Renault has revealed a prototype version of a two-cylinder two-stroke diesel engine, which aims to halve the amount of space needed in the engine bay and not increase engine noise.

The engine is 50 per cent smaller than the best-selling four-cylinder, four-stroke 1.5-litre dCi unit on which it is based. The 730cc prototype unit, which weighs in at less than 100kg, is 40kg lighter than the 1.5-litre dCi.

Renault says the aim is for this engine to be around 15 per cent more efficient than the equivalent four-cylinder unit, although it stresses that this engine is not yet at that level.

Renault has not revealed any performance figures for the engine, but says it is both supercharged and turbocharged and produces between 48bhp and 68bhp and up to 107lb ft.

A company insider said the engine has been designed with emerging markets in mind and should cost less to produce and buy than the full-sized four-cylinder version due to the reduced number of parts required. However, it will still cost more than a petrol engine of equivalent power to the 1.5 dCi.

The company spokesman also said this engine should sound exactly the same as the four-cylinder version.

Currently, the main prohibiting factor is the cost of the turbocharger. The spokesman said: "We haven't invested yet, but we know how to make it."

A second phase of development is expected before the engine makes its way into production cars.Renault also revealed a host of other new and developing technologies at its Cooperative Innovation Laboratory (LCI) in Paris. They included:

LPG/Petrol engine

A new engine due to go on sale in the coming months is a petrol/LPG dual-fuel unit. It is based on the 0.9-litre three-cylinder petrol engine found in the likes of the Dacia Sandero.

Renault says this engine is 20 per cent more efficient than an LPG engine of the previous generation, and it cuts emissions by about 10 per cent. Due to a lack of LPG infrastructure, this engine won't be offered in the UK.

Twizy Delivery Concept

Renault’s researchers have taken a standard Twizy and turned it into a small delivery truck. The prototype has no rear seat and instead has a detachable two-wheeled trailer that can carry loads of up to 150kg.

Trials are set to start in April next year before a decision is made on whether to put it into production.

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