Weber 51mm IDA Down Draft Carburetor
The Racing Beat Weber 51mm IDA carburetor is the result of extensive in-house modifications to a standard Weber 48 IDA carburetor. Developed decades ago as the result of in-house dyno testing and tuning for both street and racing applications, this high performance 51mm IDA carburetor is the end product of these efforts.
The Weber 51mm IDA carburetor is well suited for various race applications because of its simplicity, compactness, tunability and excellent float bowl design. As applied to a rotary engine, the carburetor exhibits a variety of good characteristics. However, in a stock or street-ported engine this carburetor's lack of a choke system can make cold starts challenging, even in warmer climates.
The one application where the 51 IDA carburetor performs best is on a peripheral ported 13B engine. Here, its relatively small size is compensated by the excellent breathing capability of the expanded engine porting. Although the 48 IDA carb can be used on a 12A peripheral port engine, power can be increased by approximately 10+HP if an upgrade is made to the 51 IDA unit. (Using RB suggested tuning recommendations and components.)
Racing Beat Modifications
Each 51mm carburetor is based on a standard Weber 48mm IDA and then extensively modified in-house by Racing Beat during the conversion process. Using tuning techniques discovered during Racing Beat's early racing days, these same techniques and modifications are utilized in the methodical transformation of the carburetor as it machine enlarged to become the Racing Beat 51 IDA.
At the start of each carburetor transformation, each unit is completely disassembled and inspected. The carburetor bore is machined to the larger 51mm diameter, fitted with Racing Beat's custom-made aluminum venturis, emulsion tubes, main and air jets, needle-and-valve, hand-crafted dual throttle plates and shaft, and Racing Beat's enlarged diameter air horns with retaining ring.
As delivered, the Racing Beat Weber 51mm IDA carburetor is tuned specifically for a 13B Peripheral Port engine. The Racing Beat Weber 51 IDA carburetor is also suitable for use on a number of rotary engine applications, including a 13B bridge or J-bridge ported engine, or the 12A peripheral ported engine. If the 51 IDA carb is intended for use on these engines; we offer the appropriate Weber components to properly re-tune the carb for these applications. Follow this link for a listing of tuning recommendations for various rotary engine applications. (PDF)
When considering air filtration for the Weber carburetor you have several options. Open air horns are not recommended due to possibility of engine damage if any debris are ingested by the carburetor. A simple, effective and attractive option are to install a pair of mess air screens. These offer reasonable protection from larger objects, but lack the serious filtration properties of an air filter. The K&N Air Filter Kit is an excellent and easy-to-install option, but the height of the air horns must be trimmed due to clearance concerns within the filter housing. For a dedicated racing application we suggest the fabrication of an enclosed cold-air box. We supply a simple drawing with the instructions highlighting our suggestion for a design, your final design will vary with your application.
The selection of an appropriate intake system requires that many factors be taken into consideration. Various intake systems yield different performance characteristics based upon specific engine, exhaust and driveline selections. Due to the complexities associated with these configurations, it is difficult to determine exact power gains for specific applications. Use this intake reference guide (PDF) for performance comparisons between the Weber and Holley Intake systems that we offer.