04-02-2013, 09:45 PM | #1 |
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So what really is the deal with the trunk spoiler ...?
Dear Aerodynamics Specialists
Nugent’s reply to my “Understated Wolf …?” response made me thinking: What really is the deal with the trunk spoiler on the F10 M5? This lip is so small that I seriously couldn’t believe that it would make any difference in rear axle down pressure through aerodynamics. I still believe that this spoiler is a design element rather than a functional detail. So I started digging around the web trying to find some more information. Seems impossible! All I found were German language online fora with people guessing around about the possible additional weight ratio that this rear lip would produce. The opinions ranged from around an additional 10lb at 100mph to 120lb (I would think that the latter one is way too much). Another theory was that the rear spoiler is in fact not a spoiler but a break-away edge for the airflow. Instead of creating additional down-pressure it prevents the airflow from lifting the rear end of the car at high speeds. The only official statement that I could find from BMW was a quote from Dr. Friedrich Nitschke, CEO of M GmbH who mentioned during the introduction of the M550d that body changes to the standard models were only made were technically absolutely necessary (referencing the rear spoiler on that vehicle). But again, I couldn’t find any detail on how or why that is technically necessary. I will continue my research and keep you posted. But in the meantime, does anybody have more insight? Best, (H) P.S.: Btw., the official German BMW explanation talks about the Gurney-Style of the spoiler. Does anybody know what that stands for – never heard it before. P.P.S.: I was floored to read that 68% of newly registered 5 series BMW in Germany in 2011 had Diesel engines! picture courtesy of euromotorsport.com |
04-02-2013, 11:21 PM | #2 |
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Good theory. I can't imagine it has much technical purpose since M sells a sport wing that looks larger and i would assume will change the dynamics. Again this is all theory, no concrete info. Good hunting
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04-03-2013, 12:24 AM | #3 |
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It's not only BMW and it's not only the 5 series. Pretty much the same numbers across Europe, in some countries it is even higher percentage. The petrol prices here are quite a bit different than the prices in the US - eg. for $3.2 someone in Germany gets 1 liter, you get almost 4 (a gallon) Some people need to drive a lot.
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04-03-2013, 12:28 AM | #4 |
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it's similar in design to the e9x spoiler. if memory serves, and mine usually does, I remember reading at some point that it decreases wind turbulence at high speed. not really creating downforce but more for limiting destabilizing forces.
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04-03-2013, 01:19 AM | #5 |
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Aesthetically, it separates normal F10s from the M5, dating back from the E39. Just a signature touch.. I wouldn't dismiss its aerodynamic properties. It looks prominent enough to do something at speed. We need a wind tunnel to know for sure, just my take.
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04-03-2013, 05:36 AM | #6 |
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Heres to more justification in buying the M performance spoiler
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04-03-2013, 06:26 AM | #7 |
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This device doesn't produce down force, it reduces the tendency for the body to generate lift. Same outcome in a way but not strictly the same.
The clue is in the name 'trunk spoiler', spoiler is a lift disrupting device, as opposed to a 'wing' which is a lift/down-force generating device. As for estimates of 120lb of reduced lift @ 100MPH. Do you really think that the car will ride up at the back as if it is lifted with a 120lb force? If so BMW sure suck at designing the break away on the rear trunk of the standard un-spoilered car. My view, is yes it reduces lift by some value...would you notice the difference? Nope!!! It will also induce more drag at high speeds.....again would the driver notice the difference? Nope!!! So IMO it is 80% visual / 20% functional .....at best |
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04-03-2013, 09:35 AM | #8 | |
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Quote:
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04-03-2013, 03:05 PM | #10 |
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"Right you are, Ken!"
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