If you currently own a 2003-08 Audi S4, you probably required a quality car to meet and shuttle clients. Or you made a special deal with your spouse that it would be extremely practical for hauling kids, dogs, groceries, etc. And in both circumstances, you wanted personal transport that would be understated, German, fun and fast. You picked very well, because the Audi S4 4.2L V8 is a truly awesome car with 340hp at 6800rpm and 302 lb-ft at 3500rpm.
Regardless of whether you purchased new or used, it's been at least five years since these Audis were new on the showroom floor, so your warranty is probably gone. Therefore, you're the director and financier of all your S4's care and maintenance. This is a good thing, because you can take advantage of some excellent maintenance products as well as the efforts of many tuners who've been working on the B6/B7 S4 platform to make it better than ever. Adding a few upgrades to your S4 will make it even more "fun and fast". Just don't tell anybody.
It's also worth remembering that several other Audi models had the same 4.2L V8, and many of the modifications apply equally well to those cars.
Maintain & Restore
Regular maintenance is essential for every European car, and the S4 is no different. The 4163cc V8 engines were available in both the B6 and B7 chassis and have proved to be reasonably bulletproof, covering 200,000 miles or more without major attention.
Of course, previous issues with ignition coil packs were covered under warranty long ago, along with most other VW and Audi models, but you probably still encounter that problem from time to time.
Other common areas to address are leaky valve cover gaskets and timing chain/tensioner repairs.
On the chassis side, the suspension design and weight of the vehicle mean front control arm bushings are prone to wear.
Other than that, not much seems to need attention, so concentrate on regular maintenance to keep your S4 in top condition and to preserve already rather thirsty fuel consumption - you certainly don't want it getting worse through lack of maintenance. Official figures were 14/21/16mpg.
Using the best products goes a long way, with ECS Tuning one of our go-to locations for high-quality European brands such as Pentosin motor oil and power steering fluid, Motul gear oil, ATE brake fluid and Viaco G13 coolant. ECS also offers several repair kits that include mostly OEM parts for things like timing chain, coolant system, oil service and control arm repairs at competitive prices.
To begin with, you should consider aftermarket engine software from tuners such as APR, GIAC, JH Motorsports, Neuspeed, Revo Technik and Unitronic. Each has an ECU flash that starts from $399 and up. The power gains range from 8-22hp for the normally aspirated V8, which are less than an equivalent turbo engine but you should feel an improvement.
There are several intake systems to choose from that will reduce intake temps, improve airflow and induction sound. APR, for example, offers the Carbonio intake system ($425).
Any V8 should be uncorked with a good exhaust system to really hear the benefits. Cat-back systems are available from APR, AWE, MagnaFlow, Milltek and Neuspeed, starting from $1300.
For bigger power gains and a sportier note, we could recommend adding downpipes with sport cats. Prices start at $1275 from the same tuners but please check your local smog regulations first. Switching to sport catalysts will release significant power gains by reducing backpressure, and the 200-cell sport cats will generally pass smog tests without causing an engine check lights, but speak to the supplier before buying.
Moving onto the chassis, significant improvements can be had with simple items such as a short shifter for manual transmission cars. Both Neuspeed and JH Motorsports have options starting from $230.
You could also reduce understeer with a stiffer rear sway bar. These are relatively easy DIY installations, and something like Neuspeed's 25mm bar retails at $300.
While you're at it, you will want to reduce body roll during cornering, nose-drive under braking, and get a more aggressive Euro stance with lowering springs. Many companies offer something, with Neuspeed Sport Springs lowering the ride height 19mm and costing $270. Check out H&R, KW and Bilstein for other options.
If you have a bigger budget, want to control ride height or need new dampers, a coilover kit might be a better option. We've recently tried the Bilstein B16 PSS9 coilover system with externally adjusted mono-tube gas shocks for compression and rebound settings. The threaded bodies allow ride height adjustment from 10-30mm on progressive rate springs, and the kit retails for around $1770. Again, H&R has several coilover choices, while KW has its race-inspired Clubsport coilover kit that costs around $3130.
If you to decide to fit coilovers, you should consider adjustable front upper control arms from SPC Performance ($450 per side). These will allow you to make camber and caster adjustments for proper geometry alignment to fully exploit the improved handling potential.
Before you seriously increase the engine output of your 4.2L V8, you should first consider brake upgrades. A set of high performance rotors, pads and brake fluid can improve the stock system. However, a multi-piston caliper and two-piece rotors from either Brembo, StopTech, APR or ECS Tuning would be a better solution. Six-piston caliper kits start from about $1849 from ECS.
You're now ready to add some serious power and there are several options to choose from. JH Motorsports has several solutions including a stage 1 supercharger kit priced at $8500. The Vortech centrifugal blower produces 6psi of boost and will apparently add 80-100whp, depending on your exhaust system. We're told the kit is constrained by the stock rods and pistons, so it is tuned accordingly. The blower is mounted on powdercoated, laser-cut brackets and the kit also includes an accessory belt with pulleys, rollers, tensioners, silicone hoses, air intake, oil cooler, upgraded power steering cooler and auxiliary radiator delete. The company tells us it's working on a stage 2/3 setup with a chargecooler and built internals to handle the extra power.
Another option from JHM is its $2750 direct-port nitrous oxide injection kit. The set-up is claimed to safely produce 70-80whp gains for brief bursts.
PES Tuning also has an S4 supercharger kit that 3ZERO3 Motorsports will sell you for $8495. It adds about 145hp and 123 lb-ft to your motor when running at 7psi. It incorporates an air-to-water chargecooler but won't work with auto transmissions.
Alternatively, VF-Engineering has an Eaton-based VF500 supercharger conversion that includes all the mounting and installation hardware plus software. The kit costs $7900 and produces 5psi that's claimed to generate 496hp and 434 lb-ft of torque. Like all the blower kits, this will transform your S4 into a supercar with grin-inducing acceleration, but ensure you prepare the chassis with the steps above before unleashing this level of performance on the street or thes racetrack.