a simple test can prove this, someone just tape a thermomater(sp) to the top of the fire wall, drive around, come back, do the hood prop thing, then drive around again and see if temps change. it might work, hell i'd try it myself when i get bored but it's winter here and probably won't work aswell.

edit: pg tree pWnage

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by redzcstandardhatch &raquo;</TD></TR><TR><TD CLASS="quote">

nobody said ALL the air will go down... most flows nicely over the windshield. BUT. there is a pressure area at the base of the windshield. this is a true statement.

there is positive pressure at the back of the hood, causeing air to want to enter that area. there is also however, slight positive pressure under the hood at speed, causeing air to want to escape. </TD></TR></TABLE>

agreed. which is why hood spacers work.. at high speed, air would want to vent out of the raised area.

air will flow from the front bumper, and out the vented area. i can't see it trying to flow against the law of physics.

 

I didn't want to get involved in this because noone believes anything anyone says on the internet anyways, especially H-T, but here are my thoughts and everything I've learned from all the Fluid Flow classes I've taken.

There is definitely a pressure buildup at the base of windshield, in a swirling motion. We are not in ****** imaginary land where there are frictionless surfaces, so when the wind is transferred from the hood, to the window, there is a "bottleneck" there to cause flow to buildup creating the swirling motion.

This would allow a car with ITB's to take advantage of denser( and cooler air since it came from outside the engine bay) IF THE SWIRLING IS LARGE ENOUGH.

Now the faster you go, the less the friction will affect the flow of air over the windshield therefore bernoulli's principles start to take effect and therefore the air rushing over the hood/windshield will actually pull air from the engine bay (through molecular entrainment), which means more air will pass through the radiator, therefore raising the amount of Heat transferred through the radiator to the coolant, which will lower engine temps.

Plus there is now a heat flow path for hot ambient air to be transferred to cool atmospheric air...therefore there is some thermal driving head and air wants to flow from the engine bay...

Now I cannot say for sure which of these effects dominate, as it would be different on almost every car, and I'm not even sure if the wind speeds over the hood could get high enough to pull air from the engine bay, but I do know that it will pull smoke from inside the car to the outside if your window is partially down(no hot boxing allowed), so that makes me think it would...

 

look at the wind tunnel video, i dont see any swirling motion near the windshield. all i see are those white powder used to make the air flow visible going over the windsheild and not "swirling".

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by verbal assassins &raquo;</TD></TR><TR><TD CLASS="quote">look at the wind tunnel video, i dont see any swirling motion near the windshield. all i see are those white powder used to make the air flow visible going over the windsheild and not "swirling".

</TD></TR></TABLE>

That's because the smoke was only added to the air coming in, not the air already there.

 

air thats already there will be pushed by the current flow of air and away from the windshield... its not gonna sit there and do nothing. hahahaha.

do a test, put ur hand near ur face, slope it just a bit and blow. do u feel any air hitting ur face? nope. why? cause its evenly spreads out and about.. its not gonna bounce back like that one dumb azz said,

now curve ur hand into a cup, blow, guess what, air now hits ur face.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by verbal assassins &raquo;</TD></TR><TR><TD CLASS="quote">air thats already there will be pushed by the current flow of air and away from the windshield... its not gonna sit there and do nothing. hahahaha.

do a test, put ur hand near ur face, slope it just a bit and blow. do u feel any air hitting ur face? nope. why? cause its evenly spreads out and about.. its not gonna bounce back like that one dumb azz said,

now curve ur hand into a cup, blow, guess what, air now hits ur face.


</TD></TR></TABLE>

Air is not going to go straight into the cowl then bend. It will take a graceful curve and form a pocket of air at the base of the windshield.
example:


This is why what i said about some trucks getting better gas mileage with the tailgate up is true. The air doesn't take a 90 degree turn at the edge of the cab and go into the bed of the truck, it takes a slight curve down while leaving a pocket of air in the bed (that swirls).

I'm trying my best just to make an assumption on what i think is happening without seeing solid data. I'd advise you (who obviously has a lot less knowledge in these sciences) to do the same.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by verbal assassins &raquo;</TD></TR><TR><TD CLASS="quote">air thats already there will be pushed by the current flow of air and away from the windshield... its not gonna sit there and do nothing. hahahaha.</TD></TR></TABLE>

No.


<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote &raquo;</TD></TR><TR><TD CLASS="quote">
do a test, put ur hand near ur face, slope it just a bit and blow. do u feel any air hitting ur face? nope. why? cause its evenly spreads out and about.. its not gonna bounce back like that one dumb azz said,

now curve ur hand into a cup, blow, guess what, air now hits ur face.


</TD></TR></TABLE>

1. Take the dick out your ***

2. Where do you think you get air for the AC? Why is there are holes in the windshields cowl?

3. DO anyoff these magenehelic gauge or yawn prop the motherfucken hood over some washers hood and see where where the yarn wants to go, drive fairly fast.

FACT is air GOES INTO this point NEVER OUT under pressure.

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote &raquo;</TD></TR><TR><TD CLASS="quote">park ur car, and place ur hand over the back of the hood, what do you feel? hot air seeping out of the raised hood.</TD></TR></TABLE>

Park the car do you know how the hell pressure differential works? Positive pressure will follow the negative pressure and Its created by the car moving.


Your video show proves nothing about the air flowing over the Zonda not for this conversation.

 

and the arguement heats up! haha

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by njn63 &raquo;</TD></TR><TR><TD CLASS="quote">
This is why what i said about some trucks getting better gas mileage with the tailgate up is true. The air doesn't take a 90 degree turn at the edge of the cab and go into the bed of the truck, it takes a slight curve down while leaving a pocket of air in the bed (that swirls).
</TD></TR></TABLE>

This is true. I saw it on mythbusters......

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by genocide43110 &raquo;</TD></TR><TR><TD CLASS="quote">

This is true. I saw it on mythbusters......</TD></TR></TABLE>

What sucks about Mythbusters is that they have proven their theory for that SPECIFIC model truck and that SPECIFIC bodyshape. Put a lowered pickup truck with a widebody and tubbed rear end, and everything changes. Aerodynamics only works for specific designs... Or else, how come front splitters on race cars only provide downforce when front height is below a certain height? Put a front splitter on a dumptruck that's 10" off the ground will not mean that a splitter is useless (for example).

 

verbal assassins, just google "cowl induction hood", and go find yourself an answer kid. I won't even try to explain this to you because it requires some background info, and obviously you are way out of it Do me a favour and search... Notice all the smilies? I'm trying to be nice because I am getting a lot of hate PM's from the way I "educate" newbies

EDIT: Heck, here are some links:

Taken from: (http://archives.fleetmag.com/publica...pubId=1&id=138)

PRESSURE POCKET

The second part of the Enviro-Cool system uses cowl induction to cool off the engine itself. According to Sturmon, cowl induction has been used successfully in racing for 40 years, and there's no reason why it can't be just as successful on a heavy truck. By raising part of the hood, and creating an air scoop facing the windshield, you create a pressure pocket that sucks air through the scoop and into the engine compartment, where it draws heat away from the engine block.

"So, now you have a source for air, and when that air gets into the engine compartment, now you have to find a way out," Sturmon explains. "So, we put an exit at the front of the engine compartment, and we tie that exit to the fans off the radiator. They pick up the air from behind the radiator and direct it out the sides of the hood. So you pass the air through that channel. There is a low pressure pocket there that sucks the air out from behind the radiator.

"You're replenishing the air in the engine compartment, an area of about 25 cubic feet of air, and these fans will be blowing 3,000 to 4,000 cfm past that exit, and that low pressure will suck that right out of there," Sturmon says.

The next step for Enviro-Cool is to perform wind tunnel testing, to quantify the effectiveness of the system. Sturmon says the company has been approached by a fleet for possible testing, an indication that fleets are indeed nervous about 2007 underhood heat issues…

.
.
.
Taken from (http://www.camaro-untoldsecrets.com/...es/rpo_zl2.htm)





Modified by Tony the Tiger at 11:39 PM 2/22/2007

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by njn63 &raquo;</TD></TR><TR><TD CLASS="quote">

Air is not going to go straight into the cowl then bend. It will take a graceful curve and form a pocket of air at the base of the windshield.
example:
http://www.galcit.caltech.edu/awt/smoke1.jpg
</TD></TR></TABLE>

There is no cowl induction on the picture you've shown... No cowl means no air going in...lol

 

in any case, whoever is right or wrong, who cares. hood spacers works. no matter wha tthe explanation is.. my explanation is that hot air goes out... a dumb *** explanation is that air hits the windsheild, makes a 180 degree turn and then into the hood.

so all in all, it helps reduce hood temp....

thank you.

 

The only reason I'd space a hood is if it was on a crashed car and I couldn't get the hood line straight. At least some people would see it as mad cool. lol.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by verbal assassins &raquo;</TD></TR><TR><TD CLASS="quote">my explanation is that hot air goes out... a dumb *** explanation is that air hits the windsheild, makes a 180 degree turn and then into the hood.
</TD></TR></TABLE>

Just read the links I've provided for you... I don't think I have to spoon feed you?

Air does make a 180 deg turn into the engine compartment because it is going from a high pressure to a low pressure zone. Time to go back to highschool and finish a science course, and maybe graduate this time?

 

prove it, show us a wind tunnel test... no worth of mouth crap.

i seriously remember seeing a special on the history or discovery channel to why it was "reversed" and it was for the looks.

 

some ppl have no choice but raise the hood 'cause the valve cover rubs or hit the hood. I've got 3 nipples on my hood from my valve cover hitting the hood.

I personally, honestly think raising the hood helps hot air get out more and the air goes out through the gap or viseversa... I know the fact that it DOES work. I noticed one thing how when I'm at 100km or so, I don't have to turn the wipers on as often when it rains.

yes, I know some ppl think it's gay but who cares? mind your own business... meaning no need to hate guys with hood lifted


Modified by hoya_10fintec at 9:12 PM 2/22/2007

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by verbal assassins &raquo;</TD></TR><TR><TD CLASS="quote">in any case, whoever is right or wrong, who cares. hood spacers works. no matter wha tthe explanation is.. my explanation is that hot air goes out... </TD></TR></TABLE>

Not out of there when the car is moving and I dont ANYONE needs to worry about cooling when the car isnt moving.

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote &raquo;</TD></TR><TR><TD CLASS="quote">a dumb *** explanation is that air hits the windsheild, makes a 180 degree turn and then into the hood.</TD></TR></TABLE>

That because that EXACTLY what happens.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by verbal assassins &raquo;</TD></TR><TR><TD CLASS="quote">prove it, show us a wind tunnel test... no worth of mouth crap.
</TD></TR></TABLE>

This is the last time I am going to tell you to read the links again. Don't you read the sources, and find where the information comes from? At this point, I don't really care, and I don't think I have anything to prove to a newbie anyway. As long as most of the members here have read my post are have been well informed, it's all good. You can continue to stay in your own little world

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Tony the Tiger &raquo;</TD></TR><TR><TD CLASS="quote">
PRESSURE POCKET

The second part of the Enviro-Cool system uses cowl induction to cool off the engine itself. According to Sturmon, cowl induction has been used successfully in racing for 40 years, and there's no reason why it can't be just as successful on a heavy truck. By raising part of the hood, and creating an air scoop facing the windshield, you create a pressure pocket that sucks air through the scoop and into the engine compartment, where it draws heat away from the engine block.

"So, now you have a source for air, and when that air gets into the engine compartment, now you have to find a way out," Sturmon explains. "So, we put an exit at the front of the engine compartment, and we tie that exit to the fans off the radiator. They pick up the air from behind the radiator and direct it out the sides of the hood. So you pass the air through that channel. There is a low pressure pocket there that sucks the air out from behind the radiator.

"You're replenishing the air in the engine compartment, an area of about 25 cubic feet of air, and these fans will be blowing 3,000 to 4,000 cfm past that exit, and that low pressure will suck that right out of there," Sturmon says.

The next step for Enviro-Cool is to perform wind tunnel testing, to quantify the effectiveness of the system. Sturmon says the company has been approached by a fleet for possible testing, an indication that fleets are indeed nervous about 2007 underhood heat issues…
</TD></TR></TABLE>

Note the bolded part. I don't have fans or an exit on my car for that air so i don't see how the air will be drawn in.

Think about it this way, you have a massive quantity of air coming through the grille (by my calculations, 7040 CFM through a 8"x24" grille at 60mph if you have no restrictions). That air has to go somewhere. I have a tough time believing that enough air can be pushed out the bottom of the engine bay that there is a small enough pressure (in the engine bay) to be overcome by a pressure pocket at the bottom of the windshield.

Nowhere in that camaro-untoldsecrets site did they credit a higher pressure either, just cooler/denser air.

This is just me thinking out loud of course. I'd love to see some actual results. Don't credit a cowl induction hood as proof though because those are sealed off and use negative pressure caused by the engine, not negative pressure in the engine bay. Don't take offense to this as i'm not arguing, just trying to understand the theory you're using.

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Tony the Tiger &raquo;</TD></TR><TR><TD CLASS="quote">
There is no cowl induction on the picture you've shown... No cowl means no air going in...lol </TD></TR></TABLE>

That's not what i was saying but nevermind.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by njn63 &raquo;</TD></TR><TR><TD CLASS="quote">

Note the bolded part. I don't have fans or an exit on my car for that air so i don't see how the air will be drawn in.

Think about it this way, you have a massive quantity of air coming through the grille (by my calculations, 7040 CFM through a 8"x24" grille at 60mph if you have no restrictions). That air has to go somewhere. I have a tough time believing that enough air can be pushed out the bottom of the engine bay that there is a small enough pressure (in the engine bay) to be overcome by a pressure pocket at the bottom of the windshield.
</TD></TR></TABLE>

Hey home boy use your head there's a big Vacuum drawing in air under the hood (low pressure) called a V8 engine.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by njn63 &raquo;</TD></TR><TR><TD CLASS="quote">

Note the bolded part. I don't have fans or an exit on my car for that air so i don't see how the air will be drawn in.
</TD></TR></TABLE>


You don't need fans.. The space under the engine (while the car is moving) creates a huge suction and simply carries out a lot of air underneath the car. It's way more air than what the front grill can supply, plus the radiator blocks most of the incoming air entering from the front grill. Try driving at medium speed around a parking lot on a warm day (so you can wear shorts) with your driver's door open, and you can feel a noticeable amount of hot air bleeding out from under the car. The faster the car moves, the more air passes underneath the car. Heat rises though, so it tends to stay high near the hood, but as the car moves along, the pressure changes and voila, cowl induction. To maximize the effect, the best would be to have fender vents, a really tall cowl, fans, etc.. but even on a Honda, there are just too many guys who have reported great results over the years especially on the NA forum to really support this. When I was on ITB's (all motor days), it didn't take much to notice that I was getting a while bunch of crap, like leaves, grass, etc... getting lodged on my ITB filters after I took the weather moulding off near the firewall, and a healthy reduction of air temps on average (never had a chance to do a back to back log, but the difference was really obvious).

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by MidShipCivic &raquo;</TD></TR><TR><TD CLASS="quote">

Hey home boy use your head there's a big Vacuum drawing in air under the hood (low pressure) called a V8 engine.</TD></TR></TABLE>

Not even close. My car at redline only displaces 213 CFM.

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Tony the Tiger &raquo;</TD></TR><TR><TD CLASS="quote">


You don't need fans.. The space under the engine (while the car is moving) creates a huge suction and simply carries out all the air undernearth the car. It's way more air than what the front grill can supply, plus the radiator blocks most of the incoming air entering from the front grill. Try driving at medium speed around a parking lot on a warm day (so you can wear shorts) with your driver's door open, and you can feel the hot air simply bleeds out from under the car. The faster the car moves, the more air passes underneath the car. To maximize the effect, the best would be to have fender vents, a really tall cowl, etc.. but even on a Honda, there are just too many guys who have reported great results over the years especially on the NA forum to really support this. When I was on ITB's, it didn't take much to notice that I was getting a while bunch of crap, like leaves, grass, etc... getting lodged on my ITB filters after I took the weather moulding off near the firewall, and a healthy reduction of air temps on average (never had a chance to do a back to back log, but the difference was really obvious).</TD></TR></TABLE>

Yeah, i really can't predict how much air would go out the bottom. I know it'd create suction but it's so hard to predict how much.

I'm probably going to mess around with my car next time i go home just to figure out which way air goes. I believe you it goes in but i have to see it myself.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by njn63 &raquo;</TD></TR><TR><TD CLASS="quote">

Not even close. My car at redline only displaces 213 CFM.
</TD></TR></TABLE>

Not even close? Wrong. It's low pressure, it helps also depending on how the intake is setup.