Aerodynamics discussion

[plucas]

Originally Posted by puma

just finished reading the whole thread, really nice, but in the end, nothing really came out of it, not product available or no conclusion to what woud be ideal for our cars?


any drawing or pictures of what would be the ideal wing or diffuser for our car? Same for front lip or are there things that can be improved on?


what do you guys think of the box on the Griffon where it takes the air out of the rad and sends it through the hood vents?

Ideal: Nothing can be ideal unless you have a specific use for the car. Even say it is a 100% race car, you would run different setups at different tracks. You want to find something that works for the application you use your car in. Will it be ideal, NO. Will it be better than stock, YES.

Air out of the radiator ducted out of the hood is better than out the bottom usually. Depends on lots of things.

[puma]

yeah i understand that but i mean there hasn't been many things that were found out wrong with our cars that X modification would help in pretty much every scenarios.


Maybe ideal isn't the right term but what would theorically be the best out of the available options and why. This is a pretty vague question, i'll try to ask some more specific things


My questions are all for building a race car by the way so we can go all out in the solutions.


We just started thinking about what we could do to help with the aero on our cars and this is why i am making research as i know nothing about it.


We are currently aiming at doing the same thing as the Griffon with having the air from the rad coming out the hood, in theory that would be a good idea?


1-What could be done to get the air out of the engine bay?


2-in the picture above, you can see the inner fender, we took those out on our race car, are they usefull in term of aero, theorically, good or bad to take them off (not considering the obvious mud that can enter the engine bay we don't car for that)


3-read that the base of the windshield is a high pressure zone, would putting something to cover up that part (removing the wipers) and making a better flow from the hood to the windshield help?


4- some people do holes at the base of the rear window on their lexan window, does it actually helps taking the pressure out of the cabin or does it hurt too much air flow over the car to actually help? (this is a hard one, doubt anyone ever tested that)


i'll have more questions later but don't want to overload the thread

[puma]

here is an other one, on our previous race car, i decided to make a hole behing the license plate and covered it up with loovers for aesthetics. My plan was to make an escape route for the air that enters the car (we have to run without windows so lots of air coming in), considering the rear of the car seems to be a low pressure zone, i suppose this modification must have been good?

[SkAsphalt]

Originally Posted by Malt

@plucas

Given that you've done loads of aero testing, in your opinion is there any benefit to these TRD parts or are the purely cosmetic?

This fills the gap between the rear window and the trunk lid.


How about the TRD style lip spoilers?

Super late reply but these help smooth out air flow. Just a little bit. Hence "spoiler"

[humdizzle]

i'll add my 2 cents.

most aftermarket aero is bunk. These companies dont have wind tunnels to test the product. Just because something 'looks' like its aerodynamic doesn't mean that it is. if you want what works look at what race teams are running.

[ame="http://en.wikipedia.org/wiki/Automobile_drag_coefficient"]Automobile drag coefficient - Wikipedia, the free encyclopedia[/ame]



Case in point:

The GTR has a better drag coefficent than a porsche 911.. despite looking like a giant transformer. It also generates 176 pounds of downforce at both front and rear axle 186mph. By comparison a 997 carrera generates 60 pounds of rear downforce at 180 and actually LIFTS on the front axle. the ferrari 458 makes similar numbers to the porsche. front end lift and very little rear downforce... google 'sport auto' tests if you dont believe it.

Its very very difficult to have both a low drag coefficient AND generate downforce. By adding spoilers, wider wheels, cooling systems you increase the drag alot. You'll see most sports cars on that list are > 0.30 while most economy cars (especially hybrids) are nearing 0.20 cD.

But most of all you have to remember that in order to achieve any reasonable downforce you have to be going in excess of 100-120mph AND turning to feel any added grip.

[humdizzle]

[ame="https://www.youtube.com/watch?v=e21ZjwZGjiQ"]Le Mans 1999 - Peter Dumbreck's HUGE accident! Mercedes CLR-GT1 CRASH! - YouTube[/ame]

[ame="https://www.youtube.com/watch?v=Si6mHFgkN_Y"]Nissan GT-R Flips into crowd at Nurburgring race 2015 - YouTube[/ame]

[ame="https://www.youtube.com/watch?v=Zxe_DqAkeAk"]EKanooRacing's Lexus ISF Twin Turbo Crash - YouTube[/ame]

[ame="https://www.youtube.com/watch?v=wJF06ZP7U2s"]Le Mans Car Flip and Crash - YouTube[/ame]

[Shankenstein]

If we're looking for meaningful takeaways, there are a few things that most people can agree upon:

- flat and smooth bottom
TRD Griffon got this right:


- low and long front splitter
This is dependent on your application and suspension setup. The goal is low without scraping.


- rear diffuser
This reduces the vehicle's wake, and the updraft effect can be enhanced with a trunk lid spoiler


- rear wing
This adds downforce, but you need to design a setup that has a direct load path to the frame. TRD Griffon uses a carbon lid, which transfers the downforce better than flimsy sheet metal.


- remove engine bay and wheel arch pressure
Giving the (relatively) high pressure air an exit can usually be done in a way that doesn't add lift and improves cooling in those areas.

[stevesnj]

I'm going simple, underbody panels, trunk spoiler(5Axis) not OEM wing style, and rear diffuser. I am lowering the car with TRD lowering coils so the front splitter may not be doable. Sometimes these simple things help and if I get .5 to 1% MPG increase that will work since it will be a DD.

[Gunman]

Originally Posted by humdizzle

But most of all you have to remember that in order to achieve any reasonable downforce you have to be going in excess of 100-120mph AND turning to feel any added grip.

Air doesn't car how fast you are going, it's going to start affecting the moving body as soon as it starts to move. How much it affects it, is roughly a square function, ie 2X the speed you get 4X the downforce. So it is true you get more affect the faster you go, but size of wings, splitter, dive planes, etc., affect how much you get and how soon. If you look at the current FSAE cars, most never see 60mph, but the better teams are running full aero cars.

[churchx]

Sometimes i wonder why no vendor yet released full underside aero kit (thinking of like for trd griffon). Imho it should be simple to design/make (at least if middle is modular with cutouts for different most popular aftermarket exhausts, or with templates for cutouts to be done DIY), and i guesstimate there would be market for such. Especially if some might use it as cheaper alternative to partially covering OEM underside panel set of higher trims missing for eg. USDM frs.

[troek]

Originally Posted by churchx

Sometimes i wonder why no vendor yet released full underside aero kit (thinking of like for trd griffon). Imho it should be simple to design/make (at least if middle is modular with cutouts for different most popular aftermarket exhausts, or with templates for cutouts to be done DIY), and i guesstimate there would be market for such. Especially if some might use it as cheaper alternative to partially covering OEM underside panel set of higher trims missing for eg. USDM frs.

Ive looked into making my own, and it seems you can realy screw up the cooling of the rear diff, and transmission if you dont know what your doing. note the naca ducts under the griffon car. might be more complicated to blank off the entire bottom of the car than it seems.

[churchx]

troek: if that matters that much, one can also think of adding rad to cool diff oil (as i've seen for eg. GT86 CS V3 Cup track cars). Still imho nothing that would prevent making these by vendors. If even having or not stock underside panels slightly affect mpg (if that is any of criteria to judge aero efficiency ), then imho full/even flatter one should do even better, easing high speed for underpowered NA.

[lamawithonel]

Originally Posted by Gunman

Air doesn't car how fast you are going, it's going to start affecting the moving body as soon as it starts to move. How much it affects it, is roughly a square function, ie 2X the speed you get 4X the downforce. So it is true you get more affect the faster you go, but size of wings, splitter, dive planes, etc., affect how much you get and how soon. If you look at the current FSAE cars, most never see 60mph, but the better teams are running full aero cars.

Also why cars setup for the relatively slow, switchbacking hill climbs tend to have such huge aero elements. Their straight-line speed doesn't matter as much.

[churchx]

Low weight/high power needs aero to add grip, especially on such gravel. Imho we don't see that big wings in several other motorsport areas like WRC/F1 only because these days their maximum size/area is limited by regulations, not because teams chosen to go for lesser ones.