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The Perfect Prototype - The Tuned RS4 Audi Never Made

Visions of the tuned RS4 Audi never made

Claes Nilsson
Dec 17, 2015
Photographer: Claes Nilsson

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!

Audi rs4 b5 sedan rs4 headlights Photo 2/71   |   Audi Rs4 B5 Sedan Rs4 Headlights

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.

Audi rs4 b5 sedan seibon carbon fiber hood Photo 6/71   |   Nogaro Blue perfection in combination with flat black wheels and carbon-fiber parts from Seibon.
Audi rs4 b5 sedan seibon carbon fiber trunk Photo 7/71   |   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.

Audi rs4 b5 sedan rear bumper Photo 8/71   |   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."

Audi rs4 b5 sedan recaro pole position seats Photo 9/71   |   The Pole Position seats were an expensive option from the factory, but can still be sourced from Recaro in this color way.
Audi rs4 b5 sedan jh motorsport shifter Photo 10/71   |   A JH Motorsport short shifter sits atop the six-speed Getrag box, helping when the boost runs out.

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.

Audi rs4 b5 sedan biturbo v6 Photo 14/71   |   Audi Rs4 B5 Sedan Biturbo V6
Audi rs4 b5 sedan b5 biturbo v6 Photo 15/71   |   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.

Audi rs4 b5 sedan 034 motorsport air filter Photo 19/71   |   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.

Audi rs4 b5 sedan 034 motorsport exhaust Photo 20/71   |   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."

Audi rs4 b5 sedan 034 motorsport air filter Photo 21/71   |   The black magic of carbon fiber embellishes all corners of the engine room.
Audi rs4 b5 sedan carbon fiber engine cover Photo 22/71   |   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.

Audi rs4 b5 sedan ohlins raceline ttx36 competition spec super coilover Photo 23/71   |   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.

Audi rs4 b5 sedan oz centercap Photo 27/71   |   Audi Rs4 B5 Sedan Oz Centercap
Audi rs4 b5 sedan rs6 brake caliper Photo 28/71   |   Lightweight, cross-spoked wheels from OZ—the Ultraleggera in 10x19 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!

Audi rs4 b5 sedan rs6 brake caliper Photo 32/71   |   Well-developed RS6+ 8 piston aluminum calipers bites 365 mm brake discs with Carbotech teeth behind blacked out OZ hardware.
Audi rs4 b5 sedan nogaro blue Photo 33/71   |   Fredrik Almquist's 630hp street car plays surprisingly nice in traffic, but could easily put many sports cars to shame.

Construction

Audi rs4 b5 sedan hr pss9 coilover Photo 34/71   |   Audi Rs4 B5 Sedan Hr Pss9 Coilover

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

Audi rs4 b5 sedan ohlins ttx36 coilover Photo 35/71   |   Audi Rs4 B5 Sedan Ohlins Ttx36 Coilover
Audi rs4 b5 sedan ohlins ttx36 coilover Photo 36/71   |   Audi Rs4 B5 Sedan Ohlins Ttx36 Coilover

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

Audi rs4 b5 sedan rs4 donor parts Photo 37/71   |   Audi Rs4 B5 Sedan Rs4 Donor Parts

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

Audi rs4 b5 sedan rear bumper modification Photo 38/71   |   Audi Rs4 B5 Sedan Rear Bumper Modification

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

Audi rs4 b5 sedan nogaro blue Photo 39/71   |   Audi Rs4 B5 Sedan Nogaro Blue

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

Audi rs4 b5 sedan lsd Photo 40/71   |   Audi Rs4 B5 Sedan Lsd

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

Audi rs4 b5 sedan journal holder Photo 41/71   |   Audi Rs4 B5 Sedan Journal Holder

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

Audi rs4 b5 sedan r8 v10 ignition coils Photo 42/71   |   Audi Rs4 B5 Sedan R8 V10 Ignition Coils
Audi rs4 b5 sedan r8 v10 ignition coils Photo 43/71   |   Audi Rs4 B5 Sedan R8 V10 Ignition Coils

High voltage through Audi R8 V-10 ignition coils.

Audi rs4 b5 sedan scale Photo 44/71   |   Audi Rs4 B5 Sedan Scale

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

Audi rs4 b5 sedan michelin pilot sport Photo 45/71   |   Audi Rs4 B5 Sedan Michelin Pilot Sport

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

Audi rs4 b5 sedan front view Photo 46/71   |   Audi Rs4 B5 Sedan Front View

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

Audi rs4 b5 sedan backfire Photo 47/71   |   Audi Rs4 B5 Sedan Backfire

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

Audi rs4 b5 sedan hood lock Photo 48/71   |   Hood locks are important when pushing 300—securing the light carbon fiber hood against updrafts along with the stock tie downs.
Audi rs4 b5 sedan Photo 49/71   |   The Nogaro Blue color effectively accents the dark details of the car, both out- and inside.
Audi rs4 b5 sedan center console controls Photo 50/71   |   The Audi Concert sound system with BOSE drivers delivers as the premium S8-class option it was.
Audi rs4 b5 sedan rs4 steering wheel Photo 54/71   |   Audi Rs4 B5 Sedan Rs4 Steering Wheel
Audi rs4 b5 sedan rs4 steering wheel Photo 55/71   |   The driver environment enjoys an alcantara-dressed stock RS4 steering wheel that means business.
Audi rs4 b5 sedan oem boost gauge Photo 56/71   |   The boost gauge in the center console is actually an OEM part. Ready for assembly with intake slats and all!
Audi rs4 b5 sedan center console Photo 60/71   |   Audi Rs4 B5 Sedan Center Console
Audi rs4 b5 sedan quattro dash garnish Photo 61/71   |   Aluminum interior detailing gives a fresh feel to the cockpit of the car.
Audi rs4 b5 sedan front badge Photo 62/71   |   Four rings to rule them all, situated in a matte black front grille that is as dark as the SR-71 Blackbird.
Audi rs4 b5 sedan fredrik almquist Photo 66/71   |   Audi Rs4 B5 Sedan Fredrik Almquist
Audi rs4 b5 sedan fredrik almquist Photo 67/71   |   Mission accomplished! Fredrik Almquist is proud of his RS4 effort, and he should be. His 630hp sedan is truly well developed on all corners.
Audi rs4 b5 sedan rs4 door sill Photo 71/71   |   Recaro Pole Position seats were an obvious choice for Fredrik's S4-based build. So were the RS4 doorsills.
By Claes Nilsson
2 Articles
The Perfect Prototype - The Tuned RS4 Audi Never Made
Tech spec
Owner: Fredrik Almquist
Location: Malmö, Sweden
Occupation: IT technician
Engine: 2.7L RS4 BiTurbo V-6, 630 hp/590 lb-ft, AZR CosCast cylinder heads modified by Stertman Motorsport, Stertman camshafts, Autoverdi connecting rods, ARP bolts, custom order JE pistons, balanced RS4 crankshaft with CNC-milled, forged journal holders, Raceware bolts for head and crankshaft, rebuilt and ported intake manifold with 3-inch throttle body by Stertman Motorsport. Tial S605 turbo kit, new gaskets, hoses, and check valves. Oversize injectors. Audi R8 V-10 ignition coils. NGK PFR8B spark plugs. LOBA Motorsport Y-form intake tube in carbon fiber, 35 percent OD compared to OEM RS4 dimensions. RS4 engine cover in carbon fiber. AG Motorsport boost piping. Wagner Tuning RS4 Black charge cooler and air diverts in carbon fiber. 034 Motorsport carbon fiber cold-air intake with carbon heatshield. Bosch 044 fuel pump. Stertman Motorsport custom headers. 93mm custom Hitachi MAF-sensor. Turbocenter clutch hose in braided steel. Custom crankshaft ventilation. Bailey DV30 recirculating dump valves. SPAL electric fan with adjustable thermostat. Stertman Motorsport/Setrab oil cooler kit. Balanced race clutch with sprung sinter plate. Lightened aluminum flywheel. Aluminum drive shaft. 034 Motorsport 3-inch exhaust system with 3.5-inch single muffler. AWE harmonic damper. Stasis Engineering center diff. Quaife LSD rear diff with Stern delrin bushings. 034 Motorsport Track Density engine and gearbox mounts. 034 Motorsport snubmount with bracket. CNC-milled cross brace, engine frame reinforcement and rear diff mount. Audi R8 oil filler lid modified with ventilation. Audi R8 cooling lid. Mattias Stertman mapping for E85 fuel.
Transmission: Getrag six-speed manual gearbox. JH Motorsport Short Shifter, solid gearbox linkage with stiff bushings. Upgraded centering spring.
Curb weight: 3350 lb.
Wheelbase: 102.6 in.
Length x width x height: 176.5 x 70.8 x 545.2 in.
Suspension: PSI Race Line suspension with Öhlins TTX36 coilover kit. Custom Performance Products Gen 2 control arms front and rear with uniballs. Custom Performance Products sway bar bracing with uniballs. Audi RS4 B5 aluminum uprights. 034 Motorsport CNC milled aluminum bushings in front- and rear and end links front. H&R adjustable sway bars front and back. Shock tower mounts brace and rear.
Brakes: Audi RS4 B7 365*34 brake discs with aluminum RS6+ 8-piston calipers and Carbotech XP12 brake pads in front. RS4 B7 324*22 brake discs with aluminum RS4 B7 calipers and Carbotech XP10 brake pads in rear. Steel braided brake hoses.
Wheels & tires: OZ Ultraleggera HLT 10x19 and OEM RS4 8x5x18 ET20. 265/30-19 Michelin Pilot Sport Cup for OZ. 255/35-18 for OEM.
Interior: Recaro Pole Position seats in black leather with blue alcantara centers and white logos. UUC Motorwerks gear knob in polished aluminum. OEM S- Line interior in blue alcantara and black leather. Aluminum side steps. OEM Audi fabric floor mats. Audi RS4 steering wheel in alcantara. AWE boost gauge in dash center with OEM surround.
Multimedia: Audi Concert with cassette tape. BOSE audio system with CD-exchanger and amps from Audi S8.
Exterior: Audi RS4 B5 OEM-widening. Seibon carbon-fiber hood with black mesh and black hood locks. Seibon carbon fiber trunk. Wagner Engineering front side grating with fog lite delete. Audi RS4 -01 headlights. Front lip. Windshield washer arms from Volkswagen Passat -05.
Paint: Audi Nogaro Blue
Future plans: Further engine development.
Thanks to: My wife and daughter. Fredrik Bergase at Paint IT AB. Mattias Stertman and Jimmy Saras at Stertman Motorsport. Henrik, Rolle and Kim at Euromaster Lundavagen.

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