09-23-2011, 05:57 AM | #45 |
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09-23-2011, 08:03 AM | #46 |
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You can modify wastegate duty cycle without Valvetronic. Having the wategates normally closed (M button on) decreases spool time and gives a harder/faster kick when transitioning from partial to full throttle.
Without the M button on, the wastegates are normally open to reduce backpressure/pumping losses and increase efficiency. |
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09-23-2011, 08:33 AM | #47 |
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09-23-2011, 08:44 AM | #48 |
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09-23-2011, 08:52 AM | #49 |
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09-23-2011, 09:19 AM | #50 |
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09-23-2011, 10:18 AM | #52 |
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i thought there'd be more mechanics or something on this board? this goes back to a post i created when i first joined...looking for a 1M shop/repair manual. this would explain everything! is there an M specific shop/repair manual available yet? everything that BMW does is computer/internet based, but I would sure love to have a DVD version or something for myself if I could.
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09-23-2011, 11:19 AM | #53 |
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The WG is used to regulate the charging pressure. A boost controller decides how much air to escape out the WG to keep the turbo speed at what it needs to feed the engine at its boost target. If the WG remains closed the exhaust gas always passes over the turbine which then runs at a considerably higher speed. With the M button ON and at WOT, the WG stays closed until it hits its overboost target, it holds it at that level for a couple of seconds then opens more to run the boost down to held level.
Since the M button changes the WG settings, it also changes the overboost function (500Nm of torque). M button function:
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09-23-2011, 12:10 PM | #54 |
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09-23-2011, 09:29 PM | #55 |
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Like and i others have said, the M button seems to change wategate operation and pedal position vs load requested.
That qualifies as mechanical change M button on vs off. |
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09-23-2011, 09:56 PM | #56 | |
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Not sure why you still think overboost is linked to the M button. It's not that complicated. |
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09-24-2011, 05:31 AM | #57 |
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Sorry, like others here, I have to call BS on this one. Surely just by trying this out on your own 1M you'd know this not to be true?
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09-24-2011, 05:04 PM | #58 | |
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09-25-2011, 06:48 PM | #59 | |||||||
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From BMW's 1M technical training documentation (Technical Training, E82 M Complete Vehicle, BMW Group University, ST1104)
Quote:
Quote:
Quote:
Quote:
Quote:
Quote:
Lastly, here is another paragraph of the same document: Quote:
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09-26-2011, 12:25 AM | #61 |
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I disagree with you. The document does not specify any changes to the overboost function. The programming of the wastegate valve in M mode only changes the responsiveness of the turbo and all this does is allow the turbo to spool up quicker. Overboost still occurs when the demand for acceleration is greater than 80%.
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09-26-2011, 01:25 AM | #62 | |
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The document does not specify any changes to the overboost function, but the parameters for the overboost has changed when the M button is pressed. The 80% demand for acceleration itself is just a precondition, but not a causation of overboost according to the article. Whether the overboost occurs still depends on other conditions, and optimal traction is an overriding condition. The articles further explained that the reasons why overboost rarely occurs or minimal in 1st or 2nd gear, while you get more overboost in 4th gear than 3rd gear. The article clearly stated that the M button does two things: a) changes the engine mapping, b) closing the wastegate. It also further explains this is the reason why the DSC will tend to kick in more often when the M button's pushed. With these changed parameters, the behaviour of the overboost will change. In reality, that also explains why I don't feel the overboost when M button is not on, whereas I can feel the kick when the M button is pressed. It is probably more relating to the engine mapping and the faster response that causes the overboost to come in quicker (time wise).
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09-26-2011, 01:26 AM | #63 |
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09-26-2011, 06:45 AM | #64 | |
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Try it with your 1M... if you are right, then you CAN'T be quicker on the clock with the M button ON because you would have the exact same max. torque between 1500-4500rpm (responsiveness of the acceleration - the dynamic response when accelerating from a constant speed - doesn't play a role here) !!! Last edited by GoingTooFast; 09-26-2011 at 09:55 AM.. |
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09-26-2011, 08:08 PM | #66 |
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Dan reckons he's quicker with the M button off .
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