This is a good example of an incremental improvement that is enabled by more sophisticated control technology.I know individuals who do this manually.Whenever they know they are stopping for more than a few seconds, they turn the car off.Most people leave the car running.In general, for general wear, it is better to avoid starting and stopping.Of course, this is a leftover from much older carburation technology.With older cars there was a lot of wasted fuel each time you started up.This has not been the case for a long time, but people still believe it.
One other area I have seen this, by the way, is in gasoline powered golf carts.My relatives on the farm use these to get around off road (with riser kits for the wheels).If you take your foot off the gas the engine stops.It starts up quite quickly when you step on the gas and the starter motor also recharges the battery (you use much more of that, of course).For automotive use the system was probably not acceptable (there would be some perceptible delay), but for this use it was fine.The reason they liked these, by the way, in contrast to the off road ATV (which they all had), was that they could go a couple of weeks on a tank of gas.It wasn't as powerful or fast, but it fit the bill.
Current ones in Europe are auto shut down and restart, you don't have to alter your driving at all. I've driven a 3 Series BMW with start stop and it's very good once you get over the feeling that the engine has stalled every time you are waiting at the lights. I think on some manual cars they may be linked to the clutch pedal so that the engine fires up when you press the clutch to engage 1st gear.
Re TJ's comments, I'm pretty sure Chuck has previously reported that many of the start-stop systems are implemented so that you're not repeatedly engaging a solenoid during restart. That would lead to early failures, cause it'd be like using five years worth of your current starter in a month. The point about voltage is also important. Cars went from 6V to 12V in the, what?, late 1950s? Now there are plans go to various high(er) voltage systems, which will help support new technologies. Mostly these will help on the advanced drivetrain side, including the starter issue, as mentioned in the comments, as well as in the increased use of in-auto electronics systems.
TJ is right they need a redesign. And again they know what to do but won't.
Solution is simple, lower cost, weight. First go to a 36/42vdc system and replace alt, starter, belts, pulleys, gears, etc.
Then build a motor/alternator in the flywheel. This saves at least 40lbs copper/car and another 30lbs in alum and steel plus labor. All it is is some magnets on the flywheel and some coils next to them. The coils can be made to service easily.
Plus this lead to major performance gains in Air conditioning, power steering, e cams, e oil pumps, etc all can then be electric and smaller, more eff and flexable packaging advantages. Taking al these parasitic drags off the engine and onto the electrical system if 4x's as eff about. It's things like these and lightweight chassis/bodies along with better aero that will easily get big auto to well above the 54.5mpg goal. Done right ligter, more eff is cheaper especially in the future when materials become more expensive as more people want them.
It's an automatic shut down, Rob. The car would use wheel speed sensors and brake pedal sensors to determine if it is at a stop. Then, as you point out, it would have to come back to life quickly, or acceptance of this technology wouldn't be high. To do that, suppliers want to keep the restart -- from the time you move your foot from the brake pedal to the accelerator to actual motion -- to between half a second and a second. To do that, engineers want to use a crankshaft sensor to help "know" which cylinder needs to have fuel injected into it.
Beth, in answer to your question, yes, the Prius uses start-stop technology. It's considered a full hybrid, however, not a micro-hybrid, because it uses a motor-generator to propel itself and to gather regenerative energy from the brakes. Simple micro-hybrids can't do either of those things.
And, yes, you're right about this being a short-term solution. Interestingly, though, it could have a more profound effect than pure EVs for quite a while, because there will be so many of these vehicles on our streets, all boosting their fuel efficiency by 3-10%.
Might a redesign of the starter system (instead of beefing up the existing) be in order? Maybe something that keeps the starter engaged all the time, instead of using a solenoid to pull it in and out on startup?
These adoption numbers are definitely compelling, Chuck. What are some of the Start-Stop micro hybrids now available on the market? Does the Prius fall into that category (I know it has some sort of similar technology onboard)?
One thing that strikes me about what you've been writing about lately is the variety and depth of efforts underway to address the fuel efficiency and environmental challenge. Given than no one technology can be expected to be the savings grace, it's good to see a lot of different irons in the fire, both as short-term and long-term solutions.
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