The one really dumb concept is "that the driver should not know that the engine has switched off", which is a poor concept because drivers want to know how this extra cost option is working. What will need a lot of engineering effort is comeing up with a way to assure adequate brake boost when the engine is off. I have done quite a bit of stop-start driving in my 1999 Neon, and it seemed to provide about a 25% improvement in fuel economy over driving the same route with the engine on full time. Of course this did include a lot of coasting with the engine off, in addition to sitting at lights with it off. Starts seemed to take about 3 seconds, so the trick would be to restart when the brake padal is released, rather than waiting until the accellerator is pressed.
The only sensible starter concept is one like the Buick E-Assist, where the starting driver is constantly engaged. That would remove all needs to upgrade the regular cranking motor, which, the same as the Buick, would still remain. The reason is that cold starting an engine is very different from restarting a fully warmed engine. And rather than have the computer control the shutoff while rolling, make that function a driver controlled one. That would remove the "oops, I didn't want to do that " problem.
One comment, which is about that perceived need to run the blower while stopped: That would do more to damage the reputation of the stop-start system than anything else, since it will assure that the battery is not always able to crank the engine for the restart. NOBODY need to have the A/C running constantly, although some think that they do. The heater is even less critical, unless the driver is one of those who drives with the window down and the heat on full in the dead of winter.
I used to have a 1970 Volkswagon Squareback (aka Type III) wagon w/ Bosch feul injection that shut off fuel injection in coast at engine RPM greater than about 1800. You never even knew it was happening, compression braking still occurred, but HC & CO emmissions were much lower than conventional carbureted vehicles in coasting condition. There's really little truely new under the sun!
A properly designed stop-start should feel no differant from a stop than a hybrid. It's allin the details, perhaps a two battery system, one deep cycle type for accessory loads, one starting type for momentary high current starting, more electric vs crankshaft driven accessories, minor to significant starter motor design changes, possibily even a combination starter/alternator, though I'm dubious that this makes sense, as they have very differant requirements (e.g. the alternator is a 3 phase AC machine, use for starting would require a DC-AC inverter system with its losses, and starting is a much higher current/power proposition, than accessory/charging power generation, so optimum winding & magnetic configurations would need to be quite differant for each use.)
Stuart, adding a flywheel integrated starter/alternator is a great idea but not within th capabilities of most of us. But that combination alternator and starter/drive boost package that was written up quite a few months back could be bolted on without nearly as much effort. Besides that, it would be a lot nicer to not have to replace a flywheel to gain the benefits of stop/start driving.
"The starter motor is integrated in the flywheel of the engine, so no traditional starter motor is used. This allows the engine to be started without wear on flywheel gear teeth, actuating a high current solenoid, or engaging a starter Bendix."
With the flywheel integration, the IC engine gets closer to the old 'ideal' - the steam engine. Esp no noise / engagement / wear of the Bendix.
BillFZ1, the rest of the challenge of where to put that box of parts that goes with the starter/alternator. That would be a big deal to find enough room for it. Probably my best bet would be to get another 1965 Barracuda. That car had a lot of spare room in the engine compartment. The only real enemy was the rust. Both vital and trim parts would rust away. But the car was good to work on and lots of fun to drive. And most of the work that I did was customizing, not repairs.
William, Tight engine compartments are a fact of life now in the CAD age. As a mechanical engineer myself I can tell you with we can totally pack an area with "stuff" before we ever make a part. My brother had a PT and it was very tight in the engine compartment. GM was testing a stop/start alternator before the restructure. Since they own Delfi I don't know if they will sell them to the public. It would probably work well on the PT Cruiser.
BillFZ1, now what I need is a direct drive alternator so I can add start-stop to my PT Cruiser. The run/stop switch would be on my floor shift lever, so as to be easy to control while shifting to coast. But I have not figured out just yet about where the control module will live. There is not much empty space in the engine compartment.
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