At the 21st Supercharging Conference in Dresden next week, Torotrak Group will present results from engine testing that verify previous claims for V-Charge, a variable drive mechanical supercharger.
In comparison with the incumbent fixed-ratio positive-displacement supercharger on a 1.0L GTDI engine, V-Charge achieved improved BSFC (brake specific fuel consumption), better transient performance and a maximum BMEP (brake mean effective pressure) of 31 bar.
|V-Charge system with mechanical variable drive outperforms conventional boosting methods on downsized gasoline engine. Click to enlarge.|
In a paper entitled “Simulation and Verification of V-Charge Variable Drive Supercharger Performance on a 1.0l GTDI Engine” on the second day of the conference, Tobias Knichel, Torotrak Group’s Business Development Director, will share details of the development program. These will include simulation using a GT-Power model and engine dynamometer testing which was carried out at the University of Bath Powertrain and Vehicle Research Centre (PVRC). The presentation includes full load, part load and transient test results.
The V-Charge equipped 1.0L 3-cylinder Ecoboost engine has similar performance to a 1.5L 4-cylinder version, combined with improved driveability, despite a 33% reduction in displacement. This signals the potential for a new level of downsizing, enabling the industry to further reduce the CO2 output of high volume vehicles without compromising driver satisfaction.
The ability to control compressor speed on V-Charge independently of engine speed, allows parasitic losses to be reduced and the need to de-clutch is decreased. The use of a centrifugal compressor, instead of a positive displacement Roots-type blower, reduces power consumption, improves efficiency and requires less package space.
Packaging is also simplified by the quiet operation of V-Charge, dispensing with the need for soundproofing. Test results for NVH show the sound pressure of a V-Charge installation is up to 15.9dB(A) lower than a similar Eaton system with encapsulation, and 19.7 dB(A) lower than the similar Eaton system without encapsulation.
The paper concludes by indicating that V-Charge is well placed to satisfy the first stage of boosting on the most aggressively downsized engines because it has a continuous air power capability of up to 17kW. It can also provide a flexible handover to the turbocharger at any engine speed, enabling simpler boost control. Though tested on a gasoline application, Torotrak anticipates that V-Charge will achieve similar gains on a downsized diesel engine.