MisterCorn
Well-known member
- Joined
- 8 Jan 2011
- Messages
- 9,410
CAUTION, NERD CONTENT!
I have a job to do for work to collect some brake testing data next week, in preparation I have been getting my car set up and whilst I was at it I thought I would update what data I am pulling from CAN and add a few more channels if I could. I am now getting enough data to have a look at what the traction control system does on the car when activated. As I know some of you are as inquisitive as I am, I thought I would share what I have found.
2nd gear, 4000rpm, cold but dry road, slightly uphill. Accelerating briskly and I managed to provoke the traction control.
Top to bottom on the graphs are:
Throttle position
Front brake pressure (Front right)
Rear brake pressure (Rear right)
Manifold pressure
Actual throttle angle
Basic ignition timing
Actual ignition timing
Rear right wheel speed
Front right wheel speed
Actual engine load
Ratio between average front and wheel speeds (<1 means rears are going faster)
All data is from CAN bus except for the two brake pressures which are from pressure transducers in two brake lines.
At this point on the graph boost is building, 0.9bar, actual and basic ignition angles are the same, throttle is wide open and the rear wheels are going about 3.5% faster than the fronts, all is fine and the traction control isn't doing anything.
Here the right rear is at 90km/h and the right front is at 75km/h. The rears are going about 12% faster than the fronts and the traction control is just about to step in.
I zoomed in slightly for this one, entire graph is around 2s of data here.
Traction control has now intervened, boost level is dropping, rear brakes have been applied but the throttle is still open. Ignition is being pulled by up to 6 degrees. At this point the rear wheels have regained traction.
By this point the rear wheels have well and truly gained traction but the throttle is being closed and the rear brakes are still being applied. For a short time afterwards there is also slight pressure on the front brakes.
So, it appears that the traction control starts to activate at a slip ratio of somewhere around 10%, it works by pulling ignition timing and reducing boost, as well as throttle control. It also seems to overreact and keep the power off for much longer than is actually needed!
As I was just on a public road I wasn't exactly going balls-out on this one. If I get a chance next week when doing more testing I'll push it a bit harder and see if I can see anything else interesting.
MC
I have a job to do for work to collect some brake testing data next week, in preparation I have been getting my car set up and whilst I was at it I thought I would update what data I am pulling from CAN and add a few more channels if I could. I am now getting enough data to have a look at what the traction control system does on the car when activated. As I know some of you are as inquisitive as I am, I thought I would share what I have found.
2nd gear, 4000rpm, cold but dry road, slightly uphill. Accelerating briskly and I managed to provoke the traction control.
Top to bottom on the graphs are:
Throttle position
Front brake pressure (Front right)
Rear brake pressure (Rear right)
Manifold pressure
Actual throttle angle
Basic ignition timing
Actual ignition timing
Rear right wheel speed
Front right wheel speed
Actual engine load
Ratio between average front and wheel speeds (<1 means rears are going faster)
All data is from CAN bus except for the two brake pressures which are from pressure transducers in two brake lines.
At this point on the graph boost is building, 0.9bar, actual and basic ignition angles are the same, throttle is wide open and the rear wheels are going about 3.5% faster than the fronts, all is fine and the traction control isn't doing anything.
Here the right rear is at 90km/h and the right front is at 75km/h. The rears are going about 12% faster than the fronts and the traction control is just about to step in.
I zoomed in slightly for this one, entire graph is around 2s of data here.
Traction control has now intervened, boost level is dropping, rear brakes have been applied but the throttle is still open. Ignition is being pulled by up to 6 degrees. At this point the rear wheels have regained traction.
By this point the rear wheels have well and truly gained traction but the throttle is being closed and the rear brakes are still being applied. For a short time afterwards there is also slight pressure on the front brakes.
So, it appears that the traction control starts to activate at a slip ratio of somewhere around 10%, it works by pulling ignition timing and reducing boost, as well as throttle control. It also seems to overreact and keep the power off for much longer than is actually needed!
As I was just on a public road I wasn't exactly going balls-out on this one. If I get a chance next week when doing more testing I'll push it a bit harder and see if I can see anything else interesting.
MC