SL-C ABS Feasibility Question/Discussion

[David]

If you look at the simplicity of inputs (no pitch, yaw, roll, sensors, traction control, stability control, etc) and the fact that the load in an on-road vehicle can vary by several hundreds of pounds, plus the upgrade-ability of aftermarket caliper/rotor packages for OEM vehicles means that it should function very well in this particular application.

ABS isn't speced by the manufacturer to account for aftermarket brakes. Increasing the weight of a vehicle isn't a problem. Decreasing and increasing the grip (and brakes) is as the ABS computer 'knows' how fast the car can possibly decelerate. If the computer 'thinks' that the wheels have slowed down faster than it thinks is possible (due to more grip, better brakes and lower weight for example) it will let off the brakes and so will *increase* braking distances!

 

[John Ross]

If the computer 'thinks' that the wheels have slowed down faster than it thinks is possible (due to more grip, better brakes and lower weight for example) it will let off the brakes and so will *increase* braking distances!

Are you sure this is true? A very good friend was the chief engineer for KITCO in Indiana in the mid-70s. They supplied disc brake seals and other rubber components to Detroit. At that time he told me about the ABS systems the factories were working on. I seem to recall that he said that the engineers figured out that maximum braking occurred when the tires were turning 15%-20% SLOWER than would be the case with no lockup whatsoever.

Is this still true (assuming it ever was), or are we working with a different paradigm 38 years later? Because if the computer tries to maintain 15% "lockup" during max braking, then better brakes, stickier tires, and lower weight shouldn't "fool" the computer in any way.

JR

 

[David]

You might find this interesting reading.

http://stoptech.com/technical-support/technical-white-papers/abs-and-big-brake-kits

 

[Vidal]

ABS isn't speced by the manufacturer to account for aftermarket brakes. Increasing the weight of a vehicle isn't a problem. Decreasing and increasing the grip (and brakes) is as the ABS computer 'knows' how fast the car can possibly decelerate. If the computer 'thinks' that the wheels have slowed down faster than it thinks is possible (due to more grip, better brakes and lower weight for example) it will let off the brakes and so will *increase* braking distances!

Do you have or have access to the performance specification or design specification for some of the systems installed on production vehicles?

There has to be objective and thresholds in the requirements for the systems.

 

[David]

Do you have or have access to the performance specification or design specification for some of the systems installed on production vehicles?

There has to be objective and thresholds in the requirements for the systems.

No. I just very very seriously looked into it, read the specs of the available systems, looked at all the technical stuff I could find, looked into re-programming them and came to the conclusion that while it would 'work' it wouldn't work properly, may degrade performance and with EBD and TSC could potentially even be dangerous. I'll see if I can dig out the documents and links I found.

 

[James]

You might find this interesting reading.

http://stoptech.com/technical-support/technical-white-papers/abs-and-big-brake-kits

Interesting read....

 

[Vidal]

ABS isn't speced by the manufacturer to account for aftermarket brakes. Increasing the weight of a vehicle isn't a problem. Decreasing and increasing the grip (and brakes) is as the ABS computer 'knows' how fast the car can possibly decelerate. If the computer 'thinks' that the wheels have slowed down faster than it thinks is possible (due to more grip, better brakes and lower weight for example) it will let off the brakes and so will *increase* braking distances!

You might find this interesting reading.

http://stoptech.com/technical-support/technical-white-papers/abs-and-big-brake-kits

OK. I see where you're getting your information from.

It is true that a traction control systems monitor many vehicle perimeters and require tighter tolerances. However the OP is speaking to the addition of an anti-lock braking system only.

ABS monitors the wheels and keeps them rotating to assist the driver in maintaining control of the vehicle:thumbsup:. I doubt you'll find an anti-lock brake system specification (just ABS without any type of traction or stability control) which was written with requirements for the EBCM to monitor the rate the vehicle is decelerating.

 

[David]

Admittedly I was looking at reasonably modern stuff although not current stuff, late 90's to early 00's and the Bosch rather than Nippondenso.

Some documents on the systems I was looking at (the Bosch 5.7)
http://www.bmwtech.ru/pdf/e46/ST034/14 P2 Traction and Stability Control Internet.pdf
http://www.meeknet.co.uk/E38/E38_DSC_System.pdf
http://jbbeach.com/files/bmw323ci/300-2_Electronic_Brake_and_Stability_Control_Systems.pdf

Also this one is interesting.
ABS For Hot Rods - Installing A Late-Model Electronic Stability Control System - Hot Rod Magazine

 

[Vidal]

Admittedly I was looking at reasonably modern stuff although not current stuff, late 90's to early 00's and the Bosch rather than Nippondenso.

Some documents on the systems I was looking at (the Bosch 5.7)
http://www.bmwtech.ru/pdf/e46/ST034/14 P2 Traction and Stability Control Internet.pdf
http://www.meeknet.co.uk/E38/E38_DSC_System.pdf
http://jbbeach.com/files/bmw323ci/300-2_Electronic_Brake_and_Stability_Control_Systems.pdf

Also this one is interesting.
ABS For Hot Rods - Installing A Late-Model Electronic Stability Control System - Hot Rod Magazine

Nice collection of traction and stability info.

I apologize as I was not referring to the spec type info sheet that is included or posted for an item. I was actually referring to the specification that is used to build the system. Its the engineering document.

 

[John Ross]

You might find this interesting reading.

ABS and Big Brake Kits

Indeed, very interesting. Since just changing tires can have a huge impact in braking performance (and people replace OE tires all the time), it seems to me the next step for the ABS engineers is to build a "learn mode" into their systems, so the driver can do a few hard stops in succession in a controlled environment, and the computer can "figure out" the optimum commands to make to the system when the driver lays on the brake pedal.

You know, like my cell phone's texting system figuring out a new word it wasn't originally programmed for, like "transaxle"...

JR