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How Traction control works

It was raining here in northwest today, again...

Because it was wet, traction control activated few times and thought to show you how it can be seen from the logs.

Sensor Setup is as follows:

- Wheel speed is measured from existing ABS sensors using the VR amplifier I made. ABS is still functional.

- Driven wheel speed signal: HS1 Left rear, HSI2: Right left.

- Vehicles speed signal: HSI3

- TC switch in center console, modes, OFF, Dry and Wet. Used inputs I/P SW2 and I/P SW3.

 

Autronic ECUCAL setup:

TC Setup - General TC Settings. Notice that Fuel cut is used to limit power!

NOTE: Fuel Cut is used for demonstration purposes here. Actual setting and recommended by Autronic is Fuel & Ign Cut.

 

TC Ign Retard - These settings are not used since Fuel Cut is only used

 

Wet Setup - Settings used when switch is in Wet position

Dry Setup - Settings used when switch is in Dry position

 

Functionality can be seen from the trace below. Following traces are important:

Violet - Driven wheel sensor. Since BMW is rear wheel drive car, this trace is from rear wheels. Sensors are setup in Speed setup

Turgoise - Vehicle speed. Front wheel speed, non-driven wheel

Gold - Mean injection time

Trace: (Right click - View Image to see complete image)

Now, note where the cursor is: As you can see from the gold trace, fuel injection time is reduced when the speed difference between driven and vehicle speed signals is above the limits for specific gear defined in WET settings.

I have to say Autronic TC is very good and has saved me few times...