Downsized 2 stroke/4 stroke switching engine for passenger cars (2/4SIGHT, 2/4CAR)

Project Details


The 2005 Autocar award-winning 2/4SIGHT Project (downsized 2 stroke/4 stroke switching engine for passenger cars) was funded by the Department of Trade and Industry Technology Programme: Foresight Vehicle, Engine and Powertrain, and was a collaboration between Ricardo, DENSO Corporation (Europe) and The University of Brighton and the University of Brunel.

The aim was to demonstrate an engine concept that had the potential to deliver class leading improvements of up to 30 per cent in fuel consumption and CO2 emissions together with performance.

The 2/4SIGHT engine combines an innovative combustion system, an advanced fully-variable hydraulic valvetrain and novel control technologies that enables automatic switching between two and four-stroke operation. Brighton was chosen by Ricardo to carry out the important multi-cylinder, steady-state testing of the very first concept demonstrator engine along with combustion and cooling system analyses.

A sub-project was the New Heat Flux Correlation, which involved the derivation of a new heat flux correlation for a poppet valve gasoline engine in two and four Stroke operation using experimental data and computational fluid dynamic modelling methods.

This sub-project aimed to investigate the thermal characteristics of a poppet valve engine that could operate using the two and four-stroke cycles. The design requirement for efficient operation in both modes led to higher heat generation in the surfaces of the combustion chamber using the two-stroke cycle.

The cooling requirements for 4 stroke operation are well documented and empirical correlations have been developed from experimental results. However, there was no existing data to support correlations for 2 stroke operation of a poppet valve gasoline engine. This research project aimed to address this area through the development of a heat flux correlation derived through experimental and computational studies (CFD), along with the accuracy of current heat flux correlations.

A follow-on project, 2/4 CAR, led by Professor Morgan Heikel, added further research on engine and switching control strategies carried out on the Brighton camless multi-cylinder engine in order to assist the industrial partners including Jaguar Land Rover into producing a prototype demonstrator vehicle integrating the 2/4 switching engine technology.

Key findings

The switching two-four-stroke engine was announced in March 2008 by
Ricardo and its consortium of automotive partners including the University of Brighton, who have enjoyed a close relationship with Ricardo since 1995.

The advanced prototype research programme based on the highly innovative 2/4SIGHT engine concept used novel combustion, boosting, control and valve actuation technologies to enable automatic and seamless switching between two- and four-stroke operation, aiming to deliver significant performance and fuel economy improvements through downsizing. Its direct injection gasoline combustion system enabled smooth transitions between two- and four-stroke operation without torque interruption.

The engine control system of the prototype was a DENSO rapid prototyping system working with DENSO gasoline direct injection and ignition components.

The prototype engine was built at the Ricardo Shoreham Technical Centre and installed for testing at the Sir Harry Ricardo Laboratories of the University of Brighton.

Development test results

Testing of the prototype 2/4SIGHT engine enabled development and validation of the combustion system. The flexibility of the advanced control system – developed jointly by DENSO and Ricardo – allows rapid changes to high level code which, coupled with the flexibility of the EHV valvetrain, enabled the project team to develop and optimise a new control strategy for the 2/4SIGHT engine, including the management of two-four-stroke switching.
Acronym2/4SIGHT 2/4CAR
Effective start/end date1/01/0531/07/08


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