thanks for the links... 1" vertical fin is the takeaway huh?

if true, wonder if there's any use for those 0.45" vortex generators I bought?

Who knows, maybe our boundary layer is thinner because our cars are so slick. :rofl2:

Feel like doing some tuft testing?

Awesome articles Chips! Thanks for the links!

Now, if we could only find some wind tunnel photos of a stock 370Z...

fun reading... don't know if you guys actually read through all those links but I'm going through now... friday night for married guys! any event, you'll notice from the excerpt below that the 15mm height when using a delta wing style vortex generator is within ~10% of the coefficient of lift benefit of the 25mm height... in other words, the VGs I bought should work fine... clearly on the EVO this test came from it was the right decision to go with 25mm... and I'm curious what 35mm would have looked like - unfortunately they didn't test it... but 15mm gets me 90% of the way there

I suspect we also have a tighter boundary layer vs evo, given our less steeply slopped windshield and overall better aero, which would just reinforce the choice to get a smaller VG than used on the EVO

Just finished reading all of the links myself. Very good stuff in there. Making me re-think my front air dam now too...

I do think that the Z's shape can probably get away with a shorter VG, but now I am wondering if the VGs are even going to make any positive difference at all.

even more disturbing... our car is a wing! look

http://i656.photobucket.com/albums/u...ingoverlay.jpg

I'm kidding with that last post btw!

Some of my (poorly educated) theories

- nissan was right to put the spoiler lip on the back... exactly because of the picture above... if they didn't there would be a lift effect of higher pressure below car vs above

- my car has a rear diffuser... I actually want the air to stay "attached" on the rear deck lid and to then flow under the rear wing... it will theoretically then "re-attach" with the high speed air coming from the rear diffuser and the air coming out of the rear diff cooler box... I want all that to be as laminar as possible to minimize drag... I also want all that to hug the surface of the rear deck lid to avoid having turbulent air come in contact with the wing... that part I can be certain of... goal is to get high speed 'clean air' to the wing and keep all the turbulent air associated with roof and boundary separation 12" below the wing

- therefore I need VGs at the rear roof

- therefore I need VGs on the rear decklid

What I don't know... do I need VGs on the front wind splitter? do I need VGs on the leading edge of the rear diffuser?

You may have been kidding, but you've hit the nail on the head haha. All cars are shaped like wings....the airplane kind that generate lift. Any object that has more surface area on one side vs. the other will create either lift or downforce, the side with the less surface area sees the pressure. If you flattened the surface area of the top of a car it would be much much longer than the bottom surface area which means pressure builds under the car and pushes upward creating lift. An airplane wing is designed the same way where the top half has a longer surface area than the bottom. An automotive wing is basically flipped upside down so the pressure is a downward force.

That being said, sticking the laminar air flow to the back of the car for a longer period of time actually creates more lift. So there's a trade off at some point. In one of those links they use the example of a modern VW bug which is a perfect example of aero fail despite the laminar flow of air over the rear sticking all the way to the license plate basically. As far as the rear diffuser goes, the vertical fins are basically VGs. Going back to the length of the surface area thing, rear diffusers slope upward and the fins help air stick to the surface creating a longer surface area on the bottom of the car so it better equals the top of the car basically producing negative lift, not so much downforce.

right makes sense... in fact, I've been thinking about extending my rear diffuser out another 6" now that I don't have aero restrictions... I'm also, as I pointed out on my journal, going to try and craft an under-tray... I'm sure that will be a lot of trial & error!!

btw, I'll point out for folks that are interested in this topic, the author of the previously linked articles wrote another article three days ago... here

AutoSpeed

hey one more thing sticking in my head... I head a world-known PhD in aerodynamics look at my car believe it or not about 1 year ago... he told me to try and minimize the boundary gap coming off the rear deck and keep it attached so that it would join the air coming off the diffuser... he said it would make the diffuser more effective... obviously runs counter to the car as upside down wing theory, but I remember he was adamant about it... brain hurts!

Mike, when doing the actual run, how about running without the air filters?

Also the rear quarter window I always wanted to have someone make a subtle duct for that area and channel it to the vaccum ducts in the trunk!

like these?
http://i656.photobucket.com/albums/u...amCLI_5513.jpg

and some you can buy here
http://www.uniqueautodepot.com/Nissa...dy-p/13020.htm

What are these trunk vacuum ducts you speak of?

I am sure there is an exception to the general rule I just don't know what it is. I would go with the experts. I am guessing the benefit of doing that would outweigh the negative. If there's one thing that I have learned in my very short and very basic gathering of aerodynamic knowledge is that there aren't many things out there that don't have some sort of trade-off.