MoTeC Global Forum

Is there a way to calculate Ground speed on the M1 whithout having any GPS or wheel speed Inputs?

Thanks

No, but you can determine how fast the drive wheels are spinning. Look in the firmware help of your M1 Package for "Vehicle Speed", for the compete story, but here is the relevant section for your request:

Estimated

Used if all wheel speeds are zero or faulty and GPS speed is not available. Calculated from Engine Speed, Gear Ratio Overall, Wheel Speed Rear Circumference and Wheel Speed Front Circumference.

Wheel speed sensors can also report a speed of 0km/h when the vehicle is stopped. To distinguish a stopped vehicle from faulty sensors all of the following conditions must be met for a time of Vehicle Speed Diagnostic Delay before the estimated value is used:
•Wheel speed sensors report zero or are not available
•Throttle Position is greater than Vehicle Speed Moving Throttle
•Engine Speed is greater than Vehicle Speed Stationary Engine Speed
•No fuel cut or ignition cut is effective
•Launch State is Disabled
•Anti Lag State is not Enabled
Once these conditions are fulfilled, the estimated value is used until a wheel speed sensor reports a valid non-zero value. If Gear is Neutral, the estimated Vehicle Speed will be set to zero.

Furthermore, if all wheel speed sensors are zero Vehicle Speed will also be set to zero when all of the following conditions are fulfilled for a time of Vehicle Speed Diagnostic Delay:
•At least one of the conditions that lead to the use of the estimated value is not fulfilled.
•Throttle Position is below Vehicle Speed Stationary Throttle
•Engine Speed is below Vehicle Speed Stationary Engine Speed
For the Vehicle Speed to be set to zero by this way it is irrelevant if Vehicle Speed was using a wheel speed sensor or the estimated value before the mentioned conditions become true.

Thanks David

I've been trying to use the calculated vehicle speed but doesn't seem to be working. I've unplugged the GPS and all the wheel speed sensors are not in use. The wheel speed circumference measurements are correct as well as the gear ratios . But the "vehicle speed state" is still saying "wheel speed sensors"

Thanks Don

You might need to report a bug to someone that can fix it for you. What firmware package are you using?

You don't have Wheelspeed Front Drive Sensor Resource or Wheelspeed Rear Drive Sensor Resource configured do you?

I would suggest a log file or screen shot of M1 Tune showing the relevent channels:

Wheelspeed Front Left
Wheelspeed Front Right
Wheelspeed Front Drive
Wheelspeed Rear Left
Wheelspeed Rear Right
Wheelspeed Rear Drive
Vehicle Speed
Vehicle Speed State
Engine Speed
Gear Ratio Overall
Gear
Wheelspeed Front Circumference
Wheelspeed Rear Circumference
Throttle Position
Vehicle Speed Moving Throttle
Vehicle Speed Stationary Engine Speed
Brake State