Ward

iTrader: (1)

Sorry, this isnt engine related, but i dont know where else to put it. The reason im asking is because soon I am buying 85-90 TA ground effects, a fiberglass front and rear bumper, and a spoiler. I was going to buy the older style aerowing spoiler, but i found that GT Auto Accessories now makes the 91-92 style, and it looks sweet, sorta like a 4th gen one. But does it work as good? I know neither one really do that much, but jsut wondering...

------------------
1983 Pontiac Firebird SE
LG4-Based Chevy 400
700R4 Tansmission
Modified 4 Barrel Q-Jet Carb
Accel Super Stock 8mm Wires
Edelbrock Pro-Flo Air Cleaner
3.23 Posi Rear
14X7" Cragar SS/T Wheels
35X4 CD/AM/FM Head Unit
100WX2 Amp
2 Pioneer 12" Subs in Custom Box
Third Gen Performance

irocbsa

Neither one of them do much at all. Unless you are running at 150+ speeds all the time a spoiler really won't make any difference at all. Now if we could just get those damn ricers to understand that...........
bsa

------------------
"If they do not run, Then they will die." - Stonewall Jackson

'87 IROC, 355 TPI,700R4, Trick Flow Heads, Comp Cam, Comp 1.6 Rockers, Lucas 23# injectors, Edelbrock headers, Flowmaster 3'' exhaust, gutted cat,
Mallory coil, Mallory HyFire IV ignition box, Mallory Sidewinder 8mm wires, Autolite platinum plugs, K&N filters, Transgo Performance Shift Kit, Corvette Servo, 2,000 Torque Converter

Grim Reaper

I agree with irocbsa. Virtually no spoiler does really anything aerodynamically until speeds well in excess of any legal speed.

Some of the better designs start to have effect over 100 mph, others at even higher speeds and some are detrimental. The 59 Chev is a good example of a bad one.

The early aero package from the GTA is suppose to be better aerodynamically than the later package. I believe the earlier one actually does have effect, though well over 100 mph. The later one I believe is neutral, where it does neither any good or bad.

So if high speeds are your game, then go with the earlier one. If you don't plan on travelling over 100 mph on a regular basis and prefer the looks of the later one, then go with it. Below 100 mph, both are pretty much useless.

theformula

Agreed.


I love the 91-92 spoiler.

------------------
'92 Formula
305 TPI 5speed
1LE package
Mods: SLP headers,SLP catback,SLP air foil,ported plenum,Crane AFPR (47psi),MSD6AL,AC delco cold plugs, Bosch O2sensor, homemade cold air,K&Ns,3:73s,JET fan switch, Macewen white face gauges...Comp cam (i still have to install it )

Pablo

iTrader: (1)

the fastest stock bodied car in the world which happens to be a 92 trans am (~308 mph at bonneville) has an early style aerowing, they say its an excellent peice... they found that hte later model one actually produced LIFT at high speeds

if you want function, go for the early style one the later one will function too.. just not the way you want

MrJ

Actually the opposite is true.... the 91/92 style is slightly more 'slippery' than the earlier style.... The earlier aero package was purely for styling, while the later one was designed to have at least some minute aerodynamic benefit. The swoopy valances on the sides of the car supposedly have some sort of aerodynamic effect. Look at it. It's like a small vertical stabilizer, like the vertical tail on an aircraft. There is about an inch gap between the ground effect and the door at the widest point. The 91/92 'Bird body style is the most aerodynamic F-body ever made.

And to back up Pablo, the later spoiler is rumored to cause lift at high speed, while the earlier 85-90 design is well designed for a factory piece. and does generate pretty decent downforce at high speed.

Grim Reaper

By "aero package", I was referring more to the wing and to down force. I wasn't thinking about the "whole package" and not drag coefficient. Though I have never really seen any drag numbers (be interested though) I would suspect the 91-92s would have a slightly lower drag coefficent given the shape of the car.

I too have read about the "slight lift" about the 91-92 rear wing. But I have also read elsewhere that it is neutral. Again, I would be interested if anyone had done some actual wind tunnel tests. Regardless, everything I have ever read about the rear spoilers say that neither really do anything below 100 mph, and they are basically useless below that.

From actually driving my car, (the very few times I took my car to 140 mph), my car didn't seem to have any "lift" or feel unstable. I do hit 100 mph on a more frequent basis , and it feels very stable at that speed.

So, with that clarified, I stay with my bottom line, "If you are planning to do in excess of 100 mph on a regular basis, go with the earlier wing. If not and/or you prefer the looks of the later wing, go with it". From a styling point of view, I personally prefer the looks of the later one.

Also, the later wing doesn't have that weathering/cracking problem that seems to plague the earlier wings. During some of my "scavenger hunts" through the boneyards, I have come across a few of the aerowings (far more common to see the earlier ones), and most of the earlier ones do seem to have a weathering/cracking problem. I am not sure why the earlier ones seem to have this problem more than the later one. Maybe its the material or they were often just "flat black" and not painted with body paint.

[This message has been edited by Glenn91L98GTA (edited November 30, 2000).]

dudelovett

Completely unrelated, but just an interesting little tidbit on spoilers.

Bigger isnt better! Those small little flip up spoilers on the back of 2nd gens are designed to provide 100#s of downforce at 100 mph!

I thought that was kinda cool!

------------------
1991 Firebird Formula, 305, TPI, Auto...stock till I get some money!!!
Former owner of an 88 2.8 Firebird....RIP

Ward

iTrader: (1)

I knew the early style was functional because i read an article (forgot what magazine) about a thirdgen camaro doing 184 mph on 345 hp. They lowered the car, removed the mirrors, and used an early GTA style spoiler. But they also had a wierd looking spoiler thing under the rear bumper, too.

------------------
1983 Pontiac Firebird SE
LG4-Based Chevy 400
700R4 Tansmission
Modified 4 Barrel Q-Jet Carb
Accel Super Stock 8mm Wires
Edelbrock Pro-Flo Air Cleaner
3.23 Posi Rear
14X7" Cragar SS/T Wheels
35X4 CD/AM/FM Head Unit
100WX2 Amp
2 Pioneer 12" Subs in Custom Box
Third Gen Performance

Red Devil

Ok, the coefficient of drag that was reported on all third gen Trans Ams was 0.32. If the latter ones were 'slicker' it was by such an insignificant amount that no one reported a difference.

On the wing matter. The full 'scoop' early wrap around wings were functional. And for their compact size, surprisingly so. The flat later wrap around wings were plain crap. There was no angle of attack to divert air upwards to create any effective downforce. The earlier ones were effective at highway speeds, however they were nothing to write home about. I believe Mecham designed a wraparound wing that was functional at speeds as low as 25 mi./hr. ( Huge aspect ratio and a big trailing edge). Many people have designed their own, and the easiest and most popular is the early wing style that is stretched wider (well really made of fiberglass, not really stretched) to lip up past the trailing edge of the car so as to divert a greater amount of air upward (it incorporates the air coming up from under the car). Also the design of the older wing somewhat incorporates an end fence (end plates) design that effectively increases the wing's span. Also The aspect ratio of the stock early wrap around is again surprisingly good. A really good way to reduce the drag and increase downforce on these cars is to make some panels for the underbelly.

A quick note on the 2nd gen wing, it did create a good amount of downforce, but at a stiffer price than the 3rd gens... drag.

If you really want to read some dry theory on this...
http://www.aa.washington.edu/faculty/eberhardt/lift.htm
http://www.desktopaero.com/appliedae...liftdistn.html

And a few neat programs...
http://aero.stanford.edu/WingCalc.html
http://www.rapidline.com/pcwing.htm

SpeedCat86

BTW: A few years back, the boys at Car And Driver tried to set a class record at Bonneville with a Ligenfelter-prepped '96 T/A. It made 600HP, sat less than an inch from the ground, and turned a backflip at 220mph.

Pablo

iTrader: (1)

Yeah i had the video of that on my computer i heard there was just an outright aerodynamic flaw in the shape of the car that caused that to happen

pianiy

iTrader: (2)

One sidenote I wanted to squeeze in... the flat wings that are standard on base model Firebirds are designed to be an inverted wing. Wereas a wing on an air plane as a longer edge on the top to create a low pressure area thus giving it lift. The flat spoilers, as small as it might be do have some curvature to the bottom portion which creates some [small] downward force. Ricers don't know it but the bigger their wings get, the more they hurt they're top end speed [like they'll ever get to experience that anyway].

------------------
'91 Firebird
305/TBI(L03)/700R4/T-tops
Mods: Catco high flow cat - B&M Shift kit - TA tail light conversion - K&N - White faced guages on the way
Stereo: Pioneer DEH-P8200R - Pioneer 6x9's - Kenwood 8" Tube

'87 Firebird
2.8L/MPFI/700R4/220K
Twas a good car until the accident.
Firebird parts

Red Devil

This is the Bernoulli principle and unfortunately is not the reason airplanes crate lift, nor the reason spoilers work.


------------------
"The people always have some champion whom they set over them and nurse into greatness... This and no other is the root from which a tyrant springs; when he first appears he is a protector.
-Plato

Red Devil

Pianiy,
BTW what the hairy hecjk happened to the '87? Looks like someone purposely t-boned you? Some one blow a light and smak ya? Does not look like a pretty hit!

Vader

Pablo,

I thought John's car was a Formula, not a T/A. Thanks for the info.

Incidentally, the concensus is probably correct - factor "ground effects" do very little even at higher speeds. On the other hand, enhanced factory ground effects can really suck you down hard:



With the rear of the car open, the downforce is notably better than with the factory "decorations". Top speed is also lower, since some horsepower is wasted on the vacuum created under the car.

------------------
Later,
Vader
------------------
"No matter how hard you try you can't stop us now"
Adobe Acrobat Reader 4.0

Red Devil

How did I miss this?

Vader, what did you use to fab up the skirts? And how were they attatched? Thx!

------------------
"Perfection is a trifle dull. It is not the least of life’s ironies that this, which we all aim at, is better not quite achieved."

-W. Somerset Maugham

Vader

RD,

The extensions on the skirts are a dense closed-cell EPDM/polyvinyl foam, attached just like the factory effects were connected - with plastic push fasteners. I haven't lost one yet at triple-digit speeds, but I did lose a little top end. I used to get spooked at about 110MPH because the car felt light, but this cured that problem. I still have about 2" of ground clearance at the front, and the rubber compound is flexible enough that it will yield without breaking on some of those low approaches.

------------------
Later,
Vader
------------------
"No matter how hard you try you can't stop us now..."
Adobe Acrobat Reader 4.0