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64 www.autotechreview.com DECODING TECHNOLOGY Steep rise in retail prices of fuel, a dwin- dling economy and congested roads are some of the basic reasons for an increas- ing demand in improved fuel efficien- cies. A leader in vehicle fuel economy improvement technologies, Valeo, has developed technologies that help improve fuel efficiencies by up to 39 %. One such technology is a micro- hybrid system called i-StARS, or inte- grated Starter Alternator Reversible System, which enable stop-start func- tionality and can help reduce fuel consumption of a traditional internal combustion engine by 2-3 % during the standard driving cycle and by up to 15 % in congested urban traffic. The other solution – ReStart rein- forced starter – offers the same capability, and like i-StARS, can be adapted to differ- ent transmissions. While a regular start-stop system automatically stops the engine when the vehicle is stationary, Valeo’s i-StARS starter- alternator and the ReStart reinforced starter make it possible for the engine to restart immediately. Valeo was the first auto- motive supplier to market a starter alternator, in 2004. The French manufacturer’s stop-start system has been fitted into specific car models of Renault, BMW, Mercedes, PSA, Ford and Hyundai, among others, worldwide. I-STARS The i-StARS starter-alternator replaces the conventional alternator. The engine is started immediately and silently via the belt drive that permanently links the system to the crankshaft. In alternator mode, the power electronics improve the system’s electrical efficiency making it also the most efficient alternator in the market. The integration of control and power electronics in the unit makes it easier to install in the engine compart- ment and reduces the system cost. This system can be adapted to any engine stop-start strategy specified by the automaker. i-StARS shuts off the vehicle’s engine when vehicle speed drops below 8 km/h for automatic transmis- sions, and below 20 km/h for manual transmissions. Engine restart is imme- diate (400 milliseconds), noise and vibration-free, even if the driver unex- pectedly changes his or her mind, while stopping. It can also shut off and restart the engine when the vehicle is moving slowly, which further increases potential fuel sav- ings. This func- tion cannot be provided by heavy-duty starter sys- tems with- out affecting comfort. i-StARS is a 14 V LIN- interfaced, belt-driven starter- alternator with inte- grated electronics that is scalable up to eight kW. Valeo claims that compared to previous product generations, the advanced design pro- vides increased torque and reliability, while improving cost, packaging and temperature management. In addition to LIN, it can interface with any OEM engine control unit architecture, such as RVC and C-Terminal. HOW IT WORKS i-StARS is a reversible starter generator that is located in the space of the con- ventional alternator on the front-end of the engine. While a conventional alterna- tor transforms mechanical energy into electricity and thus feeds the board net- work and the battery, a starter generator is reversible and does the opposite: it takes electric energy from the battery and through the belt drive cranks the thermal engine. It thus is a reversible machine and transforming alternating current into direct current for the battery, and direct battery current into alternat- ing current in order to function as a starter. VALEO i-StARS – GREEN STOP-START SOLUTION ADVANTAGES FOR THE CARMAKER: i. It has the lowest impact on vehicle architecture and OEM R&D. It has the best ratio cost/ consumption reduction; ii. Fuel savings and reduced CO2 emissions for a reasonable cost; iii. Easy electronic integration. The machine is adapted for a very high volume production and can be easily integrated as the packaging does not differ from conventional alternator; iv. High starter power. ADVANTAGES FOR THE CONSUMER/ USER: i. Fuel savings by up to 15 % in congested road conditions; ii. Reduced CO2 emissions of up to 25 % in heavy urban traffic; iii. The engine stops and restarts automatically; iv. The engine restarts silently in about 400 milliseconds; v. Engine noise and vibrations are eliminated, when the vehicle is at a temporary standstill, which represents 35 % of city driving time on average.
