Gearhead1

When the vast majority of F-Body owners talk about making their cars faster, they talk about doing it with more HP or torque, less weight, or less rotating mass. All of these are fine, but what have any of you done as far as aerodynamics to help your cars slip through the air more efficiently. Are there any "free mods" as far as aerodynamics are concerned?? Has anyone (not necessarily on this board) done any wind tunnel testing on the F-Bodies to see what works and what doesn't?? I drive a '98 Z and always wondered how much aerodynamic drag was created by the headlights hanging out in the breeze. (Unlike the hidden headlights on the 'Birds) Surely there are some tricks being used by some of you to help out your MPH a little. C'mon guys, 'fess up.

Ferretts

Let's hope W2W chimes in with ther .02... THey are the ones that build the serious drag cars

Farfignuten

The reason most have not focused on this is because the aerodynamic drag is a minor factor below 100mph (the speeds at which most drive). As your speed increases the aerodynamic drag increases exponentially, however, this is only a real concern for those with extremely high mph trap speeds in drag racing or high speed road racing. Most on here do not worry about this.

You may also find it funny that most race vehicles have a higher coefficent of drag than road going cars. This is because they sacrifice drag for downforce to increase the normal loading on the tires. I have read that F1 cars can have upwards of a 0.70 Cd depending on the track and wing adjustments.

Gearhead1

Thanks for your prompt responses. Are there any F-Body specific wind tunnel tests that you are aware of where the test results are available to the general public?? Anything online, maybe??

chuntington101

yes 100mhp is classed as the starting point for wings to start making "downforce"! but drag still still happens at lower speeds!

one good way to reduce it is a flat floor on the car! it not to difficult. most racers just put a sheet of ally on the bottom of the car. on a normal car you can get air actually traveling forward under the car! this drag slows the car down. a fllat floor gets rid of these.

Chris.

Jassick

iTrader: (1)

so how much trouble would it be to flat floor a f-body? and would you see any significant effects?

lt1camaro95

i heard a rumor about covering over the fuel tank and muffler area with sheet metal to smooth the bumper area out. That area is a parachute.

wabmorgan

The F-body cars are one of the most aerodynamic cars on the road today. I remember seeing the IROC races with the Trans Ams and they said the only way to draft with these cars was to be about 6 inches off the rear bumper of the car in frount of you due to the cars being so areodynamic.

I can only imagine minor improvements without a redesign, maybe in the next generaton cars. (Although, judgeing from the concept Camaro, this seems unlikley. It seems GM has decided that retro styling is more important than aerodynamics. I'm not saying they have railgated aerodynamics to the trash can, but I can't imagine that the concept Camaro is more aerodynamic than a 4th generations Camaro nor espically the 4th generation Firebird/Trans Am.)
Areodynamic cars have a low nose and raked windsheild. I remember reading somewhere that the most areodynamic shape that had been researched was a "tear drop" at about .05 Cd.

On a more pratical note... I remember several years ago when Pontiac came out with the Areo Trans Am. Part of the package was some flat wheels covers that covered the wheels. (No holes.... bad for brakes though.) The Aero Trams Am had a Cd of .29(Third Generation car.) I think the fouth gens would be even lower considering their lower windshield rake.

chuntington101

you can take it to then Nth degree (as some do) and tape up all the holes opn the car! but i think a falt undertray with a diffuser at the back and a low spliter will make a big diffrence! whatyou want is really fast airflow under the car and slower ontop. this gives you down force!

also you could think about venting the rad out through the bonnet (instead of under the car) this will help reduce lift also.

Chris.

300bhp/ton

As others have said it has little affect at the 1/4 mile. From what I've heard speeds below 120mph aero drag is not 'usually' a major factor. It's only at high sustained speeds that it becomes an issue.

But it also depends what angles you are looking at. If you want a very slippery shape that has minimal resistance you can't have good down force, and there a lack of stability also.

Take the Thrust SSC land speed world record car, it has masses of downforce which creates drag. But this drag allows stability and control at speed which is just as crucial (provided you have the power). Where as the "Spirit of America" car was more like a sleek missle. Very little resistance but also a lot less control.

So if you're aimming at 200mph in your Fbody, then smoothing the airflow over and under the car is important as is lowering the car to minimise the amount going under it.

But also remember CO drag is a pretty pointless number unless it's combined with frontal area. CO only lets you know how slippery a shape is, but frontal area is often more important.

Take a house brick for instance, it has a very poor CO due to being completley flat. But it's frontal area is much smaller than that of a car, so it would require less force to move it thru the air.

As more proof aerodynamics arn't as important when drag racing (excluding top fueles, funn cars and such) is that boxier vehicles such as Mustangs, saloons (sedans) and even pick up trucks can all acheive good ET' and trap speeds without the need for a massive variation in HP over more slippery looking vehicles (remember to exclude weight in the case of the trucks as this does require more HP and is not relative to aerodynamics).

If you want a more detailed look at aerodynamic principles (all of which apply to Fbody's) click the link in my sig.

Zeus

I heard the complete opposite. I heard that when Ligenfelter did aerdynamics testing of the F-body platform, they discovered it was actually more aerodynamic going in reverse then going foward. They concluded aerodynamically it was too much of a pig and switched over to the Y-body platform for their new program instead.

v7guy

iTrader: (1)

the F-body is about.35cd I've seen reports + or - .01 either way. It does have the most raked windshield of any production car to date.

A flat pan under the car will very likely send it airborne if it hits a decent bump, think of the bottom of the car becoming wing like.

The biggest things you can do to increase aerodynamics of the car is a front airdam that touches the ground that eliminates the air going under the car. Above 170 a rear diffuser makes a significant difference.

smaller contribution are a vent for underhood air after the front breather conversion, fender venting, brake cooling, transmission cooling differential cooling etc.

If you are the average drag racer none of these mods will make much of any difference, spend your money else where

chirp_fourth

You have a few factors affecting drag.

Drag Coefficient
Frontal Area
Rolling Friction

The drag coefficient of a 4th gen fbody is right at .35 and frontal area is around 20'. Rolling coefficient is around .002-.004.

To reduce rolling friction, keep your wheel bearings greased up and in good condition, reduce your tire width to the minimum that you need, and run a smooth/quiet tread tire. Wide sticky tires or tires that whine do nothing but suck energy. Unfortunately most of us need them (at least on the rear). This has the most effect at low speeds, but is in no means comparable to the drag force exerted by wind resistance at high speed.

You can't reduce frontal area very easily without hacking up the body. However you can stay away from big wings on the back, or tires that stick out of the fender wells, or exhaust that hangs way down off of the car. All of these increase area and increase the drag coefficient.

The coefficient of drag can be reduced by keeping everything tucked in as good as possible. The idea above about keeping the undercarriage buttoned up by paneling it up is probably the best thing to do. Also straightening out the air as it leaves the rear of the car will reduce the drag coefficient. Turbulent air flow creates more drag than laminar air flow. Check out the GT cup cars. They have air straighteners on the bottom of the rear bumper. I think the new EVO has a faux air straightener (although it might work a little) on the rear of the roof of the car.

As far as performance goes, on an average 12 second car that traps at 110, reducing our drag coefficient by 15%, to .30, would give us 1 extra mph and reduce our 1/4 time by .05, which is equivilent to adding ~10rwhp. As far as reducing our drag coefficient by 15%, I dont what all it would take to get that, but I'm sure it would take a LOT.

To me, it doesnt make sense to go to these lengths for minimal gains.

Sparetire

The Evo has "Vortex Generators" on the roof right where it tapers down to the trunk lid. They are said to reduce lift quite a bit in the auto mags Ive read. They look like a cosmetic thing, but they work. You actually see then on airplane wings a lot.

The cheapest thing to do would be to duct tape the hols in the car wherever you can. Nascar will tape over areas of the grill even if they are ona fast track, as the car gets all the airflow it needs with small openings at those speeds.

The next best thing IMHO is to use some lawn edging to make a airdamn up front. These actually a how too on this for DSMs :www.vfaq.com. You spend like 20 bucks and probably eliminate a lot of air under the car.

20 bucks and some duct tape for a quarter mile an hour and a few thousandths at least is not bad. The home and garden airdamn is not only effective, it actually looks pretty good too.

Other than that I guess lowering it would help a lot too.

I wonder how much drag the hood scoops and ra air stuff adds. My guess would be a lot for the Ram air, its a big lump right where the shape of the car is critical.

NataSS Inc

iTrader: (9)

If you are drag racing an air dam will be the single biggest improvment aero wise you can do. You can expect to pick up a tenth or two and 3-5mph in the traps. This also has alot to do with the frontal area of the car. We recently did this to my friends 63 Nova II that runs mid/low 11's. He picked up 2 tenths and 4mph by just adding an air dam and making no other changes.

But if youre looking for sustained high speed stuff, its starts getting more difficult balancing things when you need downforce for stability but dont want to give up to much speed. Air dams, belly pans, diffusers, mirrors, high pressure zones etc. 98+ camaros have a drag cd right at about .34 and the T/A's are slightly better at about .32.

chirp_fourth

So you think a bone stock lt1 fbody, that went 13.90 @ 101, would go 13.70 @ 106, from adding a body kit featuring a huge air dam?

You might wanna restate that.

N20LS1

If you are drag racing an air dam will be the single biggest improvment aero wise you can do. You can expect to pick up a tenth or two and 3-5mph in the traps. This also has alot to do with the frontal area of the car.

NataSS Inc

iTrader: (9)

No I dont need to restate it.

I also said the car we tested this on was a much faster car. A stock LT1 car that cant even trap over 100mph will see "some" improvement (but possibly not even noticable). Once you get OVER 100 mph air managment is something that can be tweaked to show gains.

I also said
The more air you can keep from going under the car the better off you are. The problem with the late model Fbodies is that they are bottom breathers and to make an EFFECTIVE air dam for one you have to convert the car to a front breather.

wabmorgan

The aerodynamics of the F-body are well known. I doubt very seriously that a corvette is signigantly more areodynamic than a F-body. The new C6 is rated at .29 Cd. That is no better than the third generation Areo Trans Am. It is a tie.
Considering the 4th gens Firebirds/Trans Am have an even steper windshield rake than the C6 or a third gen Firebird, they would have to be more areodynamic.

Lastly, there would be no reason for anyone to run an areodynamic test in reverse!!!!!!!

Jassick

iTrader: (1)

um, no.

yes, no reason to run it in reverse, unless the car spun out, and started to go in reverse, which i believe is what happened in the test that was referenced.