Superb, L&K, iv, 2021 model - Collected md Sept 2020. Car has Road signs and Predictive cruise control.

Current issues:

The road speed sign on the display change from mph to KMph randomly - I think it is only the display but it might affect the auto speed settings as well.

The predictive system tries to pick the best speed for going around bends and roundabouts. It seem Ok on the few bends that its detected but is unreliable on roundabouts.

When engaged the car will detect a roundabout and start slowing down in good time, however randomly it speed up again just as you get to start turning, which means I have to brake hard - which of course disengages the PACC.

I've also encounted a sudden drop in speed through the PACC on different roads from 70 to 50, from 40 to 19, and from 40 to 25mph.  No obvious reason, such as a new obstacle in the road. 

I suspect there are some serious bugs in the software that is combining all the various sensors with the speed control and the maps and it getting things wrong.

I've asked the dealer to investigate but so far nothing is know.

I cannot see and option to disable the Predictive part of the PACC so current not using any ACC which is a real pain

 

Anyone else having these issues???

Whilst I don't have PACC on my car, those speed drops seem to loosely tie in with the KPH and MPH problem you mentioned before. The 70 to 50 and 40 to 25 sound like the MPH equivalent of the KPH figure. 

 

Hopefully someone else (or your dealer) can help you out.

Hi @ERIK99, another MK local and I have almost the same spec as you, albeit different engine!

 

You've probably already discovered this, but for any other interested parties there are two key settings in pACC:

▶ Road layout preview - Switch the cruise control on/off according to the road profile (e.g. reduce speed

before a bend)
▶ Speed limit preview - Switch the speed control on/off

according to the permissible speed

 

I have disabled Road layout preview, as it exhibits the behaviour Erik described, inconsistently slowing for roundabouts, sometimes 40mph, sometimes 28mph. Also seeing bends that need slowing to 28mph.  I think it would work best in motorway situations. 

 

The speed limit preview again is best on motorways, for example it reduces down to 60mph for the temporary speed restriction on the M1 roadworks. It's 'mostly' ok around Milton Keynes, but sometimes goes 40mph/30mph/60mph when the actual change of limit is a straight 40-60mph. In addition side roads are sometimes seen as 30mph, sometimes 20mph seemingly regardless of actual permitted speeds.