By Marc Lachapelle
Engine stop-start systems are becoming more common and not only on hybrid-powered vehicles. Until now, carmakers had used the conventional starter or a starter-generator to restart the engine. Now Mazda engineers have come up with a simple, ingenious and effective way to do it better.
In Geneva, Mazda officially introduced i-stop, now standard with the 2.0-litre MZR gasoline engine, becoming the first stop-start system to use combustion energy to restart the engine. Combined with the engine’s direct injection system and some aerodynamic tweaks, i-stop can reduce fuel consumption by up to 14 per cent, for a combined fuel economy rating of 6.8 L / 100km on the Euro cycle.
The principle is quite simple. Using a crankshaft angle sensor that can measure rotation in both directions, the i-stop system accurately determines piston position and lets the engine rotate in the reverse direction ever so slightly after it stops, to prepare it for an instant restart. Mazda says the restart takes 0.35 second which is twice as quick as other start-stop systems.
The engine is then restarted by injecting fuel in the cylinder where the piston has been carefully positioned at the ideal spot for compression. Combustion then pushes the piston down and gets the engine going with brief assist from the starter.
No official word from Mazda Canada yet but i-stop will undoubtedly soon be included with the Mazda3’s 2.0-litre engine here too.