[Stifler]

Originally Posted by ezmaass

Call me a skeptic, but I'm not convinced the Auto Stop/Start feature is at all an economical function of the car. Does it really save any considerable amount of gas to warrant the strain it places on the motor and starter?

I have to believe that the cost of wear-and-tear is far greater than the amount of fuel saved. It reminds me of a study I saw many years ago that analyzed the cost of a kilowatt hour against that of the additional strain (and hence premature failure) on a lightbulb from flicking it on/off for a short period where you left the room. The result was a certain "threshold" of time where if under, it made sense to leave the bulb on, and if over made sense to shut it off. It makes me believe there must be a similar threshold in play here, too... but instead of a $0.60 lightbulb, we're talking about a very expensive piece of complex machinery.

Beyond the question of the ROI and whether it makes economic sense or not, I just don't like the feeling. The car shakes ever so slightly each time the engine needs to come alive... and it's not a confidence-inspiring feeling to have your car shaking back to life just when you're getting ready to press the accelerator down to move-off from a stop. I can't say I like the sensation.

For the above reasons, I leave my ASS turned OFF. If someone could convince me there's a positive ROI, I *may* find my way to overlook the latter pet peeve regarding the awkward shaking sensation.

I totally agree. I believe Auto Start/Stop function is just pure marketing. This is just another way to attract a customer by making him think he saves on fuel. The same story as eg. electric cars. This is also just pure marketing that has nothing to do with ecology and saving money. An electric car does not produce exhaust gases but is loaded with lead batteries that have to be disposed after the time of use what is devastating for the planet. Besides by now, electric cars are so much more expensive compering to traditional cars that saving on fuel hardly compensate or does not compensate the money spent on the purchase of the car.

[HighlandPete]

Originally Posted by Stifler

I totally agree. I believe Auto Start/Stop function is just pure marketing. This is just another way to attract a customer by making him think he saves on fuel. The same story as eg. electric cars. This is also just pure marketing that has nothing to do with ecology and saving money. An electric car does not produce exhaust gases but is loaded with lead batteries that have to be disposed after the time of use what is devastating for the planet. Besides by now, electric cars are so much more expensive compering to traditional cars that saving on fuel hardly compensate or does not compensate the money spent on the purchase of the car.

Isn't the primary reason for manufacturers fitting ASS to help with short term emission targets? Reports and testing show that ASS does help. More so with petrol engines than diesel, due to idling consumption.

The bigger issues are not necessarily analysed to the same criteria. If they were, we'd likely be encouraged to run our cars much longer and save the emissions of building new ones.

HighlandPete

[raleedy]

Originally Posted by ezmaass

Call me a skeptic, but I'm not convinced the Auto Stop/Start feature is at all an economical function of the car. Does it really save any considerable amount of gas to warrant the strain it places on the motor and starter?

I have to believe that the cost of wear-and-tear is far greater than the amount of fuel saved. It reminds me of a study I saw many years ago that analyzed the cost of a kilowatt hour against that of the additional strain (and hence premature failure) on a lightbulb from flicking it on/off for a short period where you left the room. The result was a certain "threshold" of time where if under, it made sense to leave the bulb on, and if over made sense to shut it off. It makes me believe there must be a similar threshold in play here, too... but instead of a $0.60 lightbulb, we're talking about a very expensive piece of complex machinery.

Beyond the question of the ROI and whether it makes economic sense or not, I just don't like the feeling. The car shakes ever so slightly each time the engine needs to come alive... and it's not a confidence-inspiring feeling to have your car shaking back to life just when you're getting ready to press the accelerator down to move-off from a stop. I can't say I like the sensation.

For the above reasons, I leave my ASS turned OFF. If someone could convince me there's a positive ROI, I *may* find my way to overlook the latter pet peeve regarding the awkward shaking sensation.

For a thoughtful skeptic, you seem very confused. Do you have any facts to support the assumption that this system stresses the engine? Have you any statistics to point to from other countries, where the system has been in use for years, to support your "hunch" that the added use of the starter leads to earlier starter failure? And are you really under the sad misimpression that the purpose of the system is to save you fuel cost, so that a proper analysis if its benefits is a fuel savings payback on . . . . what, exactly? A rebuilt starter?

A different way of looking at this issue would be to ask what good it does to keep a gasoline or Diesel engine running for periods when it is not needed, compared to the waste of resources and added pollution that the running engine causes.

No one can argue, on the other hand, with your assertion that you don't like the feeling of the system. I would just say that your personal preferences are a matter of -- at best -- indifference to the rest of us.

[BavariaExclusive]

You can set the ECO manually in your system settings on how and when you want it to work.

[RASHID007]

Ok so with temperature well over +3c and engine up to temp and no A/C/Heat even on I guess the only possible problem in that list is battery charge.

Originally Posted by AP

For the record, I've dug out my manual for my car (2012 diesel model) and these are the circumstances when ASS will NOT kick in

Ambient temperature below +3c / 37F

high outside temperature and operation of air conditioning

interior not heated or cooled to the desired temperature

engine is not at operating temperature

Sharp steering angle or steering operation

after reversing

Condensation when the automatic air conditioning is switched on

Vehicle battery in a low state of charge

Bonnet is unlocked

HDC is activated

parking assistant is activated

stop /go traffic

Gear selector in n: or S/M position

[RASHID007]

To address those that think it makes no mpg difference...I had my 2012 F30 335i for 2 years. Both winters I averaged 3mpg less than I did in the sprint/summer/fall when the start stop was working frequently. In the winter it never turned on and I felt it at the pump and by monitoring the trip computer etc.

No doubt in my mind that it makes a difference.

Plus to those that don't like the shaking sensation, it's a trade off, I love the silence of sitting a light with the car off. Music sounds better, you hear other vehicles, people on the street, sounds in the distance...I think that positive sensation or 'experience' is worth the negative 'shake sensation' on restart.

Thoughts?

[raleedy]

Originally Posted by RASHID007

To address those that think it makes no mpg difference...I had my 2012 F30 335i for 2 years. Both winters I averaged 3mpg less than I did in the sprint/summer/fall when the start stop was working frequently. In the winter it never turned on and I felt it at the pump and by monitoring the trip computer etc.

No doubt in my mind that it makes a difference.

Plus to those that don't like the shaking sensation, it's a trade off, I love the silence of sitting a light with the car off. Music sounds better, you hear other vehicles, people on the street, sounds in the distance...I think that positive sensation or 'experience' is worth the negative 'shake sensation' on restart.

Thoughts?

+1
It's just different. Some folks can't handle change.

[RASHID007]

1. So I tried disabling ASS for a few days to see if it gave battery a chance to charge. When I enabled it again I felt that the stop start worked significantly better. I'd say it went from working 50% of the time to 70% but still nowhere near the 95% of the time ASS activates on my gasoline powered 335i.

2. My 535d is at the dealer for a BMW assist problem and they gave me a 2013 535i as a loaner. It shut off (ASS worked) at the very first light even though engine was no where near up to temperature. And it has shut off at over 90% of the stops on my drive home. It's FANTASTIC!

I will keep testing the gasoline 535i loaner to confirm. So is my problem the diesel engine or more likely a battery issue?

Any more feedback please from diesel drivers on % frequency their diesel auto start stop works?

Thank you.

[Gilgorm]

Originally Posted by RASHID007

So is my problem the diesel engine or more likely a battery issue?

It could be both and would depend a lot on the type of driving you do.

Back in the dark ages (late 70's, early 80's) I owned two MB diesels. They were fantastic cars but their only flaw was the occasional battery problem. If the cars weren't driven enough at high speed their massive batteries weren't charged and therefore, failed to start the engine due to the high compression of diesel engines. I once killed two gas-powered car batteries and a tow truck battery just to start my dead car. They need significantly more battery juice than petrol cars.

While times have certainly changed, batteries have changed relatively little.

My 535xi ASS often re-starts in traffic if the wait is too long so the condition of the battery is probably crucial to the programming of ASS.

Good luck with the problem but it may simply be the design of the diesel ASS.

[RASHID007]

Thanks for the feedback.

Question: Once your vehicle is up to temperature, what percentage of the time would you say it shuts off at lights/stops? Mine is well below 50% of stops even once it's up to temperature.

Originally Posted by Gilgorm

It could be both and would depend a lot on the type of driving you do.

Back in the dark ages (late 70's, early 80's) I owned two MB diesels. They were fantastic cars but their only flaw was the occasional battery problem. If the cars weren't driven enough at high speed their massive batteries weren't charged and therefore, failed to start the engine due to the high compression of diesel engines. I once killed two gas-powered car batteries and a tow truck battery just to start my dead car. They need significantly more battery juice than petrol cars.

While times have certainly changed, batteries have changed relatively little.

My 535xi ASS often re-starts in traffic if the wait is too long so the condition of the battery is probably crucial to the programming of ASS.

Good luck with the problem but it may simply be the design of the diesel ASS.

[Gilgorm]

Originally Posted by RASHID007

Thanks for the feedback.

Question: Once your vehicle is up to temperature, what percentage of the time would you say it shuts off at lights/stops? Mine is well below 50% of stops even once it's up to temperature.

First off, I am referring to my gas-powered 535xi.

Mine doesn't even get up to operating temp before ASS starts.
I have discovered that the way I stop seems to affect ASS. If I stop with variable brake pressure it doesn't always work. Steady pressure works best.
I always use AutoH as well. If the car is moving slightly so AutoH doesn't engage then ASS doesn't engage either.
If I'm in Stop and Go traffic it will stop working by itself if the stops are short.
I also turn it off just by using Sport on the shifter for those times that I need the engine to be on all the time, such as, left turns or residential stop signs.

As I stated earlier ASS often re-starts itself at especially long stop lights.

In summary, when I want it to work, I would guesstimate that it functions close to 98% of the time. There are rare times when I wonder why it didn't work. ASS re-starts are so smooth passengers don't even notice other than the noise level changes.

[RASHID007]

Originally Posted by Gilgorm

First off, I am referring to my gas-powered 535xi.

Mine doesn't even get up to operating temp before ASS starts.
I have discovered that the way I stop seems to affect ASS. If I stop with variable brake pressure it doesn't always work. Steady pressure works best.
I always use AutoH as well. If the car is moving slightly so AutoH doesn't engage then ASS doesn't engage either.
If I'm in Stop and Go traffic it will stop working by itself if the stops are short.
I also turn it off just by using Sport on the shifter for those times that I need the engine to be on all the time, such as, left turns or residential stop signs.

As I stated earlier ASS often re-starts itself at especially long stop lights.

In summary, when I want it to work, I would guesstimate that it functions close to 98% of the time. There are rare times when I wonder why it didn't work. ASS re-starts are so smooth passengers don't even notice other than the noise level changes.

Thank you for this information. I'm very jealous.

[MELLOWYELLOW06]

I love how openly everyone discusses how their ASS is turned on or off!

[AP]

what would be useful is to see the state of charge of the battery. My guess is it might be in the hidden menu on the dashboard - don't know though for sure.

[RASHID007]

Originally Posted by AP

what would be useful is to see the state of charge of the battery. My guess is it might be in the hidden menu on the dashboard - don't know though for sure.

That's a good point. I read through coding forum but didn't see that option.

[kube]

I'm seeing the same (or lack thereof). There doesn't appear to be any rationale or pattern as to when it's engaged or not. When I would expect it when I stop after a good stretch of driving, it doesn't engage. But then again, when I would not expect it (like some mornings 5 minutes out of the garage), it kicks in when I'm not at my normal engine temp. 8k miles on the car, so I'll ask when I bring it in. I am loving the 35mpg average around town and even got 52mpg on one trip!

[RASHID007]

Problem solved!

Dealership had my car for a week to fix an SOS error problem. Finally they replaced the TCU module that was faulty.

And now the Auto start stop works flawlessly and predictably every time! I can advise it is as frequent and predictable as my 335 and the 2013 535 loaner I had for a week. Diesel ASS is no less functional.