Motor Trend: 2021 Audi RS5 Sportback First Test: Just … Wow
 

https://www.motortrend.com/reviews/2...ack-first-test

Some really nice pics with the article. The car is spec'd in the perfect color. :)

I'm curious- the RS5 launch control is different than the S5?

No, it's the same procedure.

I'm more interested in the "clever RS-specific rear differential". I'm assuming they mean the sport diff but is there a difference between the S5 vs TS5 sport diffs?

I had heard that it was the same part number as well. I don't think it's a placebo effect but to me I notice the diff in many more situations in the RS5 than I did with my S5. Perhaps because of the higher power in the RS5 and the different torque split (not even sure this is different between S and RS) the sport diff works more often? I don't know.

It is the same part number (0D3-500-043). As is often the case the author might have misheard or been mistaken or maybe something was lost in translation. The front/rear torque split is the same (40/60) for the S5 and RS5 and the way the center diff can split the power is the same between the two models.

I wonder if the programming is different. I don't have a B9 S4 to compare, but the Sport Differential in my B9 RS5 reacts more aggressively than the ones in both of my previous S4s (B8, B8.5). Perhaps its a B8.5/B9 difference, or perhaps it's an S/RS difference...

Like I said above, I feel like it acts different vs the B9 S4 and S5 I owned as well.

I can't compare B9 S5 and RS5 directly, but I can compare a B8.5 S4 to the B9 RS5 SB. And, just in case you are not aware, the S4 and S5 have the same chassis and drive train.

The reaction of the Sport Differential in Dynamic mode in my S4 was more like Comfort in my RS5. My S4 was also tuned and had about 460hp and 400 ft lbs torque, so I don't think the difference can be attributed solely to power. Additionally, the Sport Differential in the S4 was more responsive after the car was tuned so power may make a difference, but it was not a factor in my comparison.

So, power differences aside, I experienced a significant difference between the behavior of the Sport Differentials in my S4 and RS5. Perhaps there was a change in programming between B8.5 and B9, or a change between S and RS, or both. Regardless, the Sport Differential in the RS5 is noticeably more active than the one in my previous S4. For normal driving I kept my S4 differential in Dynamic mode but find Auto to be better for the RS5 on the street and reserve Dynamic for the track. Either way, Auto or Dynamic, I can generate throttle-induced oversteer without the unnecessary drama of a tail-happy RWD car. Perhaps others with S5 and RS5 experience can speak more directly about the differences within the B9 models, but my reaction is that the Sport Differential is more of an active player in the cornering process in my RS5 than my previous S4.

This video provides more information about the Sport Differential. You can see it's complex and likely to be controlled by programming. Perhaps the Sport Differentials in the B9 S5 and RS5 are tuned the same way, but I doubt it. The S models are great cars, but the RS models are factory tuned to perform better. The more aggressively you drive, the more apparent the differences will be.

https://www.audi-technology-portal.d...t-differential

The J187 controller for the 0D3/0BX 2nd gen sport diff (replacing 1st gen 0BF/0BE) is used across numerous vehicles: A4Q, A5CO, AQ5, AQ7, RS5, RS7, etc. All use 8W0 907 163, rolled to 8W0 907 163 A as of Feb 8 '21. So there's no reason not to presume it either has parameter maps for the various applications or is coded differently installed to perform as expected for the designated vehicle. edit- from the SQ7 SSP where the 0BX is documented - "The differential lock control unit J187 identifies the sport differential and the corresponding vehicle on the basis of internal data. It activates the hydraulics of the sport differential, which in turn redistributes the engine torque."