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INSTALLATION OF A 1999 MAZDA ADJUSTABLE REAR WING
Genuine 1999 Mazda adjustable rear wing
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There has and always will be a debate over "THE" rear wing. No wing, factory 1993
wing, factory 1999 wing, high flying GT style wing, or some other variant. The debate rages.
Some may argue that for the utmost effectiveness and functionality the GT wing rules.
This might be true if you regularly top 140mph or your car can actually go 140mph at all.
Or possibly you want a lot of downforce at low
speeds at the expense of some increased drag. A properly designed and installed GT style wing,
or at a minimum a wing that generates real downforce, is pretty much
a necessity once you start nudging 140mph regardless. Then there is the other
question of aesthetics. Why put a full blown GT wing on a car driven on the street?
All you are doing is inviting ridecule from those ignorant enough not to
know you actually might "track" the car. Unless of course you
want a show car. But I don't have a show car so does aesthetics matter? Well
to me it does in part. I believe the angular GT style wing destroys the smooth rounded
lines of the 3rd generation RX-7...my opinion. So how to get some of the
functionality of a REAL rear wing without blodging up the look of the car?
The solution in my mind is the 1999 Mazda factory rear wing.
This wing is actually a functional wing that I think looks terrific.
Unlike the 1993 "lip" wing, which was mostly, if not all, for looks, the 1999 wing
actually generates real downforce. Not as much as a functional GT style wing
(I say functional because there are many GT "style" wings that aren't functional at all)
but functional nonetheless. The factory 1999 wing is made of urethane not
fiberglass, a big plus in my opinion, and it comes painted in the factory colors to match your
car so no worries or expense about visiting the paint shop.
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My original 1993 R1 rear wing.
The adjustability of the factory '99 wing |
A FEW ROUGH CALCULATIONS
I have some wind tunnel data for the '99 RX-7 equipped with the functional rear wing.
This is Mazda's own wind tunnel data taken from a 1999 Japanese promotional video.
After some difficulty with the translation it was deduced that the information
was in fact lift coefficients for the front and the rear of the car.
So using these numbers I did some really quick and dirty calculations and
found them quite interesting and thought I'd include them here.
The raw data:
Rear wing angle
(degrees)
1
5
10
14.5
|
Clf
(front lift coefficient)
0.045
0.047
0.051
0.053
|
Clr
(rear lift coefficient)
0.000
-0.025
-0.058
-0.075
|
It's interesting to note as the rear downforce increases (more negative lift)
there is a small pitch change in the car tilting the nose up and causing a bit
more lift in the front end. Makes sense to me. Also note the MANY other factors
play into these numbers: ride height, front rake, spring rates, etc..
But with these numbers I did bit of scribbling. Consider the car with
dimensions approx. 170"x70" (168.5" x 68.9" to be exact) or about 82.6sqft
of surface area. So split the surface area in half and do the math to
determine lift. Like I said VERY quick and dirty!
Roughly speaking at 140mph the front end of the car gets "lighter"
by 110lbs and the rear end of the car gets "heavier" by 155lbs if using the
wings maximum angle of 14.5degrees. So with a weight of 2800lbs with 50/50
weight distribution putting 1400lbs on each end of the car, at 140mph the car
"weighs" 1290lbs in the front and 1555lbs in the rear.
I did a similar calculation with a generic/averaged wing lift coefficient of 1.5
for just the wing itself and determined that the wing alone is is capable of generating
about 200lbs of rear downforce. Neato stuff, eh?
For those geeky enough to be interested, the math:
Fl( Lift force) = Cl (lift coefficient) x A (surface area) x ½ x rho (air density) x Vsq (velocity squared)
Simple plug and chug
Wing surface area (7.5" x 48") = about 2.5 sqft
Cl value of 1.5
rho air = 0.00238 slug/ftcubed
V = 140mph = 205ft/s.s
include coversion: lbf.s.s./slug.ft
Yields about 200lbs of downforce for just the wing
Use the Cl values provided by Mazda (listed above) for the whole car with
the surface areas noted previously to get ground force on the front and rear of the car.
As a comparison some data for the 1993-1995 model years taken from
'Race Car Aerodynamics' by Joseph Katz on page 18, shows that Mazda
did quite a bit or aerodynamic tweaking for the 1999 model year as the lift numbers are much improved.
These include most notably; the front nose, the front undertray w/airdam, the front lip spoiler, and
the rear wing.
Aerodynamic Coefficients of (1993-)1995 Mazda RX-7
Baseline RX-7
RX-7 R2(R1)
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Clf
0.16
0.10
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Clr
0.08
0.08
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OK...SO HOW MUCH?
One could argue the factory wing is expensive at about $800.00.
Consider that most *non-adjustable* wings are $400-$500 plus $100+
for decent paint and you are only a few hundred short of a much higher quality factory part
which was actually designed to work as a wing and not just be a show piece.
There was no question for me as I wanted/needed the adjustabilty, so most other decently priced,
aftermarket variants were out. There a few Japanese "tuner" rear wings that are
functional and adjustable but the prices for these items were outrageous. I managed to
source a used 1999 wing in Vintage Red to match my car, albeit with a few paint chips, and
saved over $200.00. But I never answered the question why do I need a functional rear wing? Well,
as my car is fully capable of topping 140mph and does so regularly on the track,
the added downforce and resulting grip combined with the added stability
from a rear wing I felt warranted the expense of a new wing.
Plus I think it looks good, so there :-)
INSTALLATION
Perhaps the beauty of a factory part is you know it will fit perfectly.
So the worries about sanding here, grinding there, are gone. Simply bolt
on and go. Well not quite, but close enough. The lower interior hatch trim
must be removed first. This is nerve racking as the trim is popped
in place using metal spring clips and much care must be taken not to
snap the plastic trim or deform it such that it bends and leaves a
white bend line. There are also a few push pin type clips hidden
under the upper half of the hatch trim. So the upper trim must
be partially "unsnapped" near the deck strut supports in order to access
the clips. Once the trim is removed the '93 wing can be unbolted. This
is comprised on two phillips head screws on each outer side, a 10mm bolt on
the forward inner stancheon, and two hidden white plastic clips for
the rear inner stancheon. Once you have broken...err, removed these
clips the wing can be lifted off. Staring at a naked hatch you see the 8 holes...
and the scuff marks where the old wing sat. Bummer. Time for a little wetsanding
to clean up the paint as best you can. No need to do it all, just the
areas no longer covered by the '99 wing supports - basically the front of the
old wing inner stancheons.
With wing removed the 8 mouting holes are visible.
Wet sanding the rough paint where old wing was mounted.
With the paint cleaned up the '99 wing is fairly easy bolt up exercise.
Six of the existing eight bolt holes align with the
mounting holes on the 99' wing perfectly. All one need do is drill the remaining 2
holes. DRILL! Unfortunately yes...drill. How does one know where
to drill the two needed holes? Using double sided tape *lightly* attach
pieces of clear overhead plastic to the underside of the new wing. With
a permenant marker, mark the location on the clear plastic where the
mounting holes on the underside are located.
Place the wing where it is to be mounted on the hatch. I bolted it down using
the existing holes in a few places to make sure it was in the right place.
Now firmly tape the clear overhead plastic to the hatch.
Hard to see but [left] a piece of clear plastic stuck
to a wing support with double sided tape and with the hole marked and [right]
wing now bolted down and plastic stuck to rear hatch ready for wing removal.
Remove the wing,
separating it from the clear plastic, which should now be stuck to the hatch and which
will indicate where the new holes are to be drilled. As painful as it may
seem, drill the holes. I used some black RTV
around the newly drilled holes to keep the water away from
the exposed metal edges when the wing was bolted in place.
In fact rubber washers should be used on all the
bolts to stop water from coming through into the hatch. Now it's just a
case of mounting the the new wing.
With wing removed and plastic stuck to rear deck the
location of the new hole is clearly marked. So go ahead...drill the new hole!
Don't worry too much about the new hole because if you ever decide to go back to the
old '93 style wing, the new hole will be covered up. Now only one issue remains...and
this is a tough call.
By removing the '93 wing 2 of the 8 mounting holes are not used and are left exposed
after installing the '99 wing. The proper way to deal with these are to fill, sand,
and repaint the whole rear hatch. $$'s!!!! In my case I found some low profile
plastic plugs and painted them over a 4 day period (1 coat a day) with 4-5
coats of touch up paint to match the car. Not as pretty but only cost a few cents.
With painted plugs installed.
Out with the old...and in with the new.
TRIPLE-R
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This page last updated December 2, 2003
If you would like to contact me and converse about my experiences with
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free to send an e-mail to crispyrx7@yahoo.com
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