PUT IT DOWN / KRB #Audi-S1-Quattro
replica / / #KRB-Audi-S1-Quattro-replica
replica / #KRB-Audi-S1-Quattro
With a rear wing the size of Belgium, and tyres wider than J-Lo’s backside KRB’s ’80 Coupé puts down all of its 1061whp very effectively! Never has the word ‘want’ been so appropriate as now! KRB Audi-S1-Quattro replica. Over 1000bhp and wings to die for. Words: Brent Campbell. Photos: Kid A.
Pop quiz; if you had the chance to add any car from VW/Audi’s motorsport catalogue to your garage, which one would it be? We’re talking no-holds-barred, any car, be it a rough-and-tumble rally racer to a ’ring regular, a Le Mans legend to a DTM demonstrator. While we’re sure you needn’t any help making up your mind, let’s talk it through, just for the sake of conversation. First off, we can probably go right ahead and dismiss anything from the VW side of the family, as the only memorable racer VW has ever produced had two pin-stripes and a 53 painted on the side (and it’s probably landed in some California impound lot after all those DUI convictions, no?)
So forget that; let’s take a look at Audi. Lots of fine, sporty cars to choose from, eh? How about the diesel R10? It would add a nice pep to your commute to work, not to mention return excellent fuel economy, though it does get a bit dodgy around those speed humps. What’s that, weather too unpredictable for a car with no roof? Well, how about the A4 BTCC racer of the mid- ’90s? Instantly recognisable, modern and with that Quattro grip you’ve been after. Too pokey? I knew you’d say that. Well if it’s speed you’re after, we’ll need to roll the clock back a bit further. What you’ll want is one of the legendary Group B cars of the mid-’80s. Relentless power, go-anywhere Quattro capability and people will be cheering from the kerb whenever you roll by.
So you’ve decided then? Sign here… Alright, alright, sorry. Enough messing about. We all know that these cars don’t just pop up for sale and even if they did, you couldn’t afford one and neither could we. But there is another option. All of these cars are based on production cars, right? Sure, not the R10, but for the most part, the touring and rally cars were. So you’ve got some time, some skill and maybe a little spare change in your pocket; why not build your own take on that rally favourite of yours?
With all the advancements in technology over the years, not to mention the off-the-shelf attainability of performance parts and materials that once only factory-backed race teams could afford, the proposition doesn’t sound all that outlandish.
But there is a fine line. There’s a difference between building a modern take on a hero car and taking a bone-stock 80 GT and slapping a bunch of stripes and stickers on it like some motorsport wannabes. We’ve all seen them; base-model Audi repmobiles with tawdry spoilers, brushed-on livery, cut springs and no back seats. Oh, and still on stock wheels no less. What was intended to be a tribute can sometimes do more to invoke the gag reflex than inspire pride in your brand’s heritage.
Fortunately, some people do get it right. A satisfying mix of modern performance wrapped up in a retro motorsport shell; it can be done. Just look at some of other cars we’ve featured: Perry Mason’s blood-red BTCC ’banger back in the October issue; MTM’s S1 rep from 10/09; Autoparts Veghel’s V8 Sport Quattro from 08/08 and Andy Krink’s 20v rally rep from 05/08.
And that leads us to this car (finally…), which we spotted while covering a Gatebil event at Rudskogen, which we featured back in January 11. While it has the look and the presence of the greatest of the Group B and Pikes Peak-era Audis, it isn’t at all a replica, at least by conventional standards. No, this Audi has taken on the look of a bewinged S1 more by functional necessity than by choice.
It was built by Kai Roger Bokken and the boys at KRB Trading, a Norwegian-based tuning firm with an affinity for giant snails and Audi’s potent 20v five-pot. In fact, such is the affinity for this motor that they’ve fastened it in to just about any car with four wheels at some point, Audi or not! But before we get into that, let’s get to know the man behind the plan a little better first… “While I’ve always had a passion for the Quattros, I actually got started by driving Volvos,” explained Kai. “I grew up around motorsport and my first car was a Volvo 142.
Not long after that, I started racing in a budget class called Car Cross using an old Skoda with a 2.2-litre Volvo motor in the rear.” It wasn’t long before he started building up full-on race cars to compete. “I stuck with Volvos for a while due to their rear-drive dynamics and relatively low weight,” he said.
“I competed in a number of events with the cars, including a 242 built up for rallycross and a 343 track day car that I eventually stripped out and converted to tube frame.” His involvement with the racing scene from his early teens eventually led to opening his own tuning and parts-supply business; KRB Trading. “I started that back in 1994 as there was a big demand for racing parts and with my connections, I knew I could do a better job than the other suppliers,” he said. The business’ primary focus was supplying turbochargers and components, which, not surprisingly, typically found their way on to a turbo’d five.
By the early 2000s, Kai was one of the most knowledgeable Audi tuners in the country and he was ready to finally do a fullon build on an Audi. “I’d always wanted a Ur- Quattro, but the price of entry was so high, it took me about 20 years to finally have one of my own!” he joked. He built up a red Quattro from scratch, taking everything he’d learned to achieve the highest level of power he had reached with a five-cylinder so far, nearly 850whp. After successfully putting that motor to work on the track, he took the spare motor for that car and used that in his 343 tube frame racer and competed with that as well.
Now that he’d fully built a Ur-Quattro and had successfully converted his 343 to a tubeframe race chassis, the next logical step was to take what’d he’d learned from both builds and construct the ultimate Audi track-day car. “With this build, there weren’t going to be any compromises. Not only did I plan to take the five-cylinder as far as it would go, I was designing and building the chassis and drivetrain to my specs to show what the car was capable of,” he explained.
Kai picked up the donor shell for this car, a lowly 80 coupé, back in October ’07. “There wasn’t much that we were looking for in a donor since it was all coming apart anyways, but you’d be surprised how hard it is to find one of these things without a sunroof!” he laughed. “But once we had that sorted we went straight into it. There was to be no Phase 1, 2 and 3 with this build, we were intent on turning it into a race car from the start.”
Unlike many of the privately-owned Audibased motorsport cars, Kai was willing to make significant changes to the structure of the car to enhance drivability, not to mention lower the car significantly. “The primary improvements I wanted to make by going to a tube frame design, besides reducing weight, were to improve weight distribution front-to-rear and to lower the center of gravity. Typical Audis of this era have more than 65% of their weight hanging up above or in front of the front axle. This makes the car prone to understeer. By building a custom transmission and designing my own chassis, I’d be able to move the motor lower and further back, hence improving its balance.”
Of course, to undergo such a dramatic overhaul, it wasn’t just a matter of getting it up on jack stands and going at it with a spanner. “We started by stripping the car down and then putting it up on a steel jig, kind of like a rotisserie,” said Kai. With the car up in the air, all corners and crevices were now easily accessible. Kai and his mates slowly worked through the process of reinforcing the shell with a tubular frame, cutting away un-needed parts of the body, one portion at a time.
“We started with the cockpit area, building a cage around the driver’s compartment. We then cut away the original floor and welded in a new floor. From there, we built up the front and rear frames to support the suspension and the drivetrain. Since we didn’t have any engineered drawings or schematics to work with, it was often two steps forwards, three steps back, but in the end, we accomplished what we set out to do.”
The unconventional thinking didn’t stop with the chassis. On a quest to get the most power without making sacrifices in durability, Kai built the motor to withstand much more power and boost than even the 850whp from the previous motors. “Rather than using the standard five-cylinder block, the motor is actually based around a 2.5-litre VW diesel bottom end,” Kai explained. “We then overbored the cylinders to 83mm and designed our own rods and pistons.” The original 20v S2 head was used, but modified to fit the new block as well as to increase flow. “We fabricated our own valve springs and camshafts to work with long, stainless valves and titanium retainers,” Kai remembered. To allow for lower placement in the car, a Peterson dry sump system was incorporated.
To allow for placement further aft the front wheels, Kai commissioned Sellholm Tuning of Sweden to design a custom, sequential all wheel-drive five-speed ’box and center diff that would mate to the diesel block. A custom front differential was also supplied, which would now reside in front of the motor, allowing for a more centralised placement and minimal axle angle at the car’s race height. “In all, Sellholm supplied us the gearbox with center diff, the front and rear diffs, the driveshafts, the uprights and the majority of the suspension components, so it was an integral part of the build. We spec’d what we wanted and it built it for us.”
As you’d expect, the chassis and mounts were all custom-designed for the motor, so it fits perfectly. With the motor and transmission in place, the front driveshaft actually sits beside the motor as it runs up to the front diff. With the motor sitting in the bare chassis, the assembly continued, with the custom fabbed intake manifold, upgraded fuel rail and 2200 Siemens injectors now coming into play.
For the exhaust, an equal-length manifold was fabricated, which was originally mated to a GT42 turbo. That has since been replaced with a lighter and more efficient CT43 Comp turbo with triple ball bearings. This was paired with a 60mm TIAL wastegate and, ultimately, an Autronic SM4 for engine management. “We’ve been using Autronic with E85 for years now with a lot of success. The flexibility of the software makes it easy to work with,” said Kai. The remaining intake, intercooler and exhaust system was all fabricated in-house. Note that the intercooler now sits where the radiator originally did, with the radiator now relocated to the rear of the car, using giant fans to pull the air through.
Suspension components were mainly borrowed from previous Volvo projects than from the Audi donor, due to familiarity and known durability. Volvo S80 front spindles were used front and rear, supporting a McPherson-style suspension up front and a custom double-wishbone setup out back. The Sellholm coilovers use Bilstein shocks, and Sellholm supplied the adjustable sways as well as the Volvo 240-style steering rack.
XYZ brakes were chosen for the odious job of bringing the over-powered car to a stop. With the mechanics of the car all in place, Kai and the team then went about re-skinning the car over its tubular frame. Kai took an existing S1-style body kit and modified it, moving the wheel openings upwards and extending the wheel arches three inches per side. This allowed for larger wheels, which were required to fit over the giant brakes. The remaining portions of the body were constructed from carbon fibre, including the fenders, the sills, the hood and, of course, that monstrous rear spoiler.
Inside the car, a Volvo 240 column was used, but is otherwise all go and no show. OMP supplied the seats, wheel and harness, Tilton the pedals and the handbrake, and a Racepak IQ3/Autronic display is the ‘dashboard’. It doesn’t get much more hardcore race car than this!
Once the car was at a driveable state, Kai and the KRB team tuned it on their in-house 4WD dyno and gave it its first run at the start of the 2008 race season. Since getting the car running and tuned, the challenges have largely been around in getting the suspension sorted. “We initially had a lot of issues with understeer, but over the past few seasons, we’ve experimented with a variety of roll bars, toe and caster settings to make it easier to handle around corners,” confessed Kai. While running a ‘conservative’ race-tune of 831whp and 659lb ft of torque at 1.7bar, it’s no wonder the car loves the straights. Running a full 2.4bar of boost, the car put down 1061bhp and 753lb ft of torque at the wheels, incredible for an all wheel-drive car.
Competing at Gatebil and other events around Norway and Sweden, the car has already seen a lot of success. It won the Norwegian Time Attack in 2009 and 2010, taking second this past year due to a few hiccups and against a very competitive field. “The car that beat us was a Porsche GT2 that won Le Mans, so we weren’t that upset by the loss. Overall, we’re very happy with the car and have no immediate plans to build something else. We still have lots of work to do perfecting it and we’re looking forward to 2012” said Kai. Should you find yourself in Norway with a craving for some old-skool motorsport action, this is the car you want to see. This is Group B turned up to 11!
Huge twin fans out back suck air through to keep the relocated radiator cool.
ENGINE: 2.6-litre five-cyl, 2.5L #TDI
engine block over-bored, milled steel crankshaft, KRB flywheel, billett connecting rods, custom CP pistons, 10.7:1 compression, multilayered steel head gasket, S2 cylinder head modified by KRB, custom stainless steel valves, custom camshafts, #Piper/KRB
cam drive system, KRB intake manifold with 3” throttle bodies, #Nuke
fuel rail, #Siemens
2200cc injectors, Comp Turbo CT 43 71/79, 31.2psi (2.15bar) boost, #Turbonetics
wastegate,# K&N air filter, #Autronic-SM4
engine management system, MSD direct fire ignition, Magnecor 10mm ignition leads, Bosch spark plugs, #Aeromotive
mechanical fuel pump and FPR, KRB fuel cell, #Spearco-based
custom intercooler, 4- 5” exhaust tubes made from rolled 0.5mm stainless steel, Ferrita 4” silencer, dry sump lubrication, #Petersen
four-step oil pump, rear mounted PWR-based custom radiator, twin #Bosch
Race power at the wheels: 894 bhp (907 PS) at 7224 rpm. Torque: 753lb ft at 6244 rpm. E85 bioethanol fuel.
TRANSMISSION: Three-step Tilton carbon clutch, Sellholm five-step sequential gearbox with integrated centre diff, Sellholm front differential, KRB-modified Ford 9”-based rear differential, Sellholm drive shafts and joints.
CHASSIS: KRB tube chassis, Volvo S80 front spindles fitted front and rear, McPherson front suspension, double wishbone rear suspension, #Sellholm
coilovers with #Bilstein
shocks, Sellholm knife adjustable sway bars, Sellholm ‘Volvo 240 type’ rack and pinion steering. #XYZ
brakes: 380mm discs and eight-piston calipers front, 375mm discs and six-piston calipers rear respectively. #Zito-Grand-Prix
10x18” wheels, Michelin SX 27/68-18 slick tyres.
windshield frame, front half of roof and b-pillars, all other body panels carbon fibre designed by KRB, plexiglass side and rear windows.
INSIDE: Aluminium floor below tube chassis, removable transmission tunnel, Audi Coupé dash top, KRB/Volvo 240 steering column, OMP steering wheel, seats and harness, Sellholm/KRB gear change mechanism, Tilton pedal assembly, Tilton hydraulic handbrake, Racepak IQ3/Autronic digital dash logger.
SPONSORS: KRB Trading AS, Nordisk Dekkimport, Elite Bil, Nuke, Drammen Karosseri, Profilbyraa AS
SHOUT: My family, friends and everyone that lent a hand.
EDITORS NOTE: That was a reference to Lindsay Lohan and her appearance in Herbie, Fully Loaded in the second paragraph. It was reaching a bit, we know..
1061whp. We’ll say that again. 1061whp! Power like that kind of makes your Stage 1 remap look a bit silly doesn’t it?
If it isn’t needed to go faster, make more power or lap a track quicker, it’s gone.
Audi RS4 seats? Check. Quilted leather retrim? Check. Highend audio install in Alcantaratrimmed boot build? Check. Oh, no... wait...