Originally Posted by arnsbrae
Originally Posted by jmatero
The biggest "complaint" with auto stop/start in BMW's is that it has to crank the motor with the starter when you lift your foot off the brake. And it's pretty "violent" compared to auto stop/start people have experienced in hybrids which use the electric motor to easily restart the motor.
From the MB website:
The engine goes off when the vehicle is stationary and back on again when the brake is released the ECO start/stop system operates virtually unnoticed by the driver. This is all thanks to complex control functions which run in the background to ensure efficiency, comfort and safety.
How the ECO start/stop system works in detail: as a general principle, the engine is switched off every time the vehicle comes to a standstill (auto-stop function. Restarting the engine (auto-starting function) takes place almost imperceptibly; and moving off without any noticeable time lag compared to a stationary vehicle with its engine running. This rapid action is attributable to two special features: a crankshaft Hall sensor which is able to identify the rotational direction of the crankshaft enables the engine control unit to identify the cylinder in which the piston is ideally positioned for starting. The fuel is injected into this cylinder first, thereby speeding up the starting process. An additional electric transmission oil pump supplies the clutches of the automatic transmission with oil pressure prior to starting, so as to enable a swift resumption of the journey after direct starting of the combustion engine via firing of the spark plug on the ideally positioned cylinder. The starter motor engages briefly, imperceptibly, to complete the auto-start function. The starter motor (starter) has also undergone thorough modification: it is now designed to cope with eight times as many starting procedures, ensuring that it will last a car's lifetime in continuous urban driving involving frequent auto-starting. In addition, the on-board electrical system is supported by a second battery.
What a crock of crap. The MB is all vapor ware. (as in fuel vapors) It still relies on the freaking starter; otherwise, why the need to make it 8x stronger? Plus, just like it's 5 o'clock somewhere, one of the bloody cylinders is likely to be under compression when you stop. The MB suggests that the restart is accomplished by zapping the cylinder lined up for firing brings the engine to life with a little hit of fuel and a zap from the spark plugs. But, the MB misrepresentation quickly comes to life when you discover it needs a starter that is 8x ruggedized.
This is like saying an escalator can be used as a set of stairs when its motor stops because the elevator in the next room is on the second floor. It is all doublespeak and ignores the elephant in the room: you still rely upon a bloody starter to start the car.