Power control of a spark ignition engine through the variation of the intake valve opening angle

The power control developed for a spark ignition engine, with indirect fuel injection, is made through the throttle valve, which regulates the air flow used by the electronic injection system to dose the amount of fuel to be delivered, maintaining the suitable air/fuel rate. The FIAT 1580 cc 16V engine was modified to function with only one cylinder. The tests for performance evaluation were made on a dynamometric workbench for the engine using diverse load configurations. Seeking the reduction of fuel consumption, a mechanical device was designed that allows, with a working engine, variation of the angular position of one of the intake camshaft cams, maintaining the cam of the other valve in its normal synchronism. This process is characterized by the late intake valve closing. The results of the engine performance trials are presented operating with and without the throttle valve control system for many engine load configurations. The results achieved in the break tests show a considerable reduction in the fuel consumption in partial loads of 75, 50 and 25%.