Random Musings on Engine Start-Stop Systems

I frequently rent cars and I’ve been pondering the new engine start-stop systems…has anyone conducted a proper cost / benefit analysis on these systems.

I recently rented a Chevy Impala and it seemed to shut the engine off the absolute instant I came to rest. In the case of stop signs where there is no cross-traffic, it seems certain that the system is wasting fuel since there’s negligible savings on the front end (you’re only stopped for a moment) yet you’ve got to waste fuel waiting for the engine to stabilize at idle RPM before you begin to move.

Additionally, has the increased amount of starter motor, battery, and perhaps flywheel replacement over the vehicle’s life been taken into consideration? I once read that it takes four pounds of fuel to produce one pound of car (sorry, can’t recall the source) so if we’re looking at 100 extra Lbs. of replacement parts, that’s 400 Lbs. of fuel or 67 gallons before we even consider towing, pick up / drop off at the mechanic, etc…no more “nursing it home”…every stop will represent what amounts to a holistic test of the car.

Lastly, how much more break-down induced traffic congestion are we going to have years from now when there’s 10’s of thousands of aging out, poorly maintained vehicles on the road with these systems. I spent much of my youth not being confident that my car would start but once it was running, I knew my odds of getting to my destination were very good.

Can you imagine all of the people that’ll wind up with these vehicles second hand that can’t afford to keep them in good running order and live in harsh environments (say Minnesota 10.5 months of the year). I don’t mean to be an alarmist but how aren’t we going to have many people finding themselves in life threatening situations because the engine shut itself off and wouldn't restart at a problematic time / location?

Thoughts?

I noticed during googling this that the F-type has this system. So you get the loud startup at every stop sign. I assume after it did the loud downshift on the way to the stop sign too.

One thing to say- these are emissions control devices.

So they will make it to 150k miles, or will be replaced for free. Or, GM is going to try to avoid a costly recall on a high $$ item as best as they can.

I also don't think the strain on starting a warm engine is nearly as much as you think- so the re-starts are as bad as you think. Cost wise, for sure, the cost of the system was looked at quite closely. Really closely, as in a target improvement of fuel economy only can cost so much.

Reliability wise- most of the systems are very sensitive to only operate under good conditions. So they will likely never run when the engine is cooler than 150F, perhaps won't run when the ambient is cold enough (certainly won't on a cold Minnesota day)

Some of GM's systems are really good- perhaps not on your car- but some of them have a starter/alternator, so the car starts via the belt drive. Much more expensive than uprating the starter, but it's a better system;

One other note you didn't bring up- I saw on one anti start/stop video that some think that the fuel to start a car is more than a one or two min idle. That's totally wrong- it's not much more fuel than a standard fuelling. And that lasts just one single event. So the amount of fuel to start the car is less than a second of running.

Aa for your weight options- how do you come up with 100lb for a starter, battery, and flex plate? Maybe 40lb. And most of that is the battery. On a side note, the start/stop system will stop doing that when the battery state of charge is low enough. So once the battery starts to show any indicators of going low, it will stop doing it.

All of that, and it's not an endorsement at all. I'm not a big fan. But I have see the real, measured, benefit.

My biggest gripe with these systems is for 99% of drivers, they're never truly "stopped" in traffic - everyone comes to a stop, then continues to inch forward. So you're either constantly stopping/restarting(as I've witnessed with these systems), or you stay in place while traffic ahead creeps forward.

I know before I buy a new/newer vehicle I'll make sure it doesn't have this "feature".

Had it on a rental car. Freaked me out. I never got used to it. I've owned enough beaters to never let go of the feeling that an engine shutting off without me pulling the keys spells doom.

There is usually a button you can push to disable the Econo Start. I always turn it off.

All the systems I've seen (BMW) have a bypass option. I'm sure that is for the folk that don't like the idea of the motor constantly shutting off.

In reply to alfadriver:

Of course the increased wear will be wildly dependent on driving conditions…from nearly zero for a typical owner in North Dakota (but then the system is equally nearly pointless) to easily increasing the total number of starts by a factor of 10, 20, or more for someone that daily’s in stop-n-go or urban sprawl.

I just took a WAG that, on average, vehicles equipped with this system would require 1.5 extra batteries, one extra starter motor, and ½ of an extra flywheel throughout their service life. I then dumped the parts on my mental scale and they came to 101.27 Lbs. so I rounded down to an even 100 Lbs. to ensure I wasn’t being exaggerative.

Anyway, thank you for your professional insight on the system…admittedly, I’ve got a fair amount of “get off my lawn” in my personality but I also respond pretty well to facts and reason so again, thank you.

I found that by making every stop a California stop, I could thwart the engine stop/start. Just keep inching forward until the light changes and it doesn't cut off. If I roll up just as the light changes red, I'll let it do its thing.

I like it on the Insight. It shuts the car off as you roll to the stop. Starts when you put the car in first even with the clutch in.
I've also had it on a few automatic equipped cars I've driven and it's getting pretty seamless. With direct injection on a warm engine I imagine it's running within about half a revolution and the fuel/emissions savings are real.

RX Reven' wrote: In reply to alfadriver: I just took a WAG that, on average, vehicles equipped with this system would require 1.5 extra batteries, one extra starter motor, and ½ of an extra flywheel throughout their service life. I then dumped the parts on my mental scale and they came to 101.27 Lbs. so I rounded down to an even 100 Lbs. to ensure I wasn’t being exaggerative.

Well, bear in mind, 94% of these systems are on automatics, so instead of a 15-20lb flywheel, it's a 3-4lb flex plate.

The batteries don't appear to be much larger than normal, so it's not actually a 1.5x battery. That being said, it IS realistic to expect at some point a 2x battery, as the starter/generator of the GM system is good also as a very mild hybrid system. Add a couple of electric HP here and there, and it can add a lot of fuel economy. But that's a stretch of the starter motor start/stop systems.

The big relief is that they system HAS to last at least 150k, or the manufacturers are up for a nice recall.

As alfa pointed out, most of these are on autos. You don't need to wait for idle to stabilize before moving forward, the car should start & accelerate forward simultaneously.

Some may not drive great, but I think they are getting ironed out and are excellent features to have out there. Millions of cars burning fuel while sitting still in traffic makes no sense.

Related, but not. I don't think that the people who make cars actually care if they go 150,000 or more miles before a major failure.

Most people who buy new cars... well, like new cars. I venture that very few of the new cars sold are kept by the original purchaser as long as it takes to get to 150k.

My Focus RS has this.

It's a manual.

The idle is pretty stable and you start the motor pushing the clutch in from neutral. By the time you've put it gear you're rolling.

If the car isn't in neutral, stopped with your foot off the clutch and the engine isn't warm or you're not running the A/C or heater on high it won't auto stop.

There's a button on the console right next to the shifter to turn it on or off. It's next to the drive mode button.

I haven't noticed a huge difference in fuel economy from using it or not using it. The RS struggles to get over 25mpg in mostly highway driving and the tiny tank basically means you have about 200-225 miles before it natters at you about being low on fuel.

mazdeuce wrote: I like it on the Insight. It shuts the car off as you roll to the stop. Starts when you put the car in first even with the clutch in. I've also had it on a few automatic equipped cars I've driven and it's getting pretty seamless. With direct injection on a warm engine I imagine it's running within about half a revolution and the fuel/emissions savings are real.

Same with CR-Z. I just ignore it, and it does exactly what it should. I've also intentionally tried to catch it out by going from neutral to first and clutch engagement quickly, and I can't. It doesn't need very much time at all to stabilize. That could be a hybrid thing though.

I have noticed that the battery will lose bars just sitting there for a long time in auto-stop, so I have to keep it idling between runs at the autocross so I have maximum electric power for my run. That is a pretty narrow edge case.

alfadriver wrote: The big relief is that they system *HAS* to last at least 150k, or the manufacturers are up for a nice recall.

But is that all 50 states, or just the selected list of states that follow CA emissions?

My Elantra has warranty coverage to 150k on emissions items since it's a PZEV, and because I live in MA.

My understamding is that if I lived in a non-CA emissions state then the emissions warranty would only be the normal federal emissions warranties (performance and functional) that run out a 80k.

Like or not, I believe start/stop is here to stay. Much high pressure fuel injection, it will be on most vehicles in the next years. It does bring along a host of complexities for oil pumps, water pumps, and overall engine cooling behaviors which has led to some interesting innovations.

I like it. I personally do it manually at some of the longer lights around here. I do not see the need to sit at a light for two minutes with the engine running

I have it our Volvo XC70. I wish it could be turned off and left off if desired, but if I want it off, I have to push the button rach time I start the car. I have been trying to embrace it, but it seems stupid. It encourages rolling through stop signs to prevent it from stopping and starting the engine in a single second which cannot save anything. If it was programmed to engage after being stopped for 2-3 seconds I would like it a lot better.

I don't mind it so much anymore on rental cars.

The first gen systems appeared to shut down pretty violently compared to the new or hybridized ones which freaked people out.

jstand wrote:

alfadriver wrote: The big relief is that they system *HAS* to last at least 150k, or the manufacturers are up for a nice recall.

But is that all 50 states, or just the selected list of states that follow CA emissions? My Elantra has warranty coverage to 150k on emissions items since it's a PZEV, and because I live in MA. My understamding is that if I lived in a non-CA emissions state then the emissions warranty would only be the normal federal emissions warranties (performance and functional) that run out a 80k.

it's 50 states now.

Oh, and I'm not saying that if individual cars break before 150k, you'll get it paid, I'm saying if there's a clear fleet problem (which is what is being worried about), then there will be a recall to fix it. And the distance for that is 150k.

Mike wrote:

mazdeuce wrote: I like it on the Insight. It shuts the car off as you roll to the stop. Starts when you put the car in first even with the clutch in. I've also had it on a few automatic equipped cars I've driven and it's getting pretty seamless. With direct injection on a warm engine I imagine it's running within about half a revolution and the fuel/emissions savings are real.

Same with CR-Z. I just ignore it, and it does exactly what it should. I've also intentionally tried to catch it out by going from neutral to first and clutch engagement quickly, and I can't. It doesn't need very much time at all to stabilize. That could be a hybrid thing though. I have noticed that the battery will lose bars just sitting there for a long time in auto-stop, so I have to keep it idling between runs at the autocross so I have maximum electric power for my run. That is a pretty narrow edge case.

These are a little different than what people are having issues with- if you start the motor with the generator, there's less noise, and whatnot. But on the starter motor- it sounds bad.

(which is one other reason I like GM's starter/generator on the belt- it's quieter)

A rental had it. I got used to it pretty quickly. Besides, many cars are so quiet it's hard to tell if the engine is running anyway.

It was a bit unnerving the first time it happened to me on a rental car, simply because I wasn't expecting it. I've had some with it and plenty without and it seems unintrusive enough on a brand new car. I do wonder what that looks like when the car ages and gets harder to start, but I'd think it'd be fine for the first 250k miles or so.

What amazes me is that it makes enough of a difference to bother implementing it. Obviously, they've done their cost/benefit analysis and determined that there's enough reduction in something to justify the development and implementation, but I would have never guessed that it would make that much difference. Most of the systems I've experienced will shut the car off for a few seconds (10-15? I never really timed it) before starting the engine again to run the A/C. I wouldn't have guessed that would have made a difference...

I could definitely use start/stop in my commute, about half of it is stopped. I've been thinking really hard about making an electric "traffic creeper" motor setup for my Samurai, maybe geared onto the rear driveshaft.