If you haven't yet heard of Mazda's take on idle-stop, this is worth a read.
"Mazda says the system will reduce fuel consumption in the normal city cycle by 10 per cent, more in heavy traffic — an incredible saving."
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At Mazda's research and development centre in Hiroshima, engineers had a different idea. Why go to the added expense, weight and complexity of that powerful electric motor, space-robbing battery pack and gigs of computing power if the same result can be achieved using existing parts and pieces? So they came up with SISS — Smart Idle Stop System.
SISS starts with a thoroughly conventional four-cylinder engine with direct injection. The process starts when the vehicle comes to a stop and remains there for a predetermined period of time, say a second or two, as would be the case in heavy traffic or at a stop sign.
The engine control module makes sure all four pistons stop half-way between top and bottom dead-centre and stores the position of each in memory. Both the compression and expansion stroke pistons are stopped in the right position to balance air volume.
When the signal is received to start the engine — from a sensor on the brake or accelerator — a shot of fuel is injected into the combustion cylinder, and the spark plug in that cylinder fired.
The resultant explosion forces the piston down, pushing the engine backward slightly. That motion forces another piston upward and into the regular compression mode, where everything reverts to normal operation, the fuel is injected and ignited and piston pushed down and the crankshaft turned etc., starting the engine in the forward direction — without the starter.
More: http://www.globeauto.com/servlet/sto...GlobeAuto/home
Related: Mazda’s New Smart Idling Stop System for Direct-Injection Spark-Ignition Engines