300bhp/ton

Maybe that's more to gearing than aerodynamics. Personally I'd say my 2.73 geared Z28 pulls really well upto 140mph, then slows a tad to 145-150mph and upto the 158mph limiter but it's still pulling hard, certainly doens't feel like an aerodynamic brick wall just an electronic limiter.

MadBill

[QUOTE=FastKat]I'll confirm that too. (At least on the 2nd Gen Camaro) I adjusted the back of the hood up as far as the hinges allowed and taped bits of yarn along the rear edge. At any speed I drove, they were all sucked into the engine compartment.

JamesO WS6

So if I fab a skid plate with say some air difusers at the rear. I will need to let air out of the engine compartment on the top of the car. Which would create more downforce. Have I understood this correctly?

BTW, no one sells skid plates or belly pans for F-bodys do they? I have seen them for GTO's...

slick1851

This is very pop to do with 240SX,Skylines(yes I know), Civics and older Bimmers and RX7s will do this its still around and it works.

slick1851

The best and easyest thing you can do wich is PROVEN, is to make a under body diffuser. Look under a NSX look under a skyline and highend sports car and race car, it makes the under belly flat aslo making a Rear diffuser to let air out he back etc

There is alot more that I know but most peole are going to flame me, but the Japan market is huge for these kinds of aero parts since they do alot of circet and highway racing.

Look this up guys, people have made them for there DSMs and ive seen a handfull of road racing camaros use this.

chuntington101

a rear diffusre is the to act like a rear wing! it causes low preause as the same volume of air ahs to acomodate a much larger volume! this reduction in presure caauses the down force!

its the flat underbodies that help with air flow!

Chris.

MadBill

Speaking of flat bellies, here's an article on how to build your own:
http://racingarticles.com/article_racing-25.html
and another on aero tips in general: http://racingarticles.com/article_racing-52.html

Louie83

iTrader: (3)

Correct. It is solar powered so it will not reach a high speed. Regular cars, on the other hand can reach a high enough speed that if they were shaped like this, they would leave the ground.

You know how an airplane must reach a certain mph before the wings create enough lift and can leave the ground - same thing would happen with that tear drop shape.

TrendSetter

i always heard 3rd gen f bodies were more aerodynamic than 4th gen. i believe they are both shorter and narrower, which equates to (quite a bit?) less front area.

Vettish

The C5 measured 0.293cd in the wind tunnel, the lowest of any production vehicle made.

Bombguy99z28

I'll call

cd for various production cars

SSCamaro99_3

iTrader: (1)

The best cD I can get for a 4th gen is .338 with 22 sq/ft of frontal area. the 1991 GTA was .31x-.32, and the 1984 TA was .29x. I cannot find a frontal area for a thride gen, but I bet it is less.

Vettish

(In north america)

Xtreme57

iTrader: (6)

Everyone keeps talking about "front air dams" and "rear diffusers" for F-bodies .... Does anyone actually make these things for our cars?? Any pics or prices?


Great topic btw.

MadBill

So with its miniscule drag and low frontal area, if we can rescue a GM EV1 from the crusher and swap in say a 500 HP LS mill with a 2.0:1 rear gear, it should be good for around 300 MPH?

wabmorgan

The T/A was .33 and only the Areo T/A was .29 and that we with the flush mounted wheel covers!!!!!!!!!!

So for your comparison it would be a tie... with one exception the 4th gens have fatter tires and that also adds to the C/d drag equation.

MadBill

For what its worth, they did some really questionable stuff to get that 0.299 Cd on the '84 TA. Besides the grill plugs, those Fugly "bowling ball' hub caps and such, they ran the smallest wheels and tires with the lowest released springs, etc. on the test vehicle and loaded it to GVW to reduce the effective frontal area while basing the calculations on the frontal area at normal ride height..

Old SStroker

Evidently there was still some Smokey Yunick ideas running around in the halls of GM about 20 years later.

To be fair, 'most everyone takes advantage of all the loopholes when trying to get numbers to advertise. Anyone ever add air pressure to the drive tires on a Dynojet for a before-after test on a magic engine part?

Hey it beats the (sometimes) outright lying about "Advertised Horsepower" from the old days. That went both ways, of course....lower as well as higher.

HPP

Interesting thread.

Re: tricks for measuring Cd for advertising - we can assume they are all doing it, right? That kind of gives us a common ground (of sourts). So it doesn't mean that the '84 T/A is in truth much worse than the C5, as they are close under ideal conditions, so too must they be close under normal conditions. In fact, the C5 might lose more ground in normal trim from the wider tires it has.

Re: windshield rake - this would only be a factor in cases of all else being equal, and then it would largely depend on the rear of the car. 4th Gen Firebirds and Trans Ams are much more hourglass shaped. That's not going to be as good as the more cylinder-like sides of the 3rd Gen. Add to that the wider tires and wings that I suspect are more effective on 4th Gens, to say nothing of the extra holes on the front, and it's no real surprise that the 4th Gens end up with a higher Cd than the 3rd. Despite the windshield. (IOW - rake isn't all that important, unless you're talking about an flat wind screen on a Model T or something)

Re: Diffusers and hood venting - they don't create downforce so much as they reduce lift. Remember, downforce is only pressure over and above normal rest pressure, and that is almost always reduced when moving at any appreciable speed on almost any car. The cleaner (aerodynamically) the car, the lower that pressure (on the traction patches) is.

Look at it this way, a teardrop shape is the most aerodynamic shape, right? With cars, we have to lay it on it's side and hack half of it off to make it flat on the bottom. What you end up with is an aerofoil shape. Like this -


That's more or less teardrop shaped, and laying on it's side. Like a teardrop, with 0 Angle of Attack, it will generate 0 lift and move straight (because each side is counteracting the other). But.... cut it in half....


and you end up with a shape that will create lift without a positive AoA.

Front and rear spoilers/wings are used to counter this, but all you're really doing is just reducing lift. Adding a diffuser will provide some of that bottom shape, and drastically reduce lift, while also reducing (not increasing as someone mentioned) the negative pressure area behind the car, thereby increasing aerodynamic efficiency.

As for hood vents, again, they don't create downforce, just reduce lift. As the underhood area fills up with pressure, it acts a bit like a hovercraft. Venting that air can only lead to a 0 lift situation, unless you try to seal the car to the ground and use fans to create negative pressure (like that one race car from the 60s - forget it's name now).

MadBill

That was the Chaparral 2J Cam Am Series car in 1970. It used articulated skirts to seal the body to the ground and a snowmobile engine & big fan to draw the air out from underneath. Supposedly at full suck it could have hung upside down from the ceiling...