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Author Topic: ECU speed accuracy ?
WheelSpin
Member
Posts: 11
 ECU speed accuracy ?on: November 11, 2019 (GMT)

The ECU speed readout displays the speed at specific speed steps. For example it always displays 26.1, 26.7, 27.3, 28.0, 28.6mph, etc. It never reads in between these speeds. IOW I never see a 26.2mph reading or a 26.6 reading. It always stops at specific speed points either .6 or .7mph apart.

I’ve looked at this using 2 decimal place accuracy & it follows the same pattern. Always reads 26.72mph, never reads 26.71 or 26.73mph. It doesn’t matter if increasing or decreasing speed.

I’ve looked at this using a tablet & smartphone, on two different cars, using Torque Pro & Torque Lite, and tried two different OBD2 readers. Makes no difference. Always displays 26.7mph for example & the other specific speeds. If displaying with two decimal points the steps are either .62 or .63mph between the displayed speeds.

Also it never displays 60.0mph. It’s either 59.7 or 60.3mph. So how does Torque Pro calculate a 0-60mph time?

piemmm
Posts: 6623
 Re: ECU speed accuracy ?on: November 11, 2019 (GMT)

Hi!

It’s because the speed from the ECU is actually in km/h and the OBD2 specification only provides integer values (from 0 to 255km/h) – this is why when you convert to mp/h you see it going up in steps

WheelSpin
Member
Posts: 11
 Re: ECU speed accuracy ?on: November 11, 2019 (GMT)

Thank you for the information.

That would explain the .62mph difference between readings.

Since the OBD2 only provides integer values of km/h, what does Torque Pro use for calculating 0-60mph time? Is it using 96 or 97km/h, or is it mathematically calculating something in between?

WheelSpin
Member
Posts: 11
 Re: ECU speed accuracy ?on: November 17, 2019 (GMT)

I apologize for bumping this but I have not yet found an answer. I have searched but to no avail.

How does Torque Pro calculate 0-60mph time since the OBD2 only provides integer values of km/h?

Does it use the closest km/h speed such as 96 or 97km/h, or does it mathematically calculating something in between?

Thanks

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