James Cole

Wondering if the sport diff that has all this clutches inside would rob power in certain cases when using in dynamic mode, someone already reported a drop in MPGs in this mod but it could have been a mistake, either way, is there some kind of loss when using the sport diff?

Thanks!
JC

markcincinnati

Well, the sport diff does add a bit of weight. And, any weight could be an issue -- lower mileage, tire wear, and on and on. I guess the sport diff may be a robber. On the other hand, I think the sport diff has the opportunity to increase the performance of the vehicle under certain circumstances -- yet, even if the main reason for many (most?) of us to get this feature would be "bragging rights," well, the robbing that goes on would be minimal, unless the sport diff hardware weighs, oh I dunno, hundreds of pounds (which it does NOT).

Most of us, I would argue, do not drive "aggressively" enough to get much benefit from the sport diff. This does not suggest that getting the sport diff is without merit. I would have gone with it as a stand-alone option, even though I know that 98% of the time I would be "lugging" the sport diff's extra weight around.

For me -- maybe or maybe not for you -- the torque management supplied by the ABS/ESP system is appreciated and is sufficient; even this technology is only rarely engaged.

If you are considering this (the sport diff) technology and would reject it because you think it would rob power, I wouldn't sweat it -- get the feature, especially if you're OK with the bundle.

superswiss

Yeah, other than being slightly heavier than the normal diff, there is no power robbing. When driving straight it's just like an open diff and when cornering it uses the clutch packs to engage an overdrive gear set that transfers more torque to the left or right wheel. Audi states that the additional fuel consumption of the sport diff is barely measurable.

https://www.audiworld.com/articles/q...ism-redefined/

dbuxton13

These sports-diff exchanges are becoming predictable now, haha. Agree with Superswiss, mechanically all it is doing is diverting torque from both wheels to favor the outside wheel in a turn. The system weighs a little more, so that is the only penalty, and negligible on the order of ~1%. After driving my S4 with this system for a couple months, I decided to go drive the dealer's basic S4 again and see what it felt like without the SD. Understanding all the physics and fundamentals is one thing, it is another to compare the feeling at a practical level after becoming sensitized from exposure. To sum up the experience, it is exceptionally noticeable. Foot-stomper: it is noticeable in multiple scenarios, not just the often cited top-end, pushing the envelope, 98% of the limit, tracking the car scenario.

Left turn at an intersection--how to describe this? Without SD, it almost caught me by surprise, the rotation felt a bit sluggish and numb from what I'm used to. With the SD I would describe it as feeling agile and responsive, almost spring loaded. The car wants to turn under acceleration effortlessly, begging you to mash the pedal harder.

Entering autobahn from on-ramp--The difference here is starting the accelerated turn at speed versus a stand-still. Pronounced? Yes, but slightly less so. Still felt quite different.

S turns around 70mph on backroads--It shines here, but once again the faster you go the less pronounced the sensation is. The saying "as if on rails" is not off-base here. No SD meant feeling some (very little) tendency for understeer, which is absent with the SD.

Max speed on a track--Don't know yet. I'll report back once Spring returns, the summer tire/wheel set goes back on, and I head over to the Nurburgring to give it a go.

Lifting off the pedal into a turn--This was an unexpected find. Releasing the load on the engine while turning without the SD felt slightly unstable. Later on I found Audi's explanation: "If the accelerator pedal is released, torque distribution between the wheels is adjusted almost instantaneously." Indeed.

Other notable: My car also has dynamic steering, which is another system I'm happy to have optioned. I've tried the above combos with and without the dynamic steering engaged and prefer to have it on all the time now. Driving without it, or in one of my other cars that doesn't have it just feels weird and unpleasant now. Combine the dynamic steering, sport-differential, and sport suspension, and the car feels like I'm communicating my commands to it telepathically. It just goes exactly where I want it to go, with surgical precision.

Concluding with a quote (emphasis in bold) from Audi's tech glossary on the SD (https://www.audi.co.uk/glossary/q/qu...ferential.html)

Quote:

"Depending on the steering angle, lateral acceleration, yaw angle, road speed and other signals, the control unit calculates the most suitable distribution of torque to the wheels for every driving situation."

ghostrider990

If it was a stand alone option, i doubt i'd need it for daily driving, but it's "nice" to have, because when you hammer the throttle on a turn you can Definitely feel it work.

As its' now packaged with the S Sport - no need to waste time deciding.

Not sure if it effects the actual residual value in any impactful way -- but it would definitely be more appealing to buy a used S4 that was so equipped.

If you have to ask about the fuel efficiency.....you might be driving the wrong car. But i understand the curiosity!

gr