injected into the compressed air these methods include the use of a cvt and where cylinders are used partial or full deactivation of compression or expansion cylinders with a cvt the rate of rotation of a compressor relative to the rate of rotation of an expander is altered dynamically this cvt method is preferred for centrifugal compression and for turbine expansion in full deactivation of a compression or expander cylinder the valves of the subject cylinder all remain closed throughout a complete cycle in partial deactivation of a compression cylinder the cylinder 39 s intake valve is held open for longer portions of the beginning of the compression stroke or its exhaust valve is held open for longer periods at the end of the compression stroke to lower the compression ratio in partial deactivation of expander cylinder its intake valve is held open for longer portions of the beginning of the power stroke or its exhaust valve is held open for longer periods at the end of the power stroke to lower the expansion ratio the compression ratio may also be increased by adding a liquid such as water to a positive displacement compressor along with the air wherein the liquid also exits the compressor in liquid form along with the air ignition is provided by a heat source within the expander or more preferably within the combustion chamber the heat source may be an electrical resistance or spark type heater the heat source is deactivated when the combustion chamber attains suitable temperature for stable catalytic or auto ignition of.