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      03-09-2011, 01:25 PM   #23
mario486
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Quote:
Originally Posted by Douggie View Post
I'm not a big fan of this because I feel this adds strain to the car, both mechanically and electrically. Like in all machines and electronics, start-stop/power cycles are the most damaging.

Yep, I am in the IT business and re-starting hardware regularly is bad, big time.

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Originally Posted by Gatekeeper View Post
It does. But lower emissions is the name of the game now.
But how much difference does it actually make? Difficult to quantify I suppose because it depends on how long you are standing still for. However, I am convinced that S/S is not efficient if it switches off for a few seconds only. There is a lot of unused fuel going through an engine on startup.

Bit like a neon light which needs to be switched of for something like an hour before it becomes more efficient than leaving on. Interesting subject, I wonder what the break even point for an engine is?
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      03-09-2011, 03:08 PM   #24
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I don't think wear and tear is an issue with S/S systems - I'm sure manufacturers have compensated/ factored this in. And to date I have not read anywhere about failed starters that have these systems.
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      03-09-2011, 03:29 PM   #25
mario486
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Quote:
Originally Posted by manicm View Post
I don't think wear and tear is an issue with S/S systems - I'm sure manufacturers have compensated/ factored this in. And to date I have not read anywhere about failed starters that have these systems.
Hi Manicm, not sure I follow. I was referring to non-S/S cars being switched off. S/S cars are a different story, they are designed for it. I do still wonder though how effecient they really are if you switch off for a few seconds only, say in slow moving, unpredictable traffic.
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      03-10-2011, 03:04 AM   #26
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Quote:
Originally Posted by mario486 View Post
Hi Manicm, not sure I follow. I was referring to non-S/S cars being switched off. S/S cars are a different story, they are designed for it. I do still wonder though how effecient they really are if you switch off for a few seconds only, say in slow moving, unpredictable traffic.
Sure, S/S cars are designed for it, but I wonder whether, on the long run, increasing the number of engine starts by let's say a factor of 5 or 10 over the engine's lifietime has really no effect on the wear and meterial fatigue, due to vibrations, pressure peaks etc. I have some mechanical engineering colleagues who systematically switch the thing off for that reason.

Another story is the real economy you make with the system. In ideal conditions, when you wait at every traffic light 5 minutes, it sure makes sense. But I noted that in normal city traffic, most of the S/S cycles last no more than 10s, so restarting the engine 10 times to spare in total about 1 minute of its running at minimum rpm seems ridiculous.
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      03-10-2011, 03:54 AM   #27
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I agree with Nathan. In the long run, whether S/S or non-S/S, laws of physics still applies. There is definitely stress induced to the system during the start-stop/power cycles.

Besides, in the real economy, the so called "designed for" is only valid within the warranty period. It's ugly, but it's the truth.

I guess if you are the type of person that changes cars once the warranty is over, it doesn't really matter. But if you do intend to keep cars longer than that, then I would take all these into consideration.

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Originally Posted by nathan35 View Post
Sure, S/S cars are designed for it, but I wonder whether, on the long run, increasing the number of engine starts by let's say a factor of 5 or 10 over the engine's lifietime has really no effect on the wear and meterial fatigue, due to vibrations, pressure peaks etc. I have some mechanical engineering colleagues who systematically switch the thing off for that reason.

Another story is the real economy you make with the system. In ideal conditions, when you wait at every traffic light 5 minutes, it sure makes sense. But I noted that in normal city traffic, most of the S/S cycles last no more than 10s, so restarting the engine 10 times to spare in total about 1 minute of its running at minimum rpm seems ridiculous.
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      03-11-2011, 05:27 AM   #28
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I don´t remember if it is Honda or Nissan that has a much better S&S. You dont have to switch to neutral,press down the clutch and press down the brake. You just press the brake with first gear in and the clutch down and the engine stops, release the brake and the engine starts.
That is the way a good S&S should work.
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      03-11-2011, 07:39 AM   #29
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Quote:
Originally Posted by tompak23d View Post
I don´t remember if it is Honda or Nissan that has a much better S&S. You dont have to switch to neutral,press down the clutch and press down the brake. You just press the brake with first gear in and the clutch down and the engine stops, release the brake and the engine starts.
That is the way a good S&S should work.
Excuse me? When in first gear with the clutch and break pressed, normally you're about to accelerate and drive, or you stopped just for a second when manovering at low speed, so you certainly want to make sure the engine's on.

No thanks, I have a lot of complaints about the bmw S/S system but still seems much more intuitive than the one you describe. Besides, stopping with the clutch instead of the neutral gear is a good way to make the car know you DON'T want it to stop the engine.

All in all, as already said, the whole system seems to me hardly useful.
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      03-11-2011, 01:10 PM   #30
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Quote:
Originally Posted by mario486 View Post
But how much difference does it actually make? Difficult to quantify I suppose because it depends on how long you are standing still for.
To some extent it's irrelevant. Emission levels generate a tax levy in many countries (such as France). The lower the better. If switching the engine off on any cycle lowers the emission-tax band, all the better.

Having said that, I must admit that although not a "green" person, I pay attention to a car emission level, andnot only for tax-avoidance purposes...
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      03-20-2011, 08:07 AM   #31
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Hi Guys
Good to see so many replies.
It seems most of you don’t think it is a good idea to switch off the engine on an auto transmission.
On the owner’s handbook, it states that “When you stop the car for longer period, for example, at traffic light, railway crossing or in traffic jams, switch of the engine.
You save fuel event if the engine is off for no longer than approximately four seconds.”
So the questions is, does the above statement apply to all X1 or only to manual transmission.
Thanks
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      03-20-2011, 09:35 AM   #32
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Yeah well it all comes down to then that if it makes you happy/efficent to do it, then do it. If it says so in the manual... Call your BMW service and ask them?
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      03-20-2011, 10:58 AM   #33
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Quote:
Originally Posted by simon025 View Post
Hi Guys
Good to see so many replies.
It seems most of you don’t think it is a good idea to switch off the engine on an auto transmission.
On the owner’s handbook, it states that “When you stop the car for longer period, for example, at traffic light, railway crossing or in traffic jams, switch of the engine.
You save fuel event if the engine is off for no longer than approximately four seconds.”
So the questions is, does the above statement apply to all X1 or only to manual transmission.
Thanks
It's about common sense for all non-S&S cars, X1 inclusive : a traffic jam when you are literally "parked" and nothing moves after 5 minutes, yes your shut off the engine. A traffic jam when you keep crawling every few seconds, you stay in D.
Same for traffic lights... You rarely stand still for more than one minute before it goes green again, so no, you would not cut the engine.
Conversely a railway crossing, unless the train is already passing as you pull up, will hold you for a few minutes at best, in which case it does make sense to kill the engine.

Rule of thumb is 2 minutes. Under, you let it idle, over, you turn it off.

Common sense....
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