What does a diffuser do??
 

I know it looks cool to have a rear diffuser on your Z but can someone please tell me what a rear diffuser does. Thanks

A rear diffuser is supposed to add downforce, and on a race car, it does. However, I doubt the add on diffuser for the Z does anything to the aerodynamics. I suspect it for looks only.

Les

None of the diffusers for our cars are tested through data(wind tunnel etc....). Im not sure if it helps our cars are not

im sure the top secret one for example protects rocks from hitting your exhaust lol

read the top 100?s.

diffuser on any car when placed correctly will improve under car airflow. based on the theory of venturi, where a constant volume of air when moving will move faster through a smaller opening than a larger one. so when added to the bottom of the car and using the grnd as the other side of a channel, if u angle a diffuser near the rear axel, air flows faster at the axel creating a lower pressure zone, which will suck the rear end of the car down (granted again, placement and angle of this diffuser as to maintain air flow attachment to the surfaces...)

ive used the ts diffuser at the track i think it allows air to be prevented from being trapped in the rear bumper due to the design of dual
canister designs.

a good book is racecar aerodynamics. look it up on amazon.com

joseph katz i think is author...

Cheston is on the money... not the best explanation but I'm sure he never took aerodynamics.

The venturi effect... is newtons third law of motion. The increase in the velocity of a fluid (yes air is a fluid) is directly proportionate to a decrese in the fluids pressure. If you increase the air's velocity under the car by the use of diffusers you are decreasing the air pressure. You are not necessarilly creating a pressure lower than atmospheric, but one that is lower than the pressure on the upper surface of the car (the body) creating downforce. The Z has no working diffusers available for it.

adds more rasp and hp.

(This is from what I remember watching a special on the GTR and the Z... I forgot what show maybe BM)

The Z was designed to have very little downforce near the rear (or was it zero lift in the front.. i forgot). For what reason, I don't know. But the show compared (the downforce) of the Z and the GTR in a high speed ring... I'll try to find the video...

i remember seeing the same thing

A diffuser will create downforce if applied correctly, but as turismo pointed out, if the diffuser is not wind tunnel tested, like the majority of diffusers out there, it's most likely purely for looks.

Even if the design of the diffuser good, the downforce that it creates needs to work in harmony with the rest of the aero pieces on the car. Again, without wind tunnel testing, it's nothing but looks.

Expensive looks

i agree with the looks on a street car since you really do not need downforce when commuting to work

Just because it wasn't put threw "wind tunnel testing" doesn't mean it won't create downforce.

True dat, but just because someone comes up with an asthetically pleasing design doesn't mean it will produce the correct balance of downforce if any at all. That's why objective wind tunnel evaluation is essential for any practical use.

Plus - Those gawdy defusers kinda fall into the catagory of "Saladbar Wings, Rice, etc" since it attempts to make the car "look" faster than it really is. If it had some actual functional purpose on the street, I'd be all for it.

no aero pieces are going to produce any kind functional effects for street driving

The literature states that the Nismo Z creates functional downforce as low as 70mph.

But yes, for typical street driving, it does not make a difference.

Not true... I go 120mph on my street every night... and my front splitter and rear wing adds LOTS of downfarce.

a diffuser will also lighten the weight of your pocket

LOTZ huh? How many pounds of downforce does LOTZ equate too again? I don't think that one ever got covered in Physics class. Lol~

I'm pretty sure this is what your feeling, Mr. "120 every nite" Speed Racer. Lol.

Heheheh... that's why I said downfarce... ayee..