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 7:02 pm

Optimizing the slip detection could allow you to apply more torque maybe longer. Relocating the sensors/processing may speed up the response some few milliseconds, but I doubt it's huge. Wider/stickier tires will allow more torque to be applied before losing traction, even without changing the control circuits. Like many things, the synergy of improving the response should aid in the overall effect, but put the narrower tires on it, and it probably wouldn't be any faster.
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

Sat Apr 21, 2018 5:01 am

BMW claims the response time is 50 % faster with the new traction control system . I'm not sure they would have gone through the expense in redeveloping the do system if it didn't significantly improve acceleration . I'm not convinced that wheel spin has much to do with acceleration . The only time my wheels spin is on gravel . The increase in acceleration is due to a direct path of the new traction control system . Which decreases the time it takes from the data from the traction control to the the drive train . This may will occur with traction control wether or not the wheels spin.

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

Re: i3 s Traction Control adds torque

Sat Apr 21, 2018 5:43 am

I can imagine wheel spin it you like to corner too fast an wear out your tires . Which brings up a new subject . With regenerative braking and the high torque of electric motors , I find it very it very convenient to ease up on the acceleration around corners without using brakes then accelerating after I round the corner since the car accelerates so fast and easy . This seems to confuse those that are following me with conventional internal combustion engines . But I don't care . It's fun to leave them in the dust . They are driving cars with antiquated technologies , that's their choice . I don't do to annoy people . I think it helps with tire wear which is good for the environment and also good for my bank accounts . It's safer also .

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

Re: i3 s Traction Control adds torque

Sat Apr 21, 2018 2:56 pm

Wheel spin hurts acceleration, which is why having a responsive traction control system is useful...it can keep you at the peak of traction for the surface available. But, wider tires also aid in traction, allowing the car to apply more of the available traction. So, it appears BMW chose three things to improve acceleration:
- wider tires (provides more grip so more acceleration is possible before wheel spin occurs))
- more responsive traction control (keeps you at the edge of traction better)
- higher torque (higher current) allowed to the motor

The last thing you want is wheel spin, unless you want to make a big smoke cloud and noise!

Drag racers spin their tires in prep to warm them up, making the rubber stickier, so they can then apply more of the power to the ground when the actual race starts.
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

Sat Apr 21, 2018 5:41 pm

Of course . That's very basic physics . But I don't believe wheel spin occurs with an i3 with or without traction control .

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

Re: i3 s Traction Control adds torque

Sat Apr 21, 2018 6:03 pm

shellhunter wrote:Of course . That's very basic physics . But I don't believe wheel spin occurs with an i3 with or without traction control .
I rarely use the full throttle on my i3, but if you ever do, notice the icon on the instrument panel...you'll often see the traction control one flashing...the car is limiting the torque, and that's without the i3s' increased current. Just be safe about it, as your attention needs to be outside. It's more likely to occur at startup, since the electric motor is generating maximum torque then. It's very evident if you're ever on ice or packed snow...the light will be on most of the time, and you're barely moving because it is limiting torque so the wheels won't spin, but it can happen on 'normal' roads in normal conditions as well, at least at low speeds.
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

Sun Apr 22, 2018 3:08 am

BMW recommends when driving on heavy snow covered surfaces and you need added traction to turn off the traction control . If the traction control light is coming lighting up on dry surfacing
I would would think something is wrong and take my car to the shop . Do you get your wheels regularly balanced at BMW ? Do you corner fast and the light then comes on . They have a special balancing system . Its expensive but worth it . I would never leave traction control on snow covered roads . My light has never come on on dry roads . No matter how much I press down the accelerator .

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

Re: i3 s Traction Control adds torque

Sun Apr 22, 2018 1:53 pm

On very slippery roads, sometimes the only way to get started is to spin the tires somewhat...that's why they tell you to turn it off if you're stuck. As with any car, though, don't let them spin much, or you'll likely break something.

I have the staggered set on my car, but run winter tires during the winter...the smaller rear width may be the reason I can see it reaching the limits of traction on occasion, even when the roads are dry. It is rarer when I have the all-season set on the vehicle. It only happens when the car is just starting out, and that may partly be because at a stop sign or traffic light, the road tends to get more crud from the idling vehicles, but it does happen if you tromp on it.

FWIW, the tire pressure is within specs.
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

Mon Apr 23, 2018 9:36 am

Yes I would think you would have wheel spin with snow tires on dry roads . And if you use roads that use a lot of sand in the winter . I stay off roads that use sand . It's just the town roads that use it . I hate it and think it's damaging . The county and state roads here don't use sand and I can easily avoid filthy town roads . Snow tires would be even worse at a sandy intersection . Towns only use sand cause it's cheap .

KolorMeCarbon
Posts: 29
Joined: Mon Sep 11, 2017 1:23 pm

Re: i3 s Traction Control adds torque

Mon May 21, 2018 12:12 pm

A few weeks late to this thread, but my wide-tyred i3 BeV has cured the unintended drifting ( oversteer ) on fast, tight corners.
i3s will wheel-spin with and without DSC on, but not in a straight line on a dry road.

I’ve fitted 7.5J 18” rims for better grip, tyres are 215 45 18 with B rating for grip and economy.

The mod has added 30% more unsprung weight to each corner- which on paper is very bad, but in reality the car is much faster around a twisty route. There is zero difference in range.

I have a regular commute of 20 miles each way, with a mix of fun twisties and ‘autobahn’ 90mph for 12 miles.

With original wheels I had 7 miles of battery left, with new wheels there is 22 miles remaining when I get home.

I attribute this improvement to there being less sidewall distortion at the contact patch (stilletto vs sneakers) .

The tyres hang out past the body arches by 30mm (I have custom arches on their way)
which adds to the wind resistance.

The extra weight is noticeable from zero to 10mph in normal driving (still brisker than a ReX). I haven’t tested straight-line 0-60 but the traction control light never flashes, I used to see it most rainy days.

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