It makes no noticeable difference in temps. The vent is under the oil pan. You could cut a vent further up.

Correct.

Wait the fender thing is the vents installed in front of the tires? Then a modded fender in the back? Yeah that's going to do nothing for engine bay heat even with a hood vent/scoop.

The scoop is pretty much a non-starter. The potential for messing up airflow is too high without a ton of research. OEMs that use scoops have wind tunnels to use. Since we don't, were stuck with vents. Even if the vent isn't 100% dead on in the right place, it will still make a positive difference as long as its placed as far forward as you can get it.

True. But like you said, it's really all we have to work with, with the little room we have. I haven't done scientific testing but the yarn seems to flow how I want and I haven't been able to exceed 218 degrees on the oil with hard driving for like an hour straight on fast twisty country roads in the middle of summer . Next summer when the tracks open we'll see whats what. But I'm hoping Mitsubishi and Chevy did the work for us and hell the evo doesn't have much room either...

That and when stopped the heat pours out like a volcano!!! Its insane how fast and how much comes out. So in traffic you'll be much cooler.

My guess would be a vent in front of the motor and upgraded radiator and fans are going to be about all you can do.

I think I'd go look for bigger radiator fans before I try to upgrade the radiator itself. Space comes at a premium under there these days.

I did the radiator, and before next summer ill swap out the fans. At least in TX it seems like you need to do both. If that's not enough its time to start cutting into the hood.

I know my hood displaces a ton of heat during the summer.

I'm sure they do but I don't like those louvered vents on the Z.

Never fails that when I start one of these threads, I end up with more questions than I had when I started.

My 2c here:

I think that hood venting is the way to go for serious heat soak issues. It's a uphill battle trying to fight the motor by adding a larger radiator and higher CFM fan if the air is still getting trapped in the engine bay. I'd say that if you can live with the look of a louvered or vented hood, it's easily the best way to improve cooling efficiency of the car.

From a theoretical and practical standpoint, there are limits to using a combination of radiator and fan to cool a motor. One is the size aspect - larger radiator and larger fan is less space in the bay, and there is a limit to how large we can fit of both. Also, CFM doesn't necessarily mean cooler temps.

At my university, we build a small Formula-style car a competition hosted by SAE, called Formula SAE, and I'm part of the engine design team. It's a competition where universities build the car from the ground up - chassis, intake, exhaust, suspension, etc. For reference, the engine we use is a GSX-R 600cc. Google has lots of pictures of different cars - you'll get the idea if you search it. ^^

Something quite astounding that I've discovered while doing design on the cooling system is that the car (moving at an average of 30-45 mph on the track) is actually moving too FAST through the air, for achieving maximum cooling efficiency across the radiator. The solution to this problem is to design a sidepod (like the ones you see in Formula 1) that goes from small to big, back to small. This is to slow down the air. Of course, our motor is directly to the atmosphere, mounted in the rear.

The reason for this efficiency loss is as the air moves too quickly through the radiator, it builds up pressure behind and in front of the radiator, creating a boundary layer that lowers the true amount of air moving through the radiator. One might say: Why not use a higher flow fan to create a vacuum and move the air better? There are two reasons on a car: the first being that you want the air to spend a certain amount of time "inside" the radiator (not too slow where it's stopped, and not too fast that it creates the boundary layer), and second being that in most car engine bays, the bay is sealed enough that pressure builds up regardless. These speed values are different for every car, radiator design, hood design, grille design, etc.

But, of course I concede that a larger radiator and higher CFM fan usually increases cooling efficiency. I just know for a fact that venting the engine bay will, unless you are on the surface of the sun, always increase the cooling efficiency by letting nature do its work by letting heat escape. Also, with a larger radiator and larger fan, you also add weight to the car, and you change the dynamic of the water flow through the radiator, since the water pump is still stock. The reason we shoot for maximum efficiency, while still maintaining a reasonable safety factor, is literally, because racecar. :D Any amount of extra weight that isn't necessary in design, is making the car slower.

Also another thing to think about is that turbulent air and turbulent water through the radiator actually increases cooling efficiency. :tup:

You're failing to factor in the intercooler into that. With the additional flow restriction from the intercooler, not to mention the fact that now you're feeding hot air to the radiator, a larger radiator and a more powerful fan may just be getting you back stock efficiency.

Do those fancy vented fenders I see all over the body/exterior section help at all?

Not one bit for underhood temps.