Heat soak - vented hood options that are not "louvered"

Originally Posted by Alstann

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. 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.

Originally Posted by dmhenderson

Just turned out to be more complicated than I thought it'd be.

Originally Posted by dmhenderson

Edit:



...and it turns out this is a non-functional scoop - ugh. Is there a hood that looks like this or the old 350z vented hood style? I've been told modifying the stock hood (even with a fantastic metalworker) is a bad idea for several reasons.

Any ideas?

Originally Posted by luigi90210

if you cut a hole in your hood right where the hood scoop sits, you can technically turn a fake hood scoop into a real one

Originally Posted by dmhenderson

Well I'd need to make sure it would be functional first. Consensus here seems to be that the scoop shown in that picture wouldn't do much (if anything)

Originally Posted by dmhenderson

Well I'd need to make sure it would be functional first. Consensus here seems to be that the scoop shown in that picture wouldn't do much (if anything)

Originally Posted by synolimit

Maybe that's why I stay cool too. Forgot I put maybe 3/4 a gallon of Moore Cool racing fluid in (left over from doing my WRX) and a bottle of water wetter.

Originally Posted by synolimit

Maybe that's why I stay cool too. Forgot I put maybe 3/4 a gallon of Moore Cool racing fluid in (left over from doing my WRX) and a bottle of water wetter.

If you don't drive in the winter or live in a below 32 degree state, 100% distilled water and water wetter works nice like in my 600cc SS.