Dual VSS Inputs
 

OK

That's the next step!

Can't find any info about tuning the traction control. Got anything good?

Going to start with pulling boost when slipping, maybe retard timing.

Reactions should be in this order:

1. pull timing
2. add fuel
3. boost cut
4. spark cut

You can overlap 1 and 2

Boost cut and spark cut are drastic measures and it takes a long time to recover. Timing can be pulled and added back nearly instantly.

What orders of magnitude for each of those should i start with. 1 degree at a time? 5 degrees? <1 degree?

Same question for fuel.

Ben sent me here, I calibrated the TC in the car in the video.

If you run is a sequential COP ignition, my preference is to reduce torque with ignition retard. COP = no worries about rotor phasing in a distributor. This puts a lot of heat past the exhaust valve, the goal is to tune so that you're not digging too hard into the TC. Timing retard *is* gentler on the entire powertrain than Spark Cut, but Spark Cut is easier to tune when trying to stall the tire from spinning. Spark Cut also work better with a distributor that won't support extremely retarded ignition timing.

The goal is to stop the tire from spinning, so I've had more luck being aggressive on the timing retard. I would suggest allowing 6% slip to start with, and remove 8-10* as soon as slip is detected.

-Scott

Thanks Scott. Expect a PM or two in a month or so. I got it working on the bench, but I doubt I'll have everything wired and tuned sooner than that. 70% of my suspension is at powder coating.

Finally got it all buttoned up and its working perfectly. Now I need to tune it. Going to start with 6% slip as suggested, final goal is to have it adjustable via a knob.

What does your %slip/time curve look like. Do you ramp up significantly higher than 8-10*? or is it a slow ramp up. I started with some low values with no success. Going to try and get some logs tonight.

I would love to see a rolling per-cylinder fuel-cut algorithm implemented someday. Not sure if Vbox/Racelogic has some legal noose on that style of TCS, but it's vastly superior to anything else out there, IMO. Spark/boost cut obviously de-spool the turbo, ignition retard will spike EGTs, and even with a DBW setup, closing the throttle will reduce airflow through the system. Cutting fuel on a rolling per-cylinder algorithm maintains system flowrate, keeps the turbo spooled, and won't harm EGT, and you can lean on it as hard as you want.

The new 991.2 Turbos use a similar system to maintain turbo boost off throttle. In certain situations, as you lift off the throttle, it actually leaves the throttle plate open and reduces engine output by cutting individual fuel injector outputs. This maintains airflow through the system and keeps the turbo spooled up. Pretty trick.

Well ms 1.5 alpha does have provisions for DBW, make a suggestion on msextra and see what happens.

I'm pretty new to speed/toothed sensors. What is the purpose of using the VR conditioner and the logic input, rather than going right in a digital input like Nitrous In? I'm just going off the Westfield guide to put the VSS pin from an NB into Nitrous In.

The VR signal from an ABS sensor is a ~1v to -1v sine wave. The digital inputs need a 0-5v square wave. The VSS pin on an NB (and NA for that matter) is a 0-5v input. The speed sensor on an NB outputs a very similar VR signal (-1v-1v) and inside the cluster is a conditioner of sorts. So it takes in the VR signal from the speed sender, and outputs a square wave from the cluster.

https://www.miataturbo.net/attachmen...ine=1461011289

Hoh lee shit.

Look at all those picture uploads.

Thanks, makes sense. Good thing I asked, since I'm replacing the cluster with a Racepak.

You will need an alternate way of getting the speed signal to the ECU.

Yep, I'll go with the V2.1 Dual VR board. (Assuming you mean I'll have to go another route than just going right into Nitrous In, and not another route than this board). For now I'll just use the internal Racepak conditioner for speedo readout until the V8 goes in and I need traction control.

Yes, that board will work just fine. It will also work for using ABS sensors for dual VSS input (hence the title of this thread) I wish I had some damn time to tune though.

Did you use PT4 and JS10 because the other digital inputs are low frequency? Did you do hardware modifications to JS10, or just run a jumper from that to one of the spare pins?

All my other digital inputs are in use. JS10 needs a protection circuit if it is being fed by a signal from outside the megasquirt. I have a VR conditioner (inside the case, powered off the ms vref) between my external signal aand the output, so I didn't need to build a circuit. Just a wire from the VR conditioner to js10