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Old 01-06-2009, 07:45 PM   #1 (permalink)
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2008 Prius wake

After looking at this advert :

All-New Prius - The Third Generation Prius

I noticed that the wake is apparently increased by the upward kick on the back of the car.

Other than downforce, why would Toyota actually increase the size of the wake behind the car ? I thought the goal was to make the wake as small as possible .

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Old 01-06-2009, 08:50 PM   #2 (permalink)
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I don't think you can count on that animation as being an accurate representation of a wind tunnel smoke trace.

That said, Toyota has to take rear lift into consideration. While nobody here is likely to go blasting down the highway at top speed in a Prius, others apparently will and do. So the company needs to ensure the car is stable at high speed, even if it means sacrificing ultimate aerodynamics that would be safe at, say 60 mph.

Not saying that's unquestionably what the Prius spoiler is doing. It could also be reducing drag. (See the item about the "upkick" in the Volt's rear spoiler reducing drag, here: http://ecomodder.com/forum/showthrea...ures-4629.html )
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Old 01-06-2009, 09:13 PM   #3 (permalink)
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Cd -

*Whew*, I thought someone's Prius had been crunched in an accident or Toyota had canceled it.

MetroMPG -

Is this the same kind of aerodynamic issue as the Audi TT "lift problem"?

We Take Audi's Tamed TT for a Spin - First Drive Review/TT/Audi/Buying Guide/Car and Driver - Car And Driver
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The engineers continue to defend the car's original chassis settings, while quietly acknowledging that they recommended a rear spoiler to reduce lift at the rear axle, the prime source of the handling problems. Stylists resisted the spoiler.

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Old 01-06-2009, 09:39 PM   #4 (permalink)
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Looks good to me
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Old 01-06-2009, 09:48 PM   #5 (permalink)
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I'm pretty sure the Prius' choice to keep the spoiler has something to do with aesthetics as well.

Not saying that they're sac'ing anything for the sake of visually pleasing back sides, but apparently, there is a style panel that is closely adhered to when designing vehicles, and in some cases, it's the first and foremost rule, while other factors involved have to be designed around it.

Let us face facts about this: If it's cute, and handles horribly, drives slowly, and gets crappy mileage, or look like an extension of a male extremity, people will buy it regardless. The fact that it gets good gas mileage is a bonus in most cases.

The Prius has sexy curves, yes, but was that enough? Probably not. More likely that the "style" department said "put a spoiler on it - it will scream aerodynamically modified that way". And engineering and development were forced to follow that protocol, possibly sacrificing aerodynamics so the car would scream "I'm aerodynamic!!!".

That might not be the case here - but it has been in the past, as we're all aware. (Corvette - screams aero, yet isn't.)
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Old 01-07-2009, 08:04 AM   #6 (permalink)
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Old 01-07-2009, 08:56 AM   #7 (permalink)
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Worth noting that the gen 2 Prius touring edition has a larger than stock spoiler.

regular:



touring:

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Old 01-07-2009, 10:45 AM   #8 (permalink)
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it's very difficult to judge aerodynamics by this 2d and fictional representation... it's quite likely the animator had a real windtunnel pic as a reference... than again, i've done a teaser website for an automotive company and i was pretty much left to my own device, but anyway

the thing with wakes and aerodynamics in general is that when it's judged by the untrained eye the things which seem right might cause more drag. i remember when i was younger i used to think the VW beetle would be far more aerodynamic than the square 80's cars on the road than because the beetle had such nice rounded shapes at the back... unfortunately the original, and new beetle for that matter, both have horrible aero, also a somewhat related but more sleek car the porche 911 with its pretty rear that almost slopes to the ground doesn't do that good aero wise, all benefit form a rather large vertical to upward swept spoiler, which decreases their drag (on the porche it's likely more for downforce to keep it from oversteering with the engine so far to the rear).

another example is the iconic saab 900 wich also has a sleek looking trunk that slopes down, but which in most cases received a big spoiler at the base of the rear windshield... which along with other aero aids reduced drag.

just about every car with a decent to exeptionally good Cd seems to have some sort of horizontal or slightly upswept surface at the end of the trunk or roof... on some cars this is the trunk on other a notch in the bodywork, and on yet others a soiler wich looks like it was added as an afterthought
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Old 01-07-2009, 12:40 PM   #9 (permalink)
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On a slightly off-topic note, I CANNOT believe they still haven't added wheel skirts to the Prius. I understand the need for aesthetics, but maybe I'm weird, because I think wheel skirts look cool. Even if I didn't know or care about aerodynamics, wheel skirts make the car look slightly futuristic.
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Old 01-07-2009, 04:09 PM   #10 (permalink)
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Prius

I'm gonna wait until I can see the thing in the "flesh."

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