Turning car off at stoplights

[Racer X]

Forrest wrote:
It would not be safe on older vehicles to swich off the engine approaching a stop, because you would loose power steering and brakes. Hybrid vehicles are designed to turn the ICE off and still run the power steering and brakes - I assume these systems run on electric power.

Yes, they do. FAR more efficient.

I know these are really old numbers, but they illustrate the idea.

At full speed, a water pump driven fan can suck up 15 horsepower on an old American V-8 auto or truck. 765 watts equals 1 horsepower. That's @55 amps at 14 volts, assuming no power loss. So, a water pump driven fan can consume a massive amount of energy, and all but a tiny amount is wasted. An electric cooling fan, or even 2 11" or 12" ones can consume between 6 to 18 amps, depending on design. So, even a pair of big inefficient cooling fans only need 1/4 horsepower, assuming no power loss. Now you know why they went to electric cooling fans. Add to that electric power steering, electric water pumps, and electric A/C compressors. The power savings are HUGE.

[Racer X]

Forrest wrote:
If you are stopped for 1-2 minutes at a traffic light, you are getting Zero mpg. Turning the gas engine off/on is much more efficient. My Rav4 hybrid with AWD gets 34 mpg.

My 2013 Prius plug-in gets mid 50s, and high 40s on the freeway. The engine is always starting and stopping in town. HOWEVER, a hybrid's ICE is a very different design. You try this with a mid '70s American design, and the engine will wear out pretty fast.

[rz]

Wow, did not know they did this automatically. It would explain why I’ve noticed some cars restarting before the light turns green. I guess they accidentally step on the gas and it starts up again.

I’d say 90+% of the cars I’ve seen are actually Japanese cars. Seen a few Audis and BMWs. I’ve been here 3 weeks and yesterday finally saw a Ford.

[Don C]

My last year in the AF at Wright-Patterson AFB I had a junker Chevy to get from my apt to the base. I carried the battery into the building at night and eventually even at work so it would have enough power to start the car. Had I turned it off at a stoplight, I would have used the whole green cycle to get it restarted.

[Speedy]

Our Volt and Caddy ELR do this when the traction battery is ‘depleted’ and the on-board generator is running. The generator usually shuts off before the car even stops and doesn’t restart until after I clear an intersection. It’s designed to be able to cycle on/off so no problem.

[August West]

Where's Drew at?

[RAMd®d]

Nine states—Colorado, Connecticut, Delaware, Maryland, Massachusetts, New Hampshire, New Jersey, Texas and Vermont—and Washington, D.C., limit idling to between three and five minutes for most vehicles.


Ok, that sounds like if one's car is going to be idling for more than a specified time, the driver has to turn the engine off.

The post I replied to stated: Many cars now do this. In some places it’s required by law.

That read like cars are required to do this, not drivers, and I don't know that the state has that power to require it of cars.

Maybe access to certain areas?

Such as eVs only in the town square, etc.

Just don't know if that would stand a legal challenge.



It would explain why I’ve noticed some cars restarting before the light turns green. I guess they accidentally step on the gas and it starts up again.


Or might they be starting the car so they're ready to go with the light says so.

That might be drivers who aren't confident in the vehicle rolling immediately from Off.

I was aware eVs did the Start/Stop drill, but not that any non-hybrid ICE cars did.

Could that feature be turned off?

I think I saw one reference hear as to that not being possible in one make/model car.


Where's Drew at?

Japan, I believe.

[Drew]

August West wrote:
Where's Drew at?

Hey! Thanks for asking. I'm here in Osaka/Kobe. Turning headlights off at a stoplight is done as a courtesy, so as not to shine lights in the eyes of the other driver who is waiting at the same red light but going opposite direction of you.

I noticed it first time I came to Japan in the 80s. At that time, American car headlights were controlled with a knob/switch on the dash, while nearly all cars in Japan had them on a stalk on the steering wheel for this very purpose.

Now, headlights are designed to turn on automatically when dark outside and not many people bother to turn off at the intersection, I'm guessing because they don't think about the light control so much these days. However, it does seem to be an automatic feature in some high end cars, as I see them dim their lights whenever they stop, not just in a courtesy situation.

My Nissan is a hybrid. Engine usually turns off when not moving. Accelerating after that is sometimes a bit jerky when the gasoline engine takes over for the electric, though I'm used to it now.

rz is in a great part of Japan right now, hopefully having a good time and enjoying great food.

[Grateful11]

Our Prius does this, it's seamless, you don't even notice it.

[macphanatic]

rz wrote:
I’m in the middle of a 5 week business trip in Japan. Something I’ve noticed is that many drivers turn their cars off as they approach a stoplight, then start them back up when the light turns green. I even noticed a bus do this the last time I was here, but have been on several busses and none of them has done it on this trip. I think I saw a sign that said people should do this out of courtesy for people along the side of the road so there are less fumes, but this seems counterintuitive to me. Wouldn’t restarting the car generate more fumes? And wouldn’t it waste more gas? Gas is expensive here, about the equivalent of $6/gallon.

Are you sure that they are physically turning the car off and it's not auto stop/start?

As others have mentioned, this functionality was common outside the US many years ago. It's become more common in the US as it helps improve EPA fuel economy ratings.