BOSCH Motorsport ABS

I have fitted the toothed wheels and sensor brackets to run traction control and the Bosch abs. So far I have the traction control system running perfectly but I have not paid up the 6 grand odd that that want for the abs. I have good friend who is senior at Bosch motorsport. System cannot be supplied for road car use.
PM me to discuss

Guess that's not going to happen too soon on an Ultima

I thought the idea of an Ultima was to avoid all these electronic "driver aids".

Paul

Frankly i'm amazed it even got as far as the Legal team:

Potential gain: Money earnt = sales volume x profit (fairly low for specialist aftermarket sportscars, lets say 1000 pa, @ £1k per unit = £1M as a maximum.

Potential loss: Public Liability claim after an accident = £10M minimum with costs


You don't need to be a genius to see those just don't add up............


(regarding Std road system, the system is a std off-the-shelf mass produced pump/valveblock/ECU, with BOSCH's std "production" yaw and accelerometers. It uses the majority of the autogenerated code from the production system (for reliability and validity reasons), the only difference is that it comes with a "race" wirng loom and has a spare input pin hooked up to some "MAP select" logic to allow the driver to shift between several different options for tyre slip coefficient and yaw authority margin. There is a basic calibration tool that allows customers (with the help of a bosch application engineer) to modify a small amount of volatile memory with a chassis specific calibration. The A2l files released to do this "hide" the majority of the system operation from the buyer for safety reasons (and probably BOSCH IPR reasons also......)

The system does improve laptimes, and cruically also helps to avoid flatspotting the tyres in panic braking (a big deal in long distance GT racing etc!)

The strategy employed by the system uses an identical physical based dynamic model to that used in road cars (as mentioned, it's the same code for reliability reasons!) however the calibration of the "yaw limit" is modifed beyond what would normally be a the maximum for a road car calibration. This is just a calibrated tabel change. Effectively the systems works as follows:

1) brake applied by driver, hydraulic system pressure builds to all 4 calipers (with the basic mechanical front/rear split).
2) wheels/tyres start to decelerate (faster than the vehicle is loosing speed, so tyre slip is generated, which generates a longitudinal force that starts to act on the inertia of the vehicle)
3) any tyre that starts to exceed the optimum slip ratio (by decellerating excessively below the speed of the vehicle) triggers the system to cycle hydralic pressure on the appropriate caliper. The initally reduces the pressure until the system sees the wheel re-accelerate, then reapplies the full hydraulic pressure again.

However, in a Split Mu condition (say 1 side tyres on ice, 1 side on dry tarmac (worst case!) if the deceleration loads are not maintained evenly about the CofG of the vehicle, a yawing moment is generated. (in the case above, one side of the car decelerates, the other doesn't) Although this yaw is obviously damped by the inertia of the vehicle, the magnitude of the forces during braking are so large that massive yaw rates can easily occur.

Hence the system will monitor handwheel angle to work out which direction the driver is trying to go, look at the output of the Yaw sensor to work out how the vehicle is rotating arround it's CofG , and then reduce the brake pressure on one side (or end, for front-rear balance) to counteract that yaw moment. Obviously because the system has to reduce brake pressure, the average deceleration is also reduced. This is trade off between ultimate stopping capability and dynamic stability.

For a road car the calibration is set that pretty much any significant yaw moment will immediately lead to a reduction in brake force. (in a road car, you can perform a full emergency stop on a split Mu surface without even holding the handwheel and the car stays straight (i.e. the driver does not have to intervene to maintain stability.

For a race car, signifcantly more yaw moment is allowed to occur before the system reduces mean brake force, relying on the driver to apply handwheel angle to counteract the yaw moments.

On the system as small input dial is used so that the driver can select a suitable "MAP" in this case, both targeting different levels of tyre slip before pressure control is commenced, and allowing different yaw moments before the "ultimate stability law" activates.

(As an aside it is also why the old "never touch the brakes in a slide" mantra is really no longer true in a modern car, as jumping on the brakes will just mean the system helps you to control yaw!)

(and as another aside, also why one should be really rather careful of using excessive handwheel corrections, because this is what the system uses to work out where you want to go. So if you wang on full lock, it will assume you want to turn 90deg NOW !!! )

Not directly, but i have spent more hrs than i care to think about developing and calibrating all sorts of powertrain systems with Bosch application engineers

I`m expecting the ABS system to arrive this week after they built a custom loom for the Ultima (which I had to measure). I`ll post some pics later.

did you not want to sell your car 2 weeks ago ?

you would have regretted it anyway

Here`s the layout plan for the ABS M4 wiring loom. You need to decide where the control unit sits (the only place I could think of was beside the battery). Then you need to measure each cable length and send them the numbers (e.g. A1: 50mm).
I hope my measuring istrument was calibrated correctly (tape measure) - if so I could post the numbers as it`s not so much fun to measure in a finished GTR.