What is the purpose of the rear spoiler?

This was debated a lot when the '01s first came out, and someone who was supposed to be a Toyota "insider" said that their wind tunnel tests showed it helped achieve the .27 drag coefficient a tiny bit. Don't know if that's true.

 

Well this may be more than you want to know but try this thread; http://priuschat.com/index.php?showtopic=17263 My answer is that it makes my backup camera dirty and well... me clean.

 

Spoilers do not always act to increase the downforce of the car. Spoilers also act to help the overal aerodynamics of the car. A spoiler disrupts the airflow and creates a bit of turbulence right behind the car. This actually is better with regards to aerodynamics. Another example is a golf ball. The dimples help to create turbulance behind the ball, which let;s it go farther. A smooth gof ball would not travel nearly as farr with all else being equal.

So for the Prius, the spoiler is not there to create more downforce at higher speeds. It is there to help the air flow around the car better, and it does the job quite well.

 

<div class='quotetop'>QUOTE(DocVijay @ Mar 30 2006, 08:00 PM) [snapback]232747[/snapback]</div>

Yeah that and make the back up camera lens dirty!

 

Looking forward to the day when car skins are dimpled like a golf balls.

 

A spoiler should not increase down-force. That's the job of a tuned wing, as far as I understand it. A spoiler attempts to decrease the vacuum found behind any vehicle - by "spoiling" the otherwise more laminar flow of air over the rear end. Typically a spoiler should have sharp edges - unlike the one found on our cars. The one thing I can guarantee is that the "spoiler" on our cars is not there to provide down-force.

 

Actually in the Japanese Touring Package, the rear spoiler is even longer. If you saw last Wednesday's episode of South Park you would've seen it.

 

<div class='quotetop'>QUOTE(aaf709 @ Mar 31 2006, 06:08 PM) [snapback]233151[/snapback]</div>

I plan on getting that spolier from Sigma. I think it may help with the aerodynamics a bit more at highway speeds. ANyway, even if it doesn't, I think it looks nicer.

 

<div class='quotetop'>QUOTE(DocVijay @ Mar 31 2006, 09:02 PM) [snapback]233205[/snapback]</div>

If you think it looks nicer, great. If you're actually expecting it will make a difference at highway speeds, I think you're going to be disappointed.

 

Aside from the wreck that you might have, I wonder if folding in the mirrors would add much to the aerodynamics.

 

<div class='quotetop'>QUOTE(Betelgeuse @ Mar 31 2006, 09:12 PM) [snapback]233208[/snapback]</div>

Actually I think the last part of my statement precludes disappointment. Now if you look at tit form a engineering/physics standpoint, it may in fact make a difference. Will it be perceptible? Maybe not, but that doesn't mean it isn't better.

At higher speeds, the basic principles still hold, and the forces acting on and around the car are still the same, just higher. At freeway speeds, the smaller spoiler may not create enoug turbulence to disrupt the vacuum created behind the car. A larger spoiler will cause more tumbling of the air behind the car and help to disrupt the greater negative pressure.

So don't be so fast and write off the effectiveness. All else being equal will I suddenly jump from 45 mpg to 55 mpg on the interstate? Of course not, but could it be from 45 to 47? Maybe. Won't know till I try.

 

It's something for a newbie like me to lift to try to open the rear hatch!

I wasn't paying attention and started trying to lift the spoiler rather than taking hold of the hatch-release.

I'll blame my haste to get my hat out in the drizzle. Or that on my Volvo XC90 the hatch release was higher. Couldn't have just been inexperience...

 

<div class='quotetop'>QUOTE(Rick Auricchio @ Apr 1 2006, 11:57 AM) [snapback]233411[/snapback]</div>

A Prius and an XC90! Good choice in cars (we have those two as well)!

 

<div class='quotetop'>QUOTE(DocVijay @ Mar 31 2006, 12:00 AM) [snapback]232747[/snapback]</div>

Concur with your closing statement. However, re the golf ball dimples,......purpose is to decrease suction behind the ball. Wake turbulence exists without dimples. The dimples create turbulence in the boundary layer, thereby energizing the flow. As a rusult, the cross section of the turbulence wake is decreased. The suction pressure times the cross sectional area results in decreased drag force (as compared to a smooth ball). Likewise the spoiler's purpose is to help decrease the cross-sectional area of the turbulence wake, thereby decreasing the turbulence drag force.

Images below: Large wake is from a smooth sphere. Smaller wake is due to golf ball dimples. {Assuming I know how to post images}.

 

<div class='quotetop'>QUOTE(brasche @ Mar 31 2006, 04:12 PM) [snapback]233106[/snapback]</div>

Take a look at a Corbin Sparrow

 

<div class='quotetop'>QUOTE(DocVijay @ Apr 1 2006, 11:38 AM) [snapback]233455[/snapback]</div>

The XC90 got traded for the Prius. I couldn't justify 17mpg on premium gas, and most of my driving is trips of a few miles.

I realize those short trips yield perhaps 35mpg in the Prius, but I'll take it! And we do take trips often down the coast, since we're 20 miles from the nearest major supermarket and 40mi from San Luis Obispo with its better shopping. I'm going to smile double]/i] all the way down the highway: once for the lovely view of the Pacific, and twice for the MPG.

 

Those 'mechanical' engineers are totally wrong. A spoiler may 'slightly' increase the the downward force on the rear of a car (unless it is a racing car with a huge one) and the term 'spoiler' is the answer. If you have ever driven an older (pre 60's car) on a gravel or dirt road at high speeds you would look back and see two large dust vortices generated as the high pressure air around the sides of the car rolls in to replace the low pressure over the top of the car. Those vortices take a LOT of energy to generate. Strakes and delta-wing airplanes use this principle for low speed stability. The small spoiler at the rear of the car increases the pressure at that point and helps cancel out those energy dragging vortices - hence - spoilers.
Sincerely, Bud (aerodynamic specialist).

 

I think the rear "spoiler" actually acts like the tail cone you see on many aircraft, it helps the air "get back together" after going up and around, as well as below and up the rear of the car body. Perhaps the touring model's additional 2", in anticipation of longer periods at highway speeds, performs this function just a bit better.

 

The spoiler is part of the Prius' Kammback design which is supposed to be aerodynamically efficient.

Kammback - Wikipedia, the free encyclopedia