im not positive if im right about this or not, someone will have to let me know if im wrong, but it looks like those 150$ headlight intake covers are a waste of precious$$$$$$ i attached a pic of the aerodynamic flow of air on a 2nd gen, looks like no air would get into it, but i could be wrong.

 

you would be correct.

 

Hey it looks good though.
you got to agree with that.
I will buy one.
Later Matt22

 

If that aerodynamic chart were correct, then I'd never have to wash my hood or front end because there'd be an air buffer surrounding them. Bah!

I disagree with that chart on the sole basis of having driven my car on the rain-soaked freeway then looking at the dirt streaks going in straight lines up and over my hood (including the headlight covers), around the sunroof and down the back window in a V pattern...

 

Though not an engineer, if you saw the smoke trace overlayed on that image, I think you'd look at it from a different perspective. Here's my take, the longer lines at the front of the hood show a relatively strong upward push of the airstream-- the nose and the roofline have the longest lines as they actually are the surfaces pushing into the air (and collecting the rain, dirt, etc).

As you progress up the hood, these lines (I think they are vectors or something) shorten up as the airflow is actually further off the car. At the base of the windshield, this section is actually pulling the stream back down slightly, however then the top edge of the windshield is the second surface to push through the air, directing the airflow up off the car again-- although with not as much force as the nose of the car.

I think I've seen some wind tunnel shots that have the smoke stream, if I can find one, I'll post it.

That in mind, if you open a hole in the nose, there should be a pretty strong blast of air coming in. You know, they put the radiator up there for a reason.....

Greg O.

 

Airflow would follow the profile of the car body so yes you would get air through the headlight cover intake. I can't tell for sure what the graph in the picture is but it could be something like static pressure distribution around the car.

 

The dark black line is the storngest part of the airflow over the car. There's still gonna be air everywhere (what do you think would be there, nothing?). The headlight intake isn't as effective as it could have possibly been because the central airflow is going away from it, but it's still gonna get a lot of force. It's worth it.

 

Keep in mind, too. Your intake is "sucking" air at the same time, so even if air wasn't directly flowing into the hole in the headlight cover, the vacuum created by the intake would suck air through the opening regardless.

-Derek

 

the diagram that was posted in the other thread, shows the amount of pressure that the air flowing over the car creates. if theres turbulence, theres no air pressure, such as the uneven body parts: where the hood meets the windsheild, grill opening, rear end. but whre the air first encounteres the obstruction, thats where the resistance is the most, and where the air changes direction, such as when it is forced up to flow over the hood and windsheild, also has high resistance. just pretend to put numerical values on each arrow. the arrows pointing up equal + numbers, and the arrows pointing down equal - numbers. the greater the arrow length (in either deviation), the bigger the number. on the same token, where the windsheild meets the hood, there is turbulence. since the air is falling over itself, its no longer pushing down on the car (or the car is no longer pushing the air up, however you wish to look at it) but once it moves past that point, and onto the glass, its the same effect as the wind first had on the hood.

remember, air sticks to its surface. waxing does help. the air CLOSEST to the surface flows slower than the air above it, and the air flows faster than the are below it. (the same applies for exhaust pipes: the exhaust closes to the wall flows slower than in the middle, thats another thread though)

the little headlight scoop will work. but there are ways to make it work better. first off, the air flowing into the scoop goes slowly since the scoop isnt very tall. the air needs somewhere to go once it gets into car, it needs to move somewhere or else it will get backed up, and no more air will go in.

theres a peice of weather strip on the hood that should be removed, and the headlight bucket bracing should be cut away a little to allow the least amont of intrusion into the air's path. also, if you can raise the hood in the rear to vent pressure, or put some rearward facine scoops will help also. the simple principal here is "AIR IN, AIR OUT".

the only in-and-out of the engine bay are; grill opening, under the engine, and now the headlight scoop.

grill opening; high pressure air inlet for radiator and cooling
under engine; high pressure due to fast moving air (while driving, the only time the headlight cover is worth a damn)
headlight scoop; low pressure inlet due to size of scoop.

well, we obvoiusly have "AIR IN...." but what about the air out? think about that one.

btw, my scoop was free. i made it out of plexiglas, a deck of cards, scissors, 3M emblem tape, and an oven.

enjoy
chris

 

well I can tell you that after I put on my headlight cover intake and ran my car, the airbox and filter were ice cold, when I didn't have it, it was just room temperature.

 

Headlight cover intakes do NOT channel air into the engine bay. There is a big seal at the front of the hood right behind intake, not to mention the hinge for the headlight. Also, the cover, even if it did let air into the engine bay, it wouldnto be enough to do anything. The intake is just too small, and it is in a bad place.

If you want cold air intake/ram air, take your time to build a good one, and route it to the front bumper for cold air.

 

mazdaspeed: i know that, thats why i said that you have to remove the weather seal on the left side of the hood, it uses 3 10mm bolts i think. then cut out the headlight bucket bracket w/ a cut-off tool. but that was for my scoop. the other fiberglass one, the inlet is way to the rear of the cover. on my scoop its right in the center, directly above the hole on the headlight bracket. mine works, there is a straight shot air way. i know, cuz i can see thru the plexiglas into the engine bay.

another way is to get a stick-on scoop, and cut a hole in your hood, directly above where the filter is located. the area behind the head light cover. then maybe the air would get introduced above the air filter. another way, might be to cut out the fender trim directly below the air filter so that it can suck air from under the car. similar to where the intercooler is mounted on a 1g talon or eclipse.

think about that
chris

 

if you have the good inside your head you can work out a way of using the air duct in the headlight cover for a 'ramair' effect, i made my own from a slightly damaged cover i had sitting around, got out the dremel with cutting wheel and in about 5 minutes i had a scoop on my headlight.

 

i didn read all of the other post so dont yell at me for repeating what was already said.

the areas where the line is furthest away from teh car represents the highest pressure area. if you follow the line which touches the apex of that curve and follow it back to the car. that point will give you the most air.

the areas where the line goes into the car represent a negative pressure difference. the lowpressure area between the hood and windscreen shows why cowl hoods work. the vaccum created draws hot air out of the engine bay and up over the car.

Justin

 

You've got that completely backwards, you couldn't be any more wrong! The areas where the arrows go into the body are HIGH pressure areas. Why do you think the radiator inlet is high pressure? It's the first part of the car to hit the air! The air is pushed upwards violently, hence the low pressure area over the bonnet, then reattaches itself at the base of the winscreen. That's why you cabin air intake is there, it's a high pressure area. It doesn't suck air out of the engine bay!
This is why I keep saying put your ducted intake in the radiator grille and don't waste money on headlight intakes.

 

thats what i thought NZ, i though that the arrows going inward were high pressure areas, and arroys pushing away were low pressure.

i remember one day there was a wasp on the window wiper of my car, i took off because i figured it would fly off the windshield, when i hit 60mph it just walked across the window wiper a few times and i was puzzled, so i just turned on the wipers to get him off lol.

now we need an aero profile with the FTP's removed to see if that changed the air flow any.

 

quote:
[B]You've got that completely backwards, you couldn't be any more wrong! The areas where the arrows go into the body are HIGH pressure areas. Why do you think the radiator inlet is high pressure? It's the first part of the car to hit the air! The air is pushed upwards violently, hence the low pressure area over the bonnet, then reattaches itself at the base of the winscreen. That's why you cabin air intake is there, it's a high pressure area. It doesn't suck air out of the engine bay!
This is why I keep saying put your ducted intake in the radiator grille and don't waste money on headlight intakes.[B]

exactly

that would be cool

 

yeah arrows going inward are high pressure area

clearly from the picture, the headlight area has lower pressure than the windshield area, and the reason is pretty obvious also...

but it doesn't mean air won't go into the headlight scoop
i think the air that pass through the headlight scoop is already enough for the intake, it's not like the more u feed air the more the filter will suck..

there are a certain flow rate for intake i assume..
and in fact for low pressure fluid, it travels faster
and flow rate depends on velocity and cross section contact area only
has nothing to do with pressure

correct me if i am wrong

and i definitley agree with the above post saying that the scoop works..but can be improved..

IMO...$150 is not worth it, plus i don't like the look of it

 

grassroots motorsports put that, so obviously air does flow in, but very poorly

 

Don't think of the arrows as "how the air is flowing" but the force exerted by the air as it flows over that part of the car. Those are force vectors created by the airflow. Regardless, driving your car through air is going to cause air to flow into the headlight vent, and it should be effective I think.

lates~

 

Where is this diagram from? I'd like to take a look at the book/magazine/whatever it was in.

Are there other flow profiles like this for our other model cars? I'm interested to see the flow difference between Series 4 / Series 5, with/without spoiler, etc.

 

When I was flipping through an Option magazine many years back, I saw a headlight cover from Borders Racing. I wanted one really bad.
I never thought that a little opening would make a difference but it did.
Installing it wasn't hard. To have the best effect, you'll need to remove the flap that's attached to the hood and cut out a section since the duct is recessed. I took a temperature before and after at the open filter and it dropped about 30 degrees. So yes, it is effective. Of course it's effective if you have open filters. Right now I'm trying to rig up a bracket to lift the rear of the hood about 1 inch to direct hot air out.

 

By the way, $150?? That's waaay too expensive. It's just a fiberglass cover with brackets. About $100 would be right. THat's what I paid for it.
I can think of a couple companies that makes them. One is Borders and the other is ....**** I forgot. Borders has a NACA duct and the other is "bubbled" up. The Borders looks much nicer.

 

I did not read all the posts but rember low pressure creates a vacume, and if you don't belive me look at the weather, air flows from a high pressure system to a low pressure system. You want low pressure over the scoop in order to 'suck' in the air due to the vaccume created.

But it does not matter how fast it flows just how much at a time, like this

Colder Air=more air since it is denser(sp) so you can pack more into a smaller area

Warmer Air=not as much air since its not as dense(sp) so you cant pack as much air into the same size area


This is why an air intake works,
outside = Low Pressure
in intake = High Pressure

Its not hard just basic science.