dicktahoe

I find I can't use my cruise control coming down a mountain pass, because I want to use engine braking. If I have ACC on then it applies brakes whenever the grade is more than about 2% down, it's like riding my brakes down the hill. So going down hill, I must disengage the ACC and use the paddle shifters to limit my speed. Too bad, with all the sensors on-board, down-shifting is not adaptive when the car is tilted down, throttle has been released and speed is going up.

13c7a6

I think you can still use the paddle with the ACC engaged. You can also use the D -> S to drop down a gear or 2 with ACC on.

newmoon

Actually that's one of the things that impressed me the most with my CVT with regular cruise control, how it downshifts smoothly and seamlessly when going downhill to use just the right amount of engine braking to maintain the set speed. Even on a 6% grade, I don't think it uses the brakes yet.

When not using the cruise control, it also downshifts when you initially press the brake pedal, but then you can release the brakes and it will continue to hold the lower gear for engine braking until you get back on the gas or the road levels off. So there is clearly a feature in the car where it is detecting the downhill slope and using engine braking automatically. I believe it should also be present in the 8-speed auto and with Adaptive Cruise Control.

Silent Drone

I agree. It should be smarter but it isn't. In this sense the ACC is no different than the dumb CC that proceeded it. Both will hold your speed at the set parameter going down but it uses the brakes to do it. I live on a mountain and use lots of engine braking in my daily dive. I also like to use the paddles to regulate speed on the highway or in other daily driving. It bugs me when I'm on the highway and the ACC taps the brakes to make some room between me and the car I'm following when a simple downshift could have done the same.

Also, I've noticed that the new ZF tranny will not allow a downshift from M2 to M1 until the rpms are at or below ~3,250. This is quite a bit lower than on the old 6 spd where that shift could be made at around 4,500 rpms. This has caused me to have to brake a little more often in the new car to reach that rev for downshifting to 1st.

irenesbob

If the OP is correct that ACC applies the brakes in the situation described, downshifting may help, but you still may have the brakes dragging and speeding up wear. Why not just rip down the incline as fast as the happy car (and clearly the Good Lord) want it to? he, he

Silent Drone

This has been know to occur. Not that I know anything about such behavior personally.

Richard Solomon

Maybe teh 5-0?

irenesbob

Oops, oops, Officer, Sir! You're not gonna believe this, but I was stomping on them brakes but the darn ACC kept making her go faster. Sorry, sir!

Richard Solomon

In all seriousness - I actually want an instrument panel indication when the ACC is braking vs just slowing down. I'd like to know for sure when the electronic driver is making the human driver look like a brake-flashing maroon...

13c7a6

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.

One thing I don't like about the ACC - it brakes way too early when there is a slow car in front while accelerating up hill - the car behind you think you are an idiot