Abstract: A simple, reliable, compact and inexpensive automobile engine misfiring detection system includes a basic capacitive pressure transducer, attached to a bleeder pipeline equidistantly from each point where the exhaust manifold is attached to the engine, and made of two closely spaced insulating plates whose opposed faces contain conductive layers, and one of which plates is a flexible diaphragm of low mechanical hysteresis. The transducer is thus coupled to a variable exhaust gas pressure source which under normal operating conditions remains at a substantially constant pressure level. The output signal from the transducer has its high-frequency AC component attenuated by a low-pass filter, whose output in turn has its DC component substantially removed by capacitive blocking, after which the remaining AC output is then amplified by a circuit including an operational amplifier.

Abstract: An exhaust backpressure tester is provided for determining exhaust backpressure in an exhaust system of an internal combustion engine of a motor vehicle. The tester includes a pressure sensor associated with the exhaust system for sensing pressure therein and generating a first signal representative thereof. A comparator is also provided and is connected to the pressure sensor for receiving the first signal, generating a second signal having a value which is representative of substantially zero backpressure in the exhaust system, processing the first signal to compensate it relative to the second signal, and comparing the processed first signal to the second signal to generate a pressure signal which is indicative of the exhaust backpressure in the exhaust system.

Abstract: An automotive exhaust gas recirculating (EGR) system contains a pressure sensor responsive to the changes in exhaust manifold gas pressure to control the movement of an EGR valve. A water vapor/ice condenser is installed in the exhaust gas signal line to the pressure sensor so that any water vapor/ice present in the exhaust gas will be condensed/precipitated out and not cause a malfunction of the pressure sensor and an erroneous output signal.

Abstract: A one-piece combination oil fill/air breather cap for an automotive type engine positive crankcase ventilation (PCV) system that includes a filter and oil separator chambers below the filter defined by partitions or baffles upon which the oil droplets impinge during reverse flow operation of the PCV system; a double lip flared annular seal operating in tension being sandwiched between the cap lower surface and the engine rocker arm cover to minimize oil leakage.