I rode with a guy last week who just bought a Ford F150. We came to a light and he said “Man, see how quiet this thing is at a stop?”. I looked at the tach and saw the needle was the whole way down. I told him the truck must have auto start-stop. The light turned green and he took his foot off the brake and you could hear the engine starting up. He looked at me like I had figured out some unsolvable riddle. Of course, he traded in a 15 year old truck that had 300k+ miles, and he’s not a car guy. It seemed to work pretty well during my brief ride, but I can’t say whether or not I’d like it as a feature on my daily driver car.
The car companies have supposedly built stronger, more durable starters to use with this feature. Time will tell, of course. I can see saving some amount of fuel during long red lights, but during a normal stop at stop sign or short light, the savings would have to be infinitesimal.
It’s the batteries rather than the starters that concern me, in terms of wearing out. The manufacturers fit bigger and better batteries to cope with this feature, which will make them a lot more expensive to replace when they run down after a few years.
On my 2014 BMW there is a button right above the start button that I can shut this off and it stays off until I turn it back on. However I am used to it now and leave it on for the most part.
I also think a big feature of the engine shutting off is the amount of exhaust is reduced and I had heard that is one of the main reasons for the engine shutting down. Cars idling produce a large amount of exhaust. But I haven’t verified if this is one of the reasons but it seems a reasonable assumption.
Yeah, that’s true, because the battery has to keep the HVAC system, radio, lights and everything running while the engine is off. There’s also the alternator in the system, which I’m guessing is also beefed up. I just can’t imagine that the fuel savings are enough to worry about, but every tenth MPG is important to meet CAFE regs.
I tried to to a search to see if these systems are disabled during extremely hot or cold weather, but couldn’t find an answer quickly. It would seem to make sense to not shut off the engine if it’s really cold or hot out.
–edit–
I can see that these systems would help with urban air pollution more than actual fuel use.
Had a Honda Civic Hybrid that I put over 200K on that had this feature. Never had an issue with the starter. I did replace the hybrid battery pack at 150K because it had lost capacity, but that had nothing to do with the restart system. The restart system does not use the hybrid battery, it uses the start battery.
hybrids are a little different as they don’t have a dedicated starter; they use the electric motor/generator unit to start the gas engine. the IMA motor sandwiched between the Honda engine and transmission spins up the engine.
The battery (the ‘regular’ one) on my Honda Insight was about the size of a motorcycle battery. It was so tiny I couldn’t even jump start a compact car with my car.
It’s been my understanding that these motors are specifically designed to be used on a regular basis. I would certainly hope the the manufacturers would have put enough thought into them to make sure they can be used, what, 20–40 times more than a regular one. Also as the OP (and anyone who’s driven one) noted, they are different. The engine doesn’t even crank normally. These motors have to get your engine up to speed and ready to go, reliably, between before you can get your foot from the brake to the gas.
As for the cost, checking online, both an Insight and a Prius come in at right around $200 (about $150-$300). That doesn’t seem too far out of line for any other comparable car.
Discouraging those people from doing that seems to me another plus to the system.
In response to ‘is the system cancelled out in certain conditions’, yes on a BMW it’s overriden in lots of conditions as jz78817 enumerated. And for example in my car the A/C turns itself down with the engine off so in ‘comfort’ mode the system will also restart the engine with the car still stationary once the cabin temperature rises a certain amount. In ‘eco-pro’ mode OTOH it just remain off and it can start to get hot sitting at a long stop light. In ‘sport’ mode the start/stop is cancelled out all the time. To repeat as others also mentioned, there’s a button to cut out the start/stop feature in any mode, but it will default to being activated, with car in ‘comfort’ when you manually turn off and start up the car again.
As to wear on components, again I don’t see why anyone would assume the manufacturers would ignore the impact of the new functionality on all components. Nothing fundamentally against the US makers, but back in say the 50s’-60’s when they had a small oligopoly in the US market (or still felt like they did in the 70’s even when it was unraveling) that’s what they’d do, engineer crap systems to respond to new requirements and if they didn’t really work, what was the customer going to do, buy a foreign car? (they said while they ‘ROTFLMAOed’). Of course big car companies of all domiciles are to some degree bureaucracies always, but basically know they are in market will real competition, not the semi-make believe Big 3 competition of the old US market. So I don’t think the assumption they’d just have the car start 10 times more often and wear the components out 10 times faster is valid.
As to life cycle cost of bigger more sophisticated starter system components to be replaced eventually, that might offset some of the savings, conceivably all who knows though I doubt that. The ‘Intelligent Battery Cable’ (part of overall system of regenerative braking which recharges the battery for the more frequent starts) of my BMW failed, though could have been related to an impact in that area of the car, anyway dealer replaced it and the battery for free under warranty. And if you’re really optimizing the lowest possible $ cost of car ownership you don’t buy a BMW to begin with. If the systems are universal on cheaper cars, then it’s more of a point I think.
Not in my experience; it will not repeatedly do auto stop/start after a certain number of activations. IIRC on the (Ford) vehicles I’ve driven with it, it’s two or three consecutive ones, then it’ll disable auto S/S until you’ve driven at road speed for a bit.
in the Ford/Lincoln vehicles, if auto S/S is enabled it’ll show a grey A-within-a-circle icon. When it activates, the icon will turn green to let you know it turned the engine off. if it’s disabled (either via button or because conditions aren’t right for it) it’ll put a slash through the grey icon.
I confess my wincing at the thought of this system is because I grew up in the 70s when cars were a big pile of lemons and every new gadget Detroit installed had been untested, porrly thought-out and prone to failure. Seeing several episodes of Top Gear where they discuss used and old cars that had ludicrous ‘new’ gadgets that you could tell woul dbe the first things to fail in an age where engineering quality was an afterthought. Add to that the old-school mindset of ‘the worst thing you do to your engine is start it!’ which may well be obsolete thinking these days.
Well, another thing our elders…cough cough…get wrong is that actually, fuel costs are quite high compared to repair costs in most cases.
Let’s say the average car lasts 175,000 miles and the average price per gallon paid was $2.75. (wikipedia, gas buddy as sources)
If the car gets 35 mpg (typical for a recent model non-hybrid passenger car), it burned through $13,750 in fuel over it’s lifespan. These non-hybrid sedans retail for around 20k.
If he car is a hybrid, retailing for 28k instead of 20k, for 45 mpg, it burns through $10,694 in fuel over it’s lifespan. At 50 mpg (careful driving in a new prius), $9,625. You might note that the fuel saving features of a hybrid just aren’t worth the purchase cost increment. A lower end model passenger car with good fuel efficiency is going to be cheaper.
If it gets 28 mpg (older or lower end model), $17,187 in fuel. Or $3400 more, which would pay for a variety of fuel saving features.
If it gets 22 mpg (a new truck), $21,875 in fuel.
If it gets 15 mpg (an older truck still in service), $32,083 in fuel.
This is why I roll my eyes at my dad, who’s got the heavy duty model of a particular truck. He claims that since he uses the truck for light duty, it means it’s drivetrain components will last forever.
Maybe, but a newer truck with potentially more fragile drivetrain components would say $11k in fuel over it’s lifespan. Driving a passenger car instead, for trips where the cargo capacity of the truck isn’t needed, and he’d save more money in fuel than the entire purchase price of the passenger car.
I find the sound of other cars start/stopping to be grating and inelegant, but real world tests show it gives a significant fuel savings in urban driving, 5 to 10%. I would not have expected that much.
With Hurricane Irma approaching, I recently researched how much fuel an idling car uses, in the fear that I might be without electricity for a while and want to sit in the car and enjoy the AC for a while.
Turns out modern cars don’t use much gas at idle, although having the AC on does increase consumption significantly. A 2 liter engine will use about 0.16 gallons an hour, a 4.6 uses 0.39. Turning on the AC almost doubles those figures.
For a long time when the feature first came out, automatic transmissions didn’t work well with it because they relied on the engine spinning the torque converter more or less constantly to circulate the hydraulic fluids that also cooled and lubricated the gears. So the first iterations were only put into manual or dual clutch gearbox models. Newer automatic trannies were designed with this in mind.
One solution to this is the car’s battery is keeping the various accessories running. The battery needs to be a beefy one, like the one in a Prius at a minimum. (it stores 0.9 kwh, while the Bolt stores 60 kWh and the Leaf 40). So then the compressor for the air conditioning would be electric and it would keep running.
Other solution is to just keep the blower running and design the A/C system to have some buffering. An AC works by compressing gas, which is now in the liquid phase in the coolant lines, and letting the liquid expand back to gas by forcing it through a tiny hole in a valve. I would imagine that for a minute or 2, an AC might keep cooling if you designed it that way from residual liquid in the lines.
The Nissan Leaf and Chevy Volt are electric only. They’re a different class of vehicle than the Prius. Since they don’t have an engine to begin with, the AC is already going to electrically driven.
It’s been stated upthread, hybrid vehicles have a checklist of things that need to be met before the ICE will shut off, one of them involves the cabin temperature. I know that when I had my Insight it would get warm in there if it was hot out and I was stuck at a red light, but if I kept my foot on the brake and touched the gas, the engine would turn on (as would the AC) and it would stay on.
That’s pretty much exactly how the refrigeration cycle works as is. Even if you kept the fan running, you’re not going to get an extra minute of cooling out of what, maybe a pound of refrigerant? And more importantly, an evaporator the size of a shoe box. A few seconds maybe.
ISTM, on that theory, you’d be better off running it undercharged, and letting it frost over, then using the frost (or ice) to cool the car. But that’ll create other problems.
The only other thing I can guess at what you mean from ‘buffering’ is that you mean oversizing the system. But if you do that, those hot muggy days will mean getting into your car and making it cool and clammy. Oversized ACs are notoriously bad and pulling out humidity.
I meant making the coolant lines or accumulators (tanks where the liquid is stored) larger than necessary. The cooling capacity would be the same, but upon compressor power loss, liquid would continue to turn to gas, though the pressure inside the gas side would rise and this cooling effect would slow to a stop. I was speculating that over-sizing an accumulator tank would probably not add much to the cost of a vehicle, versus going to an electric compressor and a battery robust enough to drive it.
