Double Beep On New Prius

[kithmo]

Prius is Windows 11, 4 down each side, 2 rear and one front. 

I find it very annoying that the speedo is 10% out when I'm using the dynamic cruise control. The speed adjust increments are in 5mph steps, so for example if you're on the motorway you can't do a true 70mph, if you set it to 75mph you're doing a true 68mph and if you set it to 80mph you're doing almost 73mph true. 

[PeteB]

We have the EU to thank for the speedo error (+10% minus 2.5 Kph), but I somehow doubt if we'll get accurate speedos once we leave the EU.

You can set a true speed, but it's a faff - cancel CC, drive to desired speed manually, then flick the lever down to SET the speed, it will hold whatever speed you've set. 

[FROSTYBALLS]

30 minutes ago, PeteB said:

We have the EU to thank for the speedo error (+10% minus 2.5 Kph), but I somehow doubt if we'll get accurate speedos once we leave the EU.

The UK has slightly different legislation governing speedometers to the EU. In the UK, as with the EC Directives, the speedometer must never show an indicated speed less than the actual speed. However it differs slightly from them in specifying that for all actual speeds between 25 mph and 70 mph (or the vehicles' maximum speed if it is lower than this), the indicated speed must not exceed 110% of the actual speed, plus 6.25 mph.

For example, if the vehicle is actually travelling at 50 mph, the speedometer must not show more than 61.25 mph or less than 50 mph.

[kithmo]

12 hours ago, PeteB said:

We have the EU to thank for the speedo error (+10% minus 2.5 Kph), but I somehow doubt if we'll get accurate speedos once we leave the EU.

You can set a true speed, but it's a faff - cancel CC, drive to desired speed manually, then flick the lever down to SET the speed, it will hold whatever speed you've set. 

That's what I've been doing, but it's a even more of a faff on A roads where the limit keeps changing.

[PeteB]

1 minute ago, kithmo said:

That's what I've been doing, but it's a even more of a faff on A roads where the limit keeps changing.

If there's not too much traffic, and you don't need the radar function, you can always set CC to the old fashioned method by turning it off and holding the on-off button in for a few seconds.  Then after setting the speed, each flick of the lever adds or subtract 1 mph, and holding the lever up or down adds/subtracts continuously.  I must admit, I hardly ever bother with that, though.  Oh for an accurate speedo!

[johalareewi]

22 hours ago, PeteB said:

  Oh for an accurate speedo!

You can get the actual speed from the OBD port.  The 10% fudge factor is only added to the on screen speedo.  The OBD port (and the averge speed on the trip meter) have the unfudged values.

[PeteB]

Yes, I've seen that on my Gen 3 - in fact the first three Generations of Prius could display the true speed (albeit in KPH!) on the central Multi Function Display if you knew the secret sequence to get the maintenance screens up.  (I suspect it may be possible on the Gen 4 too, but I've seen nothing on any of the chat groups about it yet).

But I'd like an accurate main speedo, so that the adaptive CC and speed warnings are more useful (at least the SatNav uses the correct speed).