jslchmank

do the brake lights come on if the ACC is slowing the car if someone in front is moving slower?

jdong

Yes, any time the ACC applies the brakes, your brake lights come on.

Note that the A6 does have hill descent control, but it only activates it on more severe grades. For a 2% grade, the car probably thinks it's fine to ride the brakes instead of increasing engine noise. As previously mentioned, you need to get up to 3000+RPM before you get any appreciable engine braking.

Once you have a steeper grade, you will notice that pressing the brakes for more than a second will trigger upshifts, so a combination of engine braking and brake usage slows you down.

dicktahoe

Interesting there is a way to determine when the brakes are being applied. You watch the MPG display. As long as this display had not gotten to display at the green battery symbol, you're OK. After that as you feel the car slowing--the brakes are being applied.

dicktahoe

"The Audi has very low internal friction for the engine as well as the AWD system - experience from their endurance racing. As a result, you may need to drop 4 gears from D8 to M4 to maintain a constant speed going down hill using engine braking alone. Brake pads are much cheaper to replace than any engine parts."

Dropping 4-5 gears is necessary--coming down a 6% grade I need to go down to M3 to keep my speed near the 50mph speed limit. I don't know that there will be a need "to replace engine parts" because of using "engine braking". However, I have come up next to a car where brakes have been used all the way down this 6% grade and I can smell the severely overheated brakes.

Silent Drone

My daily drive includes a decent and return climb that is ~1,000 vertical feet at grades of 15-17% through residential with posted limit of 30 mph. It snows here in Utah so Quattro is my friend. I know these grades well because I also bike them from time to time, like I did this morning. See this http://threekings.nslcity.org/king3.html

Anyway, when in M2 on the decent the car will hold at around 38 mph, just a little too fast IMO and certainly too fast if there are slower cars in front. When there are slower cars in front I drop it into M1 and actually apply a little gas to keep the car right on 30 mph at around 5500 rpms. I'd rather use a little gas with engine resistance than ride the brakes all the way down like most people do. By the way, when I am in M2 and just coasting with the engine doing the braking (ie, around 4200-4500 rpms) the mpg display shows that the car is not consuming any fuel. In other words, even though the engine is revving the car is smart enough to know I am not applying the accelerator so it's not burning gas.

I use the tranny/engine to scrub speed in most circumstance not just on hills.

13c7a6

Coming from manual transmission, I've always use the engine braking/gear ratio to slow down the car, however, the paddle control on the A6 doesn't give you the same control because of the low internal friction and the close ratio of the 8 speed gear box. The ECU also try to match your speed instead of slowing down when you downshift by increasing the throttle and rpm when going downhill.

If you brake while going down hill - I don't mean riding the brake, the transmission will shift from D8 --> D2 based on your speed, if you shift to M2 or M3, it will hold the speed as long as the rpm is above 3k or so.

newmoon

This is not always true. When the throttle is closed, of course the MPG will increase. But the A6 also has a feature where the alternator is stepped up to increase the charging rate of the battery during times when the throttle is closed, to pick up energy that is usually lost. Sometimes you can feel the extra drag from the alternator, but it is not necessarily caused by the car braking.

On the other hand when you are braking, the throttle is also closed, so the alternator will also be stepped up and the MPG will go to green battery icon. So you should just be aware about this feature, and that the green battery can also come on with throttle closed, engine braking, but no wheel braking.

snagitseven

To put it simply, not necessarily related to braking, the energy bar indicator will usually go green when coasting.

Richard Solomon

Yes, and IIRC, TFM says that in the V8T (S6) the bar being green indicates V4 operating mode.

James517

I've also found that tapping the transmission into Sport mode just before a hill will tend to automatically downshift and hold that gear for the descent. Don't know if this would affect the ACC setting.