Mopar CAI and Ram Air Duct/Functional Hood scoops

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JoeCo

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Do you have better front end visibility without it?

Maybe just slightly, but not a noticeable difference. The sport hood is pretty mild in terms of that, I just liked the extra definition it had as oppose to the plain looking hood.
 

16RamHemi

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the better visability is looking out over the sport hood from the drivers seat. You just dont get that view with the regular hoods. Sport hood ftw!
 

Wild one

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to each their own. im just not a fan of those or the scoop hoods. I read that the new trx is getting the scoop hood. meh.

My wifes Challenger has the shaker hood,and in my opinion it's a better view then the trucks performance hood,but to each their own,i love looking at the shaker,lol
 

16RamHemi

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My wifes Challenger has the shaker hood,and in my opinion it's a better view then the trucks performance hood,but to each their own,i love looking at the shaker,lol

tbh i have not been around these really at all. see them once in a while going by. So im not giving a fair opinion. I feel the ram sport hood (4th gen) is the best looking hood. Combining the cowl and "nostrils" is perfect imo. Maybe more so for the 4th gen as i feel it blends the front and side perfectly. Giving a tough muscular look. I have a 4 inch lift and imo it is a perfect set up.
 

kurek

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Exactly on target. Also, keep in mind that to get a true "Ram Air" effect, you'd have to be going like mach1 (I'm sure I'm way over base here) to actually achieve enough forced air into the throttle body do anything.

It can be calculated, at least to the standards of a napkin.

The standard wind loading calculation (for a structure bearing the forces of wind) is 0.00256×V^2÷144=n psi* so at a speed of 40mph that's 0.0284psi at the mouth and at 60mph it's 0.064psi at the mouth. Those aren't the total story because we have a few variables like the front of the truck is compressing the atmosphere and the hood scoop is directly on the hood which means the body itself is likely serving as a partial funnel, greatly increasing the functional surface area of the scoop. And the surface area of the scoop is larger than the throttle body so there is some tunnel multiplication going on too - I'm comfortable quadrupling the estimated functional psi at the throttle body vs. at the inlet. That means about 0.256 psi at 60mph and 0.455psi at 80mph .

Those seem like believable numbers at a guess. Using an online two factor boost calculator that means maybe 10-12hp at 80mph at a guess. Probably not something you would notice since you have to already be going that fast to achieve it, effects below 60mph would be effectively non existant.


*or 0.00000177×V^2 which is one less step but harder to remember
 

Wild one

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It can be calculated, at least to the standards of a napkin.

The standard wind loading calculation (for a structure bearing the forces of wind) is 0.00256×V^2÷144=n psi* so at a speed of 40mph that's 0.0284psi at the mouth and at 60mph it's 0.064psi at the mouth. Those aren't the total story because we have a few variables like the front of the truck is compressing the atmosphere and the hood scoop is directly on the hood which means the body itself is likely serving as a partial funnel, greatly increasing the functional surface area of the scoop. And the surface area of the scoop is larger than the throttle body so there is some tunnel multiplication going on too - I'm comfortable quadrupling the estimated functional psi at the throttle body vs. at the inlet. That means about 0.256 psi at 60mph and 0.455psi at 80mph .

Those seem like believable numbers at a guess. Using an online two factor boost calculator that means maybe 10-12hp at 80mph at a guess. Probably not something you would notice since you have to already be going that fast to achieve it, effects below 60mph would be effectively non existant.


*or 0.00000177×V^2 which is one less step but harder to remember

There is a dead air space on the hood and it's usually about 2",so opening up the factory scoops isn't going to give any ram air effect to speak of.You'd get more ram air from a scoop behind the grill run to the airbox,then you'll ever get from the scoops in the performance hood.All you'll get from opening them up is another cold air intake path,but there won't be any ram air effect from them.
 

kurek

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There is a dead air space on the hood and it's usually about 2",so opening up the factory scoops isn't going to give any ram air effect to speak of..

This can be refuted with a piece of string and a piece of tape.
 

Wild one

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This can be refuted with a piece of string and a piece of tape.

Wind tunnels also dispute your claim,lol. It's a proven fact there's roughly a 2" dead air space on the hood ,manufacture's have known this for 50 years or more.There will be no "ram air effect" from opening up the scoops,all it'll give you is another cold air intake path.
It's also the reason you don't see a shaker hood scoop on a Hellcat/Demon or 1320 Challenger.The shaker is functional,but does not create any ram air effect on the 5.7/6.4 Challengers that have one.
 

kurek

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So if I take a business card and crease it at 90 degrees, tape one flat edge to my hood and drive on the highway the part that's sticking up will just stay sticking up because there's no air movement there eh?
 

Wild one

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So if I take a business card and crease it at 90 degrees, tape one flat edge to my hood and drive on the highway the part that's sticking up will just stay sticking up because there's no air movement there eh?

Not really a legit test but go try,and get back to us with what happens
Put it 1" to 2" in front of the scoop and go see what the card does,as i'm curious too,lol
 

kurek

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Looks to me like air that can't go through the truck goes over the truck pretty much directly in contact with it, so if you initiate a visual feature like smoke above that it will stay above that.

doink.png

I'll business card it up if you will so we both have flesh in the result. Snowy here right now, I don't mind revisiting this thread in a week. Hood's aluminum so I can't magnet the action cam to it but hopefully it will be visible through the windshield.
 

Wild one

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Looks to me like air that can't go through the truck goes over the truck pretty much directly in contact with it, so if you initiate a visual feature like smoke above that it will stay above that.

View attachment 192028

I'll business card it up if you will so we both have flesh in the result. Snowy here right now, I don't mind revisiting this thread in a week. Hood's aluminum so I can't magnet the action cam to it but hopefully it will be visible through the windshield.

I'm curious too,but I highly doubt you'll see much pressure against the card on the hood right in front of the scoops,i'll hazard a guess there'll be enough to bend the card,but that'll be all,there won't be any real air pressure against the card to flatten it against the hood.If there is,you've refuted many millions of dollars spent on wind tunnel testing by manufacture'rs,lol. It was well known way back in the 60's a scoop had to be above the dead air space to be of any benefit,think Ma Mopars snorkel scoop,which was one of the very first scoops that was developed in a wind tunnel from what I've gathered up reading about scoops over the years. By the looks of your profile you don't have the performance hood on your truck,so hunt up a friends truck that has the proper hood,also free's you up to run the camera.
 

novelmike

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There is a dead air space on the hood and it's usually about 2",so opening up the factory scoops isn't going to give any ram air effect to speak of.You'd get more ram air from a scoop behind the grill run to the airbox,then you'll ever get from the scoops in the performance hood.All you'll get from opening them up is another cold air intake path,but there won't be any ram air effect from them.

When I have rain water on the hood and I’m driving on the highway, the water does run toward the windshield. Yes it moves faster in some spots and doesn’t want to move much in others. So there isn’t 100% dead airspace on the hood.
 

Wild one

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When I have rain water on the hood and I’m driving on the highway, the water does run toward the windshield. Yes it moves faster in some spots and doesn’t want to move much in others. So there isn’t 100% dead airspace on the hood.

Actually calling it dead air isn't really the proper designation for it,there is a proper term for the syndrome of air being more or less semi stagnate with-in a couple inches of the hood.Here's a bit of reading on scoops,pay attention to the shallow scoop that is not a NACA duct,which applies to our trucks scoops,they are not NACA ducts,lol.

Scoop design[edit]
To be effective, a functional scoop must be located at a high-pressure area on the hood. For that reason, some functional scoops are located at the rear of the hood, near the vehicle's cowl, where the curvature of the windshield creates such a high-pressure zone, and may be placed so that their opening faces the windshield (a reversed scoop).

The scoop will be most effective if it is either mounted high enough to clear the boundary layer (the slow-moving air that clings to the surface of a moving object) or if it is a NACA duct, mounted below the surface and designed to draw the faster moving air outside of the boundary layer into the duct. A shallow scoop that is not a NACA duct may not admit a useful amount of air even if it is open.

Under the hood, an effective scoop must funnel air into the engine's intake in as short and direct a path as possible, preferably through a tube or channel that is insulated against underhood heat.

A scoop may be part of the hood, or may be part of the engine's air cleaner assembly, protruding through a hole cut into the bonnet. Such a scoop is called a shaker hood, because the scoop vibrates noticeably when the engine is running, especially under power.
 
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