Yup thats why I have a 4 VR conditioner board, there's enough available on my inputs on my pro for 4 speed sensors but only 2 would work without the conditioner, might as well do all 4.

 

Which VR conditioner board do you use?

 

The good one, MAX9926UAEE+TCT-ND. I had some canadian company proto-advantage put them on surface mount to dip adapters because I'm not brave enough to solder surface mount components that cost $20 each.

 

So after a pretty messy auto-x on cold tires I'm back to trying to implements this. Can't get the speed signal to show up for some reason, I'm using an ABS sensor ran through a 4-pin GM HEI module like this.


I have this going into PT4. Is the 1k resistor the correct value to get a 5v signal to the input? Pull up resistors confuse me.

 

Nonononono. 1k pullup to 5v, not to 12v. PT4 is a digital input, 0-5V Think of the HEI module as a switch, its either connecting C to ground, or letting it float. So when it connects C to ground PT4 sees "0", when it lets it float PT4 see's 5V (or a little less) from the pullup resistor.

 

Thank you! I figured I was being dense. So I should be able to hook my meter to C and spin the hub to see if I'm getting a pulsing signal to ground?

 

Confirmed, don't be a dumbass like me.....needs a pull up to 5v. I'll follow up with my findings when I get to tuning this hot mess.

 

You're using this for chassis or driven speed?

 

This is being used for a single front wheel speed, I'm getting the rear wheels speed from the trans VSS. I'll see how bad the left to right bias is and add the other front wheel into the mix if needed.

 

If you plan on any turning, I can guarantee a single front wheel isn't good enough for traction control.

 

Are you basing this on the calculations you did earlier in the thread or first hand experience? I'm really looking at this as a safety net to keep from blowing off the tires on loose or wet surfaces. Yeah it would be nice to be able to pin the throttle at the apex and ride TC out of the corner but I just don't think this setup it's advance enough enough to do that even with both front wheel speed sensors. Almost need a stability control element to do that

 

I used this (very simple) circuit with my Adaptronic to read 2x ABS speed sensors via digital inputs:


I've not got as far as connecting it up to my MS3 to see it the MS will also read it OK though..

 

Success.......and failure. I got the speed sensor reading and it will react when there is wheel slip. The problem is the speed drops out above 28mph......doh. There are a few things that could be causing this.

1. I rotated the speed sensor 180deg because of the way my brake ducts are oriented it clears better. The sensor head is diamond shaped so I assumed it would pick up from either of the high points.

2. I'm actually using E30 hubs (I have a whole thread on this) I believe the diameter is danger close to the miata diameter, I'll measure here in a bit and see what the clearance is. Biggest difference is it's 48 teeth where the miata hubs are 44 but I can get the speeds to match in MS.

3. Most likely this has something to do with the GM HEI module I'm using. I'm guessing I'm exceeding some internal limitations as far as frequency.

Any input or suggestions?

Edit: Just read where there is a polarity to the sensor, might try swapping the wires and see if that helps.

 

No polarity on the sensor.

My guess is number 3. Got any way to generate a frequency other than the abs sensor? If you have a spare NB speed sensor from the transmission you can spin it in a drill to generate a VR pulse. Or a function generator.

 

Thanks for the suggestions, helped narrow down the issue but unfortunately I didn't quite rectify the problem.

1. Tried swapping the leads, was reading something about the pulse going neg then pos, with the leads swapped it would be pos then neg thinking maybe that would somehow effect the HEI module. Nope......AidandJ was right no difference.

2. Hooked up a spare trans speed sensor and low and behold it worked great. Speeds from 0 to 110 mph and seemed very stable. So this confirmed that everything from the module into the ECM is good.

3. Tried spinning the speed sensor back to the OEM config since I had it 180 deg out. No change.

4. Tried a Miata hub since it was .020" bigger diameter. Interestingly enough I got nothing until 25mph and then the speed would jump up work fine all the way to 100mph. So 25-100mph worked.

5. Tried spacing the sensor out from the wheel and found a sweet spot where I could get 15-100mph. Oddly when I tried this on the road it didn't work as well and I got intermittent signal.

6. I machined the miata tone ring to fit the BMW hub and had the same issues as test 5.


***** *****........that's anoying. So this gives me 3 possible points of failure

1. Bad sensor
2. HEI module sucks for these types of sensors
3. I'm grounding the HEI module through the chassis, Should I give this a sensor ground to the ECM?


I'l probably try option 3 and then start replacing the sensor and VR conditioner.

 

What is the sample rate on MS/PT4?

As a thought experiment, would knocking every other tooth out be good enough resolution and decrease the frequency being sent to the holley unit?

Granted, this would also be a pain in the bum.

 

I had the same thought as you but in further testing I was able to get a signal all the way to 100mph, probably higher but my drill was tapped out.

VR conditioner and sensors on the way, it'll get fixed one way or another.

 

Gonna start playing with this in a couple of days as well. No idea where to start with the slip x time graphs though. Anyone care to share their settings?

 

Still following with interest.

I just ordered a Racepak hall sensor and 18t reluctor ring that should be able to clamp around the driveshaft for rear wheel speed (NA6 problems). Hopefully wiring will be straight forward.

Hookup to +5v ,ground and signal to PT4 right?

Once I obtain a front abs knuckle I'll play with vr

 

AFAIK nobody has tuned it with success on a Miata.