Abstract: A control system for the use of the main engine of a vehicle as a heat source in maintaining the temperature of an operator compartment. The system is manually enabled subject to multiple criteria, the temperature in the operator compartment is monitored, and signals for the desired operator compartment temperature within an about plus or minus 10 degrees control range are produced. The main engine of the vehicle is enabled to start and run by all standard safety features and with a fuel flow controlled idle power output. Cycling through the starting and stopping of the engine is accomplished in response only to the temperature monitor signals. Disconnect of the operator compartment temperature control is accomplished manually by the operator, usually by actuating the operator controls.

Abstract: A method and apparatus is provided for measuring detonation in an internal combustion engine. Vibration sensors located on the engine send signals through a filter which is turned to the cavity resonance of the engine's cylinders. The peaks and valleys of the filtered signals are detected and ratiometrically compared one with another to determine the magnitude of detonation. The detonation information may be used by an engine control to retard timing in response to a predetemined level of detonation.