Speed reading way high

[beetos]

Hi
New set up here, BMW N54 s7+ 1.699.

Speed is reading too high by a factor of around 1.5

Base map the tooth count on the wheel inputs is 69. I need to look at the toothed rings on the hubs to verify. Dry tyre circumference looks about right at 2.0m. Wheel speeds come in over CAN (ABS), teeth per reading is set at 1. I’ve looked at the other threads on this and some say change dry tyre diameter.

Would varying tooth count not be more effective way to calibrate speed? Pics of my stock ABS rings appear to be 48 teeth.

Also, can someone explain what ‘radar’ speed input is and its relevance in speed related functions?

[stevieturbo]

Ultimately it is nice to have all numbers correct....

If you measure tyre circumference, put that in correctly, then yes you could alter tooth count to try and get the right speed out the other end

At around 1.5x....are you sure it's on mph or kph as you wish ?

I would prefer to have the circumference correct though, in lieu of any other numbers, as you're more likely to swap tyres, than anything else.

Radar speed is just another speed input. Use it as you desire, or not at all.

[beetos]

Thanks for your response. Yes all Kph. I’ll play with teeth and circum and see what works. Radar I take it can be be ignored. Would be interesting to know the reason Syvecs used it in the first place.

[stevieturbo]

It's just a universal speed reading. It can be whatever you want it to be, if not specifically an individual wheel speed.

I have wheel speeds and radar is used for propshaft speed.

[beetos]

Now spot on with teeth readings of 111. The physical teeth are 48 but now I can have meaningful tyre circumferences and all speeds are ok.

One thing I get whenever I reverse is a device error warning and all sensors come up as a recording speed spikes. Not sure what's going on there but will log etc and check sensor set up and see if it’s anything obvious. Anyone else see this on PnP CAN speed enabled kits??

Also, when reversing the speed pegs at some abnormal value.

[stevieturbo]

Can't comment on that.

But ever since I moved my rear wheel speed sensors to the X10 expander, when then sends via CAN.....I do get a lot of spikes. Which is annoying. They were faultless when direct to the ecu

I've now had to largely ignore them and changed driven speed to a sensor on the propshaft. I still log individual wheels, just do not use them for any controls because of the spikes.

Seems odd the numerical difference in teeth is so far removed from what the base map is supplied with ?

[beetos]

Syvecs mentioned the high tooth count is something to do with scaling on that particular PnP application. My speed reading are not spiking when driving, very stable. It’s only when stopped and I start to reverse all that 4 spike and speed reading pegs at 500kph. Other than that it’s fine.

[juiweasley]

Consider adjusting the tooth count setting in your system's configuration to match the actual number of teeth on the rings for more precise calibration.

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[taronsargsyan]

hi. did you managed to fix this ?

Syvecs mentioned the high tooth count is something to do with scaling on that particular PnP application. My speed reading are not spiking when driving, very stable. It’s only when stopped and I start to reverse all that 4 spike and speed reading pegs at 500kph. Other than that it’s fine.

[beetos]

All sorted. Just had to put tooth count numbers in front/back to get wheels speed close to actual and then changed diameter slightly. All 4 are now spot on and calibrated to read same as GPS speed.

I got a new code that helped the speed spike in reverse. It sometimes now occurs just for a fraction of a second. Some unique aspect of the BMW ABS and the CAN interfacing I think.