Primer for the LASAR electronic ignition system

Primer for the LASAR® Electronic Ignition System By Jim Melvin, Bryan Quillen, and Harry Fenton February 1998 When you hear pilots or technicians talk about electronic ignition, electronic engine controllers, or electronic fuel injection...


By Jim Melvin, Bryan Quillen, and Harry Fenton

February 1998


The low voltage harness electrically connects the controller to the magnetos and airframe. The harness consists of three connectors (one for the controller, two for the magnetos) and three sets of input wires. These input wires include: a set of power wires for battery and ground, a set of the cylinder head temperature wires, and two ignition switch wires.

Electronic Mixture Control from Precision Taps into the Power of LASAR®

By Roger Hall

Electronic fuel injection has been available in the automotive industry for many years, but has yet to appear on even the most expensive certified piston engine aircraft. One of the main reasons for this is a reliability and safety concern. In order to assure continuous operation of the engine, many changes to the automotive systems would be required.

Precision Airmotive Corporation and Unison Industries have joined forces in the development of an electronic fuel metering system, which offers many of the advantages of electronic fuel injection, while maintaining the proven reliability of mechanical fuel injection. The system, known as LASAR®+EMC, combines Unison's FAA approved LASAR® electronic ignition with an Electronic Mixture Control (EMC) mated to Precision's RSA fuel injection.

Like the LASAR® ignition system, the EMC is based on proven, reliable technology, and in the unlikely event of a failure of the electronic system, control reverts back to the proven RSA mechanical fuel injection system which is currently used on all Lycoming fuel injected engines.

The EMC works in conjunction with the RSA system to improve fuel efficiency and reduce pilot workload by leaning out the mixture in response to altitude changes and power levels. The primary function of the EMC is to automatically compensate for the air density changes experienced when operating an aircraft at altitude. Additionally, the system will reduce fuel flows at part throttle cruise settings, resulting in additional fuel savings. The initial system to be certified will be installed on a Lycoming IO-360 in a Mooney MSE, and will be a "basic" system with air density compensation and part throttle economizer functions. Follow-on development will focus on "closed-loop" control, allowing aggressive leaning during all phases of flight, while maintaining sufficient fuel flow for engine longevity.

The LASAR®+EMC system consists of a controller, LASAR® magnetos, and an Electronic Mixture Control unit mounted to an RSA fuel injection servo. The LASAR® controller provides the "brains" for both the EMC and the magnetos, although the fuel control and ignition functions are independent of each other. This initial system will use four simple inputs to control the fuel/air ratio. The EMC uses induction air pressure and temperature to compensate for changes in air density. This allows the system to maintain a fixed fuel/air ratio regardless of altitude or temperature — eliminating the need for the pilot to lean the mixture as the airplane climbs. The EMC uses RPM and manifold pressure to adjust the mixture based on engine power level. This allows the system to lean the mixture at part throttle cruise settings, resulting in lower fuel flows (as compared to full rich operation at cruise).

In order to provide the reader with a basic understanding of the EMC system, some knowledge of the RSA fuel injection system is required. The RSA system is a fuel/air ratio control system. It uses a venturi to "measure" the volume of air entering the engine. The pressure differential created by the venturi is proportional to the volumetric airflow. This venturi signal is routed to a diaphragm in the regulator where the fuel flow is metered to provide a predetermined fuel/air ratio.

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