Determination of Optimum Valve Opening and Height in the Automotive Engine: Experimental Overview

There are various variables that affect the automotive engine power and efficiency. By improving
those variables, engine efficiency will be improved. The effects of the valve opening, and opening
height are very crucial in internal combustion engine. The optimum setup for the opening cam high
and timing of camshafts in engines will improve fuel economy and exhaust gas emission. This
improvement can be obtained from intake (inlet) valve timing and also from exhaust (outlet) valve
timing. The challenging technique is to set up the engine to the optimum valve opening and closing for
inlet and outlet in the combustion engine and to synchronize the timing of valves under range of
speeds of the engine. The objective of this paper is to determine the optimum setup of engine cams to
increase the efficiency. A small engine with one piston has been used to find the best valve opening
and closing by replacing cams and then drawing graphs of loads for five different camshafts. The best
points that give the highest load for the engine in a rage of speeds will be indicated after drawing the
graphs. At the low engine speed, it was found the engine requires high breathing to give high
efficiency and then required low breathing to get the best load among the designed camshafts and
then earlier breathing. It was found also the improvement reached to 15% increase in load from the
original setup after decreasing the inlet cam height by 3 mm at certain point of speed. The result
highlights the importance of designing a flexible camshaft that can change its cam size and angle at
the same time during engine operation to give more efficiency to engines.