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      11-11-2011, 03:16 PM   #1
swartzentruber
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Auto Start-Stop Shuts Off Below 38?

I know, a bit random, but has anyone else noticed that the auto start-stop shuts off once the "freeze" indicator hits at 37 F (or alternatively, can confirm I'm wrong)? I do actually fairly regularly use this feature, as it works pretty well for my commute (often, when I do have to stop for a light, it's a long light). It kind of stood out when I was driving in to work recently, and it auto-shut off once, then about a mile later, I hear the icing "ding", and then the next light, it didn't shut off. I was surprised that it didn't work more like A/C, where if the car is off too long it will restart so the car doesn't get too hot, but rather just seems to either have a hard shut-off at 37, or implements a much higher oil temp threshold at that point. I'm pretty sure it's not just not having the car warmed up enough, since I had the experience where it already shut off at 38, but wouldn't shut off later when the oil temp would presumably be even higher, but the temp now registered 37.

If my theory is correct, I can see a lot of people bringing their cars to the dealer thinking it's broken, once this feature is rolled out more broadly.
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      11-11-2011, 03:28 PM   #2
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Hmmm. Going to be a RTFM response to this. In extreme weather, and when the cabin is in a cooling or heating phase, Auto Start/Stop is disabled. As well as when your door is open, the battery is in a low charge, the wheel is turned to an extreme, the vehicle is not up to operating temp.............. I use it all the time too.
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      11-11-2011, 03:39 PM   #3
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Quote:
Originally Posted by robb7979 View Post
Hmmm. Going to be a RTFM response to this. In extreme weather, and when the cabin is in a cooling or heating phase, Auto Start/Stop is disabled. As well as when your door is open, the battery is in a low charge, the wheel is turned to an extreme, the vehicle is not up to operating temp.............. I use it all the time too.
Um, I have "RTFM". It seems you may be from TX, so I guess we can let it slide, but 37 degrees F is NOT extreme weather. 0 degrees I could see. A fully warmed up cabin is not going to cool off quickly at 37 degrees. I guess my point is, 37 degrees is pretty surprisingly high to just decide it's going to not work, as it basically means that the system won't work for close to 50% of the year around here. Maybe it's the difference between a Munich dwellers idea of cold weather (which I don't think get's that cold), and places that do like Chicago.
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      11-11-2011, 03:54 PM   #4
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37 or 38 degrees is when BMW decides to chime for extreme weather, it only makes sense that it is the same temperature the car would consider extreme for auto start/stop. I wasn't trying to be the RTFM guy. I hate that shit. If you know the answer then just spit it out.

And Dallas isn't a tropical paradise. Last January I spent a week in Alaska, and it was warmer all week there than in Dallas. There sure are a shitload of Texans here though. I'm a Buffalo native. 3 feet of snow isn't extreme to me. Go Bills!

Sorry if I came off like a dick. I meant someone else would chime in with the RTFM!
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      11-11-2011, 04:00 PM   #5
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Quote:
Originally Posted by swartzentruber View Post
Um, I have "RTFM". It seems you may be from TX, so I guess we can let it slide, but 37 degrees F is NOT extreme weather. 0 degrees I could see. A fully warmed up cabin is not going to cool off quickly at 37 degrees. I guess my point is, 37 degrees is pretty surprisingly high to just decide it's going to not work, as it basically means that the system won't work for close to 50% of the year around here. Maybe it's the difference between a Munich dwellers idea of cold weather (which I don't think get's that cold), and places that do like Chicago.
OP is from Chicago, not TX
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      11-11-2011, 04:28 PM   #6
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Quote:
Originally Posted by swartzentruber View Post
Um, I have "RTFM". It seems you may be from TX, so I guess we can let it slide, but 37 degrees F is NOT extreme weather. 0 degrees I could see. A fully warmed up cabin is not going to cool off quickly at 37 degrees. I guess my point is, 37 degrees is pretty surprisingly high to just decide it's going to not work, as it basically means that the system won't work for close to 50% of the year around here. Maybe it's the difference between a Munich dwellers idea of cold weather (which I don't think get's that cold), and places that do like Chicago.
My manual specifically states it shuts off at 3C which is about 37F. I don't know why yours doesn't.

I guess they do this because BMW has a lot of experience monitoring elctrical loads of their cars. You know rear window defoggers, seat heaters and other things come into play at those temps. Not to mention that batteries develop a lot less electrical power as they get colder.
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      11-11-2011, 04:37 PM   #7
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Quote:
Originally Posted by saeyedoc View Post
OP is from Chicago, not TX
LOL. That was the OP
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      11-11-2011, 04:39 PM   #8
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Quote:
Originally Posted by goldminer View Post
My manual specifically states it shuts off at 3C which is about 37F. I don't know why yours doesn't.

I guess they do this because BMW has a lot of experience monitoring elctrical loads of their cars. You know rear window defoggers, seat heaters and other things come into play at those temps. Not to mention that batteries develop a lot less electrical power as they get colder.
He specifically said his does stop working at 37
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      11-11-2011, 05:23 PM   #9
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OK, so yes, the manual does specifically say it shuts off around 37 degrees. I had read the section on auto start-stop, but I guess skimmed over that point. My larger point was still that I find 37 degrees extremely high to just shut it down. Maybe if other items mentioned were adding to the load, but coming from a heated garage, none of those are needed, and the heating load is low. It almost seems like they just decided hey, we have this circuit for the icing warning, lets just use the same circuit for auto start-stop.

With this being the case, I can see why the US EPA doesn't want to give credit for auto start-stop. An emissions saving feature that only works 50% of the time (in some climates) doesn't seem much worth it.
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      11-11-2011, 05:39 PM   #10
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I agree. It seems to be the easy road.
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      11-11-2011, 05:41 PM   #11
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I think the bigger question is why would you use auto start stop in the first place
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      11-11-2011, 06:16 PM   #12
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Quote:
Originally Posted by Darth One View Post
I think the bigger question is why would you use auto start stop in the first place
As I tried to describe in my first post, I have a commute that is tailor made for auto start-stop. Simplifying things, I have a 10 minute commute that averages 15 minutes due to long lights that I frequently hit red due to how the lights are timed. Theoretically, I could save 50% of my gas. Really, it's more about not wasting than caring about fuel costs so much -- why sit idling at a light for 2 minutes and adding to air pollution when I could be burning nothing. It actually works very well -- once you understand the system, you can pretty easily get it to shut off when you want it to, and keep it from shutting off when you don't (i.e. just as you are arriving the light turns green). I don't want to turn this into a "why start-stop" war, just surprised that BMW programmed it to turn off at such a high (IMO) temp.
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      11-11-2011, 07:05 PM   #13
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I've tried using the feature but it never worked well for me

i forgot i even had it until now lol
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      11-11-2011, 09:19 PM   #14
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See OP, now I'm on your side. I always use the stop/start. It WORKS for me.
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      11-11-2011, 09:20 PM   #15
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37 is unreasonable though
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      11-11-2011, 09:43 PM   #16
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I would guess that in testing, under certain circumstances, they ran into window fogging. I could see in humid, rainy conditions at 32, 33, 34 degrees the windows would start to fog up pretty quick. And it might only be in certain circumstances but they are going to build in a buffer and fudge factor of a few degrees to make certain that situation is avoided. Next time it's rainy and humid and 33 or 34 degrees, turn off your A/C and see how fast it starts to fog up.
I don't know if this was the thinking behind this, just a guess of what was probably many factors.

Last edited by MysticBlue; 11-11-2011 at 10:33 PM.
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      11-12-2011, 10:51 AM   #17
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Quote:
Originally Posted by robb7979 View Post
He specifically said his does stop working at 37
It sounded to me like he was surprised to see the car behaving exactly like the manual said it would because he said has anyone noticed?.

All of the behaviour noted is described in my manual. Why be surprised?
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      11-12-2011, 10:55 AM   #18
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Quote:
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37 is unreasonable though
I think that BMW's engineers probably have a better idea of what is reasonable. They would know under what conditions electrical load tends to go up and what load is too much for battery longevity.
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      11-12-2011, 05:09 PM   #19
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Quote:
Originally Posted by MysticBlue View Post
I would guess that in testing, under certain circumstances, they ran into window fogging. I could see in humid, rainy conditions at 32, 33, 34 degrees the windows would start to fog up pretty quick. And it might only be in certain circumstances but they are going to build in a buffer and fudge factor of a few degrees to make certain that situation is avoided. Next time it's rainy and humid and 33 or 34 degrees, turn off your A/C and see how fast it starts to fog up.
I don't know if this was the thinking behind this, just a guess of what was probably many factors.
Good point!
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      11-12-2011, 05:23 PM   #20
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Quote:
Originally Posted by robb7979 View Post
37 is unreasonable though
37 is when you start seeing slush on the roads and bridges start to get a bit more dangerous.
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      11-12-2011, 05:39 PM   #21
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Quote:
Originally Posted by swartzentruber View Post
Quote:
Originally Posted by Darth One View Post
I think the bigger question is why would you use auto start stop in the first place
As I tried to describe in my first post, I have a commute that is tailor made for auto start-stop. Simplifying things, I have a 10 minute commute that averages 15 minutes due to long lights that I frequently hit red due to how the lights are timed. Theoretically, I could save 50% of my gas. Really, it's more about not wasting than caring about fuel costs so much -- why sit idling at a light for 2 minutes and adding to air pollution when I could be burning nothing. It actually works very well -- once you understand the system, you can pretty easily get it to shut off when you want it to, and keep it from shutting off when you don't (i.e. just as you are arriving the light turns green). I don't want to turn this into a "why start-stop" war, just surprised that BMW programmed it to turn off at such a high (IMO) temp.
Not to sound rude but if you care so much about the environment why not buy yourself a Prius or a 4 cylinder bimmer.

If it only a 10 mins drive you are not making much of an impact by saving 2 mins.

When I feel like saving on the environment I take my other fuel efficient car (4 cylinder ).

When I drive the ///M is just for pleasure and the environment is the last thing on my mind.
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      11-12-2011, 05:58 PM   #22
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Yeah, 37 seems a little high and I think most of us would like to see our little warning chime come in closer to 32, or be user setable, but when you drive around, you may notice that sometimes the temperature can vary several degrees in a short distance, for instance on flat open ground it could be 37* then you drop into a shaded ravine and suddenly it's several degrees colder. Frost can form on surfaces even with 34* air temp. And as already mentioned, bridges and shady spots can still be icey even after it has warmed up several degrees above freezing. Another factor is simply instrument accuracy probably varies by a degree or two. Put that together with a lawsuit happy society, and I can see where they would put in a 2 - 4 degree fudge factor just to be on the conservative side. Sorry, topic went from start/stop to temperature warning, but sort of related.
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