constant engine breaking that makes the whole driving experience a disaster. I also found that right after being in a traffic jam when the car is being jerky it then accelerates much slower, say to a 100, as if not all the cylinders contribute or the turbine is not performing properly.
this happened to me last week. After 30 mins of stop on traffic jam, throttle does not respond as always, returning back to normal minutes after.
Seems like ECU engine self protection.
Something similar happened to me with my 2007 Passat 3C diesel on traffic jams
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