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Valeo’s OE Stop-Start Solutions - i-StARS and ReSTART

The solutions produced by Valeo are part of a complete family of cost-effective stop-start system technologies.

Stop-Start Solutions - i-StAR & ReSTART

Stop-Start Solutions

As the first company to pioneer and produce Stop-Start functionality on automotive vehicles, Valeo has the experience and product portfolio that assists vehicle manufacturers in reducing the fuel consumption of a traditional internal combustion engine by two-to-three percent during the standard driving cycle and by up to 15 percent in congested urban traffic. With the latest legislations coming into effect (55% CO2 emission reductions for new cars and 50% for new vans from 2030 to 2034 compared to 2021 levels and 100% CO2 emission reductions for both new cars and vans from 2035), Stop-Start systems are at the heart of vehicle manufacturers plans to reduce C02 emissions.


In the city, vehicles are stationary for nearly 35% of the time (traffic jams, red lights…), with their engine’s idling needlessly. The Stop-Start system automatically switches off the engine when the vehicle is at a standstill and restarts the engine immediately, as soon as the driver lifts his foot off the brake or disengages the clutch, leading to a significant reduction in CO2 emissions.


How to reduce fuel consumption and CO2 emissions

The solutions produced by Valeo are part of a complete family of cost-effective stop-start system technologies. The i-StARS starter-alternator and the ReStart reinforced starter make it possible for the engine to immediately restart.

Valeo's i-StARS

Valeo's i-StARS, which stands for integrated Starter Alternator Reversible System, is a stop-start system based on a combined starter-alternator solution replacing the conventional alternator. Similar to an alternator, it is linked to the crankshaft through the belt drive. I-StARS enables the combustion engine to shut off when the driver begins to brake and the vehicle has dropped below a preset speed.


For example, one Valeo application example in the market today stops the engine when the vehicle speed drops below five mph and below 13 mph for manual transmissions. i-StARS automatically restarts the engine in approximately 0.4 seconds, even when drivers unexpectedly change their minds during stopping sequences.


i-StARS is a 14-volt LIN-interfaced, belt-driven starter-alternator with integrated electronics that is scalable up to eight kW. Compared to previous product generations, the advanced design provides 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.


As the vehicle's alternator, i-StARS's power electronics improve the system's electrical efficiency to make it one of the most efficient alternators on the market. The integrated control and power electronics reduce system cost and makes it easier to install during vehicle assembly. The i-StARS+ version is a seven-phase design, making it extremely quiet, giving it best-in-class noise performance. It can be applied to up to 4-liter gasoline and 3-liter diesel engines and easily adapts to both manual and automatic transmissions.






Valeo's ReStart system, meanwhile, is the second solution in the company's range of stop-start innovations. This reinforced starter provides the extra durability needed for repeated stopping and starting when the vehicle comes to a complete standstill. ReStart has minimal impact on engine architecture and can be applied to a variety of engine types and displacements. Currently, Valeo is developing a reinforced starter capable of restarting an engine, while it is still rotating, for automatic transmissions and to offer additional fuel economy improvement.



Valeo provides a full range of vehicle electrification solutions, from full electric to micro-hybrids. The company launched its first belt-driven starter generator on the Citroen C3 in 2004 and programs with Mercedes, Nissan and PSA soon followed. Making automatic engine shut-down and restart more affordable is a viable solution today that is used by the majority of vehicle manufacturers to reduce vehicle CO2 emission and improving fuel economy.


Valeo's experience in reversible belt-driven machine design is a valuable asset in our development of higher-voltage belt-driven systems for mild hybrid applications. The new generation of systems have the ability to recover braking energy and provide engine torque assistance.



Valeo at glance


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