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There has to be a good co-relation/ relationship between the pedal effort applied, pedal travel, deceleration level achieved and stopping distance for “good brake feel”. Brake feel also depend upon the time lag between the force applied on brake pedal and the response of braking system. Hence “brake feel” can be improved by reducing the response time of the brake system. Many vehicles are having “poor brake feel” complaints, pertaining to the above mentioned reasons. This paper relates to an improved brake system for automobile in which reduction in reaction time was done by artificially increasing differential pressure head across vacuum booster diaphragm. Brake booster is given an input of compressed air to the valve body during actuation, thereby increasing the differential pressure across the diaphragm. The compressed air is bled from turbocharger-intercooler of the vehicle which is stored in a reservoir, with one way valve, while cruising.

Over the years the brake system of a passenger car was considered satisfactory if it met regulatory requirements. Meeting stopping distance at specified pedal efforts would declare the vehicle to be safe on roads. But beyond meeting safety requirements, the brake system response to pedal input is also important. This paper presents a case study where in the brake system met the regulatory norms, but subjective pedal feel and response was poor. This anomaly of subjective behavior was analyzed and correlated to the objective performance on the vehicle. Subsequent to this, the contribution of controllable parameters for good pedal feel was investigated. The investigations have led to identification of parameters that are critical in achieving optimal balance of performance and subjective feel. The results presented highlight the order of merit of the various components

ABS development on the Safari (SUV class) vehicle was taken up using Bosch ABS 5.3. Subsequent variants with different power trains were supposed to continue with the same ABS, however, with DICOR (Direct Injection COmmon Rail) engine there was a difference in static & dynamic axle reactions resulting in noncompliance of secondary brake performance as per EEC and IS norms. Hence a by-pass valve was introduced in the rear circuit which helped in by-passing the ABS coming into action in the secondary condition and thus helping in a reduced stopping distance required as per EEC and IS norms without affecting the performance of ABS in the condition when both brake circuits are fully functional.