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Hey everyone, Below is a very recent conversation on another group, of which racerx-11 and I belong, on how cowl induction works. The start of the convers is on the bottom and works up. Sorry thats just how it came to me. Let me know what ya'll think.
From: "HairyRedneckGuy"
True, They give you more space, but if you want to get technical the
reason that the hood scoop works is because of fluid dynamics, namely
aerodynamics. All air is considered a fluid for engineering/physics
matters because of how it acts. The general Idea for the X-11 hood
is to act as suction using fluid flow. If you have ever seen those
gutter guard rain gutters, they work on the same principle (using a
little water surface tension as well)... in this case air is forced
over the hood scoop where a vortex of air disturbance is created in
the area between the scoop and the windshield. This would be a low
pressure area under the High pressure of the flow going over the
car. However as more air goes over more air has to leave, this is
where the scoop's opening comes in, it allows the turbulence to
escape the vortex created and travels directly into the carb.
Without testing an a lot of math I couldn't say exactly where the
High and low pressure spots are, but that is the general science
behind why the scoop works.
Can you tell I used to teach Science?
Junior
"Pete Winegardner" wrote:
> also, the cowl hood gives you more room to play around versus a flat
> hood. take for instance my carbed 3.1L - the high rise intake would
> not fit with a regular hood.
>
Josh Keady wrote: Well, let's get it straight that while at speed, you will undoubtedly always see a vacuum condition at the carb or throttle body, never positive pressure there without a forced induction device. Car companies have been putting scoops and the like on cars for many years, but the only real performance gain you get is in the
density of the cool air being fed to the intake. The actual velocity is usually insufficient to create any kind of actual pressure in
the intake.
That said, I think you'll find that the cowl induction concept
works by creating high pressure in one area which creates low pressure
in another. I think. Think of the air as tumbling over the lip at
the back of the hood and into the intake. It goes over the lip,
then arcs back in to the duct to fill the void it created when the
hood pushed past it. Obviously that's not going to create any
positive pressure, but it does direct cool air into that duct.
I hope that makes some kind of sense
Josh
> >
On Aug 10, 2005, davydmanson wrote:
In many websites I have found that cowl induction creates a
lower pressure area in the lower area of the windshield Ih this
rigth?????The problem comes when people say that cowl induction hood
and cowl hoods do two direrent things, cowl induction (like X11) makes a
high pressure area (Bernulli theory) and then try to supercharge the
carb. The point is this the cowl induction helps to make a high
pressure area or a low pressure area ???????????????Or am I totally lost????????
From: "HairyRedneckGuy"
True, They give you more space, but if you want to get technical the
reason that the hood scoop works is because of fluid dynamics, namely
aerodynamics. All air is considered a fluid for engineering/physics
matters because of how it acts. The general Idea for the X-11 hood
is to act as suction using fluid flow. If you have ever seen those
gutter guard rain gutters, they work on the same principle (using a
little water surface tension as well)... in this case air is forced
over the hood scoop where a vortex of air disturbance is created in
the area between the scoop and the windshield. This would be a low
pressure area under the High pressure of the flow going over the
car. However as more air goes over more air has to leave, this is
where the scoop's opening comes in, it allows the turbulence to
escape the vortex created and travels directly into the carb.
Without testing an a lot of math I couldn't say exactly where the
High and low pressure spots are, but that is the general science
behind why the scoop works.
Can you tell I used to teach Science?
Junior
"Pete Winegardner" wrote:
> also, the cowl hood gives you more room to play around versus a flat
> hood. take for instance my carbed 3.1L - the high rise intake would
> not fit with a regular hood.
>
Josh Keady wrote: Well, let's get it straight that while at speed, you will undoubtedly always see a vacuum condition at the carb or throttle body, never positive pressure there without a forced induction device. Car companies have been putting scoops and the like on cars for many years, but the only real performance gain you get is in the
density of the cool air being fed to the intake. The actual velocity is usually insufficient to create any kind of actual pressure in
the intake.
That said, I think you'll find that the cowl induction concept
works by creating high pressure in one area which creates low pressure
in another. I think. Think of the air as tumbling over the lip at
the back of the hood and into the intake. It goes over the lip,
then arcs back in to the duct to fill the void it created when the
hood pushed past it. Obviously that's not going to create any
positive pressure, but it does direct cool air into that duct.
I hope that makes some kind of sense
Josh
> >
On Aug 10, 2005, davydmanson wrote:
In many websites I have found that cowl induction creates a
lower pressure area in the lower area of the windshield Ih this
rigth?????The problem comes when people say that cowl induction hood
and cowl hoods do two direrent things, cowl induction (like X11) makes a
high pressure area (Bernulli theory) and then try to supercharge the
carb. The point is this the cowl induction helps to make a high
pressure area or a low pressure area ???????????????Or am I totally lost????????
I have to totally disagree with you. Cowl Induction is a VERY good thing. Why would so many drag racers use it if it didnt work? See,in the vortex on the cowl, only cool air is going "directly" into the carb. Cool air is a very cood thing, engines really like it. Also, since the high pressure is on top, alot of dirt is sent over the windshield, away from the engine. Clean air is damn good for your motor. Plus, on the older mucslecar "true" cowl induction with no lid on the air cleaner, just a rubber seal (unlike the X-11's), the added air pressure on the hood increases the downforce and forms a tighter seal around the air cleaner. Less engine heat thats enters the carb is a good thing. So, as you can see, cowl induction is one of the best auto inventions ever, no real downside. Please, someone correct me if I'm wrong on any of this.
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