I am a long-time Audi enthusiast with a passion for station wagons from the 2000's: to be sure, a passion that meets its target only when they come with a 6-speed manual transmission!​

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From B6 and B7 A4's to allroads and many other models in between, I have had the pleasure of enjoying several of these very rewarding cars. This RS6 Avant is, obviously, the crown jewel.​

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And then there is the allure of that 4.2 Biturbo engine. The name Cosworth graces the engine bay of some of the world's greatest exotics. The Bugatti Tourbillion. The Aston Martin Valkyrie. The Gordon Murray–designed, V-12–powered T.50. Each is breathtakingly fast, each highly tempting, each unfortunately also staggeringly expensive.

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Going beyond the engine, without doubt there is something special about these C5 wagons: be it the quality of materials or the intuitive layout inside the cabin, or the beautifully flowing exterior shape lines, I have always felt a sense of occasion driving these cars. As exciting as Audi's current products are it is apparent that something has been lost along the way. Almost as if Audis from that era had a sense of beautiful simplicity about them that has been diluted since.

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When the opportunity arose to acquire this beautiful specimen, I had to pursue it. Luckily, this car was located only a few hundred miles from my home. My first exploratory trip to assess this car’s condition was quickly followed by a second trip to finalize my ownership of this unique piece of automotive history.

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Mind you, this car was clearly not just a "buy an engine and swap it" type of effort. To create a comprehensive RS6 conversion its creator had to swap the following parts:

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Powertrain:

• BCY engine and all accessories, including turbos, harness, exhaust, ECU etc.

• Motor mount brackets bolted to engine

• Frame rail snub mount bracket (cut and re-welded)

• Rear differential

Battery​

• Main fuse blocks

• Starter wire harness

Coolant System:

• Entire coolant system (except heater core), including pipes mounted to 2nd firewall and reservoir

• Core support and radiator, including electric fans

• Radiator fan control unit

• Radiator fan control harness, unbroken from driver's frame rail, along the fender, terminating in driver's footwell

Brakes:

• All calipers/rotors

• Rear spindles

• Brake booster + master cylinder combo

• Brake booster vacuum pump

• Brake booster pump relay and harness under the cluster

• Parking brake cables

Steering:

• Steering rack (shorter ratio)

• Lines to/from rack

• Heat shields over the steering rack

Air Conditioning

• Entire line set from the firewall to the compressor

• Drier and mounting bracket

Fueling

• Fuel injectors

• Entire fuel lines from engine bay to tank (RS6 is bigger diameter and routed a little differently in the engine bay)

• Fuel pump

• Auxiliary fuel pump and entire harness

• Auxiliary fuel pump controller

Suspension​

• Struts and springs

• Rear subframe

• Front subframe (the same, but its just easier to swap the suspension, subframe and brakes all as one assembly)

Electronics:

• ABS controller

• Cluster

• Auxiliary fuel pump controller

• Engine control unit

• Immobilizer "pill" in the key (paired to the cluster)

• Radiator fan control unit

• Horns

Exterior:

• Front (vented) fender liners for intercooler airflow

• Front bumper and crash shocks

• Grill

• Badges (if you're a poser like me)

• Front lock carrier

• Door blades

• Side skirts

• Side view mirrors

RS6-Avant specific parts had to be imported, including rear bumper and spoiler.

Interior​

• Door cards

• Steering wheel

• Door sills

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The car was in excellent condition, as the previous owner didn’t drive it very often. Upon bringing it home I quickly addressed a few small items, had a trusted specialist do a full timing belt job to bring it to its 100% current condition and set out in short order to learn and understand its driving dynamics.

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Just sitting inside the car before even turning on the engine the smell of leather pervades the cabin. Turning the key brings the engine to life with a deep, baritone burble coming from the sport exhaust. The shifter is extremely smooth and the clutch pedal action surprisingly light. Moving from a standstill one already gets the impression this engine is something special, sending low-frequency, meaningful throbs through the seat bottom.

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Rowing through the gears at regular speed generates the kind of solid, smooth and drama-free experience we come to expect from Audis of this era. Below 2500rpm nothing reveals this is a 550HP beast. As soon as the pace picks up it is easy to appreciate how well planted this car is: handling is extremely compliant, without a hint of harshness. RS6 stock brakes are powerful and remarkably resilient, at least for enthusiastic street use. But the engine… the engine is the star of the show. The powerband at low revs, though entirely tractable, makes no mystery of what is available should one elect to continue pushing on the accelerator. As revs increase the thrust and sheer power emanating from this engine are, in a word, absurd. As if the engine was taunting: “any RPM, anytime, at any speed”. The most notable feature is that prods to the accelerator pedal are met with immediate response: there is no turbo lag at this address. Toying with acceleration on the street quickly brings the driver orders of magnitude above the limits of the law, so that’s where this report ends.

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Driving this car home after a romp on the country roads one feels humbled by its sheer power, delighted by its overall dynamics, and thankful for being part of an unrepeatable piece of everyday supercar history. While parking it in the garage I can’t help myself narrowing my eyes and shaking my head just thinking of the lofty limits of this vehicle.

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What a car. Just what a car.

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