Another thread has been discussing cars where the engine stops whenever the car stops, and then the engine starts when you hit the gas. What are the technological advances that make this ok? Or has it always been ok? Did starters get super-reliable due to some technological advance? Was there an advance in chemistry that made engine oil better able to handle this? Or some materials science advance with engine metal that made the temperature fluctuations or whatever less stressing? When these cars go off warranty are repairs because of this going to be costly? Are there going to be more frequent cases of stalled cars at traffic lights because of this?
Starter motors, batteries and possibly alternators are beefier on these cars. It is reasonable to assume that these items will cost more to replace than they might have done. All the rest is just part of the steady improvement in reliability.
Always? Of course not. Once upon a time you needed to crank the engine by hand. Then even after starter motors came along you had to fiddle with throttle and choke (not to mention manual timing adjustment) to start even a warm engine.
But for a car that has a reliable starter motor and electronic start, restarting a warm engine is a breeze. Took a lot of steps to get to that point though.
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the engine doesn’t cool off appreciably when sitting at a stop, so the oil has nothing more to “handle.”
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the catalyst may cool off too much in an extended stop, but the auto stop/start logic will either restart the engine or disable auto stop if there’s a risk of that.
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the transmission has a small “accumulator” to maintain hydraulic pressure while the engine is stopped, so it doesn’t need to re-pressurize its internals before it’s ready to get moving.
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the PCM stays powered on and awake as it commands the engine to auto stop, and monitors the cam and crank position sensors as the engine comes to a halt. therefore, it “knows” where each cylinder is in its cycle when it stops, and only needs to crank the engine for just long enough for the next available cylinder to fire.
the last one is the big one. when you normally start the car from “OFF,” the PCM is awoken from a “cold” state and has no idea where any of the engine’s cylinders are in their cycles. therefore, it has to see the engine crank through at least two complete revolutions of the crankshaft to read the cam and crank position sensors before it will enable fuel and spark.
so since the starter only needs to “blip” the engine over briefly for an auto start, it’s not working nearly as hard.
There needs to be 3 things for an engine to fire - compression, gas, and a spark.
I would say the biggest advance is fuel injection. Until what, about 20 years ago, there were many things that could go wrong - choke setting, clogged needle, fuel filter clogged, too cold, too hot, etc. that would mean a car would not get enough extra gas to start on cue. (Those were the days when you cranked for a while before it finally “caught”) Fuel injection puts in exactly what it needs.
Plus over the last decades, electronic ignition has removed another issue, timing and strength of the spark. (And cleaner running cars thanks to fuel injection removes the clogged spark plug issue)
And finally, cars are basically computers now; so they have the smarts and plethora of sensors to know when to stop and start.
nope. Auto stop/start only works once the engine is warmed up, and a warm engine with a carburetor and magneto or points ignition will start almost instantly since they’re “dumb” devices.
Am I the only one that would worry about your car not starting after the light turns green when you’re in the middle of a six lane highway as opposed to your garage?
The starter isn’t starting your car in auto-stop mode the way old starters did. It plays a new role, instead of carrying the burden and being ‘dumb’, wherein it just popped out, engaged and cranked like the dickens.
Starter motors in auto stop/stars cars are different and more robust, and don’t engage the engine in the way older, dumber ones did. There is consideration given to position of pistons in the cylinders, which part of the combustion cycle each is in, and the injectors are used in a special sequence to ease and minimize the cranking to a mere blip.
The starter is working with different systems and has been redesigned for this new type of duty to handle more frequent starts, but starts that happen in auto-start mode are now easier to execute, since the whole system is working to make the car easy to start.
You won’t sit in auto-off mode forever, if you’re at risk for losing electrical power. The car should start after some period of time to produce current.
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Ok, what is the purpose of this auto shutdown and restart? I would assume a fuel economy increase is the main driver. What is the cost of this? How long is the payback time?
If I remember the oil commercials from several years back, one of the claims was that most of an engines wear was due to starting the engine. Has this been addressed. I would think the oil shouldn’t have drained down too bad at most stoplights although some of the busier intersections usually have a several minute wait.
Is this an actual improvement or just a marketing gimmick?
It appears to increase fuel economy around 10% - obviously depending on your driving patterns. This was back in 2014, so things are probably continuing to improve.
https://www.edmunds.com/car-reviews/features/do-stop-start-systems-really-save-fuel.html
Damn, that is quite a bit better than I would have guessed. Thanks:)
yes, as in “why have the engine running to do nothing useful?”
I doubt you’ll get anything concrete unless you’re privy to car companies internal information.
starting the engine from cold. Even if you sit at a stop for 5 minutes there’s still a substantial oil film on all of the moving parts.
Based on my understanding, a similar automotive advance in the case of the Prius is the use of an Atkinson cycle engine rather than the typical Otto cycle engine. The Atkinson cycle has the advantage of higher efficiency (an ideal Atkinson cycle has cylinder pressure at atmospheric at the end of expansion, having extracted all available energy from the combustion) with the shortcoming of reduced power density (typically experienced as a lack of low-end torque). Since the series-parallel electric motor in Toyota’s Hybrid Synergy Drive has ample low-end torque the shortcoming of the Atkinson cycle engine is minimized in its use in a hybrid power plant.
And of course, the Prius engine is allowed to stop under suitable conditions when the engine has reached operating temperature and its torque isn’t required even when the car is moving at speeds below 35 mph or so (depending on Prius model).
It is more of a EPA testing gimmick, it takes advantage of the emissions test procedure which has a substantial amount of time in a ‘stopped’ condition. As such it gives a advantage to it’s fuel rating better then what can be expected IRL.
Probably not. But we’re talking about a modern engine here, which very rarely fails to start and when they do fail to start it is very rare for it to be to something that happens while you’re waiting for a green light. You’re probably better off* just worrying that your engine will randomly fail during any and all drives.
*You’re not better off. Try not to worry about things that are unlikely to happen and that you can do little to prevent.
I knew about the bigger alternator/starter/battery, but I hadn’t heard of either of these modifications. Thanks. Those are pretty neat.
I understand that stop-start has a bigger effect in the real world than it does on the EPA test cycle. In fact, I understand that the systems came to the U.S. much later than they arrived on similar cars in Europe because stop-start had a very small effect on the EPA test cycle compared to the much bigger effect on the Euro test cycle. New car shoppers in the U.S. who were unfamiliar with the systems hated them. Since the fuel economy savings didn’t show up during the EPA test cycle, U.S. dealers wouldn’t even be able to use higher fuel economy ratings to convince shoppers to try them. So, automakers just left them out of U.S.-bound products.
The article below says that in Europe, where the systems took off first, the fuel economy test cycle has 25% idle time, whereas in the U.S., it’s only about 11%.
As mentioned already, and in the article I linked to, it actually doesn’t have much of an impact on EPA testing. It’s much more effective in the real world.
It does take some getting used to. For about the first six months after getting our first hybrid I would find myself occasionally getting an adrenaline surge when the engine would stop when the car stopped - “Holy crap, the engine stalled.” The first few times I would frantically grab for the key to restart the engine…
It is unclear how likely it is to happen, given how new the technology is. And it is very easy to do something about it: don’t buy such a car. I am wary of new technology when I think: what about all these possible points of failure? And the answer they give is: our computer software monitors and corrects for that.
The technology isn’t very new.
The Honda Insight had it 20 years ago.