Way to idle without engine power?
 

Do alternators harness enough power to potentially keep a 4 cylinder engine running at idle for a significant amount of time (~1 minute)? If no, are there other ways (aside from keying off) to limit fuel use at a stand still?

My buddy and I were talking about how much fuel is wasted at idle, and how this is one of the main advantages of hybrids.

You can have your alternator turn off (field wire) at idle, ie below 900 rpm. That would take a load off the engine.
You can also try to reduce the idle speed. 700rpm? 600? 500? You'll have to fool around to find a stable speed which doesn't cause uncomfortable vibrations.

Are you talking about using the alternator as a motor to keep the engine spinning while at a stop light so you don't have to use gas at that stop light? if that is the case then don't bother, the energy it takes to keep the engine turning has to come from some where and charging the battery back up once you start moving again is going to put a decent load on the engine, off the top of my head I don't remember how much power the starter draws but it would be about the same for any motor to turn the engine over for a full minute, 100 amps or so or about one HP would be my guess with the voltage drop of the battery, so your battery would be seeing around 1000 watt draw to have a motor turn the engine over for that minute you are at a stop light.
You would be much better off designing your own auto stop/start.

Yeah. A pipe dream I guess, huh?

I'm sure I don't have near the automotive knowledge to come up with a non-hybrid method of free (non-gas) idling, but it's interesting to think about.

Not worth it. Better to do the ghetto hybrid. Replace the starter motor with an assist motor supplemented by a battery pack. There's an Indian group that's producing these "low cost" hybrid conversions where you have the assist motor attached to the main motor by a belt attached to the main crank pulley instead of going through the transmission.

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This way, you can have assist and start stop without a special transmission or a complicated hybrid conversion.

Sounds like a job for a flywheel and compression release or all-cylinder cylinder deactivation, if that's what you want (why you'd want that, I don't know. :confused: ) Me, I'd just turn it off.

Do have link to that group?

KPIT Cummins & Bharat Forge Launch REVOLO Hybrid Car Kit
For trucks. Mechanical linkage.

http://innovation.hindustantimes.com...er-cheaper.php
For cars... this is the pulley kit.

Revolo - Wikipedia, the free encyclopedia

I heard about the system last year when it was announced. So far, they have yet to commercialize it, though test units have been seen in India.

The worry is whether the fuel savings down the line will pay for the kit. Obviously, having the electric motor that far removed from the wheels and only acting through the crank pulley means that it won't be able to drive on electric power alone, and the efficiency at transmitting and generating power in assist/regen mode will be compromised by the pulley system itself... but I'm hopeful that this kit will eventually go commercial.