Hello! New cars have this fun feature of turning your car off when you idle for too long. Whenever I drive a new rental care with the feature I always turn it off because it drives me nuts. I started thinking about it and I thought that idling (at least at a stop light) is more efficient than starting your car again since it takes more fuel to start. Why then do all of these new fuel efficient cars have this feature? I would assume it’s more fuel efficient since they all have them now, I was just wondering how?
Thanks!
In: Engineering
I took a Tesla taxi and we had stop and go traffic. He stopped and started every time traffic stopped and started. I just assumed he knew what he was doing was the best way to do it.
It *is* more efficient. Some reports have it up to around 10-13% more fuel efficient for city street driving. It drives me nuts and I shut it off as well. For me, the bother is the A/C compressor. When the engine is off, so is the A/C. I live in an area with hot summers so this isn’t tolerable.
It doesn’t take more fuel to start your car. Newer vehicles don’t just randomly stop the engine, like you do when you park your car and shut it off. Engineers have timed it such that one cylinder is just about to fire when the engine stops. So when the vehicle starts again, there isn’t this prolonged period of the engine cranking over and over before it starts. They start up immediately.
The trick is pretty much that when you stop at a red light, and stand there for a while, you don’t produce any unnecessary exhaust fumes if the engine is turned off.
For me, who lives rurally and drives into a large city occasionally, this means maybe half a percent on the fuel consumption, yearly.
For others, it probably cuts as much as 5%. Or maybe even 10%.
So…it’s both micromanaging the environment right next to where you are. Making the air a bit better for people who live right next to the road you commute by every day.
And cutting down fuel consumption. Sometimes more symbolically, sometimes more sincerely.
All this at the expense of the starter motor that gets more wear, and the battery that needs to provide for far more engine starts than in a car without the feature.
The math has been done, and the fuel to start a car is roughly equivalent to seven seconds of idling.
Sure, in two seconds of starting it burns seven seconds’ idle, so it’s certainly faster than normal idle fuel consumption, but not *that* much.
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