- Apr 7, 2010
GSR Autosport BMW 350R: Part II - We decimate a 335i and a Formula Drift racecar materializes
GSR Autosport BMW 350R – Click above to watch the progress of the build
Formula DRIFT is recognized as the North American professional drifting championship series. Autoblog has been invited behind-the-scenes with GSR Autosport, and their driver Michael Essa, as the team builds, tests and campaigns a V10-powered BMW 350R during the 2010 racing season. This is the second installment in our series (see Part 1) as we follow the team throughout the creation, testing and race season.
Armed with a 2008 BMW 335i coupe, a shattered BMW M5 and boxes of components stacked around the shop, the team gets busy tearing the near-perfect 3 Series apart. The bumpers, doors, hood and trunk go first, followed by the glass sunroof and remaining sheet metal on the roof (hundreds of spot welds must be painstakingly drilled out). The stock twin-turbocharged 3.0-liter N54 is carefully removed and put aside. The interior is completely gutted and the heavy glass front, side and back windows are cut out. The chassis sits bare on the cold concrete shop floor.
Starting with more than 100 feet of DOM (drawn over mandrel) steel tubing (1.75 x .095), Michael Essa measures, cuts, bends and welds a custom roll cage complete with race gussets. Once complete, the stunning metalwork is primed gray. The stock 335i battery cable (made of aluminum, not heavy stranded copper) is shortened and relocated from the underbelly to within the cabin. The rear crossmember in the chassis is redesigned and reinforced to accept the new rear differential. The stock subframe bushings are replaced with solid units. Custom motor mounts are fabricated, and the transmission tunnel altered to accept the new engine (the stock inline-six is long by design, so fitting a rather-compact V10 in the same space wasn't too much of a chore). Formula Drift rules dictate that the engine cannot be moved further rearward than the stock firewall.
The engine, a stock 5.0-liter V10 (S85B50) yanked from the donor M5, is moved into place complete with its factory cooling system (the engine weighs 50 pounds more than the N54). The stock air intake is removed and an AEM DryFlow dual-cone intake is fitted. Internally, the engine is left stock and GSR Autosport runs OEM BMW factory synthetic oil. (The factory oil sump has two oil pumps-one on each side of the engine. Under high cornering loads the pumps automatically pull from the side with more oil, thus preventing oil starvation.) The radiator is filled with water and a wetting agent. While the stock M5 exhaust headers are used, the catalytic converters are removed and a custom 2.5-inch dual exhaust with an X-pipe is aimed right out the back. There are no mufflers, so the blare of the rev-happy V10 should drown out the sound of spinning rear wheels.
Nearly all of the engine electronics are custom. Apex supplies a hand-made wiring harness and a unique engine map run through a custom Pectel ECU. The digital dashboard display is a Pi Omega. Thanks to the custom engine management software, redline is increased from a stock 8,250 to 8,400 rpm.
The SMG transmission is pulled from the donor M5 and sliced apart. The front half of the bell housing is welded to a custom fabricated aluminum plate and a six-speed Quaife sequential gearbox, with a third-pedal clutch, is bolted on. A dedicated master cylinder operates the hydraulic Clutch Masters dual-disc clutch. A custom built-to-spec rear differential, with quick change gearing, is mated to a specially-fabricated driveshaft, CV joints and axles. The stock fuel tank is retained, but it's modified with two internal pumps (one on each side of the tank to prevent fuel starvation) sending gasoline to a third external fuel pump. An electronically-actuated foam fire suppression system stands guard inside the metal cabin.
The GSR Autosport 350R has serious brakes. It uses two separate Wildwood master cylinders (in addition to the third master cylinder dedicated to the hydraulic clutch). One master cylinder is dedicated to the front six-piston Wilwood calipers (14-inch slotted rotors). The other is dedicated to the rear four-piston Wilwood calipers (13-inch slotted rotors). A cockpit-adjustable balance bar allows the drive to dial in a custom brake bias. There is a second set of four-piston Wilwood rear calipers on the rear rotors (yes, two sets of calipers on each rear rotor) just for the custom hydraulic handbrake – a necessity for drifting. However, there are no brake boosters on the car – the pedal will be very heavy, but it will offer excellent feedback to the driver.
Underpinnings include custom-made KW Clubsport coilovers on all four corners complete with remote reservoirs. Each has a three-way adjustable rebound and a high- and low-speed compression adjustment. The stock 335i steering rack has been retained, but it has been lowered and moved slightly to clear the V10's oil pan. Drift cars need a lot of steering angle so new lower control arms were fabricated from scratch. Also, there are no sway bars.
The stock wheels and run-flat tires have been replaced with Enkei PF01 10-spoke cast aluminum racing wheels wrapped in Nitto NT05R tires (DOT-compliant competition radials). The fronts are 245/40R18 while the rears wear meaty 295/35R18 rubber.
Last to go in is a Sparco Pro 2000 fiberglass racing seat with a Sparco six-point harness mounted behind a three-spoke steering wheel from the same manufacturer. The driving position has been moved back a full 12 inches. This necessitated a custom steering column extension and a unique arrangement much further rearward for the Wilwood gas, brake and clutch pedals.
BMW's signature "Angel Eye" headlights will be retained (on their own toggle switch); as will be the band of genuine wood trim on the dashboard – it adds a touch of class, the team jokes. As the last wiring harness is zip-tied down, the battery (moved from the trunk to the passenger well) is connected. Although it's mechanically complete, the 350R is still missing a front bumper, quarter panels, hood, roof and all of its windows. Those will stay off during testing allowing everyone easier access to the engine and suspension while it is being tuned.
The team gives the car its last once-over. Michael Essa, always smiling, opens the door and drops into the driver's seat. With a warning for everyone within the garage to cover their ears, he reaches over and pushes the start button. The V10 turns over quickly, and then fires to life with a raspy growl.
This Friday... Part III - We test and prepare for the Formula Drift event at Long Beach.