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Kevin
10-13-1998, 07:53 PM
What are the options on weber carb sizes that work best for a '72 2002 which I would like to be driveable on the street, but I would enjoy more HP.<br>I have just completed a freeflow exhaust system (2' all the way out).

Matt Guilbault
10-14-1998, 08:38 AM
The following information was culled from www.bimmers.com/02 check it out:<p><b><u>What carburetor should I use?</u></b><p>This response depends on the level of modification of the engine, and the horsepower increase<br>desired. The most popular replacement carb for an otherwise stock 2002 is the trusty Weber<br>32/36 DGV progressive dual throat carburetor. This nice little unit is easily installed, and yields high<br>20's highway (25-28mpg) mileage. It will bolt right on to the stock two barrel Solex intake<br>manifold, however, the throttle ports need to be matched up with a die grinder for optimal<br>performance. With a stock or mild re-grind cam and headers, this application provides a noticeable<br>increase in performance over the stock engine. This is also the only aftermarket carb legal for use in<br>SCCA's Improved Touring class on the 2002. Hence, there is a LOT of info on this carb out there<br>from many IT racers. There are also many shops that specialize on maximizing this carb for<br>performance (IT) applications. Check the Roundel for sources. <p>The next most popular setup with a stock motor is the venerable dual 40 DCOE Weber sidedraft<br>conversion. The DCOE Weber carburetor is a simultaneous opening twin-butterfly sidedraft<br>design. As the model implies, the main throttle bores are 40mm. Contrary to popular belief, this is<br>not an unreasonable setup for the street. The minor sacrifices involved with this setup are a lower<br>fuel mileage, and some initial setup time. <p>A popular myth is that the DCOE's sacrifice driveability. This is simply not true. A properly jetted<br>and synchronized set of Webers will have as much flexibility as a stock carb. These carbs should<br>be run on the street with 34mm venturis. For baseline tuning, follow recommended jetting<br>specifications given in a the Haynes Weber carburetor manual. It is also recommended that some<br>sort of header/free flowing exhaust system be used, to maximize economy and performance. The<br>best intake manifolds to use are the 2002TI sidedraft manifolds. These are well made castings<br>(BMW - they FIT!!!), and feature a rocker shaft style setup for the throttle linkage. This linkage<br>setup (used for the 2002TI Dual Solex PHH Sidedraft application) is factory designed, and<br>extremely robust. Aftermarket suppliers such as Korman Autoworks and TWM Induction also<br>offer quality linkage kits. When used in conjunction with a stock cam, DCOE Webers are legal in<br>SCCA Street Prepared autocross competition. <p>Other popular carburetor conversions for the 2002 include the Weber 38/38 DGAS (a dual throat<br>downdraft with synchronously opening 38mm throttles), the Weber 40 DFAV (also a dual throat<br>downdraft with 40mm throttles), and various facsimiles made by other companies. These<br>conversions yield better performance than the 32/36 carburetor. <p>For HOT street, and road racing drivers schools, the 45 DCOE Webers (45mm throttle bores)<br>are considered the best choice for carburetors. They provide the best flow of all the carburetors,<br>and mated to the proper cam, can really supply the top end performance needed in these<br>applications. They can be used on the street, but the bottom end does suffer. 36mm venturis with<br>125 mains, with 50-F8 idle jets seem to work well on the track. <p>It should also be mentioned at this time that another performance alternative exists for sidedrafts<br>with Mikuni. Most people believe that the Mikuni PHH sidedrafts are "copies" of the old Solex<br>PHH sidedrafts used by the factory. This is not so. Mikuni bought out the license from Solex in the<br>early 1970's. Since then, the carb has undergone a thorough redesign process. The only parts in<br>common between these two carbs is the diaphragm accelerator pump arrangement. The Mikuni<br>now resembles a cross between a Weber DCOE and a Solex. Mikuni North America offers a<br>complete 44 PHH sidedraft kit for the 2002. Mikuni's are renowned for staying in adjustment for<br>years. They are the "set and forget" sidedrafts. Their flow rates aren't quite as high as the Webers,<br>which is why they're not favored by racers, and jet availability is not as good. (Mikuni North<br>America is the primary jet supplier) The Mikuni kit does have a very high quality linkage and<br>manifolds, which makes their installation much easier. For a street or daily driven 2002, these<br>carburetors are well worth looking into. <p>One other item that should be mentioned in this section is air/fuel mixture meters. Recently, several<br>companies like TWM Induction and Camden Industries have offered electronic air/fuel meters that<br>utilize an oxygen sensor to monitor exhaust gas conditions. These are excellent devices to use when<br>setting up a set of carburetors or a mechanical injection system (see below). Basically, the meter is<br>a small "black box" with an led diode scale. The median value of the scale is the "stoichiometric"<br>(ideal) air fuel mixture for the engine, approximately 14.7 parts of air per part of gasoline. You'll<br>know immediately under what conditions your car is running rich or lean, and then can change jets<br>accordingly. <p><i>: What are the options on weber carb sizes that work best for a '72 2002 which I would like to be driveable on the street, but I would enjoy more HP.<br>: I have just completed a freeflow exhaust system (2' all the way out).<p></i>


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