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BMW developing stop-start technology for six-cylinder engines

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Old Sep 16, 2008 | 07:09 AM
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Default BMW developing stop-start technology for six-cylinder engines


BMW developing stop-start technology for six-cylinder engines

Posted on Tuesday 16 September 2008


BMW currently offers autonomous engine stop-start technology for its four-cylinder engines under the guise of its EfficientDynamics ecological banner, but the fuel-saving feature is now expected to filter across to the carmaker’s award winning range of six-cylinder engines as well. The decision comes as BMW experiences falling sales of its larger powerplants, especially in Europe, and the first six-cylinder models with stop-start should be hitting showrooms within the next 12 months.

Stop-start systems essentially shut down an engine to save fuel when a car is sitting in idle traffic, and then almost instantly kick it back into life once the accelerator is depressed or the clutch is engaged. By doing this, stop-start systems offer the greatest fuel savings around town, where high cycle stop-and-go driving is common. The savings can be substantial, with four-cylinder models regularly returning savings of around 4-6% in fuel consumption. The fuel savings are expected to be higher in the six-cylinder models.

However, because of their complex mechanisms current systems only work with manual transmissions. While gearbox manufacturers like ZF have developed new versions that work with automatics, their market roll-out is still several years away for BMW.

As most six-cylinder BMW models are sold with automatics, the carmaker has been reluctant to add stop-start systems to these cars, according to BusinessWeek. There’s been no mention in which markets BMW will first offer the option and in which models it will be available.
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Old Sep 16, 2008 | 08:39 AM
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However, because of their complex mechanisms current systems only work with manual transmissions
Interesting, I thought that they didn't work with manual transmissions. I thought that was the whole issue, especially with why vehicles like the first Insight and Civic hybrid didn't have engine start stop technology (before CVTs). I also thought that was the criticism for Porsche, since most of their vehicles are MTs. ....if thats the case sign me up for a MT, I6 BMW with cut off technology.


Though I would think that they would benefit from DIing all their engines more than from this technology.
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Old Sep 16, 2008 | 10:42 AM
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Originally Posted by SLegacy99
Interesting, I thought that they didn't work with manual transmissions. I thought that was the whole issue, especially with why vehicles like the first Insight and Civic hybrid didn't have engine start stop technology (before CVTs). I also thought that was the criticism for Porsche, since most of their vehicles are MTs. ....if thats the case sign me up for a MT, I6 BMW with cut off technology.


Though I would think that they would benefit from DIing all their engines more than from this technology.
The I6 (at least in TT form) is already DI'd, as well as running valvetronic.....
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Old Sep 16, 2008 | 10:47 AM
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What about shutting off 4 of 6 cylinders while idling? So there is no delay in the acceleration. Does any manufacture have such technology?
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Old Sep 16, 2008 | 10:48 AM
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Won't this introduce more wear and tear on the engine? I thought the engine gets the most wear and tear during the startup process?
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Old Sep 16, 2008 | 01:39 PM
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Originally Posted by ST430
The I6 (at least in TT form) is already DI'd, as well as running valvetronic.....
Right, as are their new V8s. However, as a luxury car company that prides themselves on fuel economy, I would think that they would be DIing their N/A powerplants too in order to be the best.


Originally Posted by Jujharoo
What about shutting off 4 of 6 cylinders while idling? So there is no delay in the acceleration. Does any manufacture have such technology?
I am curious to know if with Active fuel management they do this or if they only shut down cylinders while cruising.

Originally Posted by jwong77
Won't this introduce more wear and tear on the engine? I thought the engine gets the most wear and tear during the startup process?
Heavy duty starters. This is no different than how most hybrid shut down their ICEs. And so far so good.
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Old Sep 16, 2008 | 03:25 PM
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Originally Posted by jwong77
Won't this introduce more wear and tear on the engine? I thought the engine gets the most wear and tear during the startup process?
No - most wear occurs when engines and lubricants are cold. The BMW system doesn't start working until the engine has reached normal operating temperature and sensors re-start the engine if it has been switched off too long and starts to cool.

I've driven a MINI and BMW 3-series with the system and it's very good, if a little disconcerting at first. The 2.0 litre BMW returns 40mpg with it - plus significant reductions in CO2 output.
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