aerodynamic drag and body style
 

Specifficly 3rd gen Camaro [which is what I am building] especially the drag cause by rear of body shape. What shape or spoiler can help?

Or, since it is 1/8 mile bracket racing, is it a non-issue?

To me, it seems it is important because the last 1/2 of track is over 80 MPH. Also, it you are racing into a head wind the drag will be increased.

Any feedback?

Re: aerodynamic drag and body style
 

Hi Larry,
Aerodynamic drag is a function of both Coefficient of Drag and Frontal Area. Many times shown as CDA. If we keep the Frontal Area constant at 20 sq ft and the speed constant @ 100 MPH. A CD of 0.34 will produce an Aerodynamic drag of 51 HP while a CD of 0.38 will produce an Aerodynamic drag of 57 HP. The amount of Aerodynamic drag HP will increase with MPH and the HP difference between 0.34 and 0.38 will increase with increased MPH.

Stan


PS Maybe a graph which also includes 0.42 CD will show this better.

Re: aerodynamic drag and body style
 

Stan,

somewhere I saw a chart about body styles and aero drag. [may have been your chart]
that chart showed the 3rd gen Camaro with a relatively low COD and the 3rd gen Firebird among the lowest.

I have even considered installing a 3rd gen Firebird ft fenders and facia on my Camaro. Would doing that be worth the effort plus finding a Firebird ft and painting it?

Is the frontal drag the most critical? With rear drag less of an issue?

Re: aerodynamic drag and body style
 

Larry,
Frontal Area is the area that the car has when looked at from the front. You should be able to measure width and height and calculate your frontal area. Google calculate frontal area of a car What year is your car?


Stan

Re: aerodynamic drag and body style
 

The aero package on the 91-92 Pontiac Firebird was reportedly the lowest CD of any GM car . Pontiac was very proud of that fact , and that was in many magazine articles . The frontal area was similar to the Camaro , but the front shape was way different . Rear shape was similar to Camaro , but air was able to flow under the spoiler.

Re: aerodynamic drag and body style
 

Hey Larry watch this video. in this case the front end was a disaster for drag but the most gains were picked up with work done on the rear of the car.
https://www.youtube.com/watch?v=1X35-bGWpEY

Re: aerodynamic drag and body style
 

Some numbers I have.

'84 Firebird Trans Am W62 Aero 0.30
No numbers for a '84 Camaro

'88 Firebird Trans Am GTA 0.31
'88 Camaro IROC 0.34

'91 Firebird Trans Am GTA 0.31
No numbers for a '91 Camaro

Stan

Re: aerodynamic drag and body style
 

non-issue! unless you are running 130 mph in my opinion

Re: aerodynamic drag and body style
 

Seems like a lot of over thinking for an eighth mile bracket car.

Re: aerodynamic drag and body style
 

Lee, overthinking is one of my high skills. And I think overthinking is a common trait for many hot rodders. I point to stockers, got to be one of the most overthought packages ever. However, overthinking often leads to success.

Re: aerodynamic drag and body style
 

Stan,

1982 Camaro Berlinita

Re: aerodynamic drag and body style
 

An 1/8th mile bracket car will only be on the track for six seconds or so and a large portion of the run will be at a much lower speed than finish line speed which would make aerodynamics less important. I agree with Lee.

Re: aerodynamic drag and body style
 

I think 80's Monte Carlo with SS nose has CD of .34.
Question: If a car has more downforce then lift would go be faster if they were made equal?

Re: aerodynamic drag and body style
 

When considering aerodynamics of drag racing cars/trucks, etc. The assumption of aerodynamic drag only has an effect at speed is incorrect.:rolleyes: One can think of the issue becoming important at any speed over 40mph and the aero drag resistance is exponential to the speed very closely following the square law and more. That becomes a lot of free power by cleaning up (legally of course) the aerodynamic drag for the vehicle.:cool: Lots of rules of aero thumb to apply, but it is best to study and learn what can help with the selection of vehicles and how to improve them. An example is: external rear view mirrors cost about 0.6% in drag power.:eek:
Regards,
HB2:)
Dissident

Re: aerodynamic drag and body style
 

also tire width ,fender flares, ground effects ,spoilers, unnecessary openings in the grille area, upward lift attitude of the front end at speed as opposed to downward attitude--elimination of any unnecessary body parts ( mirrors etc.) ---all these affect airflow over under and around the vehicle ---You want to make the vehicle silohuette as smooth as possible ( within any rules restrictions course)--as vehicle speed increases it becomes of paramount importance to consider all of these----look at a jellybean as opposed to a brick and or a Corvette vs. a Van and you will get the idea--- modern auto manufacturers go to great lengths in "styling" their products not only for looks but to achieve the tinyest of drag reductions to increase fuel mileage

Re: aerodynamic drag and body style
 

I remember reading an article by Lingenfelter back in the early 70's.On his S/S 69 Camaro rag the car picked up a bit of MPH using only the front spoiler,and lost using the rear.The car would MPH around 115.In those days you would have to run both (as part of the SS package) or none at all.On my '71 it picks up about a 1/2 a MPH (more in a strong headwind) with the front spoiler...gsa612

Re: aerodynamic drag and body style
 

Larry I ran a 82 z28 with the ground effects and I had a large rear deck wing, car was very stable at 185 mph in 1/4 mile..LOL

Re: aerodynamic drag and body style
 

On a 79 Malibu wagon the factory rear spoiler is worth almost 3mph on car that runs just at 100 without it in the quarter.. and the reason for it is that it pulls air from the roof and routes it down the back window (to keep it clean in civilian life) which fills in the vacuum hole behind the car. and if you're wondering how big and powerful that "vacuum hole" is, it is what the cars that make turns use to create their ground effects downforce in sufficient quantities to be able to drive one across the ceiling upside down. The "vacuum hole" is also the reason behind drafting in nascar, if you can get in close enough it will damn near pull you along... need proof of what good aero can do? How about 174 on a bicycle...peddling.


what you really want to do with the front of the car is to smooth the air and keep it out from under the car, along the sides and roof you need to keep it flowing smoothly, and a the back you need to eliminate the "vacuum hole"...


Jackie

Re: aerodynamic drag and body style
 

You will find here 2 articles to add more details to this post.
https://www.scientificamerican.com/a...es-in-golf-ba/
https://www.grc.nasa.gov/WWW/K-12/ai.../boundlay.html
I also like the FED387 informations regarding the one hand out of a car test... (relate to the coefficient of aerodymanic when the front of the car is more up in the air)
Enjoy,
Charles Stewart

Re: aerodynamic drag and body style
 

The above post gave me the idea to cover the surface of my Camaro with dimples. Maybe use a small ball pien hammer or leave it outside in a Texas hail storm.

Re: aerodynamic drag and body style
 

Back in the day a few stock and S/S cars ran a vinyl roof claiming the pebble on the texture was worth some MPH,however small the gain was.FWIW,Jason Line's Buick GS has a vinyl roof...gsa612

Re: aerodynamic drag and body style
 

Wow, excellent post.

This Chevy II has a All Pro RR 427 sbc we're getting ready to race with a 300hp NOS cheater plate per the rules of DXP Street, the car will be around 140mph 1/8 mile. We have the bumpers off for chroming but we still gotta ad a splitter under the front bumper. I'm more curious about the wake behind the car. Do you know anyone who has added a rear deck spoiler? This is a leafspring 275 radial car with a set of shocks on the back with a two way adjuster on rebound the azz of the car is up at the stripe to keep the nose down, you may have seen this on radial tire cars, not real conventional for drag racing but the shocks help get the power in the car early no wheely bar allowed by rules.

I'm just fishing around for Ideas, I think we can keep the air from under the car fairly easily.with a chin spoiler under the front bumper.

Are these chevy II's known for wake issues? the rear deck is long relatively speaking. I was thinking rear deck spoiler, not sure, looking around for experience with these cars. Would rather no spoiler.

Thanks ahead of time

.https://i.imgur.com/Mv5iQCE.jpg

Re: aerodynamic drag and body style
 

Larry, you have e-mail.
Sorry couldn't get the excel to post here
are you still using the "Woodfinlarry" mail?

Re: aerodynamic drag and body style
 

This car was pretty aero..

Re: aerodynamic drag and body style
 

Sorry no chart

Re: aerodynamic drag and body style
 

ON my Aspen Wagon = a similar class to the Malibu
Wagon.....It slow the car down a MPH with the rear
factory spoiler!

Re: aerodynamic drag and body style
 

Just for discussion purposes.
https://www.youtube.com/watch?v=VUiGhyHC-1A

Re: aerodynamic drag and body style
 

Billy, that's just a justification for not doing body work.

Re: aerodynamic drag and body style
 

Great video and thanks for sharing.

Re: aerodynamic drag and body style
 

Looking at that RMS pic notice the ground hugging stance that the vehicle has---Air going underneath a car is "dirty air" and its trapped in all the nooks and crannies---better off getting the air to go over or around rather than UNDER for this reason---Why do you think NHRA has a blurb in the rule book about no underbody streamlining??? Just for that reason. FED 387

Re: aerodynamic drag and body style
 

Note the difference in the SS legal rear spoiler on my car and the RMS wing.

Re: aerodynamic drag and body style
 

Ever seen an airplane with propellers (vice jet) with a squared off tail? Go to http://www.landracing.com/forum/index.php?board=52.0 for a good discussion about aero.

Re: aerodynamic drag and body style
 

Aerodynamics is a complex subject and the results are dependent in many factors. The dimpled surface acts like a vortex generator and the size and location of the dimple. It is also affected by the shape and angle of incidence as referenced along the axis of the object.

In the 1990's when WJ was racing his Firebird Pro Stock, GM brought his car to the Georgia Institute of Technology and with the assistance of Boeing engineers, they spent considerable time working on the car to improve it. They ended changing the body panels and rake of the car. When Warren showed up at the Winternationals, the car went fast, got protested and ended hammering the quarter panels and putting duct tape.

If you want to see the aero effects, just tape wool strings to the body and take pictures and video. Done this in the past in airplane projects I had worked on and even Chrysler did so with the Mopar Missile in the early days of Pro Stock.

https://www.allpar.com/photos/racing...tests/pits.jpg

https://www.allpar.com/photos/racing...s/plymouth.jpg

Re: aerodynamic drag and body style
 

Damn I hate to put a flat wing on a factory condition 66 Chevy II.

https://i.imgur.com/btMqKPL.png

Re: aerodynamic drag and body style
 

Here we go, I run a 3rd Gen Camaro in Stock which sometimes is pretty fast. Built the car from scratch from a street car disassembled pretty much completely then reassembled as a legal stocker with stiff chassis and weight bias advantage etc.

These cars are bottom breathers if you must run a flat hood. Was never in doubt about keeping the air dam under the radiator to keep air flow and pressure in front of the radiator to assure fresh air flow to the throttle body. Use your imagination to take advantage of this with a carb, the fast guys already know. Some advise received from a very experienced racer was to seal up the area from air inlet/grill to the front of radiator area to not allow it's escape from the front of the radiator would help aero, and may help fresh air to the TB/Carb.

Another benefit of running the lower air dam (just my theory) is that it will help speed air flow under the car (along with lowering the body) not having as much getting caught up the open areas under the engine and flowing more smoothly under the trans & floor pan, can't do much about the rear axle area.



Hope this helps.
Thanks to Ray Valpreda for his thoughts and info expanding my thinking.