Ethanol boosts MIT’s mini engine

MIT researchers are developing a half-sized petrol engine that performs like a full-sized model but offers fuel efficiency approaching that of a hybrid engine at a far lower cost.

It uses a carefully controlled injection of ethanol directly into the engine's cylinders when climbing a hill or passing another road user.

The engine can go as much as 30 per cent farther on a litre of fuel than an ordinary engine, and provides high performance without the use of high-octane petrol.

The researchers believe that their ‘ethanol-boosted’ turbo engine has potential for widespread adoption and could have a significant impact on petrol consumption if widely adopted in the US.

The key to its development was using computer simulations to suppress knocking, which sometimes occurs from spontaneous combustion when efficiency changes are made to an engine.

When the engine is working hard and knock is likely, a small amount of ethanol is directly injected into the hot combustion chamber, where it quickly vaporises, cooling the fuel and air and making spontaneous combustion much less likely. According to the simulation, with ethanol injection the engine will not knock even when the pressure inside the cylinder is three times higher than that in a conventional SI engine. Engine tests by collaborators at Ford Motor Company produced results consistent with the model's predictions.