Or is it a gimmick?
Starting a car takes a fair bit of juice out the battery that is then recharged thus needing more fuel.
idling uses fuel as does having to charge the battery, for how long does a car need to be stationary with engine off before savings are made?
[Edited on 24/9/14 by 02GF74]
A warm engine will restart very easily. In traffic I imagine the saving adds up nicely. It also helps keep your emissions down when assessing your road tax.
I'm not convinced - my Yaris has this and, apart from being an annoying 'feature', the car has an enormous battery that's about
twice the size of the one fitted to my old Yaris that didn't have this functionality. Think of the difference in battery size between petrol and
diesel cars and you'll understand just how big this battery is.
tl/dr: It may save fuel while sitting in traffic, but I have the extra weight of a huge battery to lug about.
Forgot to mention - if I've got the air conditioning on the engine only stays stopped for 30 seconds or so... so fairly pointless, really.
[Edited on 23/9/14 by David Jenkins]
I believe it's more about emmisions targets being met when being averaged out so better economy is a bonus.
The problems will come when these vehicles reach high mileages.
Are these stop-starts using "normal" starters?
I saw a design some years ago that used a toothed ring inside the bellhousing and teeth on the flywheel to act as an alternator when running and as a
variable reluctance motor when starting, thus having no meshing teeth and no wear to the starter mechanism. I would have thought standard style
starters and ring-gears would be prone to early failure with stop-start.
But when your starter and/or alternator fails early due to excessive use, there's a big chunk of
your savings down the Swanee.
quote:
Originally posted by NigeEss
But when your starter and/or alternator fails early due to excessive use, there's a big chunk of
your savings down the Swanee.
As others have suggested, an 'energy saving' target is different to an emissions target. Modern generation diesels are a good example of
this, where total MPG has been sacrificed to drive EGR and DPF systems. I suppose it's especially relevant in town centres.
Up until now the individual motorist used to reap the rewards of energy saving... but you've got to tread carefully now.
[Edited on 24/9/14 by garyo]
Remember these eco systems are aimed at ticking boxes, to save on road tax and company car tax and mpg figures. The wear on any components wont worry initial owners as they have warranties and by the time they filter down the super used market the manufacturer can wash their hands of them. (or rub them together with the added work the repairs will generate).
Nothing new. In 1975 I had a mk1 Cortina that used to stop every time I pulled up
Every time I hear one of these car start up, I can't help thinking how much wear that's adding to the starter motor and the flywheel teeth,
plus the oil pressure has to build up all over again each time. Surely about the worst thing you could do to an engine’s life span.
As above, have you seen the size the start stop batteries? There massive things and there twice the price too.
Ok if you’re sat in a huge tail back switch off the engine but for a 3 minute traffic light cycle get real, it must save a few mil of petrol. Everyone
I know who has it on their cars can’t stand the feature and turn it off. I’m so glad my car is too old to have any emission garbage on it and I still
get 45mpg 
My belief is that it is mainly useful on the 'test cycle' that determines your cars CO2 rating.
This gives some savings in road tax, but by far the most important is the saving in company car tax.
The last 3 BMWs my missus has had as company cars all have the feature, and we have tried switching it off, with no discernable difference in mpg (her
car does 800+ miles a weeks so you would spot it if it were more than 0.2mpg).
I don't believe most engines are tuned well enough to notice that the alternator is charging the battery, compared to not charging it - you
don't see big mpg differences running with your lights on all winter(say 200W continuous for front/rear/side lights), compared to summer running.
The alternator is regulated to something like 50-70A, which is only 800 odd watts at 14V. Don't forget that the start current for an engine is
much less once it has warmed up, and fuel injection only gives the fuel required for the current engine temperature.
On another point, I had a honda civic which I converted to LPG and ran for 207K, during which time it stopped every time I forgot to blip the throttle
as I reached a junction or roundabout, so it probably had at least 100K starts from a normal starter without failing (or needing a special battery or
alternator replacement).
Regards
Hugh
quote:
Originally posted by SCAR
Nothing new. In 1975 I had a mk1 Cortina that used to stop every time I pulled up
quote:
Originally posted by hughpinder
My belief is that it is mainly useful on the 'test cycle' that determines your cars CO2 rating.
This gives some savings in road tax, but by far the most important is the saving in company car tax.
The last 3 BMWs my missus has had as company cars all have the feature, and we have tried switching it off, with no discernable difference in mpg (her car does 800+ miles a weeks so you would spot it if it were more than 0.2mpg).
I don't believe most engines are tuned well enough to notice that the alternator is charging the battery, compared to not charging it - you don't see big mpg differences running with your lights on all winter(say 200W continuous for front/rear/side lights), compared to summer running. The alternator is regulated to something like 50-70A, which is only 800 odd watts at 14V. Don't forget that the start current for an engine is much less once it has warmed up, and fuel injection only gives the fuel required for the current engine temperature.
On another point, I had a honda civic which I converted to LPG and ran for 207K, during which time it stopped every time I forgot to blip the throttle as I reached a junction or roundabout, so it probably had at least 100K starts from a normal starter without failing (or needing a special battery or alternator replacement).
Regards
Hugh
the few hire cars I've driven recently all had it, I just found it irritating
I found that half the time it stops the engine just as your ready to go again, especially driving in a busy town - in which case it probably cost more
fuel that it saved 
my rather thirsty tin-top claims to use between 0.2 and 0.3 gallons and hour when idling (which my maths says is 15 to 23ml/min) so if that even half
true you'd hardly save much with a start-stop
quote:
Originally posted by Mr Whippy
I’m so glad my car is too old to have any emission garbage on it and I still get 45mpg
Originally posted by britishtrident
Quote:
"Older Hondas were designed not to fail until they reach at least their 12th birthday, then one part will fail and within a week at least 4
unrelated items will break/burn-out/fall off or just crumble into dust."
Made me laugh because thats pretty much exactly what happened - about 10 (expensive) things failed when it was 12 years old - luckily all within about
2 weeks so I hadn't got round to buying any bits/arranging for it to be fixed before I decided to scrap it.
Although I believe you when you that the idle valve opens slightly when the lights are on etc, I haven't seen that produce a noticible effect on
the final fuel consumption, dispite the fact that in the winter I probably have all the lights on, rear screen heater on, blower to the screen, wipers
on and probably aircon while the screen clears. I thinks it may affect very tightly set up eco cars, but I haven't really seen a difference in
'normal' cars. Is this similar to the original question - you can see somethings happened that should increase or decrease fuel use, but
practically there is no significant change? Most of my driving is down back lanes where you are accelerating or braking almost all of the time, rather
than running at a fixed speed where you may get to back off to minimum throttle so I guess that affects my viewpoint.
Regards
Hugh
It's a shame that increase idle feature didn't come in earlier. My old 1.2 Nova would stall if you had the lights and the rear heater on, I
had to pull the choke out a little to keep it running.
Although on that subject, only one of my current circle of friends knows what a choke is/was... I'm assuming it's a much higher ratio of
knowledgeable people on here!
quote:
Originally posted by Slimy38
Although on that subject, only one of my current circle of friends knows what a choke is/was... I'm assuming it's a much higher ratio of knowledgeable people on here!
stop start cars use different starter motors that are up to the job, i dont think they are any less reliable than normal units
for a focus from 2011 onwards the whole north of England from Birmingham north to Scotland used 9 starter motors last year and 20 this year.
the standard non stop start unit has used 14 so far this year.
what is worrying is that after a while stood still the car restarts on its own and catches you off guard, i thought the car was going to set off on
its own!
Hmmmm general consensus seems there is negligible fuel saving.
It has been said that a warm enginr is easier to start than s cold one but i would imagine most peoples commutes are like mine, first .5 mile is 20
mph, the next mile is stop start, mostly stop the remaining 2 milrs at 30 mph.
So in winter, the engine will not have time to warm up anf being stationary with it off aint gonna warm it up.
One would think a spinning fly wheel instead of electric starter could be used.
quote:
Originally posted by 02GF74
Hmmmm general consensus seems there is negligible fuel saving.
It has been said that a warm enginr is easier to start than s cold one but i would imagine most peoples commutes are like mine, first .5 mile is 20 mph, the next mile is stop start, mostly stop the remaining 2 milrs at 30 mph.
So in winter, the engine will not have time to warm up anf being stationary with it off aint gonna warm it up.
One would think a spinning fly wheel instead of electric starter could be used.
I've got a mate who reckons he gets more MPG from his Astra with stop start, also I was under the impression a lot of the systems did use some
sort of flywheel method rather than a starter motor. I've never driven a car with it but it might have helped on the journey I had on Saturday
when it took more than an hour to drive 2 miles to Tesco.
My first car had an automated choke that was supposedly operated by flooring the accelerator, it usually didn't work and I'd have to flood
the carb to get it going.
Just ran the numbers but phone lost the whole lot. Yes it's worth it by miles both in fuel terms and even if you have to replace a starter and batt every 5 years.
The only experience I have of them is on a Prius which is a bit different. That worked really well and it was actually quite difficult to tell whether
the engine was running or not if you had the radio on.
The engine seemed to start instantly when the throttle was pressed. It maked a big difference to MPG compared to the Passat tdi I had previously. Both
would do the bets part of 50 mpg on the motorway but the Passat would drop to as little as 25 in central London whereas the Prius still did around 50.
quote:
Originally posted by David Jenkins
I'm not convinced - my Yaris has this and, apart from being an annoying 'feature', the car has an enormous battery that's about twice the size of the one fitted to my old Yaris that didn't have this functionality. Think of the difference in battery size between petrol and diesel cars and you'll understand just how big this battery is.
tl/dr: It may save fuel while sitting in traffic, but I have the extra weight of a huge battery to lug about.
Forgot to mention - if I've got the air conditioning on the engine only stays stopped for 30 seconds or so... so fairly pointless, really.
[Edited on 23/9/14 by David Jenkins]
I have had it in my company mondeo (manual gearbox) for 3 years now and I get confused when I drive my Quantum now and it doesn't stop in
traffic.
My only observation is:
-On a manual it only stops when you knock it in to neutral and release the clutch, unlike an automatic you get the the decision on when to stop the
engine. If you are in stop start traffic and sitting in first gear then it wont stop.
-Doesn't stop on cold mornings until the engine is hot.
-Doesn't stop on hot days if AC is running
-Doesn't stop if battery is low
-Sitting in stationary traffic / at a level crossing most people wouldn't switch off normally but after 10 mins of sit idle there must be a bit
of fuel being saved.
-Company car tax bill is definitely lower for it.
-My main concern about longevity is not the beefed up starter etc it is the fact that there is no turbo run-down. If you come tanking down a motorway
and into the services it will still just stop. The little 1600 diesel in mine is a PSA engine that is famous for destroying oil and then, ultimately,
turbos and this can't be healthy. The turbo will still either be spinning or crazy hot at least. Not aware that it has any kind of accusump
system.
Turbos spin down in seconds and generally there's plenty of oil left in the journals to cope, it's coking on the shaft bearings that that
will cause you a problem with that sort of operation - I'd have hoped they'd have a built in turbo-timer type function where if you've
been at high load it would integrate your boost time to give a delay. Obviously that's not been implemented!
As for the cost - just look at your idle fuel use using an OBDII scanner and you'll see just how much of your fuel goes down the drain sat at
traffic lights.
[Edited on 3/10/14 by coyoteboy]
One reason they're pushing stop-start is to reduce pollution in the areas near to traffic jams, lights, etc. In some European countries you can be fined if you keep your engine running while stopped in a traffic jam. Don't know how effective this technology is at dealing with that, especially as mine turns back on after just 30 seconds.
http://www.scotland.gov.uk/Publications/2003/04/16936/21249
seems to work well on my bmw. its a pain when your crawling in motorway traffic with the odd stop but there is a button to disable it.
round town its fine with traffic lights. you pull up its stops. you put the clutch down and its started again before the clutch pedal even gets half
way to the floor to put it in gear. the good thing about it is that if every car has it it will cut down fumes and noise pollution in towns when the
traffic is heavy. yeah it wont be a lot but its something.
as for it wearing out the starter. well bmw put it right on the bottom of the bell housing so its a doodle to swap. 20mins on the ramp max.
as for oil pressure, well on a tight engine the oil pressure takes a few seconds to drop anyway, the system is primed as the car has been running so
i would guess the wear will be marginal. I'm sure manufacturers did plenty of life testing.