In my not a miata build fe3n turbo truck I'm running a ford 8.8 rear end and I'm using the VR ABS sensor on the diff as a speed sensor through a JBPerf v2.1 VR conditioning board to for my MS3X vehicle speed signal. it seems like it updates too slowly on hard acceleration. When driving normally it operates accurately. When doing a hard pulls(0 MPH to 130MPH) it will lose speed signal and get stuck at a random speed. it also seems like the MPH fluctuates buy about 5MPH at the same RPM when cruising on the freeway that seems dependent on how fast I get up to cruising speed. I'M using a windows tablet running Tuner Studio MS as my instrument cluster.

I'm trying to sort this out with a more reliable solution so I can get tuned for boost by speed. Any input is appreciated.

 

Most all of the frequency inputs on the MS3 are software driven. They cannot read a frequency higher than about 100hz, and it doesn't take much to get there with a speed sensor with more than ~4 teeth, ratio dependent. This is about the only way I can see it sticking at any speed, you overran the resolution.

If you can, switch to PT4 or another high speed compatible input that actually uses CPU hardware to measure time instead of doing it in software. It will still only update ~1hz or so, just a limitation of the hardware.

 

Thanks for the info. I already cut the 108 tooth wheel down to 9 teeth in the diff. Which gives a 304htz signal at 150mph. I'll cut it down to 3 teeth and recheck. That should at least give me an accurate speedo up to 145ish mph