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2013 Audi S4 - Mission Impossible

We always want the impossible, and an Audi RS4 sedan is about as unlikely as they come…

Greg Emmerson
Mar 17, 2014 SHARE

There's a long tradition of American drivers missing out on appealing European cars. But that spawned another tradition of recreating these remarkable machines using a combination of ingenuity and sheer determination. There's also a third tradition of giving it a unique twist, with Audi's RS wagons commonly reinterpreted as more popular sedans.

Not wanting to break with this tradition, Dennis Tang teamed up with TAG Motorsports in Vista, CA to create the first B8 RS4 in the US, and the first B8 RS4 sedan in the world. This gives him huge bragging rights, and frequent sightings of the white Audi have led to online forums lighting up as enthusiasts imagine they've seen the automotive equivalent of Bigfoot.

2013 audi s4 trunk spoiler 02 Photo 2/12   |   2013 Audi S4 - Mission Impossible

So how did it all come about? Dennis has been modifying his 2013 Audi S4 ever since he bought it. In fact, it was previously featured in EC 11/13 as part of our "Coilovers vs Air" suspension test. Dennis had fitted the KW DDC and HLS system, allowing the damping rates to be varied on the move or from his phone, and the nose to be hydraulically raised to clear obstacles. It was a great comparison for the AccuAir air suspension and proved a worthy adversary in our test.

In addition to the suspension, Dennis had worked with Alex Andonian at TAG to fit AWE Tuning components such as GIAC software, StopTech big brakes and 19" HRE wheels. That was eight months ago, and a great deal has happened in the intervening time...

Playing TAG

So what does it take to build an RS4 sedan? We spoke to Alex about the build, since he'd been at the sharp-end of making it happen. "It started as a joke," he recalled. "We'd done almost everything possible to the S4 but without getting into the cosmetics too much. One day, Dennis asked what else we could do and we suggested the European RS4 as a joke!"

While it might have seemed ridiculous at the time, the seed was planted in Tang's brain and on his next visit, he asked them to investigate the RS4 conversion further.

2013 audi s4 HRE P104 wheel 03 Photo 3/12   |   Custom-finished 21" HRE wheels are bolted over a six-piston StopTech ST-60 big brake kit

"Dennis is a great guy and we became friends during the course of his S4 build. He was always dropping in to have something fitted or refined, so we were happy to look into the RS4 swap," Alex continued. "If we didn't have that relationship, we probably wouldn't have taken it seriously..."

Using two computers to compare S4 and RS4 parts lists and diagrams, the TAG team created a list of what they thought would be needed to build this very special car. The total came to around $23000 and, with regular shipments coming from Germany every three weeks, the parts were soon in their possession.

"It was when everything was laid in front of us that we fully realized the size of challenge," Alex admitted. What had seemed like an interesting notion was now an action list on a whiteboard.

With so much fabrication needed, Alex enlisted the help of local specialist, Hot Rods & Custom Stuff (HRCS) from Escondido, CA. These guys have created some incredible projects, including the "Mercedes Bent" from SEMA 2010 - it was a 190SL with SL65 running gear, built to an extraordinary standard and the star of the show. While they don't come cheap, Alex knew the quality of work would be beyond reproach.

2013 audi s4 interior 08 Photo 4/12   |   2013 Audi S4 - Mission Impossible

S4 to RS4

Diving into the project, TAG removed the front-end in order to fit the RS4's flared fenders. And that's when the problems began. The S4 fenders are about 0.25" longer. Getting the new parts to fit properly would require new door sill sections - actually it needed a one-piece item that fits into the bottom of the door jambs, locating the doors, all four fenders and side skirts.

Aware that everything could be "made" to fit eventually, Dennis and Alex decided to do it right, ordering the new door sills and cutting out the S4 panels. Because they weren't structural, it didn't affect the bodyshell but would ensure the majority of parts fitted properly.

They weren't out of the woods yet. With the front fenders in place, the RS4 front bumper and grille rapidly followed (both cars share the same hood). The side sills went on and the front doors were good, but the RS4 is an Avant and the roofline is different at the rear. The solution was to order RS4 rear doors but remove the top window frame and replace it with the S4 frame and glass.

2013 audi s4 RS4 fender fitting 11 Photo 5/12   |   Fitting the front fenders was the start of the adventure for TAG Motorsports, as it discovered that the RS4 Avant was also different under the skin

The flare for the rear fenders also starts in the rear doors, so they were needed anyway. However, TAG also discovered that the gas cap is contoured, so that was added to the parts list.

The rear quarter panels were obviously flared but, designed for the wagon, the shape continued higher and longer than it would on a sedan. So HRCS set about reshaping the panel to fit. Everything was done in metal so that the panel just needed to be attached rather than filled.

While working on the rear, they discovered the RS4 also has different inner fenders and floor area, so these parts were also ordered and welded onto the sedan to ensure a perfect replica.

At this point, everybody was looking forward to the project's conclusion. And then the rear bumper raised its ugly head. "This was probably the biggest headache of the entire build," Alex admitted. "It took 60 hours in labor alone!"

2013 audi s4 AWE tuning boost gauge 10 Photo 6/12   |   2013 Audi S4 - Mission Impossible

The problem was that the Avant's tailgate and light positions were utterly different to the sedan, so nothing was aligned. After careful consideration, the best solution was to graft the top of the S4 bumper to the bottom of the RS4 part, ensuring the original trunk and tail lights could be retained.

The S4 section then had to be flared to match the contours of the RS4 bumper, which continued the lines of the fender flare. The job initially involved heating and pulling, but would require some plastic filler as well to get a perfect finish.

"Perfect" is the right word to describe this car. Alex and the entire team went the extra mile to build something Audi might stand behind. "We aim to have it inspected by an Audi dealer once the shakedown tests are completed," he stated. "We want to assure Dennis, and anybody else who might want the same, that this vehicle is correct in every detail."

2013 audi s4 flat bottomed steering wheel 09 Photo 7/12   |   Flat-bottomed steering wheel remains S4 while Dennis saves for the real thing

The original Ibis White is also a stock RS4 color, so the car was resprayed by HRCS to their exacting standards. The window surrounds and exterior trim were painted gloss black to replicate the Black Optic package on the RS4.

With no trunk spoiler option for the B8 RS4, Dennis retained his existing S4 part, which is tastefully discreet.

Thinking of building something similar? Alex estimated a cost of around $65k to replicate it to this standard, working with HRCS. But that's without wheels, brakes, suspension, etc.

Performance

The wider fenders gave the team more room to maneuver, so they opted for a generous 20x10.5" front and 20x11" rear. With TAG's new premises next door to HRE, the guys came over to check the measurements before machining a set of P104 wheels with a 37mm offset.

"The design was close to the stock RS4 wheels, but with an aftermarket twist," Alex told us." On the S4, the biggest we'd fitted was 20x10" ET36 with 255/30 tires, but for this car we were able to fit 295/25s all round; the wider rear wheels allowing the rear tires to be stretched slightly, reducing the height of the sidewall and gaining some extra clearance," he explained.

2013 audi s4 RS4 exhaust tip 05 Photo 8/12   |   Even the black tips are genuine RS4, ordered as part of the complete makeover

The car would remain on its KW DDC suspension with HLS nose-lift, since it's about as advanced as you can buy right now. TAG had integrated the DDC controls into the console, sitting opposite the new RS4 Stop/Start button that was fitted.

The only other interior upgrade was an AWE boost gauge, although Dennis had planned RS4 bucket seats and even its carbon-ceramic brakes, but with the project going over budget during the build stage, these additions are on hold.

Returning to the suspension, Dennis had previously fitted EuroCode sway bars and its Alu Kreuz drivetrain stabilizer, both of which were retained for the makeover. He also kept the StopTech ST-60 big brake kit with six-piston front calipers and 380mm rotors.

2013 audi s4 OEM audi RS4 front bumper 07 Photo 9/12   |   2013 Audi S4 - Mission Impossible

In the engine department, the supercharged 3.0L V6 TFSI motor had initially been uprated with GIAC software, an AWE Tuning pulley, intake and heat exchanger.

For round two, GIAC would contribute a more aggressive program because Supersprint had supplied the first example of its new long-tube headers and full exhaust system. This was finished with genuine RS4 tips to complete the makeover. And while it might not match the 450hp of the original car's 4.2L V8, you might be surprised at how fast a modified S4 can be...

Tang

Speaking to Dennis, he was predictably excited to own such a unique vehicle. He's still entertained by the online speculation whenever somebody posts a photo of it, imagining they've scooped a spy shot, but generally he can slip under the radar.

"Leaving the car in its original white meant it doesn't always get noticed at first. Despite all the work, the car is a sleeper because the RS styling is more discreet than some of its competitors. But it always gets a great reception once people realize what it is," he laughed.

In addition to the bodywork, the new engine mods also made a dramatic impact on the driving experience. "The car is now significantly faster. With the exhaust headers and updated software it pulls so much harder and is a lot more fun to drive," he confirmed.

"We actually helped Supersprint develop the headers. They sent us a prototype but it was much too raspy, so we helped them tune the sound. It's now more subdued at the bottom-end, but really wails at the top," Dennis continued.

2013 audi s4 DDC buttons 12 Photo 10/12   |   In addition to a vent-mounted boost gauge, TAG placed the KW DDC buttons on the console

He also confirmed the RS4 front bucket seats remain on his wishlist, although carbon fiber interior trim will probably arrive first.

He's still contemplating the carbon-ceramic brake rotors as well, but is prioritizing an upgrade for the stock rear brakes.

"The project isn't over by any means," Dennis told us. "We're still looking at what we can do in the future, but first I'm planning to get out and really enjoy the car."

Tech Spec

2013 Audi S4

Dennis Tang
Pasadena, CA

Engine 3.0L V6 24v TFSI supercharged with GIAC stage 2 software, AWE Tuning stage 2 pulley, S-Flo intake, carbon air box, heat exchanger and coolant reservoir, Supersprint long-tube headers and exhaust system, OEM RS4 exhaust tips

Drivetrain seven-speed Audi S tronic dual-clutch transmission with GIAC software, quattro AWD

Brakes StopTech ST-60 BBK with six-piston calipers in Ibis White, 380mm rotors, StopTech pads r, braided lines f&r

2013 audi s4 V6 TFSI supercharged engine 04 Photo 11/12   |   3.0L TFSI supercharged engine gives away the car's S4 roots, but additions such as the GIAC software, AWE pulley and heat exchanger plus Supersprint long-tube headers and exhaust give it enough performance to carry off the conversion

Suspension KW DDC coilovers with W-LAN kit for iPhone control, KW Hydraulic Lift System, EuroCode Tuning sway bars and Alu Kreuz drivetrain stabilizer

Wheels & Tires 21x10.5" f, 21x11" r HRE P104 wheels in dark tinted brushed finish, 295/25 R21 Pirelli P Zero Nero tires

Exterior OEM Audi RS4 front bumper, fenders, grille (in black), side skirts, door sills, rear doors and handles, rear quarter panels, gas door and rear bumper (blendeded to S4 bumper), European-spec headlights, S4 trunk spoiler, trim painted gloss black, car repainted Ibis White

Interior AWE Tuning boost gauge, RS4 Start/Stop button, KW DDC buttons

Thanks TAG Motorsports (tagmotorsports.com)

2013 audi s4 OEM audi RS4 front bumper 06 Photo 12/12   |   2013 Audi S4 - Mission Impossible
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By Greg Emmerson
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