Mazda CX-3 Forums

Hi, I know its not much but when I set the cruise control, say to 70, the car mph according to the HUD and Dash display are 71. I know it's easily solved by setting the Cruise to 69 but it just seems a bit odd.
Any ideas?

Same here, very odd

Handy Andy wrote: ↑Fri May 11, 2018 1:48 pm Hi, I know its not much but when I set the cruise control, say to 70, the car mph according to the HUD and Dash display are 71. I know it's easily solved by setting the Cruise to 69 but it just seems a bit odd.
Any ideas?

Same. I think it is just the odd way the design engineer programmed it. Doesn't make sense to a logical person tho

Mine is spot on, but that's in kmh and not mph.
Just for a test, how about changing to kmh (metric) and see if it's still different?
I belieive you (in The UK) can change from mph to kmh via a dial on the dash, correct ?

Does it really matter? The Dash display and HUD aren't the correct speed anyway. They have to show a higher speed than you are actually doing. A sat nav that shows the speed is far more accurate (unless you are going up or down a very steep hill.

Strangways wrote: ↑Fri May 11, 2018 7:21 pm Does it really matter? The Dash display and HUD aren't the correct speed anyway. They have to show a higher speed than you are actually doing. A sat nav that shows the speed is far more accurate (unless you are going up or down a very steep hill.

The speed showed in my car in The Netherlands is less than 1% to high which is (in my opinion) very accurate for a car.
I checked it for different speeds with a mobile GPS receiver known to be very accurate.

By the way: the speed set (in km/h) for the cruise control is the same as on the dashboard and the HUD.

The speedo is driven by the speed sensors on each wheel but the HUD is driven by GPS. If you take the SD card out the HUD will stop working. That explains the difference.

anchorman wrote: ↑Sat May 12, 2018 9:14 pm The speedo is driven by the speed sensors on each wheel but the HUD is driven by GPS. If you take the SD card out the HUD will stop working. That explains the difference.

Are You sure about that?
I had a 3 loaner car last year, with the new flip-up HUD, that didn't have an SD-card but the HUD worked fine, showing the exact same kmh as the speedo.

santa wrote: ↑Sun May 13, 2018 7:53 am

anchorman wrote: ↑Sat May 12, 2018 9:14 pm The speedo is driven by the speed sensors on each wheel but the HUD is driven by GPS. If you take the SD card out the HUD will stop working. That explains the difference.

Are You sure about that?
I had a 3 loaner car last year, with the new flip-up HUD, that didn't have an SD-card but the HUD worked fine, showing the exact same kmh as the speedo.

I believe anchorman is correct that the speed sensors are on the wheels and the HUD is is driven by the GPS. Maybe the new HUD no longer requires the SD card to be installed. The difference in readings is probably due to the variation in tyre circumference which will be affected by tyre wear and tyre pressure.

I tested it with my own yesterday (late 2015 CX-3 with the old HUD) and it still shows speed in the HUD with the SD-card removed.