What is the purpose of the rear spoiler?

Thanks Bud.

Best answer.

 

I don't believe the spoiler on a Prius generates any down force but I believe it may reduce lift.

By stopping the air moving over the top of the car from flowing down off the back of the car the air moving along the sides and bottom of the car has a chance to flow over the curved surfaces of the tail lights and underside of the bumper in toward the centreline of the car. By allowing the side air to come in first the air flowing over the car stays up. If the air followed a smooth curve to be flowing down it would cause an equal and opposite reaction exerting a lifting force on the rear of the car.

The profile of a Prius is a pretty fat aerofoil shape already and if laminar flow can be maintained across the roof and windows it would create some lift. The spoiler interrupts that flow before it can flow down the back of the hatch. It is under the window to minimise the cross section of turbulent air behind the Prius, if a spoiler was added aftermarket above the window it would increase drag due to a larger cross section of turbulent air behind the Prius.

I stand to be corrected but it is my belief that good aerodynamics is about smooth flow over surfaces then a clean departure with minimal turbulence. I think this is why the rearmost side windows are set in at the trailing edge too. This slight bulge behind the window creates small eddies in the air flow which reduces the tendency of air to flow around the rear pillars and interfere with the laminar flow of air over the back window.

 

The sopiler also spoils the view out ther rear window, according to some bloggers! ound:

 

US version Touring model now has a wider spoiler than the standard one.

 

consumer reports stated this month that the touring model stops 10 feet shorter going 60mph then a base prius, maybe its the spoiler! haha

now we need to write back to cu and ask them to change the tires from touring to base to rule out that possibility

 

Interestingly, they also found the Touring model to be slightly slower, have worse fuel economy and much poorer headlights.

Some of these difference must also be due to comparing a 2004 regular Prius to a 2008 Touring.

 

There are two REAL purposes to the rear spoiler (don't quote me.on this).

1. To give Prius owners something to argue about.
2. Two words - Chick magnet.

ZC1

 

I guess the term "spoiler" has changed over the years to now refer to the small bump on the rear decklid of some cars which is there more for drag reduction than downforce generation. But back in the old days, when spoilers were huge, they were definitely for generating downforce, and as a result, they increased drag. I'm talking about spoilers like this on the old NASCAR "Car of Yesterday"



and like this on a 1979 Pontiac Trans Am:

 

and
3. To sell cars...

 

If it had a purpose it would have a better name than "spoiler"

 

yeah, i just saw that on thier website, sucky

 

The real purpose of the spoiler? To enable those behind a Prius to distinguish it from a Pontiac Aztec!

 

You are also right, Patsparks!
The airfoil shape on the sides of the
car are also intended to create low (lifting)
pressure and steal it from the top of the car -
possibly increasing the problem that 'wussy' drivers have
in the strong crosswinds. But by the time the air flow gets
to the back of the car it has gone from smooth (laminar)
to turbulent. Any bulge or spoiler at the rear will cause
high pressure boundary layer re-attachment and
smooth out the departing flow, hence, less drag.
One of the worst drag producers on the Prius
and most cars are the side mirrors
but there is not much that
can be done about that.
They are as slick as
possible with a
slim stem.
Bud

 

the spoiler isnt there to keep the rear end down as much as to improve aerodynamics and allow the entire car as a whole to have better grip at higher speeds.


one thing i noticed about the 01 prius at the track, severe understeer and i attributed this to the LRR tires and the emmense grip the rear end had

 

Guess it couldn't have anything to do with the reason why every other FWD car in the world understeers, namely having the steering wheels provide motive force, and 60% of the weight on the front tires.