The racecar
While we everyday rubes are stuck wasting time in dealerships, bargaining with the seedy types that occupy them, the guys at BimmerWorld purchase the raw chassis (body-in-white) directly from BMW. Rather than having to buy the whole car and discard 90 percent, BimmerWorld starts with just the chassis, complete with doors, hood and trunk. The hood and trunk are promptly stripped off and sent away to be used making molds for lightweight carbon-fiber copies. The chassis is fitted with a number of custom structural reinforcements, which are proprietary and thus quite secret, as well as a rollcage. As you'd see from a quick look at the shock towers, this isn't the same kind of cage you'll be getting at your local fabricator. Though technically "just" an eight-point setup, the door bars and the sheer amount of bracing differentiate this cage from the kind you see on open-track days.
The coolest bits on the BimmerWorld car are trade secrets, so we can't show them in pictures. But you'd be a fool to guess that the 2.5-liter inline-six underhood is stock. Built by Sunbelt, it makes upward of 290 hp and has a very narrow range.
"Our racecars idle at 2000 rpm and they live between 6000 and 8300 on the track," says Clay. "That's where they make power. Big cams and a wide-open exhaust work great on track cars and make good high-end power, but if you want your street car to come off the line strong, this setup will hurt your low-end power and you won't be happy with your investment. This definitely applies in choosing turbo sizes--decide what rpm range you'll be running, and remember a big horsepower number is pretty meaningless in real life."
You wouldn't want a race engine underhood anyway. This one is dry-sumped, with a sleeved block, custom pistons, rods, camshafts, lifters and springs, and it needs a rebuild after every 25 hours of operation--if nothing goes wrong. The incredible Ducati-like throttle blips are the result of ridiculously light rotating mass, primarily the flywheel and clutch assembly. You'll never replicate it on the road. Clay says that the most common misapplications of race parts are the clutch and flywheel. "The 4.5-inch twin-disc clutches on our racecars allow the engines to rev incredibly quickly and sound cool, but new clutch disc thickness is 0.106-inch and worn out is 0.095. And if you try to slip the clutch to start the car smoothly, you'll be through that material in a matter of days."
Much of the bad-ass suspension present on the BimmerWorld racecar, like the Moton four-way adjustable Clubsport spring-and-damper assemblies, is designed to work with a racecar chassis. That is, your street car has enough chassis flex that it's often tough to tell the difference between a good suspension and an extremely high-end variant, even in lap times. Feel free to try and make your chassis this stiff, though--BimmerWorld estimates about 450 hours of metal work and fabrication per car, and about 200 more building the subassemblies and putting everything back together. Even if you've pulled it off--"Race parts are meant to be strong and durable, but not always to have a long lifespan," Clay says. "We typically spend about 10 hours per car inspecting and replacing parts after each race weekend." That's after three hours of running.
It's an easy mistake to make. After all, the fastest variant of your car is invariably a racecar. Since you want your car to go as fast as possible, common sense dictates emulation. But the fact is that the parts that make cars go fast on the track aren't the same as those required to make your car fast on the street. And more importantly, as tough as race parts are, they're designed to stand up to a certain type of rigorous treatment--the kind that doesn't involve potholes, rain and snow, and soccer moms.
In some cases, race parts do work on street cars, but as Clay points out, the benefit is usually not worth the cost. Take the giant Performance Friction brake setup on the BimmerWorld 325. Just about any street car can benefit from four-piston calipers all around and floating rotors up front, but it's the brakes' ability to radiate the massive amounts of heat generated throughout the course of a race that makes them really worth the money. And as with the tires, you're not going to want to use racing brake pads on the street, because they'd simply never reach operating temperature.
According to Clay, the 2008-spec BimmerWorld cars cost about $240,000 to build, and there are now 14 people on the team, which campaigns three cars at around a million bucks a season. In a given season, the team can paint and replace as many as 30 sets of fenders. Typical damage costs range between $30,000 and $40,000, but are sometimes much higher. But the cost is finally paying off--Bimmerworld had its first World Challenge win at Road America just last year.
So before you find yourself with an empty wallet, sitting in traffic, and attempting to slip that three-puck race clutch without kicking and bucking like a rodeo bull, realize that you spend a hell of a lot more time on the street than you do on the track. And you don't have to wait until you send a race shock flying through its shock tower to admit to yourself that you've been a bit... ignorant when hooking up your ride.