ABS sensor inputs for TC

[Hodge]

I'm retrofitting ABS sensors to an NA supra and running them to the Syvecs. I only have 2 sensor inputs on the loom though, FL speed input and FR speed input. What do I do with the rear sensor inputs?

Cheers
John

[stevieturbo]

Are all the inputs used up ?

[TimH]

If I recall, there are no inputs left over that can read the other two, so you have to take them via an external speed converter box (or use an IO expander maybe).

[Hodge]

When Ryan did my old supra Hexonly connected 2 wheels but I'm not sure which one. Id have thought it would be 1 front and 1 rear.

Cheers
John

[stevieturbo]

On the cheap if you're out of inputs, use a single undriven wheel input, and put a trigger on the propshaft/gearbox ( or if there's a speedo takeoff on the diff it would do ) and just use that for traction control

If the box has an electric speedo output already, that would probably be ok

[TimH]

standard schedule suggests RL and RR - presumably for traction control since they're the driven wheels?

[Hodge]

I've just dropped Ryan a line to see what he did and I'll report back.

[stevieturbo]

standard schedule suggests RL and RR - presumably for traction control since they're the driven wheels?

TCS as currently used on the ecu's needs an undriven and driven reference.

It needs to undriven to determine slip relative to the driven wheels.

Some TCS systems and I mentioned it before, simply use a rate of change of the driven wheels ( or more correctly propshaft ) as an indicator of slip. They claim this approach is patented, whether that really prevents others using it or not, I dont know.
That method would only need a single input to work.

They build up a propshaft rpm table for optimal acceleration to reference to to help with control, but largely if shaft rpm increases too much at any given speed, it's deemed as slip and timing or fuel cuts can be applied to bring it back into check.

[TimH]

Maybe the notes on my schedule (from Ryan) are incorrect when they say RR and RL (they are only brought out to the expansion connector, not to the vehicle loom) as what you say (obviously!) makes sense.

I believe an external box is needed for the wheel speeds and I thought (again, perhaps erroneously) that this was only for two of the inputs: not sure why they would need different treatments though so maybe all the ABS sensors need the box...there are 2x AU, 2x AR and 2x AB inputs brought out to the expansion connector. Maybe the sensors *have* to use AB inputs so as not to upset the ABS system itself?

Would like to understand this, as our own prototype I/O expander is configured for AU-type inputs not AB (although it can be manufactured/modified to have AB type inputs).

[Wez]

With an S6GP or S8 you need ABS sensor converter boxes, S6Plus has them built in I think.

They look like a large orange relay, Chris Wilson on the MKIV forum was selling some modules too.

On mine we run all four speed sensors but its a stripped chassis so had more IO available.