Hi guys,
Thought I’d post this to serve as a bit of history, along with some technical insight into the B8 chassis design (and what makes the B8 special). Might be a good bit of info to any new comers to the board who want to know just a little more about their car! Excerpt from my blog:
2008 marks the introduction of the revised Audi A4 chassis (B8). The previous car had a number of accolades, and garnered a cult following for the V8 powered monster sedans that were the S4 and RS4. Each of these came with high revving, normally aspirated V8s and double wishbone (f) / multi link ® suspension + of course, the Audi Quattro awd.
Fast forward to the updated car: A multitude of revisions were made–many of which were to address driving dynamics. Even the previous RS4 variant, with all alloy front end body panels (for weight reduction), along with lighter brakes and suspension bits, the weight distribution was still an evil 62/48. As a result, the RS4 was known widely for it’s ample amount of push around corners–this is so, even despite double wishbone front suspension, and 50/50 torque split awd.
The entire front axle on the B8 was moved forward 6 inches to improve weight distribution. In addition, the entire engine bay layout is designed to keep weight as reward as possible. Even things as small as the coolant expansion tank was shifted reward to improve weight distribution. Some fluids–even the windshield washer fluid is positioned behind the motor to re-distribute weight from the front of the axle.
In the face lifted S4, things were taken a step further with a 25% weight reduction in the center differential to drop front end weight, plus the elimination of the hydraulic power steering (5lb weight reduction) to take weight off the nose of the car. All these weight saving measures combined brought the weight distribution from a very fwd-like 62/48 down to 55/45–making the B8 chassis S4 identical in weight distribution to the GT500.
To further push the handling envelope further, Audi even changed the torque split in the quattro system to 40/60 (rear bias) to reduce front end push. As well, Audi introduced the “sports rear differential”, which is an electronically controlled LSD that torque vectors with throttle application. What this does is send power to the outside wheel during cornering, so that on power, the back end of the car can be steered with throttle inputs.
Continued still is the front double wishbone suspension, along with a revised rear multi link setup. All suspension arms are aluminum to reduce weight. And controversially, the B8 generation S4 came with a 3.0 supercharged V6 in the place of the 4.2l V8 from the B7. Power was down a couple hp, but torque was up over the V8 variant. Further more, the power under the curve was greatly improved–yielding not only better drivability, but better accelleration numbers overall. An S4 with the DSG transmission can hit 60 in 4.4 seconds (and manual around 4.6)–the car was practically geared for 0-60, as 60 is reached at the top of 2nd. The V6 was not only chosen for improvements in fuel economy (and perhaps production costs), but there is a weight benefit as well. Despite it having a supercharger sitting right ontop of the motor, the motor weighs 46lbs less than the V8–further taking much needed weight off the front end of the car.
As a result, handling is greatly improved and more inline with their #1 competition: BMW 3 series. The strength of this car is its ability to exit a corner. Along with help from the sports rear differential, power can be applied early. The rear steer effect assists in mitigating understeer on the exit of a corner, making the car very well suited to those which like to adopt the “slow in, fast out” methodology (sadly, that isn’t me!).
Great care was taken into the design of all elements–even the rear springs have air deflectors to smooth out underbody airflow. The front rotor backing plates are curved in a complex manner to channel air to the center of the rotor. The front swaybar is attached to the strut for a near 1:1 leverage ratio. The intake has a flap beside the exhaust manifold which flips open when the motor is cold to assist in decreasing warm up times. There are even 2 factory specified tire pressures! 1 for full occupancy, and 1 for standard occupancy (41psi vs 35psi). A lot of attention to detail.
