This Rare Tuned 2001 B5 Audi S4 Ups the Panache of a Classic

This chapter of the S4 badge was produced from 1997 to 2001, though it was sold in America during the 2000 to 2002 model years. It's one of the best examples of German Sleeper Status ever created, with subtle sporty exterior accents that blended with extensive performance engineering underneath to form one of the most commanding on-road presences ever. Its main showpiece was a Quattro all-wheel-drive system that's driven by a twin-turbo 2.7-liter V6 that produced 250 horsepower and 258 pound-feet of torque for the U.S. market. 

That's… not a whole lot of power. Especially for an all-wheel-drive sedan that hovers around 3,600 pounds, give or take. However, the beauty of the B5 S4 lies in its ability to produce so much more power and still maintain its stature as a solid and confident highway-storming super sedan. Chris has achieved this with his, and my God, is it beastly. Like, it could cross the quarter mile neck-and-neck with a brand-new BMW M3 beastly. But straight-line fun isn't its only high card: I recently had a whole afternoon to find out that it's a pleasure to drive in any scenario.

Chris and I have been good friends for quite a long time. Our current text conversations that focus on project potential and auction eye candy originated from paging through free printed car classifieds in elementary school. For as long as we've dreamed of owning cool cars, we've dreamed of modifying them as well, and the best way to describe our shared modding preference is OEM-plus. As in, upgrading a car with a different model's better suspension, chassis bits, and wheels; installing factory and near-factory-looking aesthetic upgrades; mildly lowering instead of slamming; quality, mild-sounding exhaust; and other elevated mods.

Chris' B5 is a brilliant example of four-ringed OEM-plus. Starting from the back, he got his hands on a European A4 trunk and European B5 S4 rear bumper. Bolted up to that, probably via a couple tiny Torx bolts, is the Pièce de Résistance: the Heckblende. That’s the added bit of reflective material commonly found on many Teutonic cars of yore. Chris bought this smoked version from a European retailer and added matching smoked European B5 tail lights. Then, as a nod to fellow Audi nerds, he snapped on some B5 RS4 mirror caps. Finally, helping keep the sleek sedan attached to the ground are 18x8 BBS CH012 wheels wrapped in 225/40/18 Continental ExtremeContact Sport tires, which aren't an OEM-plus upgrade, but they have a timeless look and might as well be considered as one. They look so perfect on any German car of the era.

Inside, Chris found a tan wood-look steering wheel from a European S4 to stand out in exterior photos, which I think matches the interior wood trim well. For entertainment, there's an Audi RS4 RNS-D navigation stereo that he nabbed from German eBay. Sitting in the trunk above the CD changer is a factory toolkit with a decent selection of tools, as well as a never-been-used first-aid kit.

Outside of these minor details, the black leather interior is in good shape. The front seats are very comfortable, don't have any discernible damage, and you can tell its previous owners took good care of them. They're in far better shape than the leather found in my much-newer 2011 BMW 128i. For rowing through the B5's six-speed manual gearbox, Chris kept the stock shift knob and accompanying boot but upgraded the equipment underneath it.

Instead of a shifter that has the feel and lightness of a Nintendo N64 controller's center joystick, like most Volkswagen products, Chris upgraded to a JHM short-throw shifter. This unit gave it a much more solid and tight feeling, shortened the throw, and transformed it into something that feels better than almost every 2021 and 2022 model-year stick car I've driven. To improve the shifting experience even further, especially under wide-open throttle, he bolted up a JHM Drivetrain Stabilizer for good measure.

Experienced tuners in the modding community know the B5 S4's twin-turbo 2.7-liter V6 doesn’t need a whole lot of work to become a performance monster. A modest ECU tune wakes them up pretty darn well, and any minor accompanying mods, like a cold air intake and/or exhaust system, help it along even further.

Though, the real gains are to be found between the air filter and intake manifold. Jason Calfee, our friend and owner of Chicagoland tuning shop Mobile One Inc. gave Chris' S4 a full workover. He pulled the motor, re-sealed it, and gave it a comprehensive service, and then swapped out the tiny factory Borg Warner K03 turbocharger strapped to each cylinder bank for larger K04 units. Up next, he bolted up a South Bend Stage 3 performance clutch and single-mass flywheel to handle more power and upgraded the intercoolers to Wagner Tuning units with carbon fiber shrouds for good measure. He then threw on an 034 Motorsport intake and throttle body boot, Bosch EV14 1,000cc injectors, a Walbro 450 fuel pump, Wagner Tuning three-inch downpipes, and a three-inch Borla exhaust system downstream.

Jason then went to work with his custom Stage 3 ECU tune by changing ignition timing, redoing fuel maps, the lot. What he came up with was a relatively easy-going E85 flex tune that would make the most of the upgraded forced induction, run smoothly, and be able to run on anything 91 octane and above. At the time of publishing, Chris hasn't had the time to dyno it to get accurate horsepower and torque figures, but according to research of similar builds, it wouldn't be outside the realm of possibility to be making 400+ horsepower at the wheels. I can confidently affirm that it feels like it makes this much, as I had a hell of a time taking it for a spin recently. I equate its first-through-third-gear full-throttle shove to the same level of zest as a base G80 BMW M3's 473 horsepower and 405 lb-ft of torque.

As we ripped down some empty roads in a secluded part of southern Cook County, Illinois, Chris mentioned that he had on a set of H&R coilovers, B5 RS4 sway bars, and an LLTeK cross tower suspension brace. That's all it really needed, as the little four-door rode quite well, felt solid, didn't have any noticeable play in the steering, and didn't exhibit any weird bumps, rattles, or creaks. Surely one its previous owners replaced some bushings at some point, though.

It's always refreshing to experience a hydraulic steering rack in 2022. The B5's isn't the best, and it certainly isn't the sharpest. In fact, it feels quite isolated from the road compared to my own BMW 128i. However, the way the front end responds to inputs and the feeling you do get through the wheel is immensely better than pretty much all modern electric racks.

However, I don't think sharpness is what the S is intended for—it's better for the ratio to be a tad slower and more stable, as its true home is on the highway or a long, flowing race track and at a very high rate of speed. I imagine dialing in a sharper front-end feel would be tough with its shock towers completely aft of the little 2.7-liter V6.

While upping the pace through a limited amount of twisty roads (they're unfortunately few and far between in this part of the Midwest), the chassis felt connected, composed, had good grip, and just felt sturdy. Body roll was minimal, yet its H&R coilover damping rolled so nicely over crappy weather-beaten tarmac.

On straight bits of road, the S didn't bat an eye at revving out its long gear ratios and getting up to some eyebrow-raising speeds. It effortlessly rode so solid north of 80 mph.

The K04s, tune, and other go-fast mods make it incredibly fun to roll into a spirited first-through-third-gear sprint. First gear seems pretty short, but that's only due to the tach needle shooting up to redline once it passes 4,000 rpm, bringing along with it a battering ram of torque to press you back into your seat. Even while cruising easy down the road and pressing down half-way on the gas pedal, feeling the surge of boost build just past 3,000 rpm was an event in itself.

Adding to the experience, the aural aspect is sensational. The Borla exhaust helped the small twin-turbo six sing, yet wasn't too loud. Hearing the turbos put in the work from idle to redline was a wonderful experience, too, as was listening to all the unused boost get dumped from the system once the clutch was engaged to grab the next gear. I could've done pulls all day long in this thing.

Between being so well-preserved, tastefully modified, and pupil-dilatingly fast, Chris' Audi is a testament to what enthusiastic Audis are renowned for: comfortable and confident turbocharged all-wheel drive thrills. It was an honor to rip around in this beast. Like any good project car, it isn't finished, either—Chris is thinking some badass drivetrain mods could be next on the to-do list.

While ripping along on that beautiful Midwest summer day, he mentioned that someone recently approached him at a car show to share a deep love of the B5 S4. This person lived in Germany when the B5 was new and solemnly shared that if you saw four chrome rings and satin chrome mirror caps coming up behind you on the autobahn, you'd better get the hell out of its way as quickly as possible. Talk about the makings of a legend.

This generation of Audi—and most German cars of the era—possess timeless aesthetic appeal and is quite refreshing to look at in 2022. I hope Chris hangs onto his for a long time. Or, at least until I've got enough spare scratch burning a hole in my bank account to take it off his hands.