Hey guys. Wanted to try and get an educated discussion going for those people who are looking for aerodynamics on their Z's.

Can we try to compile a list of aero parts and the actual downforce it generates?

 

Do you know what's involved in generating downforce numbers?

 

in for this. im contemplating putting a full underbody diffuser similar to the gtr's with the exhaust piping exposed for cooling

 

That was one of the driving forces behind this. I would love to figure out what the TS diffuser and Voltex diffuser would generate for downforce.

 

Very few aftermarket companies perform wind tunnel testing on their products and even fewer if any publish the results of their tests.

 

Voltex's kit for the z33 is wind tunnel tested. As I would imagine everything from Voltex is. What those numbers are, I couldn't begin to tell you.

 

The top secret diffuser was not wind tunnel tested, but the Voltex was.





Read this thread, they discuss in great detail everything you want to know, start on page 11:

https://my350z.com/forum/forced-indu...ch-1-a-11.html

 

Dont waste your money, read the quote i posted above, and the thread for more answers as to why it is not necessary.

 

Correct about Voltex. Those pictures do not show their newer "street" version front bumper that they sell. I would imagine them being tested as well, but I have not seen proof. I also believe that same car runs the newer bumper. ( I could be wrong about last sentence )

 

i dont have a gas tank or rear exhaust on my cars underside. so theres lots of room for air to go, those 2 areas would be the most crucial for me to block off. but im a newb to this aerodynamic stuff so any input ill take

 

i can possibly make this easy for you OP.

At what speeds will you be requiring downforce?

Are you drifting? Can you get entry speed up over 80 mph at all in your areas course?

IF not, aero downforce of even a very large functional wing will be null.

Here are some tidbits of information.. im not the expert.. mi not getting into debate.. if you try, ill jsut not answer.. BUT here arre some things to nibble on.

"In racing cars, a designer's aim is for increased downforce, increasing grip and allowing for greater cornering speeds. (Starting in the mid 1960s 'wings', or inverted airfoils, were routinely used in the design of racing cars to increase downforce, but this is not ground effect.) Substantial further downforce is available by understanding the ground to be part of the aerodynamic system in question. This kind of ground effect is easily illustrated by taking a tarpaulin out on a windy day and holding it close to the ground: it can be observed that when close enough to the ground the tarp will suddenly be sucked towards the ground. This is due to Bernoulli's principle; as the tarp gets closer to the ground, the cross sectional area available for the air passing between it and the ground shrinks. This causes the air to accelerate and as a result pressure under the tarp drops while the pressure on top is basically unaffected, and together this results in a net downward force. The same principles apply to cars.

The Bernoulli principle is not the only mechanic in generating ground effect downforce. A very large part of ground effect performance comes from taking advantage of viscosity. In the tarp example above neither the tarp or the ground is moving. The boundary layer between the two surfaces works to slow down the air between them which lessens the Bernoulli effect. However when a car moves over the ground the boundary layer on the ground becomes helpful. In the reference frame of the car, the ground is moving backwards at some speed. As the ground moves, it pulls on the air above it and causes it to move faster. This enhances the Bernoulli effect and increases downforce. It is an example of Couette flow."
http://en.wikipedia.org/wiki/Ground_effect_(cars)

without getting into a crazy fluid dynamics calcualtion, basically one would need to force the air traveling between the ground and the vehicle moving forward to squeeze thru a smaller and smaller space to increase the speed of the air, thusly creating the pressure differences to suck the car down to the ground more.

UNdercarriage covers that start out with airfoils in front and back willsurely do this.. but onemustthink.. at wht speeds?

cars that have these features are rated to far FAR over 100 mph operation... and thats where this comes into play. DOnt knwo about yal, but i dont go over maybe 110 tops anymore.


JDM stuff fools us all into thinking canards help out driving on US FWYs.. id say no. You can feel a wing on yor car at 65 mph.. big time. Especially if you rock a gurney flap. But hats different. Its a reverse airfoil, and its wing load area is GIANT. Plus everyone jacks up the airfoil angle on them anyways..

but for aero kits, undertrays,and actual ground effect aeros... i think we gotta go back to the fundemental issue.. we drive 25k nissans that lucklily drive well and look rpetty cool.

BUt.. thats about it.



"Automotive aerodynamics is the study of the aerodynamics of road vehicles. The main concerns of automotive aerodynamics are reducing drag (though drag by wide wheels is dominating most cars),[citation needed] reducing wind noise, minimizing noise emission, and preventing undesired lift forces and other causes of aerodynamic instability at high speeds. For some classes of racing vehicles, it may also be important to produce desirable downwards aerodynamic forces to improve traction and thus cornering abilities.............
..........Automotive aerodynamics differs from aircraft aerodynamics in several ways. First, the characteristic shape of a road vehicle is much less streamlined compared to an aircraft. Second, the vehicle operates very close to the ground, rather than in free air. Third, the operating speeds are lower (and aerodynamic drag varies as the square of speed). Fourth, a ground vehicle has fewer degrees of freedom than an aircraft, and its motion is less affected by aerodynamic forces. Fifth, passenger and commercial ground vehicles have very specific design constraints such as their intended purpose, high safety standards (requiring, for example, more 'dead' structural space to act as crumple zones), and certain regulations. Roads are also much worse (smoothness, debris) than the average airstrip. Lastly, car drivers are vastly under-trained compared to pilots, and usually will not drive to maximize efficiency.

Automotive aerodynamics is studied using both computer modelling and wind tunnel testing. For the most accurate results from a wind tunnel test, the tunnel is sometimes equipped with a rolling road. This is a movable floor for the working section, which moves at the same speed as the air flow. This prevents a boundary layer forming on the floor of the working section and affecting the results. An example of such a rolling road wind tunnel is Wind Shear's Full Scale, Rolling Road, Automotive Wind Tunnel built in 2008 in Concord, North Carolina."
http://en.wikipedia.org/wiki/Automotive_aerodynamics

More on ground effect... but for an airplane...


"Principle of ground effectWhen an aircraft is flying at an altitude that is approximately at or below the same distance as the aircraft's wingspan there is, depending on airfoil and aircraft design, an often noticeable ground effect. This is caused primarily by the ground interrupting the wingtip vortices and downwash behind the wing. When a wing is flown very close to the ground, wingtip vortices are unable to form effectively due to the obstruction of the ground. The result is lower induced drag, which increases the speed and lift of the aircraft while it is in the ground effect.[3][4]

A wing generates lift, in part, due to the difference in air pressure gradients on the wing surfaces: both upper and lower. During normal flight, the upper wing surface experiences reduced static air pressure and the lower surface comparatively higher static pressure, these air pressure differences also accelerate the mass of air downwards. Flying close to a surface increases air pressure on the lower wing surface, (the ram or cushion effect) improving the aircraft lift to drag ratio. As the wing gets lower the ground effect becomes more pronounced. While in the ground effect, the wing will require a lower angle of attack to produce the same amount of lift. If the angle of attack and velocity remain constant, an increase in the lift coefficient will result,[5] accounting for the "floating" effect. Ground effect will also alter thrust versus velocity in that reducing induced drag will require less thrust to maintain velocity.[5]

Low winged aircraft are more affected by ground effect than high wing aircraft.[6] Due to the change in up-wash, down-wash and wingtip vortices there may be errors in the airspeed system while in ground effect due to changes in the local pressure at the static source.[5]"
http://en.wikipedia.org/wiki/Ground_effect_in_aircraft

its even weirder in a helicopter.. i posted all this becuase i was JUST talking to a helicopter pilot about all this stuff a month ago during my flight home to AZ, we looked at pictures, charts etc.. he was a marine, now trainign for heli pilot, had a test on his ipad.. we basically both tookk the test..was kinda fun.



I believe the issue you have with most cars and race cars that use an undertray are this.. ( thikn F1 car) ..

the reverese airfoil is really what is creating the down force to plant the tires on the road. Thers a large reverse airfoil over the power wheels, and theres a very low reverse airfoil at the leading edge of the car to aid in steering pressure at speed. if these cars were 100% flat onthe bottom and thats it, well, all it would take is a bump to lift that wing up and viola, you now have a airplane car that will catch lift from oncomming wind forces at speed and flip that car up into the air like a racing boat.. weve all seen those crash videos.

so the issue is to create that panel to deal with ground effect and bernoulli principle and to divert air over it as well to create a pressure differential to allow the car to NOT lift, versus create downforce. Ferrari 360 etc.. its flat on the bottom, but air goes thru that whole car over that panel as well.

Cd makes a differnece on drag, propoising and lift at speed,and surely has something to do with downforce as well, but again.. at what, 130 mph?

Aside from the diffuser plates under the front and the giant wings you can buy to go over the rear, i doubt theres any available ground effect bumpers, skirts or aeros for the 350z production car that will have large advantageous changes to the cars handling or down force.



Either my post will add some cool links for ppl to read and check out, or it will bore ppl to pieces and theyl run away, or people will beocme anbgry and post back in an epic fight.


either way, doubt theres much benefit to buying an INGS kit versus OEM etc.

 

ha in the time it took to write my novel, tons of similar post.
well fawk it, at least we all god something to keep us busy for a bit w this thread.

sure beats talking about headlights n wheel spacers for sure. haha/

 

^ Jesus bro

Agreed.

 

cut n past my brotha..
cut n paste.

but i did get gangsta w it and added links as references.. thats gangsta still right? Or am i out of the loop.. haha, jk.

 

Epic post lmao! I've got my BSME so this really intrigues me. I do realize that most people wont be pushing their cars far past 100 unless they are tracking it. I did find it interesting that at just under 80mph the Nismo 350z generates as much downforce as it does. I thought it would be far lower than that. As to Mr. Bernoulli and his principle, I do know of one car that "changes shape" as it goes faster to create more downforce, the Veyron . As to my intentions for the car? Mainly street driven with occasional track use.

 

http://www.aprperformance.com/index....sk=view&id=181

Info on the APR race wing for the Z. You can also find a lot of good aero info over on timeattackforums.com

I'm in the middle of installing a Nismo V2 bumper , adding a front splitted (about 2 inch forward and boxing the ends) , V2 sides , V2 rear add ons and an APR GTC-300 wing.

 

that gtc 300 wing is major. were talking big downforce startring at speeds of even like 70 mph. If you run at a big drift track or autocross, youll feel that thing all day long. Video of guys going thru redonk-fast corner entries are all over youtube too.

the undertray stuff and all that is totally different tho... for epic and major high speed driving.. certainly nothing an autocrosser or a drift guy will ever see haha. OR you will ever be able to pull off in Vegas hee hee. I can see this JDM crazy aero stuff w canards etc being cool in tokyo where everyone drives at 140 mph to keep from getting nailed by cops..

That wing is ILL tho. in retrospect i should have bought it instead of this goofy and pointless Elia wing, but i wanted to be a little different i guess. DUnno we shall see.

 

It could be possible (if the downforce on the front and rear are known) to calculate a spring rate that compresses at a certain speed to decrease airflow under the car therefore creating more pressure over the top increasing the overall pressure the car feels as it is going faster. Sorry if that didn't make sense.

 

read:
Competition Car Aerodynamics: A Practical Handbook, 2nd Edition by Simon McBeath
ISBN-13: 978-0857330079

and

Race Car Aerodynamics Designing for Speed, by Joseph Katz, Ph.D
ISBN-13: 978-0-8376-0142-7


then come back.

 

x100

If you have any interest in aerodynamics this book will give you what you need.

Read the book, lots of examples on lots of cars to give you an idea on numbers.