Does stop start really help MPG ?

[sparckzero]

35 minutes ago, KenONeill said:

What actually is the fuel consumption of a modern 4 cylinder engine when idling? I'm expecting any sensible answer to be in volume per unit time.

 

My 2015 1.5 TDCi Focus quotes between 0.1-0.2 gal/h (0.5-0.9l/h) when idling with climate control running. The trip computer seems to be fairly accurate with general MPG figures, so I have no reason to doubt it.

[GeneralPurpose]

On 19/07/2017 at 15:00, mrgf said:

As with all things, there is going to be a plus and a minus... Plus, (Debatable) Amount of fuel saving, less pollution if stopped for longer periods/in tunnels etc. Minus, Battery fatigue will be considerable as starting the car is the single biggest drain on the battery... All other drains come with a running engine! Also, wear to starter motor will be a contributing factor, long term but this will most likely be ten years down the line! Simply turning off on longer stops but keeping the engine running for very small stops/short stages of movement will be better overall. Oh, Fuel consumption will increase on starting as most vehicles will use more, just to START the car again and will also cause MORE fumes to be pumped out so any gains made will be slimmer then anticipated. It is also well known that driving at slower speeds uses MORE fuel and causes MORE pollution so the so-called safer 20MPH zones are not really safer at all. More fumes at pedestrian level aside, pedestrians and indeed, other (Not me, Guv).Motorists, KNOW you can stop easier, so deliberately pull out in front or cross at inopportune intervals, safe in the knowledge you won't hit them!

Gone a little off topic there but bares a relevance too. If the car is in stop mode and someone starts to cross, technically, you are "Parked" So the pedestrian or other driver will have priority over you. You might want to debate this but a vehicle with its engine off, is NOT driving, it is stopped.

I know someone will say "Not true as I got fined when stopped, for using my phone"! To that I say, serves you right you stupid twonk!

 

On today's modern fuel injected engines, extra fuel use during the restart doesn't happen in anyway that causes a measurable extra use of fuel. There is no carb accelerator pump being activated during the restart. Eu rules don't allow it on a hot engine. And it isn't necessary either. Instead the engine stops itself in an easy to restart configuration requiring no more than the slightest turn of the engine to get things going again. Starter motors are suitably beefed up as is the alternator. Technically, you are not parked when in traffic with the engine stopped and hand brake on. You are stopped! Parking is clearly defined by the UK highway code and is only allowed at the roadside or in suitable legal parking bays or some other areas. Pedestrians actually have the priority at ALL times! What you going to do, run someone over if you see them in the middle of the road? Or try to miss/give way to them? Yes, I know peds have specific areas of defined rights of way ie: pedestrian crossing etc but you are not allowed to run em over if you can help it when you come across them in other road areas.

Edited 21 July, 2017 by Estate Man

[GeneralPurpose]

On 19/06/2017 at 14:02, sparckzero said:

 

I'm with you there. In ~12 years of motoring, I've had one starter motor go bang on me, and that was in a car without stop-start.

 

 

...is this a big issue on the MK3 Fabia? How does it manifest itself?

 

It is mostly something affecting short journey, low mileage drivers where the battery doesn't get a good charge. The stop/start with draws it's services to make sure you have plenty of battery power.

[vc-10]

Nice to see some logic here @Estate Man

 

I've only had to change 1 starter motor too, in my old 2002 Polo. It still started the car, it just made an awful noise doing so!

 

When the battery charge is too low, start/stop is disabled. Same if the power draw on the engine is too high- for example, when the A/C is on high in order to cool down a hot car. There are other conditions too, such as the angle at which the car is stopped.

 

The manufacturers don't want the starter motor to die on a regular car just as much as a stop/start car. As such, the starter motors are beefed up accordingly. A warm engine is easier to start anyway, especially a modern fuel injected engine. 

 

Nobody complains about stop/start in hybrids- why in other cars? What these cars are is basically a 'micro hybrid'. The hybrid assist isn't to spin the wheels, but to reduce the electrical drag on the system by charging when braking, and to turn off the engine when it's not needed. 

 

I'm all for stop/start. It saves me money- when it's behaving, my mpg is noticeably better and that means less money spent at the pump. Unlike in an old carbed car, there's no issue with emissions when restarting the car when it's warm- the starter motor spins it up to idle RPM, and it starts fuelling/sparking. Simples.

[GeneralPurpose]

vc-10, yeah I too find stop/start saves money. It varies according to the type of journey and the traffic conditions as to how much, but my experimentation has certainly proved beyond any doubt it's worth leaving it switched on. I must confess I was a stop/start hater when I first got this feature on a car, but I decided to leave it switched on to see what would happen and very quickly found it works great! I rarely turn it off now.

[mrgf]

Yeah, you're right when you say you are stopped but still, you are stopped with a non-running engine, hence, the point remains. Peds Do have priority so again, true but you can't use that as an excuse to jump out in front of a vehicle when its travelling at speed. The idea is that a pedestrian already IN the road, has priority not a pedestrian who just happens to want to walk in front of moving traffic, applying stupid logic! I did say, if you read the whole post, you might want to argue that you are not parked, you are stopped but this is still a vehicle which needs to re-start to continue its journey, so any other vehicle on the road MAY legally take precedence over it. You are actually arguing MY point, not adding a new one. As for the Beefing up of the starter and alternator, it could be argued that this beefing up will make them more durable but to what cost? Most likely a larger fuel usage. Again, debatable as they will have better design so parrallels become unquantifiable... You argue about less fuel usage on startup, comparing it to carbed engines but they are obsolete in modern vehicles now so its old technology... Like comparing a modern tennis pro to one 50 years ago... The game has moved on and even a fairly average player would be classed as top notch by 60's standards.

Stop start technology of today will be considered rubbish in another 20 years. Hybrids, petrol engines, all a thing of the past! Electric will be being usurped in that time or perhaps an additional 20 years. 

[Rooted]

Works great though and i have done 78 miiles of Edinburgh stop start held up in flooded roads and torrential rain in the past 12 hours.

What people consider about Euro 6 vehicles with Stop / Start has no real importance if you like what you get now.

If you do not like it just do not buy into it or do not use it.

Many do not buy into it anyway they just lease and hand back so what they are like in 3 or 4 years is neither here nor there to them.

[JCP]

My 1.2 dsg is my first stop start car-I have driven others like a Fiat Punto hire car which I could not get on with. In contrast the Yeti is very intuitive and useful, it only kicks in when the brake is  firmly applied- a momentary stop with gentle pedal pressure does not trigger it. The hill hold and dsg interface is flawless and all in all I cannot see a downside to it. 

It is a natural and useful thing I will never find out what it might save in fuel because I cannot see the point i  turning it off.

[mrgf]

Re-reading the thread about parked, the definition is not really cut and dried. It could be argued one way OR the other with neither being right or wrong... Its semantics. If you had the engine off, another car pulled out just as you started again, and you hit them, (Unlikely but possible) Their lawyer will argue YOU were parked so their client had priority as they were driving/moving traffic. Your lawyer will argue you were merely stopped in traffic and started to proceed when the other car pulled out, whilst you RETAINED priority. Either way, lawyers make money, insurers lose and so do the clients. Stopped... Do an emergency stop and someone hits you from behind... Their fault! Drive off again without doing the blind spot checks, then get hit, your fault as you were parked! That was without the engine being turned off! After stopping, you "Gave up" Priority. 

 

Stop-start will not negate any legal issues. You can't say someone else was to blame if you stop and have the engine off, then start off again without safety checks. That said, even in a running car, stop then move off and hit something, its gonna be your fault! Heating/cooling is gonna be compromised a little too... Hot or cold conditions will make you want to keep the engine running unless the stop-start technology counteracts this. I assume high end vehicles already do but this again, will give batteries a harder life. I remember years ago, a concept SAAB that had a glass roof. The roof incorporated a solar panel that ran the air-con, that was needed due to the build up in heat, created by having a glass roof! Things will change... Cars sill have stop start more and more and it will become unreliable as they get older. One guy said he never had a starter motor fault on a stop start car and only one on a non stop start in 12 years of motoring... Thats a daft remark as firstly, 12 years is no time How many people have a starter motor fault in that time though? They are common enough to be stocked as spare by euro, etc. Also, stop-start... How long has he driven one? My guess is a few years at the most. Let the cars on the road now get to 15 years old, then see if they are  reliable. Some will, many won't. thats the nature of things. I have been driving for over 30 years and have only had one starter motor fault, on a car given to me as it was getting old and worn (Hillman Avenger). That said, I have had other faults, sometimes on a particular car, fault after fault. The more complexities a car has, the more likely, with age, it will become unreliable. The payoff is reliability from new and better "Toys" in it.  Hill hold technology is now allowed in the driving test, used to be banned but more vehicles fitted it so it became the norm. What will happen though, to driver who use it and it fails?  They will blame the technology, not their lack of skill in driving the car. Anyway, this is all going off topic and its meant to be discussing a certain point so i'll shut up!

[Rooted]

The engine not running is not the ignition off.

Have you actually driven modern cars with Stop / Start where there is no delay or hesitation because they do exist.

The car counteracts cold conditions and other conditions and Stop / Start is inhibited.

[jon15]

I keep my Start/Stop system on most of the times, except when I know that my car will be idling for less than 10 secs. (I read some research that idling for more than 10 secs uses more fuel & emits more CO2 than restarting the engine. Not sure how reliable it is, though.)

[GeneralPurpose]

On 22/07/2017 at 20:32, mrgf said:

Re-reading the thread about parked, the definition is not really cut and dried. It could be argued one way OR the other with neither being right or wrong... Its semantics. If you had the engine off, another car pulled out just as you started again, and you hit them, (Unlikely but possible) Their lawyer will argue YOU were parked so their client had priority as they were driving/moving traffic. Your lawyer will argue you were merely stopped in traffic and started to proceed when the other car pulled out, whilst you RETAINED priority. Either way, lawyers make money, insurers lose and so do the clients. Stopped... Do an emergency stop and someone hits you from behind... Their fault! Drive off again without doing the blind spot checks, then get hit, your fault as you were parked! That was without the engine being turned off! After stopping, you "Gave up" Priority. 

 

Stop-start will not negate any legal issues. You can't say someone else was to blame if you stop and have the engine off, then start off again without safety checks. That said, even in a running car, stop then move off and hit something, its gonna be your fault! Heating/cooling is gonna be compromised a little too... Hot or cold conditions will make you want to keep the engine running unless the stop-start technology counteracts this. I assume high end vehicles already do but this again, will give batteries a harder life. I remember years ago, a concept SAAB that had a glass roof. The roof incorporated a solar panel that ran the air-con, that was needed due to the build up in heat, created by having a glass roof! Things will change... Cars sill have stop start more and more and it will become unreliable as they get older. One guy said he never had a starter motor fault on a stop start car and only one on a non stop start in 12 years of motoring... Thats a daft remark as firstly, 12 years is no time How many people have a starter motor fault in that time though? They are common enough to be stocked as spare by euro, etc. Also, stop-start... How long has he driven one? My guess is a few years at the most. Let the cars on the road now get to 15 years old, then see if they are  reliable. Some will, many won't. thats the nature of things. I have been driving for over 30 years and have only had one starter motor fault, on a car given to me as it was getting old and worn (Hillman Avenger). That said, I have had other faults, sometimes on a particular car, fault after fault. The more complexities a car has, the more likely, with age, it will become unreliable. The payoff is reliability from new and better "Toys" in it.  Hill hold technology is now allowed in the driving test, used to be banned but more vehicles fitted it so it became the norm. What will happen though, to driver who use it and it fails?  They will blame the technology, not their lack of skill in driving the car. Anyway, this is all going off topic and its meant to be discussing a certain point so i'll shut up!

 

Kind of wondering why you introduced 'parking' and now 'legal' issues into the thread. It is completely clear cut that you are not parked when at a junction or in traffic when stationary with stop/start engaged. Its exactly the same as if your engine is still running, except you are not wasting fuel and money. Remember, your ignition is still switched on, and the car is ready to go with you in control. Stop/start has no discernable delay when it restarts my engine. As I take my foot off the brake the engine is restarted and ready to go before I'm even back on the gas (mines a dsg). Stop/start doesn't have any effect whatsoever on your normal driving or moving off observation...why would it? Normal driving rules, funnily enough still apply! On the point you make about reliability, I'm a retired tech and engine design and development engineer. I have been driving for 47years. I have only ever suffered one starter motor failure in those 47 years which occurred on a Ford diesel. The first ones (cars) used a starter motor from their petrol engine cars and those failed early in just a couple of years. They were not beefed up to cope with diesel compressions. Ford fixed it quite smartly. Having assessed the new kit on these stop/start cars, and knowing that the starter doesn't have to work very hard to restart the motor anyway (listen to a stop/start hot engine restarting, it barely has to do a revolution of the crank) I have little doubt that the starters won't give any issues for years and years, just like non stop/start engines. And let's not forget that this tech is not entirely new. It's well tried and tested on many many high mileage cars in the VAG group stable and many other brands. You don't need to have worries about the system...just enjoy!

[stephen321]

Im just thinking with the stop start battery are very expensive.If i bought a normal battery at around £100 quid and turned the stop start facility of.would the battery be ok.

[AGFalco]

Stephen321,

 

No. Cars with stop start technology require the correct battery for the system to work.

A non stop start battery will not last long, about 6 months on one car I know of.

Also beware there are two types of stop start battery.

EFB enhanced flooded battery and AGM absorbent glass mat.

 

Thanks AG Falco

[threadbear]

On 20/07/2017 at 12:25, threadbear said:

I use stop start all the time. I am current getting well over 500 miles on a tank of diesel and my Octavia is the best car I have ever had. I now detest drivers who leave their vehicles running unnnecessarily. It is amazing how many taxis at work on the rank sit there pumping out fumes and throwing £££s away in wasted fuel and profit. 

 

Since this post I have noticed on the Skoda servicing website that there are now batteries specific for stop/start cars for sale so obviously a stronger battery? So I wonder if starter motors have been strengthened too? 

[rum4mo]

I can only think that the addition of "stop/start" specific batteries being mentioned on the Skoda servicing website is just an indicator that some of the early EFB batteries time is now up and they need replacing - more than VW Group suddenly beefing up batteries being supplied to replace original factory fit "stop/start" batteries.

 

Edit:- if Skoda etc did not make it clear about which type of battery to use on each type of car, some people, with an eye on their wallets would just go and buy the cheapest which by far would be a standard battery, and that would soon lead to some disappointment as if the stop/start did not age them quickly, the regenerative braking type of charging would probably!

Edited 26 August, 2017 by rum4mo

[GeneralPurpose]

10 hours ago, threadbear said:

 

Since this post I have noticed on the Skoda servicing website that there are now batteries specific for stop/start cars for sale so obviously a stronger battery? So I wonder if starter motors have been strengthened too? 

 

Yes, the starter motors are heavier duty units. Some cars don't even have starter motors, instead using the generator as a starter. This saves weight and is also very efficient.

[Warrior193]

And then, of course, there is the Mazda I-Start, where there is no starter motor (or starter-alternator) at all - the engine is started purely by injecting fuel into the best-placed cylinder and then ignited. It will be interesting to see if this (Mazda) technology catches on.

[Breezy_Pete]

Hehe, wish I'd thought of that.  If that works it's 'revolutionary'...