A few months ago I rented a car for a business trip.
It started shutting off at intersections. Then, it would start agin when I went “what the hell?” and took my foot off the brake.
Why? What’s the reason?
To conserve gas, of course. When it’s running, even just idling, it’s burning gas.
Got it in one. Saving gas and not polluting the air are both good things in my book.
It’s called a start-stop system.
There have been a number of threads on this topic before (here’s one).
The gist is that it really does save a significant amount of gas during city driving.
modern cars with fuel injection and electronic ignition (and computerized fuel and timing controls) are far easier to start. Many now have a one tap push-button start rather than a push and hold to start. Thus, unlike the old carburetor system, they don’t take a lot of time or extra gas to start, especially when the engine is still hot. Starting automatically when you take your foot off the brake (or wiggle the steering wheel) is fairly simple tech. So turning off when stopped is very fuel efficient. I should note that when the air conditioning or cabin heat warrants, the engine will start automatically once the heater/cooling has gone beyond optimum temperature.
I think we’re all stuck with the intuitive notion that starting an engine is, in some sense, a stressful and inefficient operation (for the engine, or battery) and it’s best not to do it too much. md2000 notes that this was the case with older engines with carburetors.
I saw somewhere (years ago) that it was most efficient to stop and re-start the engine if one expects to idle for more that 90-or-so seconds, but if idling for less time than that, keeping the engine running wins out. Obviously, that isn’t the case for modern engines.
Airplanes seem to have a much longer life than cars for some reason, and lots of little airplanes from the 1980’s and even earlier are still flying. They all have carburetors. Newer airplanes, like cars, are fuel injected. But I suspect they all still keep the engine running at red lights.
I just got a new Subaru, and initially thought it would annoy me. But I’m giving it a chance, I discovered that it’s pretty smart, there are certain configurations where it doesn’t shut off - notably if you are signaling a turn when you’re waiting for a gap in traffic. So in that situation there’s no safety concern unless you’re a dick who doesn’t signal.
Our most recent vehicle, a 2017 Kia Sorrento, lacks this, but I work manual shutoffs and restarts at obvious delays like roadwork blockages - I don’t bother killing the ignition at the five stoplights in this county. (I think there’s that many.)
Electric vehicles of course don’t burn juice while awaiting traffic signals, and neither do steam vehicles. Steamers would be ideal quiet, low-emission, no-burning-fuel-while-stopped vehicles for urban congestion. If Big Oil wants to keep selling the usual petrol to consumers, they’d better push development of modern steamers.
I foresee a future where existing internal combustion vehicles are grandfathered past the upcoming electric mandate but all ICEVs are chipped for external control that kills their engines at traffic stops. Governments will likely demand autonomous-run kits for older vehicles, too. Enjoy the ride.
Come to Europe where it’s already happening. Any car here built this century will probably have the stop/start feature. It was the inevitable response to the ever-tightening rules on exhaust emissions and increasing fuel costs/taxes. By 2040 or so (reducing) ICE-powered cars will be history.
The concern about wear and tear from the start/stop function is widespread, and in groups relating to my car, I have seen many requests from people who want to turn it off (It can be done). The other thing I see on those groups is that people whose cars are around five years old are reporting that it has stopped functioning (along with some other electric gadgets). This is because their batteries are beginning to fail. If the voltage drops below some preset point, the car progressively switches off un-needed features. Stop/start is the most power-hungry so it goes first, followed shortly by the heated windscreen (it may be vice versa).
I rented a Jetta about a month ago that did that. The odd thing was that the restart at intersections was quite different than when starting the car from a cold start. In the latter case, you pressed the button (it was keyless start) and you could hear the starter motor cranking and the engine starting in the normal way. But when stopped at a red light, say, the engine would just go quiet, and taking your foot off the brake or turning the steering wheel would suddenly cause it to come alive without any of the normal sounds of starting. It was as if the engine wasn’t really off, but in some kind of “sleep” state. It was also a feature that you could optionally turn off if you didn’t like it, and then it would idle normally when stopped. I left it on because I thought it was kind of cool, but it struck me as one of the many, many things that can go wrong on high-tech cars as they age.
Yeah, I rented a Volvo a few years ago right when this was getting implemented. Drove me nuts at first, and I kept restarting it until it dawned on me what was up.
Even before the push button starts they did that. I had one or two cars that were designed so that you’d turn the key like any other car, but you could let go right away and they would crank until started. I got so used to it, if I started a regular car, it wouldn’t start on the first try because I’d let go of the key to early.
They (or at least the car that I had that did the stop/start thing) have a high power starter, designed to start the car much quicker than a regular starter. Presumably it also has a longer life since it might have to start the car 50 times a day instead or 3 or 4 times.
Also, a trick I learned, and this is surely different for every car. If I wanted the engine running while at a stop, I could keep my foot on the brake and tap the gas pedal. That would get it started and it would stay running until the next time I stopped. Helpful if I wanted to get the AC kicked back on or if I’m waiting to pull onto a busy road and didn’t want the half second lag before I could go.
One would think, but stop-start systems have been around for 10 years now and I haven’t heard any reports that they require more repairs than other cars.
My 2010 Prius did this, and I never noticed a lag starting up again when it turned off the engine at an intersection.
Push button ignition is new, but after car thieves scooped out my ignition twice when I lived in Cambridge, I wired my car with a toggle switch and a button to start it. Worked fine.
The Prius is a bit different, being a hybrid. It starts moving on battery power before the engine kicks in. On conventional cars with a start-stop system, the engine needs to start before the car can move.
As I understand, when the engine is temporarily stopped, the engine controller remembers exactly what angle the crankshaft is at. So the spark plugs and fuel injectors can start firing immediately, before the crankshaft even makes a full revolution. And of course the engine is already warmed up.
My 2019 Cherokee has a button I can hit to override the start-stop system, but I have to hit the button every time I first start up . If I stop and go into a store or something and shut it off, I have to disable it again when I start driving again.
Interesting. That would imply that it really is in a kind of “sleep” mode, ready to self-start, and the first cylinder to fire would be the one in position to do so at the moment the engine was stopped. That’s certainly consistent with what it sounds like – the engine stops running, and then it’s running again, with none of the normal startup sounds.
Yes, they are all like this. The reason is that the EPA will only give full credit for the improved efficiency if they are designed this way with a “non-persistent” off switch.
There are hacks for some vehicles to be found online, and even companies that sell devices for some vehicles to override the electronics and allow a persistent off setting, so I assume it’s not illegal to do so.