The S2000 I picked up 9/1999 has an opening in the bumper at the upper license plate area that is covered by a removable metal plate. Later model S2000s do not have this slot. I have removed the plate in hoping I will allow air to escape from behind the bumper through this slot, as if that will happen and hoping that will make a positive aerodynamic difference.

 

Another thing to consider on a diffuser.

From what I have read the diffuser if it is at an 8-12 degree angle increases the downforce without increasing drag as a wing does.

 

No, I never saw your diffuser. Though my understanding of the aerodynamics is obviously not complete, I imagine installing your diffuser would probably help. That is, assuming it was designed in conjunction with the rest of the car. I don't think just an arbitrarily-shaped diffuser could be tacked onto a car and develop good results. Also, is it heavy? Might be another thing to consider. If it was designed to go on your car, I'd say go for it. Adding the diffuser could allow you to dial in less rear wing (making less drag) without losing downforce. This kinda ties in with what David b said, and the reasoning is this:

When a wing is used to generate lift/downforce, you get high pressure on one side of the wing and low on the other. When you get to the tip of the wing, the high pressure air tries to roll over the tip to the low pressure side. This results in vortices forming at the tip of the wing. These are sometimes visible in F1 races in high humidity locations (e.g. Brazil) b/c the vortices are very low pressure. Low pressure --> low temperature --> water vapor condenses, making "fog". Airplanes get em too...they're unavoidable. These big vortices cause drag because all the air in the vicinity has to flow around them. This is called "induced drag," and will always be found when lift is generated by a wing. (Incidentally, this is why wings on race cars (and some airplanes) have endplates on them...the end plates help inhibit the rollover of high pressure air to the low pressure side). A diffuser, I believe, will not have this induced drag since the low pressure air is contained inside/under the car, so no vortices are generated. Hence, you can get increased downforce without increased drag. Plus, if the diffuser smooths out some of the turbulence behind the car("filling in the void"), that will further reduce drag. Whew, that took longer than I expected...hope it makes sense.

 

[QUOTE]Originally posted by Prolene
[B]The S2000 I picked up 9/1999 has an opening in the bumper at the upper license plate area that is covered by a removable metal plate.

 

My office just got a digital camera, so I hope to be able to post pics in a few days.

 

[QUOTE]Originally posted by Tedow
[B]Can't be. Conservation of mass says mass flow in must equal mass flow out. Mass flow = density * velocity * cross-sectional area. If we assume density is constant (ok assumption, given the relatively low velocities --> air is incompressible) that leave V1 * A1 = V2 * A2. Area increases towards the rear of a diffuser, which means A2 > A1. Therefore V2 < V1. The flow decelerates.

 

Crap, you're right...the pressure peak is right as you enter the diffuser. In the diffuser itself, the pressure is increasing, just as my initial thoughts indicated it should. How'd I miss that? Well darn that kinda shoots my rapid-volume-expansion theory to hell. Now I'm confused again . So the presence of the diffuser is causing the air to accelerate just before the entrance. Why is that? I need to ponder this some more...