Boosting the appeal of small engines

Interested in a device that promises big car performance from a small car engine? Mark Fletcher seized the opportunity to find out how it works

An integrated air management system that features an electronically controlled, electrically powered supercharger is set to make a big impact in the automotive world. By offering big-car performance from a small-car engine Visteon believes its Torque Enhancement System (VTES) will help resolve some of the environmental issues confronting the world's car manufacturers. Boosted engines, both diesel and petrol, are commonplace on the UK's roads, as the leading manufacturers endeavour to squeeze as much power as possible from smaller engines. But this new concept promises all of the advantages of traditional boosting methods without the disadvantages of heat, power loss and limited compressor mapping. In essence it is an electronically driven, on-demand inlet air compressor which integrates the air filter, battery, compressor and control architecture in a single module. The subject of more than a dozen patents, VTES will cover a range of power plants from 1.2litre naturally aspirated engines to 3litre V6 turbo diesels. However, the greatest potential exists within the 2litre turbo diesel market and this is where Visteon has concentrated much of its initial research and development. It is expected that VTES will see its first 'airplay' in a European model sometime in 2005, with Japan following a year or two later and the US after that. The main driving force behind the design is the need to address the Euro Stage IV and Stage V emission targets in 2005 and 2010 respectively. Emissions will need to roughly half each time to meet these targets. The simple solution would be to downsize engines but drivers like performance which means that smaller engines are considered viable only if more power can be extracted. When fitted to a naturally aspirated 1.2 litre engine VTES contributes to a 30 to 40% increase in torque at peak power. And when compared with a 1.8litre engine, a 1.2 with VTES will offer similar performance when accelerating from 70 to 100kmh in the highest gear (11seconds versus 9.5seconds) but with the fuel economy of a 1.2 engine (6litres/100km versus 8.3litres/100km). This equates to a £2,500 fuel saving over a one year period of a typical driving cycle. One of the main benefits that will be gained from the use of VTES in turbocharged engines is a reduction in turbo lag. A 2.5second reduction is predicted by Visteon for a car accelerating in third gear from 2,000rpm. This high torque at low rpm is essential for the diesel market. : Traditional methods of boosting power, including turbochargers and superchargers, are nearing the limits of their performance with regard to the finite space, power and functional infrastructure provided by the modern car. The most common means of boosting – turbocharging – is efficient in its use of waste exhaust gasses but suffers from a noticeable lag at low revs. Variable geometry turbos have certainly addressed this aspect but are afflicted by heat sensitivity. Further developments such as dual-stage turbocharging offer good transient response and high boost but suffer from packaging, control and air handling issues. Supercharging also offers commensurate gains but suffers from poor efficiency, upheat problems, NVH and parasitic losses. One possible solution is the introduction of electrically-assisted turbochargers but they also suffer a number of problems including the necessity to mount the electrical infrasructure in close proximity to the exhaust manifold.