BMW 502 Race Preperation

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Find Safety In Braking, My Son. (continued)

     But what about power assist for the brakes? We tried driving without---way not safe. Original 502s used a dual master cylinder system with a vacuum booster mounted on a shelf under the hood, but in converting to modern safer systems we definitely wouldn't be using that part. Due to the narrowness of the engine compartment, there was inadequate space for mounting a modern vacuum booster. An aftermarket remote booster was considered, but would have required considerable plumbing and some additional engineering. We finally decided to use the hydraulic booster system used by the factory for the E23/E28 BMWs. That system consists of the hydraulic booster itself, a hydraulic pump, a device called a hydroaccumulator, the valve to which it mounts, a bunch of hoses, and a reservoir/filter assembly. Fabrication began with mounts for the hydraulic pump on the engine---of course after choosing which pump we would use. It continued with mounts for the hydraulic booster and master cylinder. This mount was actually made using the booster mount from a 1974 2002 modified to fit the firewall of the 502.

     There are different boosters for different cars and we chose the E23 booster because it extends out from the mount less when installed. Simple bracket mounts were also made to attach the valve and hydroaccumulator assembly as well as the reservoir to the firewall. High-pressure hoses were made to the right length locally to run from the pump to the valve and from the valve to the booster. Later, after we learned that the system would overheat without it, another hose was made with a restrictor in it running from the valve back to the reservoir. This hose and its restrictor simulate the power steering system not used on this car but present in the vehicle for which it was designed. Braided steel protected hoses for the low-pressure lines were run from the reservoir to the pump and returning from the booster to the reservoir. 

      Brake performance is now outstanding—the car now stops much better than it accelerates. 

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