2008 Audi RS4 B7 - Proven

Can You Improve On Perfection?

From the February, 2010 issue of European Car

By Pablo Mazlumian

When it comes to understated cars, the B7 Audi RS4 is the flagship. Its wide stance doesn't scream for attention, but if you're lucky enough to get a second glance you'll find yourself staring, studying every high performance detail, from the massive brakes inside 19-inch wheels, to the flared fenders. It's lovely, but with a rated 420 hp it packs a meaner bite than its looks.

Going against logic, and fueled only by our passion for performance, we took this silver 2008 example to see how it could be improved with basic upgrades. To start, we took our PerformanceBox from VBox USA, and established braking and handling baselines.

First up was a set of lightweight wheels from Forgestar, wrapped with Continental SportContact 3 tires. This combination was ordered in factory 9x19 and 255/35-19 sizes for the wheels and tires, respectively. At two pounds lighter per corner, performance slightly improves in every department, but when compared to the previous Michelin Pilot Sport all-seasons on the factory Audi wheels, the softer Conti tires helped our 100-to-zero mph braking improve from an already impressive 383 feet to a breath-snatching 355 feet. This also showed in peak braking g-forces, with a 1.01g to 1.11g improvement.

The RS4's road holding prowess around our third-gear test turn also benefited from the new Conti shoes. A jump from an average peak 1.12g lateral acceleration to 1.16 confirms this.

Vehicle Data
Engine: 4.2-liter V8 FSI, 32-valve
Transmission: Six-speed manual
Mileage: 8,000
Current modifications: Forgestar wheels,
Continental Conti Sport 3 tires
Dyno data: Dynojet 424x
Temperature: 73-82°F
Humidity: 16-25%
Test gear: Third

Baseline
Peak power: 321 hp @ 7400 rpm
Peak torque: 268 lb-ft @ 3400 rpm
Temperature: 73° F
Humidity: 22%
3000-8000 rpm dyno
acceleration: 8.38 sec

Test Notes
The most notable part of the car is its direct-injection 4.2-liter V8 revving to a claimed 8250 rpm. But we're still determined to improve this.

To ensure no power spikes or dips from poor fuel or spark we filled up with good 92 octane fuel and drove to Modified by KC, our dyno and installation facility in the Midwest. There, we also swapped in a new set of O.E. NGK "R" sparkplugs ordered from Sparkplugs.com (part no. PFR7W-TG), which saved us around 25 percent off the dealer cost.

After several dyno pulls on MKC's Dynojet 424x dynamometer and using their OBD-II scan tool to monitor for proper intake and coolant temps, and taking note of total ignition advance, we established a baseline of 321 hp to all four wheels. Flat torque lovers will appreciate 268 lb-ft sustained from 3400 to nearly 6500 rpm.

Since there appeared to be no power differences between third and fourth gears, testing was done in third to limit the strain on the engine. The RS4 is equipped with a Sport button, which opens up a second chamber in the muffler system that's audibly evident. But we dynoed both ways, and while the throttle response improvement was evident, ignition values didn't change and, thus, neither did power output.

Last, although the car is advertised to have an 8250-rpm rev limit from the factory, the dyno showed fuel cuts out just under 8100 rpm.

Test 1
Performance
Peak power: 328 hp @ 7200 rpm
Peak torque: 274 1b-ft @ 3400 rpm
Max power gain: 13.5 hp @ 6100 rpm
Max torque gain: 13.0 lb-ft @ 5200 rpm
3000-8000 rpm acceleration: 8.16 sec.
Temperature: 76° F
Humidity: 19%

Parts: Revo Technik Stage 1 software upgrade Options: 91-, 93- and 100-octane tunes available, Revo multiple program switching control module Installation time: 15 minutes MSRP: $699

Pros
• Completely reversible, "zero" physical modifications
• Rev limiter increased to 8300 rpm
• Top-speed governor removed
• Improved throttle response
• More power
• Custom tunes available with Revo distributors
• Handheld flashloader provides more options, including valet mode

Cons
• None

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