Wheelie control in BMW BMS-K / BMS-KP - why not?

In this 1st generation of control units with anti-wheelie function, the slip control is misused to reduce the torque when the front wheel is lifted. The control unit recognizes that the driver continues to accelerate, the rear wheel is becoming faster and the front wheel is becoming slower due to the lack of contact with the road. As with the spinning rear wheel, the torque is now reduced by the ratio by which the rear wheel rotates faster than the front wheel.

Result

Since the front wheel gets slower and slower over time and the rear wheel gets faster and faster, the following control behavior results:

  • Little to no torque reduction at first
  • The longer the wheelie lasts, the more torque is reduced
  • If the front wheel hits the road again, the torque is immediately set again as requested by the driver.

Driving feeling

Most drivers find this control behavior annoying. On the one hand, a strong and fast wheelie is hardly intercepted, because until the front wheel is slow enough you have half rolled over. On the other hand, most drivers are used to adjusting the wheelie themselves with the throttle hand and have to increase throttle the longer the wheelie takes. Once you have reached 100%, the motorcycle still regulates against it and the front wheel often slams back onto the road. Since the driver's request is now back at 100% torque, the front wheel shoots up again. This often leads to an unwanted "kangaroo" behavior that lasts the entire straight.

RS²E Solution

After many unsuccessful attempts at optimization, we are convinced that this type of control bothers the driver more than it helps. Therefore we deactivate this slip wheelie control and hand over the control of the wheelie completely back to the driver. We do this, as shown in the graphic, by calculating a virtual equivalent speed for the front wheel. This is calculated from:

  • S1000RR 2010-14: Change of speed before wheelie
  • HP4 2013-14: Longitudinal acceleration (via updated cluster sensor)

Difference between HP4 and S1000RR although both have BMS-KP ECU

The HP4 already has the cluster sensor II, which was used until 2019. In addition to the lean angle, it can also measure the longitudinal acceleration and thus provides a better basis for calculating the virtual front wheel speed.

On request, we can also make the longitudinal acceleration signal of the cluster sensor II available for a S1000RR 2010-2014. The sensor fits with a little trick plug & play.

And how does that work with the newer models?

BMS-X and BMS-MP ECU, e.g. S1000RR from 2015
In this 2nd generation there are options to influence the timing of the control intervention. So we can turn the intervention logic around here. With our Race Mapping after the front wheel has been lifted off, the regulation is strong (depending on the driving mode) and then weaker and weaker until driver throttle wish is reached again. The result is a driving aid that does not allow the driver to simply drive at full throttle and leave the rest to the motorcycle, but which makes it easier to keep the wheelie tendency under control.

BMS-O, e.g. S1000RR from 2019
From this 3rd generation onwards the cluster sensor III was installed, which can also measure the vehicle pitch (i.e. the wheelie). This comes together with a significant expansion of the functions for controlling the wheelie. We have already found many parameters for optimization there and have incorporated them into our mappings. Nevertheless, the wheelie remains a major challenge for the electronics and the driver - also due to unrecognized environmental conditions (e.g. hilltop).