navin in KC

Is the cylinder deactivation exclusive to the S8 or do the A8's also have this feature?

2012s4

All 4.0 T engines have it

BigBoy11

And it works seamlessly. The stop-start system; not so well. Turned it off the first day and have left it off.

navin in KC

I'm surprised that the gas mileage isn't better, but I guess it is a 4000Lb monster, so maybe it makes sense.

jakematic

Was surprised at that too when looking at the newer models.

My 4.2 regularly gets 29+ highway and around 18 city.
As calculated manually and by the bordcomputer.

I wonder if the mileage loss is due to higher RPM requirements on 4 cylinders...
The 4.2 with the 8 speed just coasts in comparison to what D3 did - typically 400-500 RPM less.

DeerHunter

RPM at any particular speed is dictated solely by gearing and wheel diameter. It matters not whether your car is a 2-cylinder 2-stroke or a W16 quad-turbo.

4-cylinder mode on the Audi V8TT improves mileage because the throttle has to be opened more in order to produce the power required to motivate the car. This reduces pumping losses, which are significant for a 4-stroke gasoline engine.

My S6 gets better mileage than my 2005 S4 Cab with the 4.2 V8, despite being heavier, larger and more powerful. Audi must be doing something right with this technology.

Speednet

Totally agree. Stop-start is the worst technology put into a car since the automatic seatbelt.

navin in KC

what is so wrong with the stop-start technology? Is it any more than a slight delay when stopped at a traffic light when you hit the gas? Are there other concerns/problems with it?

BigBoy11

Just give it a try and tell us what you think. I thought it was a royal pain.

Dr.Aronis

The start stop sometimes makes my V1 restart. Otherwise it works well. I almost alway have it off though.