Moochier

Thanks Steve, who are you down here testing for? Tyre company? It's a stunning part of the world down there, especially in spring or autum (fall).

I understand the changes I have made in general, but is it not really as simple as the ABS units job is to stop wheel lock upon the application of the brakes. So ice mode is essentially the system saying that 1 or more wheels are going to lock, thus releasing pressure to avoid this?

If you are getting pressure reduction from the ABS on OEM spec cars then change your braking technique or buy a Motorsport ABS.

On modified cars the above applies too but also trying to understand if any modification is causing out of balance braking ie my front brakes now way outperform the rears compared to OEM setup, so could the pressure release be, the ABS is trying to stop the fronts locking because the programmed acceptable bias level between from rear is now out of its programmed parameter? By decreasing the front bite or increasing the rear bite of the brakes with say pad type or another modification, could go to rectifying the issue by putting the bias back into acceptable parameter for the ABS? I understand there is no guideline for this, more trial and error, but is the logic correct?

Is any of this making sense?

Tom@TPC Racing

Thanks for posting the great info, Steve! To your points, I switched brake pads to a more linear torque curve compound and adjusted my initial brake pedal application, and I use my programmable electronic suspension to change suspension damping force to raising brake line pressure. All have been effective in increasing the threshold since I don't have a way to program the ABS unit. Cheers!

nwGTS

wait what? you are programming your suspension unit to also raise brake line pressure via dampening?
can you elaborate?

ZMC-ZH

I think what he meant was that he can stiffen the shocks based on pressure on the brake pedal, basically having a setup predicting the g-forces about to come in. Same exists based on accelerator pedal travel.
I have been toying with the idea of getting this DSC box for a while now, already read the manual but still haven't pulled the trigger.

nwGTS

thats sounds more like it. And would love to know how to do this on the DSC.

Steven_S

Hi Moochier, I'll try to answer your questions the best I can:

The primary job of ABS is to prevent wheel lock so the vehicle remains stable and the driver can steer. If the wheels are tending toward lock, the ABS controller will release pressure. But the RATE at which the wheels are locking will determine the amount of pressure release. If a wheel is just slipping slightly past the ABS threshold, the pressure release will be small. If a wheel is blowing past the threshold very quickly, the pressure release will be much larger. These ABS thresholds are carefully tuned for the OEM vehicle configuration. But changes to tires, brakes and suspension affect the wheel behavior enormously.

The Bosch system will not release pressure on the front wheels based on a set front/rear brake bias. EBD will release pressure on the rear axle before ABS entry to prevent rear wheel lock as weight transfers off of the rear tires during braking. Changing the front/rear braking bias with different pads or tires WILL affect EBD entry. Again, the EBD thresholds are tuned for the OEM vehicle configuration. If you could somehow duplicate the F/R OEM brake distribution with your setup it would minimize the affects to EBD performance.

Best Regards,

Steve

Steven_S

Hi Tom, the changes to brake pads and initial application are directionally correct. How are you changing the damping force relative to increasing brake pressure? Are you decreasing the compression damping to increase the rate of weight transfer to the front?

Tom@TPC Racing

Yes, I am using DSC Sport controller and DSC Sport tuning software to tune the dampers to counter dynamic weight transfer.



I am using DSC Sport controller, the damping commands to the load is an additive of a minimum damping value, which in my car is set at 10% in Normal Mode/20% in Sport mode with zero load(zero brake pressure or g force). Below are screenshots of two examples of Brake pressure tuning tables that I have been using:

This example shows when brake line pressure is at 30 bar the 55.5% damping is added to the front dampers for compression event and 33.5% damping added to the rear dampers for rebound event. The rear rebound is to assist the front compression to reduce nose dive thus reducing toe deviation as well. The "Decay" is 1000 millisecond of holding this damping command after pressure drops.



This is example at 50 bar.



The brake pressure damping commands works in conjunction with G force damping commands.



No, since the electronic suspension system I am using doesn't have a default(or base) damping value that starts high. Instead its starts low and adds. I suppose the software can be written to work the opposite way but I have it tuned well to paired with the mods that I've done this way.