I saw a Euro spec S4 today and saw a couple of things on it and I'd like to understand what they are.

The first was a dark bulb looking thing to the right of the front right foglight. The car is equipped with Adaptive Cruise Control, but from my understanding the ACC radar sensors are on the front bumber beside the headlight washer nozzles so this bulb wouldn't have anything to do with ACC.

The second was what looked like a lens attached to the rearview mirror housing pointing forward out the front windshield. I don't imagine this is the rain sensor for the wipers. My current Canadian Spec A3 doesn't have this much gear on the rearview mirror and it is equipped with rain sensing wipers.

Any ideas?

That round lens by the foglight is in fact for the ACC (I'm 100% sure about this). I don't recognize the mirror sensor, but it may be related to ACC too. Someone on the B8 A4 forum with ACC may be able to confirm.

'round lens by foglight..' yes as confirmed, it is (part of) ACC - I coincidentally confirm w/Dealer earlier this week.

'Mirror lens ....' I am not yet familiar with but I suspect a) it is part of Automatic hi-low beam adjust feature [it is a sensor device camera as opposed to image camera, part of feature set with Electrochromic Mirror in some markets / OEM models] or b)that it could be part of the lane change warning system i.e. do the Door Mirros on same vehicle have warning indicators on the 'inside wall' of Mirror housings ...as viewed by Driver?

the 1st one

Part of the sensor on the windshield is the 'high-beam assistant'. It detects oncoming traffic and off the high-beams automatically and then turns them back on when the traffic passes. The other part is the rain and light sensor for headlights.

It is not available for North American cars at this time.

The big thing up ontop of the rearview mirror isn't high beam assist, it's Audi's Lane-Assist system. Audi doesn't have a high-beam assist yet

The sensor on the windshield is the high-beam assist. Audi just doesn't offer it in North America.

This car was sent to us for auto shows and product testing in Canada. It is a German spec car and was built with the high-beam assist feature. The lane assist feature is not on this car.

What does a high-beam assist do?

It detects oncoming traffic and automatically toogles between the high-beams and low beams.

It detects oncoming traffic and automatically toogles between the high-beams and low beams.

........... also works for forward traffic in your own driving lane i.e. it detects rear tail lights of forward car, at OEM preset forward distance(s), and automatically toggles to low beam - so detects onward coming traffic AND also forward traffic which you may be approaching, auto toggling to respective low beam, OR hi-beam in case when neither lane car is detected.