I've recently noticed more and more drivers turning off their engines at red lights, or even when traffic is slightly congested. I always thought it's a myth and it actually consumes more power and petrol to restart the car. Do you do it and if so, why?
Turning off Engine at Lights. Why?
BargainCowboy on 22/06/2017 - 09:34
Poll Options
- 28I always do it
- 117I've noticed others doing it, but have never done it myself
- 58I have no idea what you're talking about
Comments
This
Wow, thanks, I didn't know it existed in non-hybrid cars.
They have their own names for it. For e.g. Mazda it's part of their Skyactiv platform.
Mazda I-stop Explained - Idling Stop:
http://discoveryourmazda.com.au/mazda-istop-explained/
http://www.mazda.com/en/innovation/technology/env/i-stop/
Your poll is missing frequency options between always and never.
And also;
- My car does it by itself, I'm just the driver
John Cadogan an automotive God ? Surely, you can't be serious ?
He is the biggest (profanity) i've ever read.
And don't call me Shirley.
But that isn't James May
Name calling seems to be one of his strong points. That and foul language. I wonder why he doesn't act like that on A Current Affair?
And I've always been taught that 80% of the wear an engine gets over its lifetime is from the starting cycle.
Surely any miniscule savings from stopping for a minute here and there is blown away by the shortened life or increased maintenance required as a results?
Engine design has changed a lot, and now they are designed using different techniques and materials, and are able to perform this no problems!
And I've always been taught that 80% of the wear an engine gets over its lifetime is from the starting cycle.
That figure seems grossly exaggerated for any typical use. Does it come from an oil manufacturer by any chance?
Secondly, the conditions prior to starting are a factor in engine wear due to oil coverage, oil temperature, differing thermal expansion of different materials, etc. So re-starting an engine that has been driving but switched off for a few minutes would cause less wear than starting a cold engine.
Yes, but from cold starts. Starting an engine when it's already hot does very little wear.
You'll find stop-start systems don't operate until the engine is up to proper operating temperature.
This answers your question properly.
"… engine is up to proper operating temperature." … and all contact surfaces are lubricated.
I remember back in the UK, my car's stop/start system wouldn't work from the time I bought it - midwinter. I returned to the dealer to report it and he pulled out the manual and pointed out the section where it said that it was disabled when the ambient temperature was below 6 degrees centigrade.
Its been done so that the cars can meet emissions/fuel economy standards. Of course the extra starter motors and batteries that these cars go through are also a bonus for the dealer. its win/win, for them.
This system works a little different. Typically the fuel consumed during start is the highest, but with the start stop system, the cylinders are charged with air/fuel and the piston is at the compression stage, so, essentially the engine is primed to start, missing just the ignition spark.
The cold start perhaps.
This is starting a cold engine due to lack of lubrication.
A warm engine does not have this issue, it just uses the starter more often.
Poll needs a new option: "OP has no idea what he's talking about."
That's why I'm asking… no too proud son
If you don't like it, you can normally disable it, or ask your garage to do it in the car's firmware.
Yeah it's an automatic shut-off.
The car turns off while on the compression stroke, and resparks to get the engine going again. No strain on the starter motor either.
So couldn't cars be designed to always turn off on the compression stroke to put no strain on the starter motor? Or will the cylinder/s slowly lose compression after a few hours?
Also engine temperature. Motors are a lot harder to start when theyre cold compared to when theyre still hot and fresh
you sure it doesn't damage the starter motor ? Or at least on every car that this exists on ? My brother disabled it on his Polo GTI after reading on a massive community forum that this has been killing starter motors. It'd be nice to link him something to say otherwise.
That was the first thing on my mind when i first seen it im sure that it wouldnt be a cheap replacment when it goes
Cars with start-stop systems have larger starter motors than cars without them, by design.
I think first gen start stop systems had issues from what i read, supposedly better designed starter motors now..
Or in the cases of some manufacturers (I knoe Mazda is one of them) they dont use the starter motor at all to restart, so 0 extra wear on itIf he has an automatic then he has bigger things to worry about with his Polo GTI (my boss went through 2 transmissions before the warranty ran out)
Compression is lost quickly.
Fuel hangs around in there longer and makes it too rich to ignite.A modern direct injection actually is able to start with a lean injection into an unpresurized cylinder, if the computer gets it right and everything is in perfect shape. Too much chance of a failure though so starter motors are still required and simpler to ensure reliable operation.
In a typical 4 cylinder motor, only one cylinder will be on the compression stroke at a given time.
I'd guess the stored pressure is what assists with the engine restart, which while at the lights for a <2min stop the valves can contain the pressure, but after leaving the car for use the next day i would say the pressure would leak out.
Which raises another question, I'm pretty sure the sequence is run sequentially through the pistons, or do all hit each of the 4 stages in unison?
Sounds like a load of rubbish. How does an engine stop on "compression stroke"? And I can tell you, even well engineered engines would have enough cylinder leak down after sitting for a few mins. If this was how it worked, cars would not have starter motors. Chances are on a compression cycle is that the piston is moving upwards. So, igniting the mix would send the piston back down, thus turning the engine backwards (this isn't easy to explain why without a massive post with videos, just google how a crank and pistons work). The piston would have to stop at TDC or just after.
The only company I know of that toyed with this way of doing it is Mazda. It wasn't very successful and was later reworked to incorporate the starter motor. It was just the engine keeping a track of what cylinder was almost ready to fire and after the starter turned the engine over and this "almost ready" cylinder got to TDC, it would fire to "assist" in starting… almost every other vehicle I have worked on just use the starter motor to turn the engine and very heavy duty batteries or capacitors to start the car.
You are correct in that you cannot simply stop on a compression stroke. All cylinders will be in different parts of the 4 stroke cycle, it's impossible to stop all cylinders on a compression stroke.
@BensonP - It does put more stress on starter motors. Mazda have upgraded their starter motor of recently, but it will still kill it. Effects on battery lifespan are variable, but it can kill your battery faster since its draining more and charging more and using up more of its limited recharges.
In the mazda 3, it only triggers on three conditions - engine is at the right temperature, air conditioner is off and battery has enough charge. Air con can still run if it's in Eco mode and you have enough charge on your battery, but as soon as your battery depletes too much, it will restart your engine.
It will only trigger if you depress the brake pedal to a certain point. Since it does burn a little more fuel to restart the engine, manufacturers leave it up to the driver on when to trigger it. I usually only trigger it on intersections where I know the lights are slow. It also won't trigger again immediately if you restart the engine to creep forward in traffic.
Is it possible to make the delay longer? I've heard these cars turn off almost within seconds when pulling up at the lights. I always wondered why they don't make the delay like 10 - 15 seconds while stopped. I also agree with @pegaxs explanation.
@sv123: yes you can. As mentioned, it only triggers when you depress the brake pedal to a certain point. Usually you have to press the pedal about 1cm below the pressure required to stop the vehicle to trigger the engine stop. All you have to do is avoid pressing the pedal to that point.
That also brings me to another point. Long term, it can imprint your brake rotors if you are triggering the stop start when the brakes are hot since you have to apply a fair bit of braking pressure.
All cylinders will be in different parts of the 4 stroke cycle, it's impossible to stop all cylinders on a compression stroke.
Umm actually:
https://en.wikipedia.org/wiki/Big-bang_firing_order
Also, if one cylinder could produce enough power to complete the compression stroke of the next cylinder, that would be enough to start it.
Unfortunately a lot of cars enable it each time you start the car, so you have to disable it every time.
My mate was doing this in his GTI, but eventually gave up as it gets tedious.
As people have mentioned above it does depend on how hard you press the brakes, so you can learn to adapt to it.
@Scrooge McDuck: whilst your point has been taken, the topic on hand relates to stop start functions in cars, most of which would have conventional internal combustion engines where each cylinder is operating on a different part of the cycle at different times (yet to see a rotary engine with stop start). The crankshafts in 4 cylinder engines have mounting points for the conrods that are horizontally opposed and they are all usually in different parts of the cycle in order to maintain engine smoothness. Once you start working with with boxer engines and v8 engines and larger it is possible to stop two or more cylinders on a compression stroke depending on the setup, but you cannot stop all cylinders on a compression stroke at the same time as they are all doing different parts of a cycle to maintain smoothness.
From that article, big bang engines are used in motorcycles. From the design aspect they would not be used in cars as they are not smooth running, they would be lumpy and would require a high idle to avoid stalling.
@sv123:
I just got a new car with this feature. There is a delay, but it doesn't seem to be constant, I suspect there's a computer algorithm involved. I'm still getting used to the brake pressure sensitivity that Danger Noodle mentions.Most of the time it's not annoying. If I'm at a red light behind another car then I can lift my foot off the brake and the motor starts before the car in front of me gets going. The cutout doesn't happen when the motor is still cold.
In my first tank of fuel (approx 50l), I drove 583km, a mixture of city and freeway driving. The counter said the motor had spent 1 hour 5 minutes stopped at the lights, estimating about a litre of fuel saved. So far there's only been a couple of occasions when it's been annoying to me so I'm keeping an open mind.
I am surprised at the lack of understanding of modern engine technologies here, so will educate.
You only need one cylinder beyond top dead centre on the start of a compression stroke. In fact the engine will stop at a neutral point of least resistance, not necessarily at the exact compression cycle point for any one cylinder. Accordingly, the engine will not be stopped by any mechanism at the exact ideal point in the 4 stroke cycle as one poster implies.
The electronic injection system knows from the crankshaft position sensor which cylinder is best to inject first for a re-start. It doesn't have to be compressed, it could be just over Top Dead Centre and into the power part of the 4 stroke cycle. This is also why it doesn't start in reverse as another poster says. Keep in mind all injected engines start when cold in the right direction without any compression needed.
The engine must be warm for this task to work so there is much less turnover resistance. Even the Aircon may be disengaged for the restart.
If any cylinder compression leaks during the wait time, you have enormously bigger problems as your engine or a cylinder is worn out or scored. Ever done cylinder compression testing? But as above, this compression is not a critical need. Your engine starts from cold without compression.
When the engine shuts down there will be no fuel in the cylinders. The electronic injection ceases feeding fuel to get the engine to stop. Pretty basic stuff. So no flooding is possible as another poster suggest.
Yes, a more robust starter motor is needed. Some manufacturers did not get this right.
Pressing down on your brake pedal harder while at a stop does not warp brake discs. Repetitive hard and fast stops is the only way to create the necessary heat for warping to occur. Thermodynamics 101.
PS: Am an engineer whose has worked on all sorts of heavy machinery and car engines, compressors and now designs automated factories.
@Musing Outloud: if you reread my post, I wasn't referring to warping discs through depressing the brake pedals harder. Brake discs are made out of thick solid steel, warping discs requires temperatures well beyond what the brake pads can handle, even racing pads. Usually the shudder is a result of disc thickness variation, as brake pads do not apply pressure to the whole disc at once, they only apply pressure to one part of the rotor. As a result, there is uneven wear of the rotors.
I was referring to hot brake pads imprinting onto the disc.
@trongy: it depends on the car. The car I drive is a Mazda 3 sp25, and it's in this car that I have acquired a feel for brake pedal level at the feathering point, full stop point and start stop point.
@DangerNoodle:
I agree that I will depend on the car. I have a Subaru Impreza 2017 and I'm still acquiring the feel for the brake system.While driving yesterday after reading your comments I did pay close attention to the brake pressure required to stop the motor. It's actually less than I expected and I now have no concern of brake pad imprinting on my model unless the driver is heavy footed. When learning to drive, I was trained to ease off the brake pedal pressure just before coming to a complete stop and that's the way I've been driving for a couple of decades.
@trongy: Mmm, that's the way I've been trained to drive as well to smooth out the weight shifting. You'd only really imprint if you were driving very spiritedly and pressed sufficiently to trigger the stop start. In the mazda you do have to press fairly hard to trigger the stop start though.
@Musing Outloud: What about the impact on battery life? I've read in a few Ford forums that batteries don't last as long as a result of the constant start-stop.
On another unrelated note…I hate how disabling the feature has to be done each time you start the car and doesn't remember your preference. surely the control system could have a latched on bit (flag) to make this work.
I disable it straight away every time (no way to turn it off entirely without hacking the car).
The biggest problem I find is that it's not intelligent enough - it just knows you're stopping, not why. So you get situations where you stop to turn right across a road (not at lights) and the engine will shut down. Then you get a gap in the traffic, put your foot down to turn.. and then you get this 1-2 second delay that completely throws off the timing, which, if the gap wasn't huge to start with, makes it unexpectedly dangerous by reducing the time you had to cross the road.
Also, it has a habit of shutting off juust as you're coming to a stop, which disables the power steering while you're still moving. Annoying.
@hcca: Wow, I cant believe that this is allowed. Sounds like it introduces a whole bunch of dangers to everyday driving.
Mazda doesn't use the starter motor to restart the engine. It still needs a starter motor to start from cold.
Wrong! But thanks for playing…
Mazda tried that, and it was a dismal failure. I-stop uses the alternator to try and stop the pistons in the right place. When a restart is required, the starter motor turns over, a blast of fuel is sent to a particular cylinder and it ignited to assist in restarting. Basically because Mazda didn't want to put bigger starter motors in.
And here are some links to Mazda websites explaining this. Even has pictures for you to see how it works.
Hahaha they have very craftily worded it in that case. I actually read the first link… it's only the second link that has their diagram and mentions it with 1 word i could find out of the whole article?
I couldnt ever feel/hear starter motor and it was so fast which was what convinced me. When i drive the vw's its heaps more of a normal start
edit
Seems more obvious here
http://www2.mazda.com/en/csr/environment/special_features/20…
If you ever listen to these cars restart, you will always hear the starter motor turn the engine over
More and more new cars has this new function and that's why you noticed it more recently.
it's not a driver turn it on and off. It's automatic function that comes with a lot of car these days.
P!ease add to the poll: "I've noticed cars that come with a start-stop system"
Bikies as well.
As bongom said it's start-stop technology which is built into more modern cars to save fuel, these cars are built with more robust parts to deal with the constant on-off.
Note I once had an accident in a older car without stop-start and damaged my radiator that caused overheating whenever I was idling, so I started to turn the engine off every time I would be idling for a while and surprisingly I saved like 10-15% fuel!
Sounds like you may have had another problem with the car. It shouldn't be using 10-15% more fuel for the few seconds that its stopped at the lights.
The future is now!
P!ease add to the poll: "I disable it, when I need to drag someone at the lights;)"
I disable it everytime I start my car up for this reason. I wish there was a permanent off.
just leave it 'echo' disable? is yours reset each time it start or something?
Auto off is on automatically each time the car is started.
What type of car do you have? Next time you take it in for a service, ask if it can be disabled by default. Some cars can be reprogrammed. :)
In the mazda 3 I've figured out how far I can press the brake pedal without triggering the start stop.
You're going to get clutch failure extremely early. What you're doing is feathering the brake so your car doesn't register a stop. If it doesn't register a stop, it won't take it off gear either.
Very bad compromise
@tshow: it registers a stop. To trigger the engine stop you need to depress the pedal about 1cm below the amount of pressure required to stop the vehicle completely. It's excessive pressure compared to what you'd need. The feather point/engaging point is about 1cm above this point. If you test drive a Mazda 3, you'll get what I mean, there's a fair bit of range in the pedal.
Good to know it is different on a Mazda.
I code my auto start stop out completely to avoid this issue but I am fortunate to have access to the hardware required.
@tshow: Unless you are using torque converter which doesn't use clutch. Even with dual clutch, your clutch won't fail "extremely" early. When you slowly crawl on heavy traffic, that's what will wear down the clutch really fast.
@rave75:
Not on a torque converter.I have smelt the burning clutch in an Audi A3 S-Line where a mate was bypassing the auto start stop by feather footing the brake. The TPU will apply the clutch in such situations. It was a recurrent problem that the driver felt wasn't alarming but since getting him to stop tricking the auto start stop, the smell is gone. We have since disabled the start stop.
It seems different companies have a different implementation of the start stop. It's just easier to disable start stop via VAGCOM or similar.
@tshow: Yeah feather footing the brake will prematurely wear the clutch, same with playing with the brake to go forward in heavy traffic. A friend of mine had to replace the clutch on 30k km
What car is it. Most start stops can be disabled through the onboard CPU.
mine can be turned off from the system menu / driving mode (i have a custom one for me that keeps all the setttings i want) also got a great big button on center console that turns it off.
For some stupid reason my wife like to turn it on when she drives it, the only way to permanently disable it would be banning her from driving it
if i do that i'll end up with some more annoying feature to deal with that isn't related to the start stop
Boomramanda got a fix for that too i have a button that isn't part of Launch control bit more subtle brake and click a hold used for for hill starts won't let the car roll or turn engine off all you got to do is wait for the green and trample
https://www.mbloveland.com/blogs/747/how-does-it-work/merced…
Its only work, when you turn it on, so its remember which mode you set before you turn off the engine/car.
and it does save fuel, I have driven one week turn on and one week turn off, you can see the difference.
So when you feeling excited or grumpy, turn it off ;)@boomramada: hill start mode works constantly nothing to do with cut out but if something is there for fun i just tap engine mode before engaging the halt
not as demanding on the car as the full launch and normally more than enough to slaughter the toy next to me
full launch was fun but disappointing the Porsche GT3 i was challenged by let me down he didn't know how to drive shifting at the wrong time ended up no contest
What car do you have? So weird that there's no permanent off setting. I've got a physical switch for it on my Alfa and it remembers how I've set it. I've had it disabled for a couple of years and now it doesn't work any more. I asked about it when I was getting the car serviced and the guy said the battery was drained so I guess an option would be to just keep at it and hope it dies one day lol
There is but when my wife changes the driving mode it turns back on there is a menu item on car settings i can turn it off from, or the electronic switch below nav screen, it's cool i can understand why.
Thats why i have my own preset built in to the menu for my fun time so i can click straight back into it where i have it set off.
I have my suspension settings, engine mapping and allow it to turn off non critical systems like A/C, stability and traction control if i want and need full power from the engine, they turn back on as soon as i'm not demanding 100 % from the car.
she prefers the more comfortable smooth and quiet version to be honest somedays i,m quite happy leaving it there.
Soon enough will be the post: I've recently noticed more and more drivers not touching their steering or pedals while driving, are they kamikaze?
I saw someone park a car without touching the wheel, are they using their knees?
i freak people out with this quite often, as long as it can pick up the lane markers it will keep it centred, especially effective when your pretending to look at something else while going around bends in a road
great feature but like everything you can't be over reliant on these things. mine gets angry if it thinks i'm not driving.
I sometimes turn off my engine when stuck behind rail way crossings. Sometimes you can wait a good 5 minutes.
Thank god they are getting rid of railway crossings in Melbourne.
Let me tell you…Toorak Rd, I think the longest I've been behind a crossing is 23 minutes.
lol..
I was referring to Toorak Road. I can't say I've been stuck for anywhere near 23 mins but it god damn feels like it.
I turn my engine off to save a tiny bit of petrol and to save the environment.
next, please get rid of pedestrian crossing.
Zebra crossings are the way forward. Not the traffic light types that stay on red 3 times longer than they need to.
Haven't you heard of stop start systems ?
They've been around for over 5 years
Nope, I drive an old car…
Driving an old car doesn't mean you still live in the old world…
I think he does, as this question could have been answered with a vague google search, but now we have this thread.
I remember there was a myth going on early days, its not good to stop start all the time, it could destroy your starter motor and its sux to be a pizza deliver, since they need to stop and start regularly.
Modern cars sometimes have an auto stop/start feature. On Volkswagen its called Blumotion.
Whether it helps or hurts depends on the type of car, the engine temperature, etc.
I thought it was called DSG on a VW.
DSG is the transmission (direct shift gearbox) and unrelated to Blumotion
I have a car with DSG but not Blumotion.
https://en.wikipedia.org/wiki/Start-stop_system