5 ms·

I wonder if the lower emissions are really worth it if the car breaks down sooner. All the electronics and gimmicks to lower immediate emissions at the cost of

• mcv 4y ago
  Why would it not be good to turn your engine off? I sometimes come across stationary cars with a running engine, and I honestly wonder why anyone does that.
  • zelos 4y ago
    It's actually an offence in the UK to do that. Not that it stops anyone.
  • zxexz 4y ago
    A good portion of the mechanical wear and tear on an engine comes from starting/stopping it.
    • canbus 4y ago
      probably only when cold.
    • Tade0 4y ago
      cold starting, actually. Oil is viscous. It takes time for it to flow down.
      • mcv 4y ago
        I thought cold starting was only an issue in the distant past, and not for modern models.
        • Tade0 4y ago
          Time to full lubrication and working temperature has been reduced greatly, but it's still there.
          • SketchySeaBeast 4y ago
            As I understand it, when your car comes off its fast idle (which even at -30 is less than a minute) you're good to gently go now.
  • capableweb 4y ago
    > I sometimes come across stationary cars with a running engine, and I honestly wonder why anyone does that. As someone who frequents very warm countries, I think most people do it because of the AC. If the engine is not on, the AC won't adjust the temperature that you've selected.
    • gambiting 4y ago
      I have a Volvo hybrid where the AC continues running even when the main ICE is off(as long as you have charge in the main battery pack). It's honestly fantastic.
      • radicaldreamer 4y ago
        Toyota Hybrids do this too and it’s an incredible experience to sit in a parking lot blasting full efficiency AC with the engine off. I’ve heard of people camping overnight in their Priuses this way with minimal engine use.
      • fomine3 4y ago
        Hybrid (or PEV/BEV) car's electric A/C is heavily underrated feature compared to pure ICE cars. Idling engine only for A/C seems to really inefficient. I think every police cars should be at least hybrid, but still not here.
  • belval 4y ago
    As a general rule, most machines break during state changes like start/stop. Keeping an engine running means no piece is subjected to the extra acceleration of restarting and your starter isn't used.
    • drcoopster 4y ago
      You mean besides the constant vibration and acceleration of pistons changing direction multiple times each second?
    • emmelaich 4y ago
      Yep, which is why diesel cars auto-off/on when stopped is a mixed blessing. Saves fuel but wears out the battery and starter motor much faster.
  • deleted 4y ago
    [deleted]
    • blowski 4y ago
      https://www.rac.co.uk/drive/advice/emissions/stop-start-engines-common-myths-busted/ https://www.rac.co.uk/drive/advice/emissions/stop-start-engi... Summary - if you simply turned an old 1988 car on and off all the time, it definitely would damage the engine and the battery and produce more emissions. But modern cars with auto stop-start are designed for this from scratch. Emissions are lower for the same reason. If you're right - that this is bad for reliability and emissions - that would suggest some conspiracy from governments and manufacturers who are pushing for this.
  • michaelt 4y ago
    If you grew up poor a few decades ago, you probably saw your parents begin every journey praying the car would start. Because loads of vehicle faults manifest as failing to start - flat battery, spark plug problems, cold weather, no fuel. Starting the engine is a stressful experience if you're used to vehicles where sometimes the engine won't start. Especially if you're at the front of a queue of traffic.
• jsolson 4y ago
  > My car, for instance, turns off the engine when stopped, that can't be good for the engine and battery. I understand the intuition behind this, but one could also see a place where starting the engine while it's still hot is better than idling (less wear, fewer opportunities for deposits to build up from wasted combustion), and where the impact to the battery is minimal as the hot engine makes it easier to turn over for the very few cycles it takes to get it going again.
  • snovv_crash 4y ago
    It isn't about heat, it is about the main crank bearing which is a fluid bearing that needs oil pressure to work. When your engine isn't running there isn't sufficient oil pressure so the first few revolutions are pretty tough on the engine. Hot is actually worse because the oil that is there is thinner and more likely to result in metal on metal. Engineering an ICE for an order of magnitude more starts is probably mostly upgrading the battery, starter motor, and main crank bearing.
    • calvinmorrison 4y ago
      they coat the cranks with a special polymer to help with start/stop and hybrid engines that undergo frequent cranking
• Tade0 4y ago
  > My car, for instance, turns off the engine when stopped, that can't be good for the engine and battery. It's largely irrelevant. More than half of the wear and tear in an engine happens during cold starts. Unless you're in utter gridlock, you won't experience them more often than when at the start of the trip. Toyota's hybrids turn the engine off and on on a regular basis, even during cruising, and have a proven track record of reliability.
• ezfe 4y ago
  A Prius starts and stops the engine constantly while driving, not just stopped - and they are known for lasting a very long time as well
• cowmix 4y ago
  My 2013 Volt has 150+ K miles - the engine runs like new. I've never touched the brakes, only 2 oil changes, etc.
  • belval 4y ago
    Regenerative breaking is an amazing piece of tech. I really like electric cars that have it baked-in the "gas" pedal so that releasing it slows down the car without using the brakes. You can achieve "optimal" driving by always recouping the kinetic energy as electricity instead.of heat in your break pads.
    • vel0city 4y ago
      Most of my EV driving is in single pedal mode. I absolutely love driving in this mode. I feel like I just have far more control over the vehicle by having a single pedal to directly control the speed instead of the vehicle just rolling when I get off the accelerator. Also, the fact the car just stays put when stopped instead of constantly rolling forward in drive is really nice. Sometimes my car loads my wife's profile when I drive which changes it back to standard driving. It is jarring having the car just always want to roll forward. It just feels so much worse than single pedal driving.
      • frosted-flakes 4y ago
        I'm assuming the standard driving profile imitates an automatic transmission with a torque converter, which continually creeps forward if the brake isn't held down. As opposed to a manual or dual-clutch automatic transmission, which does not creep (except by gravity). Is disabling this "creep" independently of braking with the gas pedal an option in any electric vehicles? I seem to remember that some cars with continuously variable transmissions had this as an option.
        • vel0city 4y ago
          There is still often an "Auto Hold" feature that will engage the brake when the vehicle comes to a complete stop. My EV can have auto hold engaged while not being in the single pedal drive. I have this in my ICE as well, but it doesn't seem as smooth overall, so I don't end up using it much. It is still not quite the same experience though, as the ICE will just keep rolling at low speeds forever without actually ever coming to a stop until you press the brake. Auto hold will only engage when the vehicle actually stops. For my EV, when I get off the accelerator pedal it'll come to a complete stop on its own and then hold itself there. Other than turning on my EV, most trips don't involve me touching the brake pedal at all.
• ljf 4y ago
  Diesel engines in particular, do not like being run under no load - it is far far better to have them switched off rather than running. Boat owners struggle with this when moored, as they can't charge their leisure batteries by just running the the engine without engaging the prop. I don't know anyone with a stop/start engine that has ever complained to me about having to replace their battery sooner. Personally, I drive clunkers, and have never had to replace a battery on one of those, despite me turning off the engine whenever I can. I think modern batteries are pretty damn hardy.
  • scrumper 4y ago
    Yeah. While the instantaneous power draw is absolutely colossal, the actual energy drained from a battery starting a (healthy!) engine is fairly minimal, and its replaced very quickly by the alternator once it's up and running. Stop/start engines also use the ECU to stop the engine at the right point in the compression cycle for it to fire immediately, without cranking, so there's even less drain. (Even pre-stop/start engines in cars with modern ECUs tend to leave them in a position where they fire almost immediately.) What kills batteries is deep discharge cycles. Sipping a bit of juice to start an engine and replacing it quickly does almost nothing to reduce its lifespan.
• gambiting 4y ago
  >>My car, for instance, turns off the engine when stopped, that can't be good for the engine and battery. A friendly reminder to everyone on the internet that your instinct and "gut feeling" isn't worth all that much. It's trivial to find out stats on this, and they prove that the inclusion of Start&Stop systems in cars had zero impact on reliability since their introduction over 10 years ago. But I still see people on forums saying "this can't be good for the engine!".
• NavinF 4y ago
  I was with you until "turns off the engine when stopped, that can't be good for the engine". That was a concern in the mid 2000s when start-stop hybrids were just starting to become mainstream. Today nobody notices or cares because the concerns never materialized.
• twobitshifter 4y ago
  Sometimes the autostart can be an annoyance but newer cars have got it down to almost imperceptible. The restarting shouldn’t be rough like a cold start.