Ugly rear wing on WRX

[Ignignokt]

I live in a small town of about
30,000 people and I am the only one who has an STi in our entire
town.

SNORT!

- Greg

Alanson, MI. Pop: ~620

 

[Ignignokt]

I can't agrue with you there. The STi did compromise some comfort for
performance. But, it doesn't ride anywhere near as hard as the EVO.
And I was impressed by the EVO. But, less impressed by the brutal
ride and twitchy handling. And you have to drive it like you stole it
to get any power out of it!
The STi doesn't pretent to be your ''daddies Buick". The seats are
firm, the handling is tight and the suspension doesn't wash out in the
corners. I think you will almost always give up ride comfort for a
firmer, stiffer suspension.

Are you insinuating that the 350Z is Nissan's equivalent of my "Daddy's
Buick!?" There's a pretty wide range betwen STi and LaSabre...

Now, you won't come away unimpressed by the manual on the STi. With
the 6-speed you will always be in a gear that's appropriate for the
situation. An automatic in the STi? Heaven forbid! I've never
driven a Forester. So, I don't know how they handle.

They don't. Or rather they do, but like a truck. Or maybe a Buick. I'm
guessing here, not having driven a Buick since we sold the 1978 Century my
father-in-law gave my wife and I. That was about 15 years ago.

I did quite a bit of research before I bought my STi. And I looked at
and drove pratically every car on your list. Yes, even the 350Z.
But, after I took the STi for a test ride I fell in love/lust. It's
power is intoxicating and it's got a grip like Spiderman. For the
money, the STi was the best bang for the buck hands-down.
Earlier this year Car and Driver did a "Sports car shoot out" with
all the cars you mentioned. It had a STi on the front cover. I
highly reccomend you buy this issue before you make your decision.

I've subscribed to C&D since I was 13. Their articles are very useful in
helping me decide which cars to consider, but one's own personal taste
inevitably wins out over somebody else's personal taste, and can sometimes
outweigh every *objective* measure the testers can conceive. C&D does a
fantastic job of doing what they do -- and that thing isn't telling me what
car to buy, it's telling me their impressions of the various cars that are
out there. Don't misunderstand me: I like fast cars. But it's not the
*only* thing that I like. Your preference obviously places more emphasis on
power and handling and less on the aforementioned coddling than my own.
That's fine. There's nothing wrong with that. But neither is *my*
preference to opt for a little more coddling at the expense of performance.

And I've never denigrated the performance of the STi, or its value when
measured strictly as performance / $. But as I suggested before, there are
other considerations than just performance. There are cars that turn down
the performance and turn up the comfort for the same price. (Nissan 350Z.)
There are cars that keep the performance and turn up the comfort, but also
turn up the price (Audi S4). I've never suggested that any of these cars --
or any other -- are objectively "better" or "worse" overall than any other.
It all depends on your tastes (and your budget).

And I most definitely never intended to imply that anybody had made a bad
choice by going for the STi. Unless they did it just for the ugly wing, of
course. ;-)

- Greg

 

[Ignignokt]

I only get 148 hp/l.

Poser.

- Greg

 

[Cam Penner]

Poser.

I had that coming.

 

[Homer]

Sounds like the WRX STi you test drove. The WRX is either has no spoiler or
a low, flat one. The WRX has an 8-inch high wing spoiler. Though there are
those who say you can remove it, the thing is functional and it is best not
to. However, if you do, you can exchange the trunk lid for a WRX one that
has the low deck spoiler or none at all. As for the hood scoop, you need
it.

With regard to the "functionality" of any spoiler or wing:
It MUST be mounted in such a position as to encounter an undisturbed air
flow to be effective in any aerodynamic sense.
With regard to the "8-inch high wing spoiler":
In order for the wing to have an effect, it would have to be mounted at
least 4 or 5 inches above the roofline of the vehicle.
Its position causes it to contact air that is mostly part of the boundary
layer flowing off the roof of the vehicle, thereby negating any aerodynamic
effect. The ends of the spoiler do become involved with some of the small
Karmann vortices that are generated by the vehicle's passage through the
air, but these forces are negligible and fail to generate enough down force
to have any significant effect on handling.

 

[Patrick Fisher]

With regard to the "functionality" of any spoiler or wing:
It MUST be mounted in such a position as to encounter an undisturbed air
flow to be effective in any aerodynamic sense.
With regard to the "8-inch high wing spoiler":
In order for the wing to have an effect, it would have to be mounted at
least 4 or 5 inches above the roofline of the vehicle.
Its position causes it to contact air that is mostly part of the boundary
layer flowing off the roof of the vehicle, thereby negating any aerodynamic
effect. The ends of the spoiler do become involved with some of the small
Karmann vortices that are generated by the vehicle's passage through the
air, but these forces are negligible and fail to generate enough down force
to have any significant effect on handling.

I see. So you're saying the Subaru WRC Team, rather than spending hundreds
of thousands of dollars on professional mechanical and aerodynamics
engineers to design the spoiler for the WRC Impreza (which is not unlike the
spoiler on the road WRX STi), could have just read Usenet instead.

 

[Fuzzy Logic]

I see. So you're saying the Subaru WRC Team, rather than spending
hundreds of thousands of dollars on professional mechanical and
aerodynamics engineers to design the spoiler for the WRC Impreza (which
is not unlike the spoiler on the road WRX STi), could have just read
Usenet instead.

I have to question the logic as well. It may be true at lower speeds but
apparently Porsche and many other sports car makers think differently.

Look at the tiny wing on the Audi TT which was added when too many of them
became uncontrollable at high speeds. In all cases these spoilers are well
below the roof line.

http://www.detnews.com/2000/autos/0002/10/02090104.htm

 

[Bonehenge]

I have to question the logic as well. It may be true at lower speeds but
apparently Porsche and many other sports car makers think differently.

Look at the tiny wing on the Audi TT which was added when too many of them
became uncontrollable at high speeds. In all cases these spoilers are well
below the roof line.

Every American stock car has an adjustable spoiler that runs along the
rearmost edge of the trunk. <G>

But as someone else pointed out, they all could have skipped the wind
tunnels and gone straight to Google.

Barry

 

[BlueSTi]

With regard to the "functionality" of any spoiler or wing:
It MUST be mounted in such a position as to encounter an undisturbed air
flow to be effective in any aerodynamic sense.
With regard to the "8-inch high wing spoiler":
In order for the wing to have an effect, it would have to be mounted at
least 4 or 5 inches above the roofline of the vehicle.
Its position causes it to contact air that is mostly part of the boundary
layer flowing off the roof of the vehicle, thereby negating any aerodynamic
effect. The ends of the spoiler do become involved with some of the small
Karmann vortices that are generated by the vehicle's passage through the
air, but these forces are negligible and fail to generate enough down force
to have any significant effect on handling.

See attached file on the scanned page from Subaru regarding
aerodynamics of the rear wing.
BlueSTi
"Scary-Fast"

 

[CompUser]

See attached file on the scanned page from Subaru regarding
aerodynamics of the rear wing.
BlueSTi
"Scary-Fast"

Got a link?

 

[Homer]

I see. So you're saying the Subaru WRC Team, rather than spending hundreds
of thousands of dollars on professional mechanical and aerodynamics
engineers to design the spoiler for the WRC Impreza (which is not unlike the
spoiler on the road WRX STi), could have just read Usenet instead.

Please don't put words in my mouth.
What I wrote, paraphrased in the simplest of terms,
is that the amount of down force generated by a wing,
such as that mentioned in this thread,
is roughly equivalent to a flea fart in a hurricane.

 

[Ken Gilbert]

Please don't put words in my mouth.

What I wrote, paraphrased in the simplest of terms,
is that the amount of down force generated by a wing,
such as that mentioned in this thread,
is roughly equivalent to a flea fart in a hurricane.

instead of generating downforce, how about cancelling lift?

 

[BlueSTi]

Please don't put words in my mouth.
What I wrote, paraphrased in the simplest of terms,
is that the amount of down force generated by a wing,
such as that mentioned in this thread,
is roughly equivalent to a flea fart in a hurricane.

Subaru specs states that the spoiler "increases down force up to 38 Kg
at higher speeds". I don't know if that is considered a significant
amount of down force or not. I do know that a lot of research was put
into the aerodynamics of the body design. I can't imagine they did
all that wind tunnel work than just "threw" an big wing on the back
for the heck of it.


BlueSTi
"Scary-Fast"

 

[Homer]

instead of generating downforce, how about cancelling lift?

Regardless of the terminology involved, the vector addition is the same.
In this case it is a negative number because the wing is mounted upside
down.

 

[Homer]

Subaru specs states that the spoiler "increases down force up to 38 Kg
at higher speeds". I don't know if that is considered a significant
amount of down force or not. I do know that a lot of research was put
into the aerodynamics of the body design. I can't imagine they did
all that wind tunnel work than just "threw" an big wing on the back
for the heck of it.


BlueSTi
"Scary-Fast"

Please don't misunderstand me, I do respect the engineering that went into
the wing.
Analysis of a typical wing of 6 foot span, optimally mounted, yields a
force of approx. 58 lbs.
The well designed and mounted STi wing generates significantly more force as
stated in your post.
The key to the mystery is the differential between the force generated by
the wing and the mass of the vehicle.
With a 1499.01 Kg (3,298 lbs) vehicle, and 38 Kg (83.6 lbs) of negative
lift, there is a 2.5% differential.
IMO this would be significant on the track , but for street use it plays a
more aesthetic role.
BTW 38 Kg. is roughly equivalent to 65% of the fuel tank capacity,
and the effect of the mass of the fuel in the vector equation is present at
any speed.
Therefore, keeping the tank topped up as much as is practical should do more
to improve handling at all speeds,
than the wing adds at the higher speeds.

Homer

 

[Florian Feuser /FFF/]

instead of generating downforce, how about cancelling lift?

That amounts to the same.

By design, a car moving at speed is generating lift quite efficiently at two
points:
The air passing underneath is compressed between body and road creates lift at
the front axle; airflow above and around the body, especially the downdraft in
the rear creates upward lift at the rear axle.

Two things can be done about this:
1. minimize the amount of air entering under the car using a front spoiler/skirt
and
2. attaching a wing that generates downforce proportional to the speed and the
lift generated by the rest of the body.

Creating foils that counteract the upward forces with downward oriented lift
will also increase overall drag the effects of which is a reduction of top speed
and fuel economy.

That said, the sedan design with the step between trunk lid and roof line is
generally not ideal for fast moving vehicles and the application of spoilers.
Hence the need for such a big wing on the WRX.

florian /FFF/

 

[Ross]

Therefore, keeping the tank topped up as much as is practical should do

more
to improve handling at all speeds,
than the wing adds at the higher speeds.

Not Really. Adding 38kg of downforce from a wing does not add 38kg worth of
inertia to accelarate both longditudionally and centripetally when
cornering. 38kg of downforce is almost (The wing weighs summat) inertia
free and adds to the grip in the tyres without increasing the lateral load
when cornering. The 38kg of fuel will increase the lateral conering load
and cancel out the additional grip because the tyre has to work harder under
more load to hold the same G in a turn.

R

 

[FNO]

Please don't misunderstand me, I do respect the engineering that went into
the wing.
Analysis of a typical wing of 6 foot span, optimally mounted, yields a
force of approx. 58 lbs.
The well designed and mounted STi wing generates significantly more force as
stated in your post.
The key to the mystery is the differential between the force generated by
the wing and the mass of the vehicle.
With a 1499.01 Kg (3,298 lbs) vehicle, and 38 Kg (83.6 lbs) of negative
lift, there is a 2.5% differential.
IMO this would be significant on the track , but for street use it plays a
more aesthetic role.
BTW 38 Kg. is roughly equivalent to 65% of the fuel tank capacity,
and the effect of the mass of the fuel in the vector equation is present at
any speed.
Therefore, keeping the tank topped up as much as is practical should do more
to improve handling at all speeds,
than the wing adds at the higher speeds.

Homer

The one thing you haven't looked at is the design of the rear wing. It is
not an inverted airfoil like an upside-down wing. It has slightly less
curvature on the top than on the bottom. The spoiler is a box spoiler and
the actual downforce is produced by the lower plane; which is a conventional
ducktail-type spoiler. The wing's job is to bisect the airflow comming off
of the roofline at lower speeds, and compress the air onto the lower plane.
It smooths the air over the rear deck. At higher speeds, the wing will
produce a bit of downforce, and it reduces lift because it is swept back and
the vortex is somewhat behind the car. Its actually a pretty ingenious
design. Though I have never calculated the downforce at speed, it appears
to be pretty balanced and roughly consistent at all speeds. The lower
element of the spoiler would have little on no effect at very high speeds,
while the wing forces air onto the lower element at lower speeds. Subaru
says this effect will become noticeable at about 85KM.

In addition, the gas tank is roughly in the middle of the car and applies
roughly equal pressure to all wheels. It holds approx 50KG of fuel, which
equates to roughly 12.5 KG of force on each tire. The spoiler produces a
little over 30KG of downforce, which is about 15KG of downforce on each back
tire if the spoiler was located over the back axle; which it is not. It is
actually located nearly a meter behind the rear axle, and so will produce a
small amount of leverage, still further increasing the downforce on the rear
wheels.

The job of the spoiler is not to counteract lift forces, it is to balance
them between the front and rear of the car; although because it does produce
some negative lift, it does counteract some of the lift forces.

 

[Onne]

Interesting thread -
the 30kg of downforce on the rears, does that mean 30k (approximately
because of the "leverage") less on the front tire?

FNO wrote:
snip

 

[FNO]

Interesting thread -
the 30kg of downforce on the rears, does that mean 30k (approximately
because of the "leverage") less on the front tire?

There would obviously be some effect, but it would be negligible. The
spoiler is nearly a meter behind the rear axle. But the front and rear
axles are nearly two meters apart. Therefore, also because of leverage, the
amount of force reduction on the front wheels would be something less than
half; around 15KG over both wheels. But, that would be more than offset by
the downforce on the front end because of its shape. Remember, the
spoiler's job is to balance the lift forces between the front and rear of
the car.