actually, it means that the disc is not solid. if you were to look at the side (edge) of the disc you would notice that it is actually two discs sandwiching vents between them. Kind of hard to explain.

 

I think you are confused between "vented" and "cross drilled" or maybe even "slotted".

"Vented" means there are fins/spacers in the center of the disk that separate the two faces. You won't be able to see them in pictures.

"Crossed drilled" are when you have small holes at a diagonal in the rotor facing itself. Those you can see easily.

"Slotted" are small cuts in the face, also at a diagonal.

All are ways of dissipating heat

 

It's been said that it can weaken the rotor. Will only make a heat difference if you take it tracking. The best all around heat diffusion is vented with slots.

 

Another problem with Cross-drilled is it is difficult (or maybe impossible) to get them turned, leaving you having to buy new rotors when the current ones get warped. I have Powerstop crossdrilled rotors on my 300 and they stop pretty well and I can notice a difference in brake fade between the stockers and the drilled. Still not perfect, the car (300ZX) needs bigger rotors to be any more efficent in fade, and im so glad the 350Z has huge rotors on the standard and track models.

 

Heat dissipation is not the reason for slotting or cross drilling disc brake rotors.

The biggest reason is that brake pads w/ asbestos lining material can become fluid (not solid) at high temperatures and in that case there is truly no pad to rotor surface contact. To counteract that phenomena, slots or drills are used to carry that fluid away from the friction surface. The 350 Z Brembo brake pads do not contain asbestos and therefore do not need to be slotted or drilled.

Truthfully, more metal volume in the rotors can dissipate more heat since the brake rotors are "vented" in the center section. The brakes would not perform any better with the specified calipers and pads due to venting or slotting. Those would be completely aesthetic modifications. Most likely, brake fade would increase if you slotted or drilled the rotors because of less material with less heat sink.

 

So stopping distance/performance between the standard and track brakes should be about the same in normal driving (not at the track)? I thought perhaps the Brembos would stop better with the 4-piston calipers in the front. Of course I don't know too much about brakes.

 

C&D reported that the Brembos probably won't decrease individual minimum stopping distances compared to the stock brakes which are actually very adequate.

The main differences will be in stopping distances from high speeds and in decreased brake fade with prolonged high performance (track) use.

That's where the Brembos will make a difference.

 

Cross drilling increases the surface area of the rotor exposed to air, which will enhance its ability to expel heat, especially while in motion.

Just make sure the rotor holes are chamfered, to reduce the chances of cracking to a minimum.
Also make sure the rotors you are purchasing were CAD plated AFTER the holes were drilled, to minimize the possibility of rust.

 

This is my understanding of what vented brakes are.