09-04-2014, 03:46 PM | #23 | |
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High altitudes combined with hot air temperatures results in much thinner air. Normally aspirated (no turbo) engines really suffer under those conditions. Typically, a normally aspirated engine can only achieve about 75% of its sea level rated HP at an altitude of 8000 feet or so. And that's on a so-called standard day. A "standard" day is described as 59 degrees temperature at sea level and the barometric pressure is 29.92 inches of mercury. In other words, non-standard days are the norm. In the case of our turbocharged cars, a big part of the equation is how much reserve do our turbos have (if any) to maintain sea level HP at higher altitudes and/or higher than normal air temperatures.
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09-04-2014, 04:31 PM | #24 |
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Different outfits use different methodologies for acceleration testing.
For example, C&D normalizes their results to account for differing weather conditions during testing. http://www.caranddriver.com/features...braking-page-2 C&D, MT, R&T use rollout, Automobile and Edmunds do not: http://forums.anandtech.com/showthread.php?t=2009715 Due to these differences, one should only compare 0-60 times with others from the same magazine, group, site, etc. |
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09-04-2014, 04:49 PM | #25 | |
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09-04-2014, 06:02 PM | #26 | ||
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09-04-2014, 06:52 PM | #27 |
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So they (the car mags) say. Your mileage may vary.
Maybe one of these (cool) days I'll take my car out on some level, desolate road and do my own 0 to 60 testing. Just for grins.
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09-04-2014, 08:59 PM | #28 |
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Maybe I'm just naive, but before I decided between RWD and xDrive, I read that there's a claimed 4.6s for the m235xi while a claimed 4.8s for the m235i. This seems like it would explain the quoted numbers changing when the xDrive variant was introduced for 2015.
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09-04-2014, 09:31 PM | #29 | |
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