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  1. #1
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    increasing air pressure ( ram air scoops )

    Has any one seen / know about the use of "air vanes " WITHIN a scoop to increase the air pressure , as in Ram Air hood / brake scoops. I have heard references to " Rifling the Air " . This would seen counter intuitive , since it would seem like the vanes would be creating turbulence . But would the increase in turbulence be off set by the increase in pressure . Any science to back this up ?



  2. #2
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    never heard of any. the biggest hurdle is an aesthetically pleasing scoop that works, the only one i know of that really works is the cowl induction on 68-69 camaro z/28 roadracers. and the cowl induction on older nascar grand national cars. What kind of car are you working on? the ferrari testa rossa had vanes in the doors and quarter panel scoops. ferrari said it was for looks since the area was so large they felt it looked a lot better. no performance improvement as a result that i have ever read about

  3. #3
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    You won't get any "ram air" effect unless your going faster than 160mph. Below that it's just cold air, hard part is making it look good and have the total scoop aera equal or greater to the area of the air filter your using or else it will be a restriction. (If your running it a sealed scoop)


    JORDAN

  4. #4
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    I believe you may be off (MPH wise ) as far as Ram Air working speeds . The right configured scoop , will START to work at high way speeds . And just because it LOOKS Cool dose NOT mean it works . As in , how cool Cowl induction may look . Remember you are asking the air flow to change direction 180 degrees . A high pressure area like the base of the windshield dose have it's uses . But the question is , at high way speeds is one getting a Ram Air effect . If one is to get the biggest bang for one's buck in investing in a given scoop , why be wasting your $$ on Cosmetics ? Grand National Race Car rules forbid any hood scoops , so cowl induction is the next best thing . But given a chose ALL other racing seems to be choosing Front facing scoops . So sorry my Chevy brothers , but it would seem science would trump "Coolness" . Cowl induction is less efficient ( then a properly configured front facing scoop ). I am currently working on the Hard numbers of science ( air flow # at high way speeds ) to show the difference , please check back to see if your car's scoops were tested .

  5. #5
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    Along the lines of the original question, but in a totally different application. I have an AFE Turbo Inlet tube installed on my 07 Duramax 2500HD. The AFE inlet tube is equipped with internal air vanes which help direct the air flow around a 90 degree turn to aim the air flow directly at the turbo wheel. I can't give you any numbers, but I do know there was a noticeable improvement in power and turbo response when it was installed. So using vanes to direct the air flow is possible.

    http://afepower.com/shop/details_new...9&diesel=true&



    As for cowl induction v forward facing air intake, I disagree with the previous posts comments on the effectiveness of cowl induction. I know for a fact that cowl induction does work and work well. Cowl induction has the ability to tap into the cool higher pressure air that builds up at the base of the windshield while at the same time not disrupting the air flow over the hood as opposed to a direct head on hood scoop. The cowl induction was proven to be effective by GM's engineers way back in the late 60's which is why it was developed and used on the SCCA Trans Am cars of the era. In addition, a front mounted intake will ingest all manor of debris from bugs to rain where a cowl induction is much less likely to ingest that same debris. All that said, there is obviously some advantage to picking up fresh air at the base of the windshield since nearly every passenger car and pickup on the road today uses that area for cabin air intake.



    Chevrolet never officially called this the “Cowl Induction” hood, but that’s how it’s generally known; on Camaro order forms, it was RPO ZL2, introduced for the 1969 model year. The hood channeled cooler, high-pressure air from the base of the windshield into the engine air cleaner, increasing power by as much as 10%.
    Steve Hayes
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  6. #6
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    duplicate

  7. #7
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    I would cowl induction is chosen mainly for packaging decisions, same for nascar, they are anti hood scoop for stock appearance all the way back in the 60's, because of car design for them the cowl is a high pressure easily accessed inlet area at their speeds, IMO.

    Regarding nascar, I wonder if there would be extreme inlet air pressure changes a carb would have a tough time adjusting for it there was a low mounted forward facing hood scoop inlet that close drafting would really upset? With current efi, maybe not, but nascar is slow to adapt as we have seen for decades.

  8. #8
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    I'm not certain what the OP is asking but I will give this a go.. (side note - I'm not even sure j-c-c is speaking English)

    If you have a volume of air traveling at extremely high velocities, you can indeed use vanes to increase pressure. In fact, that is exactly how compressors work. Unfortunately, even at 160 mph there is not enough air velocity to create an appreciable amount of pressure increase.

    quick calculation,

    80mph = 117ft/s
    Density of air = 0.00237 slug/ft3

    dynamic pressure = 1/2 * density * V^2 = 16.267

    and you are thinking, wow - 16.267 psi, that's great!! but you forgot about units. 16.267 lb/cubic foot which is roughly 0.1 psi increase over atmosphere.

    So ram air is effectively non existent unless you are racing around an oval at high speed, even then would be lucky to see a half pound actually enter the intake.

    JDMan did bring up an interesting point - in turbo machinery it is generally a requirement to have 3x the inlet diameter of straight length pipe entering a compressor (aka turbo). Having turbulent flow enter a compressor can very well lead to less than expected performance.

  9. #9
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    Cowl induction setups are setup to use high pressure areas against the windshield. In other words, it is a different sort of ram air setup.

    Besides that, the idea is to get the air to your throttle blades in as large a volume as possible, as fast as possible, at the lowest temp possible. Things can be done to manipulate the air but.. you better learn to use OpenFoam.

  10. #10
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    Have you ever seen a "cowl induction "actually work. I have one on my 1979 Z-28 RS Pro-touring car ,with a sealed cold air box.I have driven them at 35 mph while it was snowing.And it was funny how the snowflakes would turn 180 degrees after flowing at the base of the windshield. NACA duct hood scoops like the 1979 Z-28 Camaro and the AAR Trans Am Cuda .And the dual snorkel with ducting to the bumpers is another way to do it.All different ways to get forced air into the engine.And you use cold air box with an air filter on street cars,and mostly without on race cars.IMSA.Trans Am .NASCAR.http://flic.kr/p/fcqU3J
    Attached Images Attached Images    

  11. #11
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    I used to have to park under a tree which lost it's leaves in the fall. Often too lazy to blow them off the car before driving I would watch them get "sucked" into the cowl scoop. They wouldn't just enter but would end up roughly 12" forward and down through the hole in the hood and settle into the sealed off air cleaner housing, some stuck in between the crinkles of the K&N air filter. It would seem illogical that the leaves were sucked all the way up there by engine vacuum so the other option is they were pushed by incoming air flow. This would happen regularly at driving around town speeds, around 30+ mph. It may not be the same as ram air, however air does apparently get "pushed" clear up to the carb. It would make sense that it's greater than atmospheric pressure or the leaves would simply enter the scoop and settle on the hood just inside the opening. In my book that's a form of, however low pressure it may be, "ram air" as the constantly incoming higher pressure air can only travel one way and that's into the carb.

    I'm left brained so I have no calculations to back this up but I do have visual evidence and at least a small degree of "well that would make sense" arm chair logic.
    Last edited by [email protected]; 05-05-2016 at 02:52 PM.
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  12. #12
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    Quote Originally Posted by 1BADBET View Post
    You won't get any "ram air" effect unless your going faster than 160mph.
    You've apparently never taken the opportunity to wonder what a dog feels and stuck your head out the window at 35 mph. If you open your mouth your cheeks fill up like a hot air baloon pretty quick. I think if you had to go 160 to experience this unique pleasure you might get sucked out of the car before you had time to open your mouth, you know, like all those cool broken in mid flight airplane scenes where the bad guy always gets sucked through the hole in the fuselage... lol!
    -Ben, Creative Director at Speedtech Performance
    We sell some really cool parts, build cool cars, and do cool concept renderings too!
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  13. #13
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    Thanks, Ben ...you said what I was thinking as the math looks good I'm thinking something Is off a bit. Just for this same reason you sure can feel the wind at 35/50 kms ...and quite a bit at 55/ 95 kms
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  14. #14
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    Quote Originally Posted by [email protected] View Post
    You've apparently never taken the opportunity to wonder what a dog feels and stuck your head out the window at 35 mph. If you open your mouth your cheeks fill up like a hot air baloon pretty quick. I think if you had to go 160 to experience this unique pleasure you might get sucked out of the car before you had time to open your mouth, you know, like all those cool broken in mid flight airplane scenes where the bad guy always gets sucked through the hole in the fuselage... lol!

    The average velocity in a cylinder head is 235-245 feet per second, or ~160MPH. Can't have ram air unless the air is moving faster than what's already in a running engine. At 6,000 rpm the valve opens and closes 50 times a second, so the air is moving a little faster than what you feel at 35 mph with your head out the window.

    In an airplane where the "bad guys get sucked out" is because of the pressure equalization between the cabin of the plane and the air at flying altitude. Much like when a piston goes down and creates a negative pressure, valve opens and air rushes in. The high altitude air is low pressure the cabin is pressurized and when the wing falls off the pressure wants to equalize so the air in the cabin rushes out.


    JORDAN

  15. #15
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    No math to back me up but I've seen a 25 degree drop in intake temp at the IAT with a Ram-Air hood and radiator scoop in a 95 Caprice in the OBD-1 tuning tables FWIW.

    Jim
    1968 Camaro --502HO, ATI 10" TreeMaster, Hughes TH400 with Gear Vendor's OD, Moser 12-bolt, RideTech StrongArms and MuscleBar, Chris Alston G-bar rear suspension, 2 1/8" by 4" Lemon's Headers through 3" Pypes X-pipe and Hooker AeroChambers.

  16. #16
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    Motorcycles have been using ram air for years.
    Kawasaki Ninjas would make less HP on the Dyno with no ram air but would make more power with the ram air. IIRC, test have shown of about 10-15 HP difference.
    Also IIRC, the bike/Ninja would need to be going about 120-140 MPH to see this 10-15 HP increase.

    I fabricated a ram air box & intake setup for my YSR 50.
    I did a test on my YSR 50 years ago using a sensitive pressure gauge 0-1 PSI, ran the bike up to 60 MPH and it made positive boost pressure, 1/10 of 1 PSI!

    I believe this setup helped me to win a championship. Guys in the pits would ask me, does my ram air setup work?,, I would say yes.

  17. #17
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    Here's a calculator to determine how much intake pressure a ram air will create: http://wallaceracing.com/ram-air-calc.php

    regarding the "engine is sucking faster than the scoop is feeding" argument. That maybe true depending on the situation, but even when there is still a vacuum if you can reduce that vacuum with a ram air the engine will make more power. Any blanket statement like "you must be going 160mph for any effect" is just plain wrong. A properly designed scoop will give *some* improvement at any speed, the question is how much improvement is worth while.

  18. #18
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    Making an air box or scoop that gets colder air or less restricted air will make an improvement on any engine. You will not see positive manifold pressure unless the the air speed coming from the scoop is faster than the air already moving through the engine.

    The Kawasaki engine has an ITB set up, like a lot of GT cars do, the air box acts as a common plenum equalizing pulses from the other runners and giving the engine a larger "reserve" of air to pull from. That's why it picked up on the dyno. How can any ram air effect (pressure above atmospheric) occur on a dyno where the engine is stationary. On an ITB set up and with no sealed air box and no common plenum (where boost gauges are always mounted) I see no place you could install a pressure gauge and receive an accurate reading. You can have pockets of faster and slower air and high and lower pressure and that could be the reason behind the gauge reading, I don't doubt the air box made more power and the bike went faster there's just a physical impossibility that the engine actually saw boost.


    JORDAN

  19. #19
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    You are confusing air speed, with pressure and flow. They are vastly different.

    you can have 100 different size pipes, all flowing the same volume of air. Every pipe will have a different air speed, yet they all move the same amount of air.

    It makes no difference how fast the air is moving in the engine, what matters is how much air is moving.

    (for the sake of argument lets ignore airflow at or above the speed of sound, and it really complicates the matter, and rarely comes up in the stuff we are dealing with)

  20. #20
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    I understand they are different but all interrelated. You can't get more volume of air going through an intake manifold without more speed. The faster the air moves the more pressure goes up. So how fast the air moves is important because it is directly related to the volume of air being moved and the density of that air.


    JORDAN

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