Substitution of Hydraulic for Pneumatic IC Engine Valve Control System

Abstract

Research into computer control of the operation of the engine intake and exhaust valves is continuing at Minnesota State University in Mankato to further the goals of improved gas mileage and reduced emissions from IC (internal combustion) engines. A major source of energy-wasting pumping losses can be reduced by controlling valve timing and duration, combined with the elimination of the throttle, while promoting more efficient combustion. An ideal system would allow complete variable computer control of valve lift and timing during all portions of the stroke cycles. Our first paper reported earlier Senior Design Project work, in which a spark ignition internal combustion engine was modified to allow computer control of the engine’s valves. These projects replaced the mechanically operated intake and exhaust valves with pneumatically operated valves controlled by computer in the form of a Programmable Logic Controller. The valves controlled by the solenoids switched compressed air to pneumatic cylinders that operated the existing poppet intake and exhaust valves on the engine. It was found that the use of compressible air was unsatisfactory for the higher RPMs due to the inability of the system to operate the valves quickly enough. Hydraulic operation could theoretically allow more accurate valve control at higher engine speeds. A follow-up research team found out that putting computer-controlled hydraulic valve actuation into operation on a real IC engine introduces other problems, however. We had hoped to present preliminary data from tests of the new hydraulic system, but inadequate hydraulic pressure plus equipment purchase order problems and hydraulic component failures allowed only limited testing using external power by the end of the semester. While we could not get the engine to run under its own power, the analysis pointed the way to future improvements. This paper summarizes the background and pneumatic valve results of the first paper, and discusses the operational issues and problems, and presents the analysis of the follow-up research into the use of hydraulic valve actuation.