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COMPETITION AUTOMOBILE DESIGN

 

   

RACING BMWCCA

The BMW Car Club permits tube frame cars to run in its club racing events in the Super Modified category provided the cars conform to specific construction criteria. Most BMW Club Racing competitors would want a car to be a PTG clone running the biggest engine and the biggest tires, and certainly this can be achieved. It would be wise, however, to build a car that for the most part conforms to the SCCA's rules for GT2 or GT3. This would make it possible for it to be campaigned in more venues; otherwise, one might end up with a rather expensive car that would have both limited use and resale value such as older PTG cars which really can't be raced anywhere else and are expensive to maintain. A BMW Club Racing car obviously does not have to conform exactly to SCCA rules, so some "bolt on" modifications such as the tall PTG adjustable rear wing or the GTR wing can be substituted on the GT3 design for the current 3" rear spoiler, and the wheel size can be changed from the restricted 15" x 8" dimensions to a more stylish 16", 17" or 18" design.

The most sophisticated conforming configuration is for one to build a Grand-Am legal car, but this is a professional racing category and most BMW Club Racing Competitors won't find themselves there. The cost of running in a professional series is considerably more to the competitor. There is the length of the events and the costs related to engine run time and tire usage. Plus there is a need for crew assistance and the related travel expenses to get back and forth. The car, however can be built to a slightly less sophisticated level at reduced cost. Such modifications would not diminish speed potential, however. The interesting aspect of preparing a Grand-Am car is that the M5 V8 engine is not particularly expensive by race car standards, and it has proven to be particularly reliable. The owner of such a car might build it to SCCA GT2 standards and simply substitute the S50 inline six for the V8 to conform to the SCCA category and thereby be legal in that type of racing as well. In fact, the inline six could be the backup engine for the V8 in the Grand-Am classification if one were trying to save money and still maintain the versatility of the car and equipment. Read the Grand-Am section to gain insight about the potential fiscal advantages of owning such a chassis version.

As a cautionary note, each chassis would be designed for a specific tire size such that the desired ride height, which is approximately 2" from the underside of the frame to the ground, is maintained. To substitute tires of a different diameter is to reduce the efficiency of the suspension design. Modest tire diameter modifications may not be noticeable to the driver, but may result in slower lap times with the same tire contact patch. As an example, one configuration that would improve the appearance of the GT3 look would be to run the legal GT2 version 16" BBS modular race wheels that are very attractive and add a wider contact patch. The point here is, however, that the GT2 chassis which is set up differently from the GT3 chassis would run these wheels more efficiently than would the GT3 chassis. Using the GT2 chassis and fitting 18" wheels which would be legal in Grand-Am, may not work as well as using the designed 16" wheel because of the large tire diameter difference.

Tire availability and price are always a consideration. Race rubber to fit these cars is common in 16" and 18" diameter wheel sizes. There are few options in the 17" diameter wheel, so this size would probably not be a wise choice. The M1 or 3.5 CSL bias ply tire combination could be utilized (23.5x10.5x16" front and 25.0x12.0x16" rear), and they are readily available from Goodyear costing in the range of $230 each. These 16" tires are about $150 cheaper than the 18" tires and the 18" diameter BBS wheels are about $200 more expensive than in 16" diameter. Keep in mind that the wider the tire the more drag you will have down the straights. The four cylinder engine (GT3 version), therefore, won't match up well with wider tires. It really depends not only upon your individual budget, but on careful strategy to determine the proper tire and wheel combination to run.

Customers may purchase a tube chassis to any level of preparation or buy a chassis totally bare and install the components themselves. This is quite straightforward and a good learning process for those competitors who are so inclined. Engine configurations of either the M42 1800cc four cylinder or the M3 six cylinder engine need to be installed vertically to conform to the design of the chassis. The V8 S62 installation requires a bespoke front clip to fit that engine, but the inline six or the M42 four cylinder which are considerably narrower would easily retrofit in such a chassis. Installation components are available to effect a simple installation. Such items as oil pans, intake manifolds, exhaust headers, motor mounts, bellhousing adapters, etc. are all available to adapt the configuration of your choice to the chassis. The key factor is that the engineering has been done to ensure a car that is both reliable and quick, and GT Technic provides full support to component buyers as they construct their cars.

The pricing for a car built to your specifications will vary only slightly from the GT3 pricing found in the cost estimates section.

Keep in mind that a stock M3 engine in this lightweight chassis will yield considerably better acceleration performance than in the stock M3 body because of the weight difference of almost 1000 lbs. Furthermore there are several bolt on performance enhancements required just to fit the engine into the chassis. One of them is dry sump oiling which reduces the resistance of the crank churning through several quarts of oil thus increasing horsepower. Also the stock engine management system needs to be replaced by one that allows instant PROM reprogramming with a laptop computer for properly adjusting the various performance enhancements. Our custom intake and individual butterfly manifold is required to maintain the correct intake angle for the vertically installed engine. A specially designed tuned header and free flow muffler eliminates back pressure and is needed just to route the exhaust out of the car. You will probably have well over 300hp just from these simple bolt on additions to the basic stock M3 engine.

We don't use the Euro M3 engines. The Euro engine was designed to be technically similar to the 3.5 litre M1 engine so that European customers would feel they were getting something special that could run with Porsches on the autobahns. BMW never intended this car and engine configuration to come to the U.S. and smogging it to California standards is probably very difficult. The individual butterfly injection system is superior to the that of the US engine, and the individual cambox and cylinder head castings of the Euro engine are not necessarily performance enhancements but they add technical superiority and are costlier to build. Truth be known, the US and Euro engines in full race trim are power rivals. Why spend $10,000 for a core most of which either cannot or will not be used? Engine development of the U.S. M3 engine with individual intake runner butterflies, larger valves, solid tappets and compatible high lift camshafts reveals this fact. Furthermore, the Euro engine is not legal in SCCA competition.

For those competitors who run the stock E36 or E46 chassis, our body panels could be substituted for the stock steel components saving weight and gaining additional fender clearance for wider tires. We have engineered a solution for increasing the front track on the E36 chassis which gives the stock tub chassis car a broader footprint and fills out the wide PTG flares. See pricing for these body components in our catalog section.