An electric supercharger unveiled this week could provide small car owners with the kind of thrust enjoyed by more powerful vehicles without costing any more in fuel.
Developed in the UK by Visteon Advanced Powertrain Systems, the system allows a1.2-litre engine to perform like a 1.8-litre unit.
The supercharger came about in response to the dilemma facing car makers: they have agreed to progressive reductions in carbon dioxide emissions and hence greater fuel economy from 2004, but drivers do not want to sacrifice performance.
The Visteon Torque Enhancement System (VTES) is designed to be fitted to existing naturally aspirated petrol engines, and to turbocharged petrol or diesel engines, without any modifications to the engine or powertrain, to provide an ‘intelligent boost’ at or near full throttle.
For petrol cars it will improve performance or provide better economy for a given level of performance by allowing a smaller engine to be used, or through longer gearing. For turbo engines it will improve torque, remove turbo lag and allow engine downsizing.
Turbocharging is efficient and uses otherwise wasted exhaust energy but suffers from ‘turbo lag’, a delay in response when the driver wants to accelerate. Dual-stage turbocharging addresses this problem but adds complexity. Supercharging, driven directly by the engine, does not suffer from lag but is less efficient than turbocharging and more difficult to package.
The heart of the VTES is an electrically powered and electronically controlled supercharger or inlet air compressor. But because of the high power demand of the compressor, it is combined with an electronic control module to prioritise electrical demands when boost is called for.
This momentarily cuts off non-vital but power-hungry features such as heated seats, while a ‘smart alternator’ is more effective at recharging the battery.
Jeff Brown, customer applications manager at Visteon, said that in a Fiat Punto-sized hatchback with a 1.2-litre petrol engine the VTES gave a 30-40 per cent improvement in torque. Acceleration from 70-100km/h improved from 18.1 to 11 seconds, compared with 9.5 seconds for a 1.8-litre version of the same vehicle, but with fuel economy remaining 27 per cent better than the 1.8.
On a turbodiesel installation the VTES complements the main turbocharger. Tested on a 1.9-litre Renault Laguna-sized turbodiesel, it improved torque by 10 per cent and provided 30 per cent more boost after 0.5 seconds under acceleration, removing the turbo lag effect. ‘The faster response to transient demands means it drives as if it had a larger-capacity naturally aspirated engine,’ said Brown.
No modifications were made to the existing power units of the test vehicles except to add an electronic throttle on the hatchback.
Car makers are evaluating the system and Visteon hopes it will go into production in Europe on 2005 models.