zeitgeist

Curious about effective angles for diffusers/canards/spoilers. Looks like everyone just puts stuff on without thinking about this

Sleepy_Steve

Ya'll need to go to an ALMS (now Tudor) race and just snap ungodly amounts of pics of the prototyles and their dive planes / diffusers / splitters / belly pans if you can see them..... Just figure they've scienced most of this out, so its a good pool to pull ideas from and learn from.

__________________
'95 240 | @SleepySteve72

Otto347

Lol I've been doing stuff like that for years. Photograph suspension and all kinds of things to get ideas. They have money to burn for r&d on that stuff.

__________________

crzsteveo

they have definitely put some effort into scientifically testing all aspects of it.

There are ssssooo much articles and websites online explaining about the size, angles etc and how much it affects air pressure around the vehicle. ive been researching more along the lines of time attack cars to see if I can tie those designs into a road car, for like high way speeds.

Its sucks because its all a balancing act. you lower your car and increase the angle of your front splitter towards the ground more, by doing so you increase down force creating more grip but increase the drag and change the air pressure around your vehicle.

what I want to accomplish with my car is creating that balance of air moving around my vehicle and kill that turbulent air that sits behind my hatch.

if you have a smokey car you can see this just by driving. the smoke curls and spins around the taillights and continues to do so without going anywhere.

I think that's because the low pressure going under my car and the high pressure going over my car and around, are moving at different speeds or created turbulence somewhere else along my car causing a whole mumbo jumbo type shit.?????

Z_Spool

Yup... that's pretty much the long and short of it.

__________________
-Robert R.

ehhhregartless

RE style diffuser with some strakes might get you in the right direction

__________________
www.zeedakay.com
IG: @zeedakay

Bushido

__________________

crzsteveo

Bushido thank you!!!

Def

The guys on ecomodder don't know near as much about aerodynamics as they think they do. Although every once in a while they do some interesting stuff.


3 degrees is NOT the ideal diffuser angle, especially when you have a compound divergent upper surface (a boat tail), that is working the airflow as hard as it can. Which BTW, flow is NOT attached to the rear hatch window on a stock S13. It separates 1/3-1/2 of the roofline back from the front windshield. Boundary layer is around 3/8" at the start of the rear hatch, and grows quite a lot from there. Vortex generators will reattach it, at the expense of drag. Your rear aero determines if attached flow is worth it.

So to sum it up, they're working the air over the top of the car extremely hard, with really aggressive divergent angles, and then say 3 degrees is the ideal rear diffuser angle? That's completely crazy. You can easily go to 6-8 degrees and ensure you won't have separation in a diffuser if you're expelling to a low presssure area (i.e. the rear bumper), and probably even if you completely boat tail the rear (higher pressure at the diffuser exit). But really, even diffuser angles of 10-12 degrees can work when pumping to a low pressure area, but at that point, you probably need to start considering the 3D effects of the flow like how it's coming in from the side skirts and around the rear suspension area.

For the average car here, you could easily do a 7 degree diffuser and be fine. But I would not even think of bothering for a street car. You probably won't feel much of a difference unless you get a big splitter, flat bottom leading to the diffuser, and wing. The splitter and wing do most of the work, the splitter pumps more air out the underside of the car and makes the splitter and underbody produce more downforce. Just putting a diffuser on the rear doesn't really help much just because there's not a nice large area of attached flow to accelerate and get a benefit of.

And BTW - the stock S13 gas tank actually makes a halfway decent diffuser, but the angle is a bit steep at the end, bordering on 12-15 deg by my measurements.

__________________
S13 Hatch - Goes around tracks quickly
DEFSPORT

ehhhregartless

^Ideally, sector times should change on a given track between the turns and straights. Turns should be faster because you're able to put down all the power that you make with max grip. And straight line speed would go down a bit. But not enough to negate the gains from the turns. Yes, overall your gains would eventually become less and less after which you'd adjust and add power.

__________________
www.zeedakay.com
IG: @zeedakay

OBEEWON

^^^

__________________

ehhhregartless

At 4:35 is what i was trying to explain. The whole video is definite worth the watch.

http://youtu.be/v_767VQBFi0

__________________
www.zeedakay.com
IG: @zeedakay

ehhhregartless

__________________
www.zeedakay.com
IG: @zeedakay

ehhhregartless

__________________
www.zeedakay.com
IG: @zeedakay

ehhhregartless

__________________
www.zeedakay.com
IG: @zeedakay

kognition

Looks great!

kognition

GST Motorsports driver Jeff Westphal reset the all time track record at ButtonWillow at the recent GTA/SLB time attack event this past November. They use our 76" span chassis mount kit for the GC8.

Xplat

Figured this video belongs here.

https://www.youtube.com/watch?v=quDLzxmJl5I

ehhhregartless

That's a very informative vid, definitely learned a lot from it. Looks like I'll couple that with this DIY for aero testing/development in the spring

http://www.autospeed.com/cms/article.html?&A=108656

__________________
www.zeedakay.com
IG: @zeedakay

crzsteveo

^same here. that's definitely the best alternative to a wind tunnel

crzsteveo

I love time attack cars.

http://www.youtube.com/watch?x-yt-cl...-ts=1422411861

ehhhregartless

__________________
www.zeedakay.com
IG: @zeedakay

voiddweller

Thank you!

The summary you put together pretty much sums up all the research I've been doing over the past several months and should definitely be 'stuck' for the benefit of the community.

__________________
97 S14 SE w/S13 Blacktop
04 CL9

ehhhregartless

__________________
www.zeedakay.com
IG: @zeedakay

ehhhregartless

__________________
www.zeedakay.com
IG: @zeedakay

NISSeAN

I generally don't like body kits but the GP sports looks awesome and functional

ehhhregartless

^2nd, one of my favs

__________________
www.zeedakay.com
IG: @zeedakay

ehhhregartless

__________________
www.zeedakay.com
IG: @zeedakay

silviasandbeer

cliff notes.. add canards
cool vid ehhhhhregardlessssss

https://www.youtube.com/watch?v=Pgpawejpi6o

__________________
IG: @3SoulXX
"I never fucked a ten. But one night, i fucked five twos ”

voiddweller

Interesting video!

__________________
97 S14 SE w/S13 Blacktop
04 CL9