[2][3] In 1904, at the end of his first year at Cambridge, Ricardo decided to enter the University Automobile Club's event, which was a competition to design a machine that could travel the furthest on 1 imperial quart (1.14 L) of petrol.

His engine had a single cylinder, and was the heaviest entered, but his motorcycle design won the competition, having covered a distance of 40 miles (64 km).

[4] Before graduation, Ricardo designed a two-stroke motorcycle engine to study the effect of mixture strength upon the combustion process.

He succeeded in designing a new six-cylinder engine with reduced smoke emissions, which was also much more powerful, and still fit into the same space as the existing one.

[7] In 1917 his old mentor, Bertram Hopkinson, who was now Technical Director at the Air Ministry, invited Ricardo to join the new engine research facility at the Department of Military Aeronautics, later to become the RAE.

He realised that turbulence within the combustion chamber increased flame speed, and that he could achieve this by offsetting the cylinder head.

This design embodied intense swirl with a reasonable rate of pressure rise and good fuel consumption.

This advantage was lost to the United Kingdom as a result of the heavy tax imposed on diesel fuel in the budget of 1938.

A number of sleeve valve aircraft engines were developed following this paper, notably by Napier, Bristol and Rolls-Royce.

[1] Ricardo's work on the sleeve valve affected the development of British aircraft engines in the thirties and during the war.

He enhanced the Rolls-Royce Merlin engine in the Mosquito by giving it an oxygen enrichment system to improve its performance.

[16] Ricardo also assisted in the design of the combustion chambers and fuel control system of Sir Frank Whittle's jet engine.

In this year he was contacted by the Royal Naval Air Service to help with the design of a device to manoeuvre battle tanks into position aboard railway wagons.

The success of this venture yielded £30,000 in royalties and led to Ricardo being able to buy the land and set up the company on its present site in 1919.