High-Revving Horsepower, Computer-Controlled Shifting
The RS5 keeps the RS4's high-revving, naturally aspirated 4.2-liter V-8, but now it’s stronger by 30 hp, for a total of 450. The compression ratio is 12.3:1. High-revving in this case means up to an 8300-rpm redline so long as the oil is up to temperature; the engine is protected by a 6000-rpm limiter otherwise. It's no secret that with this engine Audi wanted to show BMW that Munich wasn’t the only German town capable of building high-revving V-8s.
You can say bye-bye to the crisp six-speed manual transmission of the RS4, as the RS5’s power is shunted only through a seven-speed dual-clutch automated manual. When we asked whether there would be a standard gearbox offered in the future, Fröhlich told us, sadly, that "the majority of customers in this segment are used to automatic transmissions.” In its favor, the dual-clutch unit—Audi calls it S tronic—allows the driver to include transmission setup as part of the configurability offered by the optional Audi Drive Select (ADS) adjustable chassis system. It also helps that the S tronic box is good. In the RS5, shifts occur without any hesitation, and the quickness produces some sweet burbles and overrun from those twin exhaust cannons out back.
The all-wheel-drive system is upgraded with Audi’s first use of a self-locking crown-gear center differential, and it helps cut nearly seven pounds out of the drivetrain. The new center diff will make its way into other Quattro models as well, and it can direct up to 85 percent of the power to the rear wheels or up to 70 percent to the fronts as grip dictates. Under normal driving, the power distribution is split 40 percent to the front and 60 percent to the rear.
For the first time in an all-wheel-drive car, Audi has added a software-based, wheel-selective pseudo torque-vectoring system. Based on inputs from the vehicle's ESP system, it slightly applies the brakes to the inner front wheel during cornering to effectively curb understeer, a behavior long associated with Audis, but which was mitigated a bit by the more rearward position of the engine in the company’s latest longitudinal modular platform. Torque-vectoring at the rear is handled mechanically, by Audi’s optional Sport differential, a heavy piece of hardware that nevertheless makes the car feel more light on its feet, shifting power from left to right in search of more grip and balance.
The Audi Drive Select system sharpens responses even more, and it controls settings for the suspension, the Sport differential, the steering, the transmission, throttle response, and exhaust sound. At its hardest-core setting, Dynamic, it can virtually eliminate body roll, while Normal and Comfort modes progressively soften things up. (There’s also a mode that allows drivers to program the various chassis elements individually.) Carbon-ceramic front brakes are available, and they bite right now.
To further tighten up body motions, Audi also will fit its Dynamic Ride Control (DRC) system, whereby each set of diagonally opposed shocks is connected via hydraulic lines that incorporate a central valve. During cornering, the valve allows fluid to flow to the outboard front shock almost immediately, reducing lateral roll. The system works in concert with Audi Drive Select’s variable suspension settings.
Source: Car & Driver