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The intake valves of a 1.0 liter, 16-valve production engine has been phase shifted to increase the intake air charge, aiming at improved performance. The engine has been tested in a dynamometer bench to verify the performance attained with the modification and its influence on raw exhaust emissions. Total hydrocarbons, carbon monoxide, nitric oxide and oxides of nitrogen emissions were analyzed for varying load and engine speed. The results have shown that shifting the valves of a dual intake valves engine can provide increased performance, while keeping emissions at acceptable levels.

The piston and intake valves alternate movements produce pressure waves that propagate throughout the intake conduit. Such waves can adequately increase the intake air mass charge to the engine cylinders. In the present work an experimental study on the engine intake valves phase shift was carried out with the objective to analyze its influence on the intake air mass charge. A production 1.0-liter, 16-valve engine was used, with two intake valves per cylinder. Preliminary tests were conducted in a flow bench, simulating the engine intake air flow conditions, and, then, the engine was tested in a dynamometer bench. The results in the flow bench showed that the intake air mass charge is increased up to a phase shift angle of about 30 degrees. From the tests conducted in the dynamometer tests, results are shown for a phase shift angle of 7.5 degrees, with one of the intake valves opening late with respect to the original opening angle.