Verybumpy

Just wondering, is this 4.0 V8 feature seamless and undetectable?
How do you know if it's 'engaged' or when it's working?

Thanks.

sushistrip

Undetectable. Even at 125k miles I'm averaging 21mpg combined, and have never been able to feel it engage or disengage.

TinyElviss

On my '15 it is undetectable as well. There is a graphic you can display that monitors fuel consumption and the graphic will indicate when the cylinders are deactivated, but as stated you never feel it turning on or off.

MP4.2+6.0

x3. Not detectable. You look at the MPG screen with the bar graph. When the bar flips from gray to green it is engaged.

sushistrip

Is that screen only on 15+? Or perhaps S8 only?

s4ddriverr

I just picked up a 13 S8 and it also has cylinder deactivation, works just as described above and it is seamless in operation from 8 to 4 and back to 8 cylinders.

sushistrip

Can confirm, '13 A8 does have the graphic. Bar goes green when cylinder deactivation occurs. Never even knew that screen was there, that's just neato burrito.

Verybumpy

Interesting that no one notices a thing, stating undetectable.

I can definitely notice it on my RS7. I wasn't sure what my noise was until this thread mentioned that the Green bar means 4 cylinder mode is engaged. Then it was easily confirmed that only in 4 cylinder mode there was an issue.

Cruising at 40-50mph@~1200rpm the car omits a fairly loud drone sound and vibrations to go with it. It's more noticeable going up a slight incline. My wife commented on it also when we cruise down smoother city roads. The car also sometimes has a jerk or hiccup type 'thing' in the drivetrain when it goes back into 8 cyl mode by simply adding more throttle.

I do have the Audi sport exhaust option but I'm not sure if that should be a factor.

Regardless, I'm thinking something is not right. It's rather annoying often times.

dwboston

I've never noticed my 2015 A8 4.0T going between 8- and 4-cylinders, even while looking at the fuel economy bar as it switches to green and back. It's entirely seamless and imperceptible. It's really impressive.

sushistrip

A8/S8 has active noise cancelling in the cabin specifically for cylinder deactivation. RS7 does not have this because the exhaust is louder.