Turbocharging Single Cylinder Internal Combustion Engines

Technology #16438

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Single cylinder turbocharger air capacitor concept. Fresh air output by the turbo is buffered in the air capacitor. The pressurized air capacitor forces fresh air into the cylinder during the intake stroke. The air capacitor stores the fresh air pressurized by the turbocharger when it is powered during the exhaust stroke.Pressure drop in the air capacitor at the end of the intake stroke, non-dimensionalized by the turbocharger pressure versus the volume of the capacitor non-dimensionalized by the engine capacity.Projected fill time of the air capacitor at different engine speeds versus its non-dimensional volume.
Professor Amos Winter
Department of Mechanical Engineering, MIT
External Link (gear.mit.edu)
Managed By
Christopher Noble
MIT Technology Licensing Officer - Clean and Renewable Energy
Patent Protection

Turbocharged single cylinder internal combustion engine using an air capacitor

US Patent 9,222,405
Method for Turbocharging Single Cylinder Four Stroke Engines
Proceedings of the ASME 2014 IDETC, August 17, 2014, Vol. 3
Experimental Evaluation of a Method for Turbocharging Four-Stroke, Single Cylinder, Internal Combustion Engines
68th Annual Meeting of the APS Division of Fluid Dynamics , November 22, 2015, Volume 60 No. 21


Turbocharging technology for single cylinder engines is applicable to a variety of current and prospective single cylinder diesel engine markets, including tractors, generators, water pumps, rickshaws, motorcycles, lawn mowers, and landscaping equipment.

Problem Addressed

Turbocharging increases the power per capacity of internal combustion engines by forcing more fresh air into the combustion chamber to burn more fuel. However, single cylinder engines are difficult to turbocharge because the intake valve is closed when the exhaustive valve is open. This problem is usually surmounted by adding more cylinders, but in smaller vehicles such as tractors and generators, the engine cost is a large fraction of the overall price of vehicle production. Thus, turbocharging single cylinder engines would have an economic advantage over turbocharging multi-cylinder engines. 


This invention presents a solution for turbocharging single cylinder internal combustion engines by adding an air capacitor to the intake manifold of the engine. During the exhaust stroke of the engine, the turbocharger is mechanically powered by the exhaust gases to compress fresh air. The fresh air is stored in an air capacitor until the intake valve is opened, at which point the pressure in the air capacitor forces fresh air into the cylinder. An optimal capacitor to engine volume ratio allows 80% or more of the turbocharger pressure to be delivered throughout the intake stroke and will not contribute significantly to turbo lag. For smaller capacity engines in the range of 625 cc, the increase in engine size due to an additional air capacitor would be minor. Experimentally,  30% more power has been achieved with a turbocharger single cylinder engine with an air capacitor, compared to the same naturally aspirated engine. It should be possible to produce 40-60% more power in future iterations. The capacitor can be modified to include cooling fins, which would increase the density of its stored air. The capacitor can also be built into the structure of the vehicle such as the frame tubing on a motorcycle or a rickshaw. 


  • 40-60% higher specific power output of turbocharging single cylinder internal combustion engines compared to engines using natural aspiration (30% achieved so far)
  • Lower cost of production for single cylinder engines compared to multi-cylinder engines 
  • 80% or more of turbocharger pressure delivered throughout the intake stroke
  • Only a small increase in engine size for smaller capacity engines