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Old 07-30-2010, 10:46 PM   #75
JamesClay
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Join Date: Jul 2003
Location: BimmerWorld
Posts: 184
My Ride: Any BMW with 4wheels
"Finally, an update" you say. Yup. I warned you guys that this was a scramble to build. Stack on the UTCC day at VIR, a PM photoshoot with the car, a tripp 4 hours north to Summit Point, and a weekend instructing the BimmerWorld Club Racing School and I was nicely behind. Now, I am starting to dig out.

Now, in the style of the great George Lucas, this is Episode I of the Final Mid-Project BimmerWorld Update Trilogy. And if I can get it in gear, USA Network-style, you will get one per night to fill your weekend with reading fun. If.

First a quick disclaimer - "Mid-Project"? Uh-huh - the UTCC was the very fast initial build of this car and had a stopwatch nicely attached to the event so the results were evident. But we still have a few items in prototype stage and some in final design. So the project will go on a little further - probably until someone buys the car, moving all our tinkering efforts back to my street car.

Episode I - Build Catch-Up

Right - we aren't going to jump right into the UTCC results. You wouldn't pick up a book and read the last chapter would you? So here is a short retrospective of the final stages of the work that got the car out the door.

Checklists. If you are organized you use them along with good pre-planning to eliminate surprises. Ours is getting shorter here.
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What is missing here?
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Pretty black Performance Friction calipers you say? Remember they aren't part of our budget. Rust? No - we have that, taunting our wallet to spend more money... Caliper retaining clips! Those little pieces of spring steel that keep a BMW rubber-mounted, single-piston floating caliper from twisting quite as much as they might want to. One of our little tricks typically for street/track cars, not full street or a lot of inclement weather use - Solid Brake Guides. These brass bushings replace the [typically worn out] rubber caliper guides with something precise. Like a solid suspension point - less movement means more accuracy. These won't get us to BBK territory, but with the PFC Direct Drive rotors and some good pads, we made a nice jump that direction for a bit less money.

Aero... The wing was easy - we already designed that piece, so it was a 30 minute bolt-on. But getting rear downforce is always easy. What people neglect is the matching and very hard to create front downforce. The best we can do on a car built to this scope (no relocated engine, semi-tube chassis, etc) is a good front splitter and undertray. Thanks to friend and customer Josh's build, we started our fast design project with an ebay lip.
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After mounting the lip (we like to call it a riser - part aerodynamically connecting the bumper to the undertray), we design the undertray with cardboard - going back as far as possible - typically the centerline of the front wheels.
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Now recreate with alumalite (we will do carbon for a production part, but this is the fast and cheap route)
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And mount on the car. We made standoffs to mount the undertray so if the splitter rips off on(off) track, the bumper doesn't feel the need to follow.
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Racetech seats and Schroth Profi-II harnesses for track use - standard seatbelts also installed for street duty, because 1)I feel like an idiot driving with harnesses on the street and 2)a 3-point is specifically designed so than in a wreck on the street, where help may not be quite so trained or quick as the track, 1 cut gets you out - that's just good safety.
BW_E46M3STC (57)

The Hotchkis logo. On our Hotchkis swaybars. They're the biggest in production, which works the best in my opinion. And they are tubular so they are light and very adjustable.
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And the results are in. On 93 pump gas, no trickery, and in full street trim - 338 rear wheel Hp. BAM!
BW_E46M3STC (61)

Stay tuned for Eposide II - the UTCC (and Summit Point) report...
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James Clay
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