My understanding is that the EPA fuel economy test downplays any benefit to stop-start, as there are no significant stops in the test. As a result, there is no visible benefit to the consumer when comparing the "sticker" mileage of vehicles.
Start&stop tech is no news in Europe at least, marketed with different names by all the vendors. I personally own a Volkswagen Tiugan, diesel, year 2011, which uses the same tech marketed as "bluemotion". All I can say is it works painlessly, engine shuts down exactly when I want, restarts quickly, saves quite some fuel when transit stops - but make sure you do not use it for short stops, might not save fuel at all, but the opposite. From my experience, a 2-3 minute or more stop is worth using S&S, less than this does not.
In fact, as I wrote in the story (page 2), hybrid/electric assist vehicles experience almost no delay in power from a stop, due to the instant availability of power from the traction battery to the electric motors.
The issue is when we try to do this on our non-hybrids.
Non-hybrids must rely on a run-of-the-mill starter motor, which is usually too weak for a seamless reboot. That results in that slight partial-second delay in gasoline cars. One solution is to increase the size of the starter motor. But this would add weight and cost.
Where gasoline is very expensive, like Europe, it was not unheard of that people turned off their engines at red lights. Whether or not their vehicle was "start-stop."
One thing you didn't explain, Junko, is how you keep the heater or air conditioner running, when the engine is off. In practice, many/most/all(?) hybrids do not stop the engine if you are running either heat or air. Try it on any car. Turn off the engine at a stoplight, either during cold weather, or while it's raining and the windshield is fogging up, or on a hot summer day. With the interior fan running just on battery power, see well this works. Not very well! The heater core cools down very quickly when the (mechanical) water pump isn't running, and the blowing air warms up very quickly when the (mechanically driven) air compressor isn't running. I haven't seen either electric water pumps or heat pumps used in regular or hybrid cars just yet! I'm not sure how safe an electric water pump would be, for that matter. (Possibly, it could be designed to run on battery power only if the car is stopped, but that would put a heavy load on that battery.)
These days of computer-controlled machinery, this all can be made intelligent enough. But then, what this really means is that often, the engine won't turn off. Or if it does, not for long.
I would not be nearly as concerned about off-the-line performance as I would be about the need for continuous operation of the A/C. If you live in a climate where the interior temp of the car immediately starts rising the moment the A/C shuts off, then the prospect of sitting through a red light cycle without A/C will prove to be very unpopular.
I have been driving a Honda Insight which has this technology for a couple of years now. The delay from the start is practically not an issue. By the time that I have finished releasing the brake the engine is started. The lack of AC is annoying, particularly for my wife. I tend to not think about it much unless it is a hot day, and even then it doesn't bother me that much. The engine kicks back on if I have been sitting for very long, and if the car has been running for a while the heatup isn't as quick. One advantage here in SoCAL is that practically all of the lights have sensors, so long light waits are really not all that common. I sometimes find myself wishing for a longer light when I want to reach for something in the car!
I drive a Prius (in Europe) and as you say the delay isn't really an issue with a hybrid. There is though a noticeable change of torque as the ICE kicks in and this can be annoying if it happens while cornering but you get used to it.
There are still quite a few cars around with manual transmissions here and they can take forever to pull away, sometimes so long that the traffic lights change before cars behind get through (lights can have quite short cycles here). Fuel is so expensive that people don't want to waste it on an automatic transmission. So stop/start might actually be faster as well as cheaper in that situation.
>>I would love if this automatic start-stop mechanism can be fitted to the old
>> cars ( with good starter motors!) as they are not as fuel efficient as today's cars .
I would think that your engine has to be designed for stop/start. Shutting off and restarting engines can be hard on the engine if it is not designed to take it. You always hear that electronics or mechanical devices break when you start them, and rarely after they start operation.
I think instead of completely stopping the motor/engine in fossil-fuel based vehicles, the automobile industry perhaps could draw parallels from electronics industry to use a quiescant mode of operation. The traffice lights in many metropolitan areas are long enough to implement this to realize fuel savings, not to mention reduction in atmospheric and noise pollution. There could be more fuel efficiencies to gain in idle-mode operation of the engines...
Continuing my chain of thought... there may already be ECU's that implement variable fuel injection in today's automobiles, thus saving fuel when the car is idling at traffic lights or in stop-n-go traffic.
I wouldn't worry about the need to leave the engine on when defrost or air conditioning is needed. Determining if the engine should remain running based on environmental parameters would be an easy taskwith the amount of computing power available in todays cars.
As for the delay in restart, that's really only an issue for the first one or two cars in line at the intersection. Add a wireless transmitter to the traffic signal and cars could automatically re-start a second or two before ther light changes.
<<Of course, knowing that your engine will shut down if you miss the green means more people will try to outrun them>>
I've been driving one for over 2 years. It only shuts down if I put it in neutral; if I sit with my foot on the clutch, it doesn't. So, it's my choice whether to shut it down or not. If I decide to shut it down, it takes as long as it takes to press the clutch and put it in first (0.5 seconds?), which is probably less time than the red and amber and as I'm not am amber gambler...
I'd rather prefer EVs or even Hybrids for stop start feature to work well. They already have start-stop features builtin.
I wouldn't care for the stop start on a gasoline car without hybrid, but rather consider safety and comfort features instead. I guess the total savings in gas will be insignificant unless the stop time is huge... in which case most of the drivers turn off the engine when not needed, or would like the engine to be on for comfort.
I've just returned from Japan, where I drove a Nissan mini-van with stop-start. The lag on re-start was less than a second. Since it is winter, I don't know about air conditioning, but the heater worked fine while the engine was off. If the red light was sufficiently long-- say a minute or more-- the engine would restart even with the brake pedal depressed, and then run for a short period of time, perhaps 2 or 3 seconds. I guess this would circulate coolant, keeping the heater core warm.
I looked under the hood, and the battery, alternator and starter are all larger than normal. I'd say the battery was at least 50% larger than typical for an inline 4 cylinder.
I very quickly became accustomed to it, and I don't think the short lag is a problem.
"Since it is winter, I don't know about air conditioning, but the heater worked fine while the engine was off. If the red light was sufficiently long-- say a minute or more-- the engine would restart even with the brake pedal depressed, and then run for a short period of time, perhaps 2 or 3 seconds."
Right. That's the way one would expect it to work, and it's also a mode of operation that is unliklely to save a lot of gasoline. Similarly, on a congested freeway, where you move and stop incessantly, but you don't stop for a long time.
Time will tell how well the engineers design the start-stop logic to work. That will determine whether batteries AND engines AND catalytic converters last an acceptable amount of time. It shouldn't be surprising if car companies go through growing pains, with such innovations.
In Australia, my wife got a new Subaru Forester recently, with stop start technology. It works fine, and to my mind is quite non-invasive. There is a slight delay as you take your foot off the brake, but it is less than a second. When we were evaluating cars we rejected one with Volkswagen's Dual Clutch Transmission, which had horrible "pedal delays".
With the Subaru's S/S, you can control if the engine will stop by how hard you brake. Brake gently, and it doesn't stop. That means in congested traffic, where you move a few centimetres at a time, the engine doesn't stop all the time. When stopped at a red light, the engine will re-start if the ECU decides power is needed for the A/C.
The car also has continuously variable auto transmission, so it can always use the optimum gear ratio for the conditions.
As an aside, Subaru also has adaptive cruise control, that maintains a constant distance from the car in front. We didn't buy that option, but it was fun to play with on the test drive. It will also warn you if you drift across the white lane dividing line.
BTW: On my regular commute I turn off the engine in my older car at traffic lights where I know there will be a long wait.
Back in college I drove a 1966 Envoy Epic, the North American version of a Vauxhall, and used stop/start technology whenever the clutch cable broke (which was often). Learned how to shift a manual transmission without releasing the clutch by matching engine revs, killed the ignition at traffic lights and stop signs, restarted in 1st gear with the starter. Eventually I would get around to replacing the broken clutch cable...
Here in Boston, we aggressive drivers will never put up with this. Even if all cars come standard with thsi feature, we will figure out how to override it. Even if we don't override, we will simply start going before the light turns green. We do that now anyway.
I can see this is going to be hell on batteries and starters.
I drove a diesel Focus in belgium with start-stop. I suppose it would be OK if you sit at stoplights a lot. Stopping at a stop sign for a few seconds and having the engine quit is an annoyance. But I quickly learned to just keep the clutch down.
The problem isn't just waisted fuel while stopped, it's more the energy that is waisted in braking. Many of the problems raised with the start/stop technology have to be addressed with hybrid as well. This certainly applies to heating, cooling and maintaining proper engine temperature.
It would make sense to drive air conditioning compressor with electric motor run off the same battery system as traction motors. Any heating not immediately available from engine should be derived from directly oxidizing some of the fuel.
I used to drive a 2009 Chevy Silverado hybrid pickup and my wife currently drives a 2012 Prius, both of which stop the engine when the vehicle stops (assuming certain conditions such as engine is warmed up, battery is sufficiently charged, etc.)
The Silverado being such a heavy vehicle (5000+ lbs) with a large V8 engine is more similar to a start-stop vehicle than the Prius. Even though the Silverado had a 300 volt battery driving a powerful starter motor, there was a noticable delay when transitioning from stop to start. On more than one occasion, as I pulled onto a rural highway not far from a blind curve, an 18-wheeler abruptly appeared from around the curve necessitating immediate action on my part. With the gas pedal on the floor, I could almost count the milliseconds while waiting for the engine to start. (The Prius is far more frightening in this situation since the engine is very small by comparison.)
Admittedly, this would not happen with a start-stop vehicle since the car wouldn't be driving into the busy highway before the engine started. But I can imagine a situation where such acceleration would be necessary from a complete stop.
With a manual transmission, I assume it would be less noticable since the driver is more in control of when the engine starts (by depressing the clutch). But what about an automatic? If an emergency situation requires immediate power, will the gas pedal be on the floor before the engine has had time to start?
Jim re "I used to drive a 2009 Chevy Silverado hybrid pickup..."
I'm glad you commented on your real-world experience. I was wondering specifically about this vehicle. I suspect it's much more representative of what we would expect. In concept, it sounds great to start movement with a big electric starter while the gas engine is starting up. However, the need for immediate power can overwhelm it on occasion.
Back when early electronic fuel injection came along, I noticed a delay between hitting the accelerator and the engine reving up. With a carburator, the accelerator pump would squirt extra gas in as the pedal was pressed, causing immediate response. However, with the first throttle body fuel injection I drove, you press the accelerator, alowing more air in. After that air passes through the engine, the oxygen sensor would detect an overly lean mixture and then add more gas.
That delay, though quite short, was enough to cause a concern now and then similar to your Silverado concern. Even a half a second can be quite unnerving in a setting you described.
I've no idea about the claimed times but from personal experience with rental cars in Europe and now a recently acquired Mercedes CLA it's so slight as to be a non-issue - my Father-in-Law hadn't even realised the card Mercedes was actually shutting off at lights until we pointed out the rev counter was at zero!
I don't understand why this isn't standard in more cars.
I like the thought of a vehicle that makes the possibility of saving fuel at red lights more convenient.
I just think the implementation is bad. I don't think it should be based on whether or not the vehicle has come to a complete stop. This has safety implications because as another reader pointed out, there are times where you may be at a stop sign where you likely will want to proceed at any random time, and at that, promptly. My own neighborhood has but three exits and the closest one of them meets a heavily travelled two-lane each-way undivided highway with no traffic light. There is also a nearby hill causing reduced visibility of traffic approaching from the right, and the lead cars in each group of traffic departing from the traffic light 1/2 mile away in that direction are typically speeders. In this and many other conceivable situation, an extra 0.3 seconds delay in resuming travel after every stopped state would be unacceptable.
However, these days, we could consider more sophisticated instrumentation for whether or not such a stop would be appropriate. How about a directional low-intensity RF, microwave, infrared or possible even visible, signal that could be issued to only the cars in the lanes that are being stopped by red lights? The signal would mean "All engine computers modern enough to understand this signal, please stop your engines now" engine-off behavior. Such a signal could be removed or terminated max-actual-engine-start-up-delay seconds prior to the light changing to green. This way emergency vehicles could terminate the signal early when they want people's engines on so that they can contribute to clearing a path. There should also be an over-ride in the car itself.
I really think you're making too much of the time to restart. In the Mercedes system with an automated transmission, the engine only shuts off when you have your foot on the brake. The engine restarts autoamtically as you move your foot front brake to accelerator and it's delviering power pretty much as soon as you get to the gas pedal so there's no more risk of being caught out by speeding motorists than with a conventional transmission.
I have been driving a car with stop start technology for over 2 years in the UK. I find it utterly unobtrosive. I wonder whether this is because, like the vast majority of cars in the UK, it is manual and so I am in control (the engine only stops when I put it in neutral). Surely one of those letters next to the gear stick in an automatic is the equivalent of neutral? If so, shouldn't the engine only stop when you put the stick next to whatever letter that is? (I have never driven an automatic, so am rather ignorant on the subject)
However, given automatics use more fuel, if you want to save fuel, wouldn't it be more sensible to switch to a manual (with or without stop start technology)?
I'd assume that even well designed automatics based on torque converters would be more efficient than most manuals driven by people who either aren't paying attention or who haven't been taught to drive efficiently.
As you say, most modern multi-gear automated manuals should be even better as they don't suffer the losses in the oil-based torque convereters, and I'm not sure I could pick the best option from 7 gears anyway!
I think you would soon manage a 7-gear manual. My last three cars have had 6 gears and I find managing that a no brainer. I guess it depends on where the 7th gear is: my current car is best with 30mph (4th), 40mph (5th), 50mph (6th), so there is room for a 7th (60mph) and an 8th (70mph). And at that rate, most British drivers would find room for a 9th and many a 10th! :-)
My automatic, VW Golf (gen 6) TDI with DSG will shift to 6th, and be quite comfortable, somewhere around 36 mph if I let up on the accelerator. It will eccelerate from there without downshifting with the further application of torque. Of course the car gets best fuel economy in the range of 35 to 45 mph. As the speed gos up from there it's mostly a question of air resistance going up in proportion to the square of the speed. I wish RPM, Load and Fuel Consumption charts were available for auto engines as they are for marine engines.
I've driven 6 speed manuals too, but I don't have any illusions that I'm doing so optimally. And never mind other drivers on the road. Many people who drive cars with that many gears skip a gear here and there. Also, speed is not the only criterion for when to shift. It has to do also with your torque demands at the time.
Just like humans can't hope to beat a computer at adjusting the spark advance or the fuel/air mixture, or for that matter a manual choke, all tasks humans had to do in the days of the Model T Ford, humans equally are unlikely to manage transmissions with many gears properly. That is, well enough to beat a computer.
I think you'll find that this isn't true anymore. Automatics now have more gears than manuals very often, and they have had lock-up torque converters for many years now. These days, 6, 7, or 8-speed automatics are becoming commonplace -- more ratios than a manual transmission driver could hope to use effectively. This means that the car operates in a more efficient regime more of the time, and there's no wasted energy in a slipping torque converter, once the gear has been selected and settled down. So really, there aren't many downsides anymore. Car companies that do keep manuals in their inventory do so more because of consumer demand than out of necessity.
Companies like Mercedes Benz are trying to wean drivers off of manuals, specifically because it's easier to meet tough new fuel economy requirements with automatics, these days. When manuals are sold in the US, at any rate, in some cases the transmission automatically "urges" the driver to shift (with a light on the instrument panel), and even to shift to a specific gear. And it's logical. Even something as simple as the manual choke had to disappear years ago, when catalytic converters were first introduced. Why? Because humans are too sloppy. A manual choke would kill a catlalytic converter in short order. Ditto the old mechanical carburators, when the three-way catalytic converters were introduced.
So, it should not be surprising if one of the few remaining manual controls (aside from steering, braking, and throttle) would disappear in time. Not to mention, automatics have also become more maintenance-free than manuals.
I think it's instructive to see how many start-stop car drivers know how to, and habitually defeat, that feature. I'm sure that software control of the feature will improve in time, across all brands, to where drivers won't feel obliged to manually override it. It will also be interesting to see whether, long term, they create maintenance surprises. (Probably something that will vary by make and model.)