Richard_P_Harve

When I picked up my E400 from the dealer the guy who showed me all my new toys told me that Mercedes' start/stop feature was done differently than most companies. Rather than spin up the starter motor they fire off the cylinder that's at top dead center. I thought, how cool. But yesterday I had a passenger who commented on the feature and I told him what I had been told by the dealer and he called BS on that. He said they use the starter motor just like all car companies do.

Anyone know which is true..?

nauticalx

I was wondering same but was told the TDC by service adviser. I looked for any literature on the technology but didn't find any. Would be nice to read anything explaining how it works.

Richard_P_Harve

Found this after a few Google searches -
Those quick, smooth restarts begin with what’s called a crankshaft Hall sensor. It identifies the rotational direction of the crankshaft, enabling the engine control unit to identify the cylinder in which the piston is ideally positioned for starting. Fuel is injected into this cylinder first, thereby speeding up the starting process.
At the same time, an additional electric transmission oil pump supplies the clutches of the automatic transmission with oil pressure prior to starting. This preps the transmission for a quick take off after the engine starts.
The starter motor has been beefed up to cope with eight times as many starting procedures and, an additional 12-volt absorbed glass matt battery supports the on-board electrical system when the engine shuts down.

So I guess both are true....!

nauticalx

so, it seems, at least in some sense, the starter is used to re-crank the motor.

Harold1898

all i know is it works.

400ixl

And it runs off of a different battery to the main one for this (in the boot) which is one of the conditions for it to be active.