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sport differential effect at ~25mph

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Old 11-12-2017, 12:42 AM
  #1
jlc
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Default sport differential effect at ~25mph

I was making a 90-degree turn, starting from a dead stop, when I hit either a pothole or a poorly executed inflection point in the road. I expected the car to respond as all my previous cars (including the '07, '10, '12 quattro A4s, and an AWD '15 Volvo XC60) have done: w/a (granted brief) moment of hesitation and uncertain steering, before I felt wholly in control again and could steer back on track. Instead (and much to my shock), it just...powered its way around, whipping through the turn faster than expected. No hesitation, no moment of "eh" in the steering, I didn't have to correct the wheel at all; it felt as if the car was driving itself around the turn, and having a lot of fun while doing it. (I don't have DAP, so it wasn't that.) I got half a block before I realized what must have occurred (i.e., sport diff kicking in, and perhaps dynamic steering as well, though the latter is harder to parse out), and a very large grin took over my face.

The sensation was akin to watching a pack of long-distance trail runners race down a steep hill at speed over rough terrain: awe at the power and sheer athletic physicality as feet (and sometimes hands) are intuitively placed, pushing off against rocks, tree roots and trunks, all to keep their bodies upright and under exquisite control as they tear downhill.

For an experience that couldn't have lasted more than 3 seconds, it was...revelatory. Also, shockingly fun. (It was not, till today, remotely obvious to me that you could have fun while driving <30mph.) For the first time in my 25 years of driving, I'm actually looking forward to winter.

I really can't thank enough all the posters (glisse, superswiss, mplsbrian, dbuxton, and others I'm sure I must be forgetting) who have been banging the drum for ordering the sport diff. W/o your repeated posts, odds are we'd have followed our SA's advice to skip it--and to think of what we would've missed if we had!
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Old 11-12-2017, 06:29 AM
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Aww, now this is really pissing me off.

Thanks, AudiUSA, for bundling the sport diff.

While I still believe the sport diff will not be an issue at least 80% of the time we're behind the wheel -- the previous gen's $1,100 asking price for the SD would have been a no-brainer.

While I am unhappy with Audi's decision, I am happy for you, jlc.
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Old 11-12-2017, 07:20 AM
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Happy you found it a worthwhile purchase! My snow tires are fitted and the roof box goes on for the season today. I will get my first chance to whip around in the snow this coming weekend, most likely, which will admittedly be the first time I'll have "played" with the sport diff since A/B-ing thru some corners at quasi-legal speeds back on my test drive. Since taking delivery and airing down my tires to the correct pressures, I legit have not found a place to unhook the rear end safely. The tires, when aired correctly, are too sticky and I live in too dense an area.

What are your thoughts on the dynamic steering option? As you may have read it's the one non-cosmetic thing I passed on. At the time I picked my S4 up, I felt it was too beta of a technology (yeah I know it's been out for 7-8 years now) and a fat wad of money for a car that would never see a race track. By that first part, I mostly mean that a lot of automotive reviews had weird takes on it. I never did get a chance to try it.
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Old 11-12-2017, 09:30 AM
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Right on. You had your first aha moment with the sport differential. Glad I could help convince you. The diff is really being greatly underestimated by many. I don't think most folks realize just how big of a difference it makes in keeping the car composed even in daily driving situations. The diff keeps the weight transfers under control at all times, so things like this that would upset most other cars the S4 etc. with the sport diff simply powers through. In your case it was mostly likely a combination of the sport diff and the sport adaptive suspension. The big improvement in the B9 is the new chassis ECU, which is dedicated to chassis dynamics and controls suspension, sport differential etc.

Last edited by superswiss; 11-12-2017 at 09:44 AM.
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Old 11-12-2017, 12:18 PM
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I learned to drive and found the twisty roads around the S.F. Bay Area to be the most fun, around Mt. Tam, Mt. Diablo, and the Santa Cruz mountains. A good road has turns posted with advisory 5 MPH limits and 15 MPH is very challenging! These are switchbacks where the vertical elevation change and banking would even be a little awkward to a pedestrian. These are the kinds of turns you can find on back roads in the Sierra Nevada or the Alps, but without the sheer cliffs and dire consequences if you were to skid off the shoulder.

I actually think it was most fun in an old, underpowered 2WD pickup truck, where you simultaneously had to sort out some frantic gear shifts, braking, and extreme penchant for over-steer. This was particularly true in the rain. However, even at these low speeds and in these rolling hills, things could get too dicey to be reasonable. I've heard of people hitting cattle around blind corners, and you also see worse situations when roads get popular and you start having drivers and motorcycle riders pretending they are on a closed course and not keeping to their own lanes...

I've never had as much fun in one of my Audis (always with quattro), because I'm too aware that reaching the handling limits is just not safe or sane. The closest I've gotten is in winter conditions where I could pass the same icy and slushy corners every day for a week and work my way up to some power slides as my memory of the road and the predictable conditions slowly converged on perfection. Otherwise, quattro has been a more cerebral engineer's enjoyment as you describe, flickering through my mind after the car has already completed something effortlessly and I've thought about the technological performance seething beneath the surface. Two of my most memorable drives in my old A4 were on dirt roads in the mountains. One that was torn up enough to feel like a 4x4 trail, and one with soupy mud that made me feel like a tug boat pilot.
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Old 11-13-2017, 07:49 AM
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Originally Posted by superswiss View Post
Right on. You had your first aha moment with the sport differential. Glad I could help convince you. The diff is really being greatly underestimated by many. I don't think most folks realize just how big of a difference it makes in keeping the car composed even in daily driving situations. The diff keeps the weight transfers under control at all times, so things like this that would upset most other cars the S4 etc. with the sport diff simply powers through. In your case it was mostly likely a combination of the sport diff and the sport adaptive suspension. The big improvement in the B9 is the new chassis ECU, which is dedicated to chassis dynamics and controls suspension, sport differential etc.
I agree - I think the sport diff is a must-have for the S4 platforms. It makes sense there is a new chassis ECU because the whole chassis feels much more integrated in it's behavior vs. my B8 chassis.
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Old 11-14-2017, 11:33 PM
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Originally Posted by markcincinnati View Post
Aww, now this is really pissing me off.

Thanks, AudiUSA, for bundling the sport diff.

While I still believe the sport diff will not be an issue at least 80% of the time we're behind the wheel -- the previous gen's $1,100 asking price for the SD would have been a no-brainer.

While I am unhappy with Audi's decision, I am happy for you, jlc.
Mark, I owe you a thank you as well, for your numerous screeds about the 19" tires. Had we gone with "pretty" as opposed to "sensible" (the 19s on stanj's car are my all-time favorite, while I find the 18s decidedly meh), I have no doubt my husband would have bent a wheel 12 hours after taking delivery of the car. As it is, all we have is curb rash...which we will deal with after the winter is over.

Generally, I'm not a fan of bundling (though I'm mostly on the other side of the fence from you, when it comes to the particular choices: I'm still irritated that we couldn't get the top-view camera without the acoustic glass or DAP, and I really don't get bundling the red-painted calipers w/the rest of the sport package--I want the bang sans flash), but I can understand why Audi might insist on pairing the sport diff with the adaptive suspension. I've only managed ~80 min of driving in the car, mostly of the slow, plodding sort on entirely boring roads, but already I can tell that it handles weight changes better than anything I'd previously believed possible. As you have pointed out elsewhere, the standard suspension and brake-based torque-vectoring are superior to what's in the vast majority of cars, so it seems to me that if you're going to the trouble of doing something better, then you want serious improvement--which my instinct says requires both the adaptive suspension and sport diff. While I might be indulging in post-purchase rationalization , I feel like getting one w/o the other is akin to ordering a 3-wheel-drive car. For people like me who drive on a lot of snow & ice, powering 3 wheels is better than 2...but why the **** would anyone do that?
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Old 11-15-2017, 12:28 AM
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Originally Posted by mplsbrian View Post
Happy you found it a worthwhile purchase! My snow tires are fitted and the roof box goes on for the season today. I will get my first chance to whip around in the snow this coming weekend, most likely, which will admittedly be the first time I'll have "played" with the sport diff since A/B-ing thru some corners at quasi-legal speeds back on my test drive. Since taking delivery and airing down my tires to the correct pressures, I legit have not found a place to unhook the rear end safely. The tires, when aired correctly, are too sticky and I live in too dense an area.

What are your thoughts on the dynamic steering option? As you may have read it's the one non-cosmetic thing I passed on. At the time I picked my S4 up, I felt it was too beta of a technology (yeah I know it's been out for 7-8 years now) and a fat wad of money for a car that would never see a race track. By that first part, I mostly mean that a lot of automotive reviews had weird takes on it. I never did get a chance to try it.
Have fun--and please tell us about it, so we can live vicariously. I'm feeling envious as it will be a while before I get a chance to really let the car out. I swear, every time I start the engine, the car sounds positively annoyed w/us.

Dynamic steering: haven't noticed it, except for once when I was backing into a parking space from a completely bizarre angle. (Packed lot, acres of circling cars and moseying pedestrians, no way to be pretty about it.) After I was in, w/the steering wheel alllll the way over hard...I realized it was only at a quarter turn. Gave me a bit of a laugh, since the previous night my husband had asked me if I was *sure* they'd installed the DS on the car--he'd never noticed it either, despite a month of circling a garage ramp near-daily while parking at work. It really is unobtrusive/intuitive, which I'm grateful for. We worried it'd do weird stuff like switch over mid-turn, but we got it in the hope that it'd improve driveability on snow/ice, however minutely.

Last edited by jlc; 11-15-2017 at 12:32 AM.
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