Building the B5-Generation Audi RS4 Sedan that Audi Never Offered

Audi never released an RS4 B5-sedan, not counting two secret factory prototypes. Sad, Fredrik Almquist thought, who took matters into his own hands and composed his own, tuned version with bells and whistles. 630 hp of Nogaro Blue perfection at its finest!

When it comes to his custom specification RS4 Sedan build, Mr. Almquist has really done his homework. Since the project start in 2001, a whole 14 years ago, it has been a constant development process. Every winter being invested into further build progressions to enable full driving recoupment during the short Swedish summers.

The build is now optimized at all corners to get close to some kind of factory perfection. Fully loaded with solid bushings, cross braces, frame reinforcements, together with a precision engine build. A potent ’90s dream with up-to-date performance, including character that cannot be found with newer cars. The ’98-’99 cars being the last ones without ESP or DCS from the factory on the S4.

The lightweight Seibon trunk saves a few high kilos and takes down the roll center a bit closer to the grown.

The exterior hides more development than meets the eye. With a sedan version of the RS4 front bumper not being available from the factory, the estate version has been sectioned and carefully stitched together to fit the short body type. This, together with donor car OEM RS4-fenders all around, gives a massive factory impression. All covered with Audi’s very appreciated option color Nogaro Blue, which Fredrik’s car sported even from the beginning.

Countless hours have been invested to get the estate version of the RS4 rear bumper to become the sedan version that never existed.

“I have a lot to thank my friend Fredrik Bergase at Paint IT AB for. He was irreplaceable when it came to the body- and paintwork,” Fredrik explains. “We have together put in many hours to reach this level of finish.”

The Pole Position seats were an expensive option from the factory, but can still be sourced from Recaro in this color way.

The interior continues in the Nogaro Blue theme with matching Recaro Pole Position racing seats—an expensive factory option for the RS4 back in the day.

Tuned twin turbo V-6

Fredrik calls the engine specification for his beast RS4+, built to handle all of 1,000 ethanol horsepower with enough boost. 2.7L, acoustically pleasing V-6 BiTurbo—constructed from atoms and massaged in all corners. Forged, modified, and balanced with cunning consulting and performance from Stertman Motorsport in Sweden. Everything from MIRA-machined, flow-optimized AZR-heads to fully forged interiors. Boost pressure is made by twin TIAL R605 snails starting at 3,300 revs with 630 hp at 2 bars at the top.

The compact BiTurbo V-6 is balanced, modified and reinforced to handle up to 1,000 hp, but de-tuned to provide a reliable 630 on the pavement.

The main objective being all encompassing reliability and cooling, a goal that has been fruitful.

“Since I thoroughly enjoy track days, I’d like to enjoy them to the limit. Running up a whole tank of E85 fuel without having to go into the pits to cool off. And now I can do that,” Fredrik says.

Oxygenated! A massive amount of air is transformed through a well-dimensioned 034-Motorsport filter with matching carbon shield.

By the same reasoning, the exhaust noises have had a focus—where 95dB sound levels are faithfully held. A 3-inch 034 Motorsport exhaust system ends in a single 3.5-inch silencer in the rear, delivering sonic nirvana at sane levels.

A well-ventilated yet quiet 034-Motorsport exhaust system keeps the audio levels down to track day limits.

In total, the car has been lightened more than 200 pounds. And a verified corner weight of 3,350 fully loaded up brings the total in at around 330 pounds below the current RS4. With 630 hp and 800 Nm in the rear pocket, there is—to put it mildly—some performance reserves in stock.
“I have been able to keep up the pace with the 997 GT3 RS and similar cars on track days,” Fredrik humblebrags. “It is truly amazing for me to say! A lot of the driveability has come with my optimizations of the differentials and chassis.”

Even the smallest of components have gotten their high value, composite additions.

Optimized four-wheel performance

Hence the driveline has been an important cause, effectively helped by a Stasis Engineering center diff together with an LSD-rear diff. Bolted with solid aluminum bushings; a great deal of understeer has been handled. Furthermore, Fredrik has focused on the suspension, with great result following. Currently, a custom PSI Raceline coilover kit is mounted, based on the hypercar quality, Swedish pride, and Öhlins TTX36-kit. This after throwing everything from lowering springs to modified PSS9 in the garbage during the development phase.

Swedish pride! Öhlins Raceline TTX36—competition spec super coilovers. Costs as much as a used RS4 B5 but are worth every penny.

“Now I have a chassis that performs on track and is surprisingly comfortable on the road. A lot of chassis optimization has gone into this, and now a great deal of camber to get the Michelin Pilot Sport Cup tires to perform at their maximum,” Fredrik says.

And perform it does! It brought in 1.23.30 at the Bilsport Superstage track battle in Sweden, well under Porsche GT3 RS times! But more is apparently to come.

Lightweight, cross-spoked wheels from OZ—the Ultraleggera in 10×19 inches size, performs great both on and off track.

“I have now gone up three width increments on the OZ wheels and am now running Cup tires with 265 width compared to the former 235. So more cornering grip is to be expected for improved times.”

The long time prototyping of this unique S/RS sedan continues, with more track time and development in the garage. Reliability combined with power, chassis, and methodic detail orientation—truly a winning combination!

Well-developed RS6+ 8 piston aluminum calipers bites 365 mm brake discs with Carbotech teeth behind blacked out OZ hardware.

Fredrik Almquist’s 630hp street car plays surprisingly nice in traffic, but could easily put many sports cars to shame.

Construction

Modified H&R PSS9s weren’t good enough for Mr. Almquist and got rejected to the scrap heap.

The Swedish Öhlins, hypercar-worthy, TTX36 coilovers were the select and expensive choice for Fredrik’s build.

Donor parts from a written-off RS4 estate. A flashback to attest the bodywork that has been invested in this build.

A great deal of fitment work went in to create the unique RS4 sedan rear bumper.

The luxurious Nogaro Blue color begins with a solid layer of straight-up character.

A key component to the performance of the project is the solid hardware within the drive line.

The forged journal holders are tightened to specification by Fredrik himself.

High voltage through Audi R8 V-10 ignition coils.

The mythical 1,525 kg fully loaded corner weight of this beast, surprisingly light.

Brand-spanking-new Michelin Pilot Sport brings some grip to the well-constructed chassis.

The car sees a lot of track driving, something that Fredrik set out to achieve from the start.

Fire reigns from the exhaust when Fredrik puts down the hammer.
Photo captions

Hood locks are important when pushing 300—securing the light carbon fiber hood against updrafts along with the stock tie downs.

The Nogaro Blue color effectively accents the dark details of the car, both out- and inside.

The Audi Concert sound system with BOSE drivers delivers as the premium S8-class option it was.

The driver environment enjoys an alcantara-dressed stock RS4 steering wheel that means business.

The boost gauge in the center console is actually an OEM part. Ready for assembly with intake slats and all!

Aluminum interior detailing gives a fresh feel to the cockpit of the car.

Four rings to rule them all, situated in a matte black front grille that is as dark as the SR-71 Blackbird.

Mission accomplished! Fredrik Almquist is proud of his RS4 effort, and he should be. His 630hp sedan is truly well developed on all corners.

Recaro Pole Position seats were an obvious choice for Fredrik’s S4-based build. So were the RS4 doorsills.