The decision was made for our team to build a new car for the 2013 Formula DRIFT season. It's a E46 BMW 3 Series to replace our current 2004 BMW Z4.
Two years of door-to-door racing, fender rubbing and wall "tapping" has taken its toll on the Z4. We're retiring it from competition use at the pro level and will repurpose it for drift demos and time attack events. However, some of the parts can be transferred to the E46 including the engine, transmission and our quick-The first step was to find a donor car and we located a salvaged E46 Coupe with flood damage: perfect for what we were planning.
Ditching all the creature comforts, we ripped out the interior and tossed it out along with the strange smell that emanated from it. Next came the flood damaged engine and transmission, as well as the stock bodywork. After a few more hours pulling the wiring harness, brackets, windows and other items we were left with a rolling chassis.
The next step was to devise a rollcage design. Using the Formula D rulebook, we mocked up a race seat and checked driver head, arm and leg clearance. We then repositioned the seat a few inches back to improve the front/rear weight distribution.
The stock pedal assembly and steering column were also replaced with racing parts and were moved along with the seat.
Cage fabrication began with the removal of the sound deadening material that lined the floorboards and transmission tunnel. The cage's base plates was then cut and welded into the chassis and the rear upper shock mounts reinforced to compensate for the added stresses of a coilover suspension system.
From there, seamless DOM (Drawn Over Mandrel) steel tubing (1.75" diameter, 0.095" wall thickness for the main hoop, 1.5", 0.095" for everything else) was measured, cut, bent and welded into the car.
We used thicker tubing for the main hoop in recognition of the expected weight of the car as well as the number of critical attachment points to it. The Formula D rules specify a ratio of weight to rear tire width, so our target minimum weight for the car is 2700 lb (with driver), that would let us run a 260mm rear tire, or 2800 lb, which would require a 270mm tire.
For our road racing builds we normally run the A-pillar cage tubing through the firewall and to the front shock tower to reduce chassis flex. However, this isn't allowed in Formula D so we had to devise a different solution.
After almost 70 hours of hard labor, the rollcage was finished, with all the necessary tubes and gussets for driver safety and chassis rigidity.
With the mock-up seat in the car, it was time to measure pedal and steering position. We hung the Wilwood pedals on the rollcage dash bar and chose the position of the steering column. Brackets were made, and everything TIG welded into position. A steel channel was also welded to the floor to allow the perfect seat position and angle.
Sheet metal was then cut and welded to the firewall to close all holes that were no longer needed. With the dashboard trimmed and re-fitted, the car was now starting to look like a racecar.
The front and rear frame horns were cut off the chassis, and the trunk area removed. We will eventually fabricate tubular steel bumpers that can be easily replicated. They can be sacrificed without damage to the chassis or needing to send the car to the frame shop for expensive repairs if we should rub the wall or bump another car.
Pro Drifting is an extreme form of motorsport, designed to create a spectacular show for spectators. We push the cars to the absolute limit, trying to perfect the lines laid out for us by the judges, making it as exciting as possible for the fans.
Coming from a road-racing background, I love the technical aspect of drifting - forcing the car and tires beyond the normal limits, while still being fast and smooth. The runs are short and intense: very different to road-racing where you have more time to plan your strategy.
Now that the E46 chassis preparation is almost complete, we're anxiously awaiting the arrival of our Bilstein suspension components so we can work on the layout and setup. We're also looking forward to receiving a new exhaust and intake manifold for the turbo engine from Doc Race. Exciting stuff!
We'll have another update in a couple of weeks.
Follow us here at www.europeancarweb.com as we chronicle the build of the GSR Autosport BMW E46 Formula DRIFT competition car and the 2013 drift series. Or visit www.gsrautosport.com for information about the shop and team.