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  #11  
Old 07-05-2022, 12:15 AM
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I don't remember the exact values but on my e53/m54 I think it was +50 from stock on each combination: eg in neutral, drive, each with and without AC.

On my N55 E70, I think I added 30rpm it was pretty subtle but I have a perfectly smooth idle.
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  #12  
Old 07-09-2022, 12:44 PM
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Ok, so I got the idle reduced by 50 RPM (from a target of 861 to 811) which has made a noticeable difference especially when coming to a stop but still eats gas like crazy when idling. I have a disabled son who spends a lot of time in the car with it idling so this problem totally cancels out the 10 to 14 percent better gas mileage that the E70 gets over the E53 and that really sucks! ;( If anyone has some more info on how to fix this (maybe roll back on the Daten??) or even why it was necessary in the first place it would be greatly appreciated.
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  #13  
Old 07-10-2022, 08:37 AM
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BMW has done this on every 5 series since the E28. Both my E60(N54) and E70(N52) bump up the idle speed w/AC on. The reason is likely to improve AC performance. 650-750 RPM is ~15% add'l cooling capacity. Not sure why anyone would want to defeat this function.
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Old 07-10-2022, 09:58 AM
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@pshovest -- I explained the "why" in my previous posts. My E53 A/C cools nicely with the variable displacement compressor and engine idling at 550 to 600. It seems that the E70 gets updated to 850 to 900 RPM which is a problem for me and some others.
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  #15  
Old 07-11-2022, 02:19 PM
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Does anyone know what the BMWAPP is were the OP says he noticed a "Code" for this ??
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  #16  
Old 07-13-2022, 01:12 AM
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Quote:
Originally Posted by 80stech View Post
Ok, so I got the idle reduced by 50 RPM (from a target of 861 to 811) which has made a noticeable difference especially when coming to a stop but still eats gas like crazy when idling. I have a disabled son who spends a lot of time in the car with it idling so this problem totally cancels out the 10 to 14 percent better gas mileage that the E70 gets over the E53 and that really sucks! ;( If anyone has some more info on how to fix this (maybe roll back on the Daten??) or even why it was necessary in the first place it would be greatly appreciated.

I actually highly doubt you are killing your overall mpg as much as you think but also you may be missing out on one of the best features of the e70; air circulation with the car off! I will often eat lunch in the car when ambient temp is between 40 and 90 and almost always I can be perfectly comfortable with the engine off and just using the iDrive menu option to run the engine off ventilation.

That said, my mpg went from 20 to 23 typical mostly highway and 17.5 to 21.5 mix (15-20% better) with my 300hp e70 vs. my 225 up e53!

When I sit and idle with AC on I'll see my avg drop to 18-19 with the e70 but the e53 dropped to 14-15 !

Pull up your mass air flow numbers when idling and with and without your AC running and post so we can compare.

Which engine?
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  #17  
Old 07-13-2022, 10:28 AM
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I have the 3.0L N52 engine. I've done a bit more digging and am coming up with bit of a theory. I think the valvetronic is more sensitive to carbon build up on the valves and if there is a correction needed to the idle, ends up overcompensating and causes the car to stall or lurch forward. The variable displacement compressor adds to the problem because it's increasing the load with the engine slowing down. There was a old thread on another site (I think it was with the N54 though) where the poster complained of the lurching problem with the A/C on to the dealer and was told that the problem was that he was not using premium gas. So I'm thinking that BMW fix was to bump up the idle speed based on the customer complaining. The much faster idle not only helps prevent the lurching, the customer is also going to have their foot firmly on the brake. I also noticed that cruise is a bit overly sensitive, noticeably reacting to wind and undulations in the road especially at about 80km/hr. probably related to the same carbon build on the valves in combination with the sensitive valvetronic.
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  #18  
Old 07-13-2022, 01:45 PM
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The N52 is a port injected engine. Valve stems should be carbon free, bright and shiny because they are sprayed/rinsed w/fuel on every intake stroke. My E70 w/N52 and 4 zone climate makes 37F air at idle. I will not even consider changing this for an imaginary fuel saving. I don't have any surging issues. I remain convinced that the idle speed increase is for AC capacity. The diesel doesn't need the idle speed bump because they can spin the compressors faster at normal idle. With only a 5k(?) redline, they don't have the problem the gas engines have. N52 A/C compressors must survive on an engine that can spin to 7k.
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