Compact Differential Compression/Expansion Ratio Engine

Period of Performance: 01/01/2013 - 12/31/2013


Phase 1 SBIR

Recipient Firm

Mainstream Engineering Corporation
200 Yellow Place Array
Rockledge, FL 32955
Firm POC
Principal Investigator


Automotive manufacturers have investigated many technologies to achieve ever-increasing, federally- mandated fuel consumption requirements. However, alternative approaches must be considered to meet the upcoming efficiency demands. Differential compression/expansion ratio (DCE) engines have been investigated for nearly 100 years, with all thermodynamic studies showing between an 8 and 20% increase in fuel efficiency. Historically, DCE engines can be categorized into two types; mechanical DCE in which the stroke is physically larger during expansion (most popular is the Atkinson cycle), and valved DCE in which the cylinder charge is reduced by modulation of the intake valve timing (most popular is the Miller cycle). Mainstream Engineering Corporation (Mainstream) is proposing to develop a DCE engine that is more efficient than traditional Miller-cycle engines, and is far less complex than competing mechanical DCE technologies. The efficiency improvement leads simultaneously to fuel savings and an ability to downsize engines, which provides a tremendous public economic benefit. Mainstream calculates a realizable cost reduction of $179 per engine, a payback period for the cost of installation to be less than 2 years, and an annual nationwide fuel cost reduction of $760 M from the proposed DCE engine. To complete this effort, Mainstream will perform a complete system design in Phase I that will incorporate the proposed DCE mechanism into our existing 3-cylinder turbodiesel vehicle engine, the AMD45. Also in Phase I, Mainstream will experimentally quantify the friction from such a DCE engine, and use the data to improve the predictive accuracy of our computational models. Phase I will complete with the generation of machine drawings for the DCE-variant of the AMD45. In Phase II, Mainstream will leverage its relationship with Rivian Automotive to accelerate the development of the engine and provide an experimental demonstration in a Rivian automobile.