GT WING AND AERODYNAMIC QUESTION AND ROOF SPOILER W/GT WING POINTLESS?

[po_bo]

HI! I HAVE A 1995 NISSAN 240SX, I HAVE FULL AERO BODY KIT READY TO INSTALL AND PLANNING TO GET FRONT SPLITTER AND REAR LOWER DIFFUSER, BUT I WANT TO GET REAR WING NOW, AND WAS LOOKING AT SOME OF THEM, PLANNING TO GET A 2 DECK GT STYLE WING, BUT WHY THE TOP DECK IS SHORTER THEN THE BOTTOM ONE? HOW DOES HAVING 2 DECK WORKS BETTER COMPARE TO SINGLE DECK ONES, AND NEW GT WINGS NOW A DAYS ARE CURVED AND HAVE A HUMP UPWARD AT THE MIDDLE (SEEMS LESS SLOPE, LESS DOWN FORCE)? DOES IT REALLY INCREASE MORE DOWN FORCE WITH THE HUMP IN THE MIDDLE OF THE WING AND HAVE IT BEING CURVED COMPARE TO TRADITIONAL STRAIGHT FLAT GT WINGS? OR JUST GETTING A FACTORY KOUKI S14 SPOILER IS GOOD ENOUGH?

ALSO ABOUT ROOF SPOILERS.... IS IT POINTLESS TO ADD A ROOF SPOILER AFTER I ADD A GT WING? BECAUSE THE SPOILER SPOIL THE AIR MOVEMENT RIGHT AT THE END OF THE ROOF PANEL, BY THE TIME IT GET TO THE REAR WING THE AIR MOVEMENT IS DISTURBED OR DIFFUSING AND THE WING WILL NOT BE ABLE TO DO ANY EFFECT? OR SHOULD I MOUNT THE WING HIGHER?

I KNOW I MAY NOT MAKE ANY SCENE OR SOUND STUPID BUT I'M JUST STARTING TO LEARN HOW AERO WORK AND WANT TO MAKE SURE I'M MAKING THE RIGHT CHOICE, SETTING IT UP RIGHT SO THAT IT FUNCTION, NOT JUST SITTING THERE AND LOOK RICEY, ANY INPUT HELPS! I KNOW NICO IS THE RIGHT PLACE TO FIND ANSWER WITH THE HELP WITH ALL SERIOUS MEMBERS, THANKYOU!!!!!!!

[NismoRacer34]

uh, your caps lock is on...

And i might be wrong, but it seems to me that the items you are looking at are not functional. Roof spoilers are most often for looks only. The wings, if functional, should have a curved surface almost like an upside down airplane wing.

I don't know what it is that you do with your car or what kind of power you are making that you would need 6 different forms of downforce.

[raw0330]

I guess I'll start with the rear trunklid spoiler.They're only functional on the s14 chassis either within 2-3 inches of the roof height, or iirc 16 inches or so behind the rear of the trunk to catch the aerofoil. Factory spoilers are aerodynamically useless.

Roof spoilers, such as the Origin style ones are only for asthetics and shade, but can actually interrupt airflow to a functional spoiler. The only functional ones are generally splitters--ie evo or sti. Their function isn't to add downforce, but to smooth air flow to a spoiler. In rallying because the car spends so much time sideways, it helps keep downforce consistent from the rear.

The splitter under the front bumper is supposed to do exactly that. Split the air between under- and over-car. Splitters work most effectively when under car air flow is also controlled. Front downforce is usually determined by bumper design and adjusted with canards.

While you mentioned aero, thought it might be worth mentioning side skirts are only effective with approx. ONE inch of the ground.

[seang]

Now you can hit 160+mph on your way to work and not have to worry about flying off the road.

[2_Liter_Turbo]

I guess I'll start with the rear trunklid spoiler.They're only functional on the s14 chassis either within 2-3 inches of the roof height, or iirc 16 inches or so behind the rear of the trunk to catch the aerofoil. Factory spoilers are aerodynamically useless.

Roof spoilers, such as the Origin style ones are only for asthetics and shade, but can actually interrupt airflow to a functional spoiler. The only functional ones are generally splitters--ie evo or sti. Their function isn't to add downforce, but to smooth air flow to a spoiler. In rallying because the car spends so much time sideways, it helps keep downforce consistent from the rear.

The splitter under the front bumper is supposed to do exactly that. Split the air between under- and over-car. Splitters work most effectively when under car air flow is also controlled. Front downforce is usually determined by bumper design and adjusted with canards.

While you mentioned aero, thought it might be worth mentioning side skirts are only effective with approx. ONE inch of the ground.

You are incorrect with a few points. First the Evo/STI roof "spoilers" do not smooth out the air, they actually cause turbulence. This will increase the amount of skin friction of rear of the car allowing the air to cling to the car's surface longer and separate farther down the air stream than it would with no roof spoiler. The reason why this is useful is because it causes less of a pressure difference (which causes drag) between the front of the car and the rear of the car. It also allows the rear trunk spoiler to be more effective as streamlined air is now lower due to the later separation point of the airflow.

As for the rear spoiler, the effective height of a rear spoiler all depends on the separation point of the airflow over the car (see previous paragraph).

Rear splitters just streamline the air underneath the car causing less drag. Front splitters will cause downforce (as will front canards) and side skirts help streamline the air.