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      02-11-2013, 12:49 AM   #1
dragonxflare
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Full stops

Hello all,

I recently purchased a 2013 328i, and I heard that at full stops, the car shuts off to save gas. I always thought that when you turn off a car, then turn on a car, it uses more gas, so why does the auto shut off, "save" gas?

Has BMW changed something with the engine?
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      02-11-2013, 12:55 AM   #2
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the quick fix to that is, dont use the ASS, always turn it off.
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      02-11-2013, 12:57 AM   #3
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I read somewhere that the break even point is four seconds. If the car is off for four seconds than you use less gas than restarting it.

Can't remember where I read that.
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      02-11-2013, 01:11 AM   #4
dragonxflare
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So it's true? There's no point in using this system?
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      02-11-2013, 01:24 AM   #5
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You will ultimately save fuel using the auto start/stop if tend to hit a lot of stop lights. It is not that bad and you get used to it quick. Sometimes it is annoying if you are getting ready to pull out into traffic, but really.. it is not that bad.

And it is not only for saving fuel, it is also for saving the environment... My guess is most cars will have ASS over the coming years.
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      02-11-2013, 01:27 AM   #6
chrisny
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Quote:
Originally Posted by dragonxflare
So it's true? There's no point in using this system?
Depends on your driving conditions. Constant stop and go traffic, maybe it's not worth it or too annoying. If you spend more time with prolonged stops at lights, becomes more useful. You can easily turn it off if you're in stop-and-go traffic.
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      02-11-2013, 10:06 AM   #7
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Personally hate the judder from the engine turning on/off from ASS. May be less noticeable in the summer, but right now it's very noticeable. Had it coded asap.
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      02-11-2013, 10:15 AM   #8
chrisny
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Quote:
Originally Posted by Tsuyoi
Personally hate the judder from the engine turning on/off from ASS. May be less noticeable in the summer, but right now it's very noticeable. Had it coded asap.
I actually haven't found it to be that bad. Don't know if it's different for 335 vs. 328, but I could swear it was worse in test drives than on my car.
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      02-11-2013, 10:26 AM   #9
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Quote:
Originally Posted by Carnook View Post
I read somewhere that the break even point is four seconds. If the car is off for four seconds than you use less gas than restarting it.

Can't remember where I read that.
I've heard and believe this too.
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      02-11-2013, 10:43 AM   #10
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So does saving the amount of gas using ASS offset the extra wear and tear on your engine?
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      02-11-2013, 10:53 AM   #11
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Quote:
Originally Posted by stom_m3 View Post
So does saving the amount of gas using ASS offset the extra wear and tear on your engine?
This is what i want to know too. I always leave mine on because i get stuck at multiple traffic lights on my daily commute. Seems like it's not good for the alternator but I'm not a BMW engineer..
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      02-11-2013, 10:57 AM   #12
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Quote:
Originally Posted by Handozizle View Post
This is what i want to know too. I always leave mine on because i get stuck at multiple traffic lights on my daily commute. Seems like it's not good for the alternator but I'm not a BMW engineer..
Also, do you remember the days when people with turbo cars would have a turbo timer to leaver their cars on so the turbo doesn't bake after being run hard? I don't know if this is a non-issue now but I did wonder that after I did some sprited driving and at the next stop light the engine turned off.
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      02-11-2013, 10:59 AM   #13
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Quote:
Originally Posted by Carnook View Post
I read somewhere that the break even point is four seconds. If the car is off for four seconds than you use less gas than restarting it.

Can't remember where I read that.
Sounds about right to me. Starting a cold engine uses much more fuel, which I think is where some confusion comes in, but cold starts are irrelevant for the ASS function (the engine should still be fully warm for ASS restarts).
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      02-11-2013, 11:08 AM   #14
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Quote:
Originally Posted by Carnook View Post
I read somewhere that the break even point is four seconds. If the car is off for four seconds than you use less gas than restarting it.

Can't remember where I read that.
Having just read it prior to browsing this thread, I can confirm that it's in the manual!
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      02-11-2013, 11:10 AM   #15
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Saving some gas mileage is an adequate motivation for me to endure a jolt restarting. The great mileage pushed me towards the 328 rather than the 335, and this car rather than a Mercedes, Audi, or Cadillac. And I do like the silence of the motor being off when stopped. Also, I tend to consider BMW and legislators experts of how things should work for engineering and energy policy, unless it impedes me getting from here to there quickly.

Given the uncountable daily irritations, ASS doesn't even make my top 100.
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      02-11-2013, 11:50 AM   #16
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Quote:
Originally Posted by SomeRandomer123 View Post
I've heard and believe this too.
Me too, I'm hoping it came from BMW and not urban legend.

I think since the cars are direct injection there is less economy loss with the start/stop than if it wasn't. I'm no expert though...

It also seems like I read that, while it provides for an increase in fuel economy if you sit longer than 4 seconds, it's primarily aimed at reducing emissions.
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      02-11-2013, 11:58 AM   #17
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Quote:
Originally Posted by stom_m3 View Post
Also, do you remember the days when people with turbo cars would have a turbo timer to leaver their cars on so the turbo doesn't bake after being run hard? I don't know if this is a non-issue now but I did wonder that after I did some sprited driving and at the next stop light the engine turned off.
I remember heavily modded cars with big turbos having them. So i think a BMW with factory turbo would be fine.
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      02-11-2013, 12:44 PM   #18
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I would have no problem using ASS but after I read in the manual that this feature will "cause additional wear to certain components" (engine?) I decided better not use it since I plan on keeping the car for over 10 years. People complain that the ASS sounds harsh on the engine when it starts up after a stop but surprisingly I found it to be very unnoticeable and quite subtle.
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      02-11-2013, 12:52 PM   #19
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Quote:
Originally Posted by chrisny View Post
Constant stop and go traffic, maybe it's not worth it or too annoying.
Thankfully the system is smart enough to not shut down the engine in constant stop and go traffic. At least it's supposed to be that smart. I always deactivate ASS in rush time traffic...
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      02-11-2013, 12:57 PM   #20
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If you want a real mind-blower, imagine what it's like when the motor shuts off when you're going 80+mph
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      02-11-2013, 01:15 PM   #21
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Quote:
Originally Posted by Bradbury
Quote:
Originally Posted by chrisny View Post
Constant stop and go traffic, maybe it's not worth it or too annoying.
Thankfully the system is smart enough to not shut down the engine in constant stop and go traffic. At least it's supposed to be that smart. I always deactivate ASS in rush time traffic...
Doesn't seem to do so in mine, unless it takes a certain amount of times before it shuts itself off and I just do it before it gets to that point. But I've had it shut off, then I move ten feet, shuts off, 10 feet, etc...
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      02-11-2013, 01:22 PM   #22
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Quote:
Originally Posted by dragonxflare View Post
Hello all,

I recently purchased a 2013 328i, and I heard that at full stops, the car shuts off to save gas. I always thought that when you turn off a car, then turn on a car, it uses more gas, so why does the auto shut off, "save" gas?

Has BMW changed something with the engine?
It uses slightly more gas. That being said, the engine would only have to be off for a very short amount of time for it to use more gas than letting it idle.
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