Ricardo switching two-four-stroke engine

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March 26, 2008 Ricardo and a consortium of automotive partners today announced the completion of an advanced prototype research programme based on the highly innovative 2/4SIGHT engine concept. This gasoline engine concept uses novel combustion, boosting, control and valve actuation technologies to enable automatic and seamless switching between two- and four-stroke operation, with the aim of delivering significant performance and fuel economy improvements through aggressive downsizing.

The 2/4SIGHT engine concept uses a direct injection gasoline combustion system in which the design of intake and exhaust ports, combined with appropriate changes in boost supply, fuel injection, ignition and valve timing, enable operation both in two-stroke and four-stroke modes. An advanced control system coupled with flexible valve actuation manages driver demands and coordinates operation of the boost system, valves and fuel injection equipment at an individual cylinder level. This enables smooth transitions between two- and four-stroke operation without torque interruption in both transient and constant torque conditions.

The research prototype engine is based on a single bank of a 2.1 litre V6, which in 6 cylinder 2/4SIGHT configuration is intended to deliver levels of performance and driveability more usually associated with a 3-4 litre V8 gasoline engine. In order to enable the project team to assess control strategies in a completely unrestricted manner, an electro-hydraulic valve (EHV) actuation system was used for the prototype development rig.

The air handling system of the 2/4SIGHT concept is based on two-stage boosting and intercooling using a Rotrex supercharger and Honeywell turbocharger. For simplicity in the initial test bed prototype configuration however, boosting is provided by an external compressed air supply. The engine control system of the prototype is 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 has enabled development and validation of the combustion system which has been optimised for operation in both two and four-stroke modes. 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, has 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.

Significant improvements in fuel economy

Following completion of the test programme, Ricardo has carried out a vehicle drive cycle and acceleration performance simulation based on the steady state fuel consumption and full load performance of the 2/4SIGHT engine.

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