Heat extractor hood

[Mtrhd329]

It will certainly not be negative pressure. On a car with a squared off nose, the farther forward you go on the hood, the better chance you have for negative pressure.

so where would be an optimal position for a 73-87 c10 be? Close to the front of the hood or as far forward as possible on the hood while still being behind the radiator.

[sccacuda]

I'll throw in my $.02. I look at the car backwards, sort of. The hood area is a huge surface area that has air pressure pushing on it, downforce. The windshield then becomes a deck spoiler of sorts, so yes, high pressure air. The transition from hood to windshield will provide high or low pressure depending on it's angle (great place for Vortex generators if seeking high pressure and using more of the windshield for downforce). When you take away hood area for ducts, your losing front downforce potential, no way around that. So the duct needs to perform a function greater than the downforce forfeited, or alternative means of adding front down force needs to be introduced, i.e. splitter, dive planes, etc... Then the question becomes how to merge the air from the duct to the high pressure air on top of the hood. The wicker lips in front of the ducts seem to "kick" the air up, leaving a lower pressure area from the duct, allowing the airstream to merge more easily, and possibly create a vacuum effect on the duct. My only concern with having these too far back with a wicker is losing the downforce on the windshield. The air is kicked up and hits the windshield at the middle or top. If I had to chose a hood duct, I personally like the idea for the rear hood exits, exhausting in the low pressure area at the windshield base, as not to disrupt airflow or give up too much downforce. Exhausting from the sides of the car seems a better alternative, as it doesn't give up downforce or disrupt airflow, but probably not very practical. With all that said, I too am extracting from the hood!! I played with all sorts of ideas and designs, and in the end I chose a compromise of aesthetics and function. That should be the name of my car! I'm using the shaker bubble as the extractor vent, and leaving the front vents open to allow air "through" to create a venturi effect. Not sure if it will function that way, but that's the plan. As you can see, keeping the acres of hood downforce!

[dontlifttoshift]

Where is there low pressure at the base of the windshield?



I have no science but.....isn't it likely that the pressure entering the front of the shaker will be higher than under the hood? That will not allow air to escape from under the hood at speed.

If you vent high(er) pressure air from under the hood to the top of the hood in an area of low(er)pressure with a properly designed lover, would there not be a net gain in down force?

[j-c-c]

Where is there low pressure at the base of the windshield?

I have no science but.....isn't it likely that the pressure entering the front of the shaker will be higher than under the hood? That will not allow air to escape from under the hood at speed.

If you vent high(er) pressure air from under the hood to the top of the hood in an area of low(er)pressure with a properly designed lover, would there not be a net gain in down force?

I agree pressure at base of windshield at speed is normally positive. I also think the spoiler analogy has merit, and a big cause of this high pressure area. I also raise an eyebrow on the comment that the hood, in its entirety is a DF generating surface, not normally on our type of cars from what I know. The easiest least effort for extractor location determination is driving 70+? mph with as many tuff yarns taped onto the area in question as you feel the effort warrants and get some idea whats happening at the surface and where, for starts. Use a go pro to spice it up.

[Mtrhd329]

In comparison to the radiator opening how much larger or smaller should my extractor vent be? I am thinking smaller will cause the air to speed up coming out of the engine bay and help join outside air at the same speed? Thoughts?

[medbali76]

I am thinking to put trackspec product ( http://trackspecmotorsports.com/shop...d-louvers.html ) on my 72 Nova hood. Any idea where would be the best place to install to get the best results?
My cowl went grille panel was blinded also to get a little smoother look so that is the other reason I want to install these vents.
Thanks