shellhunter
Posts: 12
Joined: Tue Jul 04, 2017 8:40 am

i3 s Traction Control adds torque

Wed Apr 18, 2018 8:46 am

I have read that that bmw has increased the acceleration on the i3 s by changing the way the traction control works . The old traction control doesn't allow the full benefit of the electric motors torque to give the full benefit to acceleration . The new traction control works differently which increases acceleration . I wonder if the traction control on older i3 models can be modified to use the new traction control system ?

viking79
Posts: 110
Joined: Wed Apr 16, 2014 3:04 pm

Re: i3 s Traction Control adds torque

Wed Apr 18, 2018 10:28 am

If you look at the power bands from the i3 to i3s, you will see it is almost entirely at higher RPM. Meaning the vehicle will be much faster passing on the highway or merging on the interstate.

Maybe there are traction control differences as well, so I don't mean to derail your question.

jadnashuanh
Posts: 5036
Joined: Thu May 22, 2014 2:07 pm
Location: Nashua, NH USA

Re: i3 s Traction Control adds torque

Wed Apr 18, 2018 6:03 pm

The rear tires are wider, which should also provide more grip, which would allow more torque to be applied before the system detects slip. So, just that item may allow it to accelerate faster. Throw in that it also allows higher current levels to the motor, and that adds to the performance as well. They used lower friction, higher performance bearings in the motor, which is one reason why they can let it run to a higher speed. So, the torque control mapping may in fact, be the same, but the car doesn't actually slip as early as the original versions because of the tires.
Jim DeBruycker
2011 535i x-drive GT, 2014 i3 BEV
Soon (hopefully!) A 2021 X5 45e will replace the above

shellhunter
Posts: 12
Joined: Tue Jul 04, 2017 8:40 am

Re: i3 s Traction Control adds torque

Thu Apr 19, 2018 5:21 am

I think that traction control slow the acceleration down and BMW may have found a way to eliminate this or modify it

websterize
Posts: 519
Joined: Sun Sep 07, 2014 3:39 pm
Location: USA

Re: i3 s Traction Control adds torque

Thu Apr 19, 2018 9:38 am

I wonder if the traction control on older i3 models can be modified to use the new traction control system ?
No.

See https://www.press.bmwgroup.com/global/a ... ini-models for more details on the new TCS.
At the heart of this innovation is the control system’s 50-times-faster routine, made possible because – unlike conventional driving stability systems – the control process is now calculated directly in the powertrain instead of in a remote unit requiring long signal paths.
2018 i3 Sport BEV | Coding spreadsheet

shellhunter
Posts: 12
Joined: Tue Jul 04, 2017 8:40 am

Re: i3 s Traction Control adds torque

Thu Apr 19, 2018 11:02 am

So I assume it we turn off the traction control we will see a significant increase in acceleration . I've done this on dry pavement and did not notice any wheel spin . I'm not suggesting to do this as I don't fully understand the safety issues involved . But when researching this I've read that some people do not trust driving with traction control . They would rather trust their own instincts , I assume . But if you are pulling into a highway and you might need that extra acceleration . Is there any harm in turning it off and turning it on after you are safely in your lane ?

alohart
Posts: 2122
Joined: Sat Nov 01, 2014 7:36 pm
Location: Honolulu, HI

Re: i3 s Traction Control adds torque

Thu Apr 19, 2018 4:08 pm

shellhunter wrote:So I assume it we turn off the traction control we will see a significant increase in acceleration .
There's Dynamic Stability Control (DSC) and Dynamic Traction Control (DTC).

According to the Driver's Guide, DSC prevents driving wheel traction loss when accelerating and cannot be turned off.

DTC ensures maximum headway over slick surfaces. It is normally off but can be turned on temporarily when trying to start moving on a slick surface.

So you would need to turn DTC on, not off, to allow some drive wheel spin. I don't know what affect this might have on acceleration, but the Driver's Guide does warn that it can reduce stability during acceleration or in turns.

Then there's Roller Mode turned on via the service menu. Roller Mode apparently shuts off DTC, DSC, antilock braking, and who knows what else. Roller Mode might allow the fastest acceleration, but turning it on is not something that could be done quickly, and it is not as safe to drive in Roller Mode.

Please report your acceleration test results :)
Aloha,
Art

2014 BMW i3 Arravani Grey, Giga World, Tech + Driving Assist, Parking Assist, DC Fast Charging, JuiceBox EVSE

jadnashuanh
Posts: 5036
Joined: Thu May 22, 2014 2:07 pm
Location: Nashua, NH USA

Re: i3 s Traction Control adds torque

Fri Apr 20, 2018 12:36 am

on most surfaces, applying enough torque to just before the wheels spin will give you the maximum acceleration. Traction control detects spin, and reduces the torque so the wheels can regain traction. Wider tires have more traction (on most surfaces, snow not being one or sand or gravel), so just the action of wider tires will allow more torque to be applied, thus, better acceleration. The i3s allows a higher current to flow, producing more torque, but without wider tires, it probably wouldn't do much. The higher HP will help at higher speeds, but it's the torque that really moves things out from a stop, and like with all electric motors, it's maximum at stall (zero RPM) speed. More current, wider tires, allow the greater torque to actually be applied before spin, which would be arrested by the traction control. How quickly and aggressively you attenuate the torque when detecting spin could make a difference, and that logic may have been tweaked, but I don't think that's the main part. Grippier tires and more torque available probably are.
Jim DeBruycker
2011 535i x-drive GT, 2014 i3 BEV
Soon (hopefully!) A 2021 X5 45e will replace the above

shellhunter
Posts: 12
Joined: Tue Jul 04, 2017 8:40 am

Re: i3 s Traction Control adds torque

Fri Apr 20, 2018 4:50 am

But as I understand it the old traction control which is a separate unit and not part of the drivetrain like on the new traction control reduces the acceleration even before it detects wheel spin as it takes time to process the information in the separate units which then has to relay the information to the drivetrain .So if you turn it off are you not bypassing these separate traction control units and allowing the torque to go directly from the motor to the wheels . The only time I notice wheel spin is on gravel . As I said I'm not advocating driving without traction control . Although I started driving at 16 in 1966 , I drove bmw's MG's Renaults Chevy's none of which had traction control and i love in upstate NY with lots of winding roads hills and snow and ice . My mom didn't drive and worked at a factory so I had to get her there no matter what weather . I never had an accident . And you learned how to drive on unplowed roads up hills and down hills .

shellhunter
Posts: 12
Joined: Tue Jul 04, 2017 8:40 am

Re: i3 s Traction Control adds torque

Fri Apr 20, 2018 5:31 am

As to the above post the state's the stability control can not be turned off . I'm not convinced . When I switch to traction from normal there is a symbol on the control panel that indicates the stability control is of . It shows the symbol as the rear of the car and says OFF .

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