Glad you guys like it!
I've done the tuft testing on other cars; both the Volvo (big-ish turbo, over 400 wheel HP) and the Bug (2275cc's) are vented with good, measurable results. So I wanted to go a step further on the Montero since there was more real estate on the hood to play with! <img src="/forums/images/graemlins/wink.gif" alt="" />
In someone else's words, this is the concept I was working with: the nose of the car, and the base of the windshield, are higher pressure. The center of the hood is lower pressure. The "prop" at the back of the hood creates a gap at the fender which extends more than half way down to the nose of the car. So while the base of the windshield and the nose are high pressure, the center is canceled out - and this is where the heat will gravitate out the vent and the side gaps. I will do some "real" testing (with numbers) when I can, but I can tell you I have seen enough difference already...and once I install the extra oil and trans coolers I have sitting here, that would more than offset any situation where the vent/gaps might not work as efficiently. It might run TOO cold, actually, so I will have to wait until I can monitor temperatures a little more accurately!
Summary, as you drive faster high pressure builds up in front of the nose of the car (in front of the radiator/intercooler), decreases just as the nose flattens out (think 6 inches after your radiator), then builds back up as it approaches the windshield. In order for any heat exchanger to work you want high pressure in front of it, lower pressure behind it, for the directional movement of the air across said heat exchanger. A hood scoop will dump air into your engine bay, increasing it's pressure, which in turn will decrease the pressure difference across your radiator (albeit small unless you seal the bottom of your engine bay) reducing the effectiveness of your radiator. What anyone would gain from that, I don't know, you'd have to vent that extra pressure somehow and for most of us it's directly under the car, just like before your hood scoop except now you've increased drag, decreased the effectiveness of your radiator, all for a small reduction in under-hood temps...
I would have done "pretty" louvers, but I neglected to mention...this truck was totaled when I bought it, and it already had a mismatched black hood. I don't have the time, money or patience to make it look like an OEM fitment, so this was just fine for my intents, purposes, and budget...the grill was $14.97, and the paint was $3.97. Grand total was well under $40 and under 2 hours of work. <img src="/forums/images/graemlins/kewl.gif" alt="" />
