increasing air pressure ( ram air scoops )

[boss rods]

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 ?

[Tom Welch]

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

[1BADBET]

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)

[boss rods]

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 .

[TheJDMan]

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.php?partno=46-60039&diesel=true&

https://static1.pt-content.com/images/pt/2015/12/4660039B1600_400-1.jpg

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.

https://static1.pt-content.com/images/noimg.gif

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%.

[j-c-c]

duplicate

[j-c-c]

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.

[glr0212]

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.

[HellPhish89]

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.

[Zspoiler]

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

[Ben@SpeedTech]

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.

[Ben@SpeedTech]

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! :pat:

[raustinss]

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

[1BADBET]

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! :pat:


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.

[camrat68]

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

[mean buzzen half dozen]

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!:woot::woot:

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.

[Handy Man]

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.

[1BADBET]

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.

[krom]

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)

[1BADBET]

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.

[raustinss]

the basics of hydraulics apply here too guys ...where the area is small the pressure will be higher and vice versa . so somewhere here the volume of intake tubing must be taking into account . the same speed on the same car with a 2" vs a 4 " will have 2 different pressures not that im a rocket scientist

[krom]

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.

raising the pressure will increase the volume without changing the speed.

Also all N/A engines the manifold is at a lower pressure than the atmosphere.

Any increase in pressure to the intake manifold will increase the volume of air flowing, it doesn't matter how fast the air is going when it gets to the intake

[1BADBET]

You can not increase the volume without changing the size of the intake manifold lol.

If you increase the pressure in the intake manifold on a n/a engine it just has less vacuume.

You need to look up the definition of pressure and volume and understand how they are related. A cliff notes on basic physics book would be a good start. I think you could get one for like 6 bucks on Amazon.

[krom]

You can not increase the volume without changing the size of the intake manifold lol.

If you increase the pressure in the intake manifold on a n/a engine it just has less vacuum.

You need to look up the definition of pressure and volume and understand how they are related. A cliff notes on basic physics book would be a good start. I think you could get one for like 6 bucks on Amazon.

You should take your own advice, as you are wrong, on almost everything you have said in this thread.

I still have my fluid dynamics book from getting my BSME from a private school.

I'm sure this is over your head, but give it a read : https://en.wikipedia.org/wiki/Ideal_gas_law


btw, I fixed the spelling errors in the quote, but didn't bother with the grammar.

[raustinss]

Jesus... think some cream might be in order for that burn lol....if I was wrong on anything please roast me in the same manner ...lmao

[TheJDMan]

Be nice guys!

[1BADBET]

With all the comments I've received on this thread and the "haven't you stuck your head out the window" analogies I wouldn't think what I said would be viewed as disrespectful however if you took it that way I apologize.

Now the best illustration I have heard is a water pipe with water flowing through it. If the water is flowing at 5gph and the pipe size is fixed how can you move more water through the pipe without increasing the speed of the water? If you increase the speed the pressure would also increase. If there is something that doesn't make sense please let me know. Or better yet explain to me in small words, as I am no engineer, how exactly you can move more volume at the same speed with a pipe of the same size.

I did go to the best school in the country for automotive machining and race engine building. We have students in every form of racing from nascar to pro stock and everything in between. Our instructors have more industry contacts than anyone in the industry so if he says it, it's not because he thinks he knows everything it's because the top guys in the country are saying it. So I might not have an engineering degree but I'm not dummy either.

Also if you could explain what average port velocity actually is the induction system if it's not 235-245fps and how you could get positive manifold pressure without having the outside air move faster that what's already going through the engine that would be awesome. I don't mind if I'm wrong, or if anyone has a differing opinion but explain it in plain English so we can all learn and see from others perspective not just post a Wikipedia link that less than 10% of the people would understand.

[raustinss]

And Wikipedia pages can be edited

[Zspoiler]

Hood scoops and the like also reduce air intake temperature as well. And that makes more Horsepower as well.Haven`t you notice on cold days once the engine warms up .The cars runs stronger.

[raustinss]

Oh 100 percent yes ...a dry winter day here even in a daily driver I notice it .....I mean a cold a** winter day -20C ..or more

[kevmurray]

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 ?

I have no experience with vanes within a scoop but I'll give my thoughts. I see no way for vanes to actively increase pressure (and I doubt that was your thought). They could be used to induce a laminar flow but their placement and shape would be crucial. There would have to be extensive testing to prove the design, as it's very easy to upset airflow despite the best intentions. I agree that rifling the air would cause turbulence which is bad. There is the dimple technique (golf ball) which works by upsetting the boundary layer, thereby reducing pipe-friction. But I imagine anyone with the room for dimples could just increase the diameter of the pipe instead. This would slow down the flow and reduce the pressure drop on the way in.

JDMAN posted an interesting photo. The vanes seem to be there to help the air around the short side radius and achieve a laminar flow on the down-wind side of the bend. What is your application? Are you interested in getting air around a corner or are you just looking for a way to reduce turbulence?

[Handy Man]

Now the best illustration I have heard is a water pipe with water flowing through it. If the water is flowing at 5gph and the pipe size is fixed how can you move more water through the pipe without increasing the speed of the water?


The problem with this analogy is that air is compressible, water is not. If you replace the water in your scenario with air, and then you increase the pressure of the air (or, in other words, decrease the vacuum),while keeping everything else constant, you will move more air mass.



If you increase the speed the pressure would also increase


Increasing speed by itself actually decreases pressure. This is why cowl induction works. Air slows as it hits the windshield, creating higher pressure.

To make more power you don't need more air speed, or air volume, or air pressure. You need more air mass, which is a function of all three (see the ideal gas law)

[raustinss]

ok i didnt lay it down like that but did i not draw this same picture in post 21.....when i referred to smaller area higher pressure ...larger area lower pressure ....clearly a larger area will flow more air . the point to all of this i now believe is keeping a large area and still trying to increase pressure . everyone knows that water isnt compressible BUT, IT SEEMS YOU MISSED THE POINT THERE . the basic concept is the same


Can someone please define for myself how air volume is different than air mass ?????

[mean buzzen half dozen]

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!:woot::woot:

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.

My engine was small, 50 CC's the point where I installed a pressure gauge was in the plenum box, that hooks up directly before the carburetor, the pressure gauge I used is extremely sensitive 0-1 PSI full scale, I did several 60 MPH runs and were very consistent.
All test runs I saw a positive pressure of 1/10 of 1 PSI.

I am pretty sure if I have a larger engine, I would have never seen any positive pressure.

Kawasaki tests on the dyno where done with simulated 160 MPH air entering the ram air scoop.

[krom]

ok i didnt lay it down like that but did i not draw this same picture in post 21.....when i referred to smaller area higher pressure ...larger area lower pressure ....clearly a larger area will flow more air . the point to all of this i now believe is keeping a large area and still trying to increase pressure . everyone knows that water isnt compressible BUT, IT SEEMS YOU MISSED THE POINT THERE . the basic concept is the same


Can someone please define for myself how air volume is different than air mass ?????

Volume has no way to account for density.


1 cubic foot of air at 5 psi is less dense, and has less mass, than 1 cubic foot of air at 50 psi. Therefore it has less oxygen, so it can burn less fuel, and will make less power.


Give the wiki link a read: https://en.wikipedia.org/wiki/Ideal_gas_law, or look for different explanations of the ideal gas law.

The more n we get into an engine, the more oxygen, we can add more fuel, and make more power.

[raustinss]

sorry yes you're correct ....i took this as a more "common" misused term ....in the correct wording yes air mass would be a perfect definition of density
now back to the topic ....do they work definitely otherwise you wouldnt see so many factory cars with them , ram air, cooling ..etc . my thoughts are still i believe it would be more then 1 psi on a typical engine . what would be fantastic would be someone having a sensitive pressure gauge and a car already with a ram air set up ...then tape it off and go for another drive . we also have to account for ambient air temperature ..dont we ...? again with the hand out the window thing but the air always feels cooler under pressure so to say

[1BADBET]

I was just using the water pipe as a visual example so you could "see" what I'm trying to say.

You are right speed goes up pressure goes down, I got that one backwards. My bad.


I think everyone understands the general concept, and we are just tripping each other over the scientific definition of the words we are using to explain our thought, I think we are all the same page though. An engine doesn't "suck" in air the desending piston creates a negative pressure and the higher pressure air equalizes filling the cylinder, but we all understand the general "the engine sucks in air" illustration tho not scientifically or in engineering technical terms correct.

I've been told a forward facing scoop on a prostock is worth .03, if you look at what they're running this year with the new rules that doesn't sound too far off (they also have rev limiters and fuel injection to sort out) the point is they are going way faster than most people on here would. You would have to design a scoop large enough to feed the motor at a rate faster than the additional drag it creates. The best thing for a pro touring car is going is going to be to grab the coolest unrestricted air we can without causing more drag as we don't have the power or the speed for it to make a difference, aero on the car would make a difference tho. So, let's not worry about what really doesn't matter.

The 160mph figure is calculated at 14.7 atmospheric. Elevation, air temp, air density, grains of water (humidity) all have an effect on what's happening in real life. Also the 235-245fps in the manifold is the average as I mentioned, so is it possible to see a fraction of a pound of boost at slower speed, yea. Does that boost out weigh the drag it creates? In a motorcycle with a small frontal area maybe, in a full bodied car, nope. But again, who cares.

FYI I've heard of several guys going faster when switching from forward facing to cowl induction but they weren't 200mph cars either.


Let's just try to help each other out and stay positive and try to "get" what a guy is saying and ask for clarification if needed. As to the original topic, I think anything you do to help directionalize air to where you want it to go will help, there's tons of aero stuff that helps on the outside of the car but how effective are vains in a ram air scoop? There are so many variables in design and actual car speed and engine speed I don't know if they'd be worth the effort. 10hp isn't something pro touring car guys usually worry about, if it does matter do a cam swap and make 50 more and be done lol.

[raustinss]

100 percent agree.... So have can we all agree we aren't engineers and none of us are ever going to be .

I would think that vanes of whatever size ,location and direction are designed and put into some aftermarket cold air set up a for a reason . This reason is definitely not to hurt,limit or, restrain power levels . So thus yes I'd say they can help where to locate them ? Size? And direction ? Pfffff that crap is quantum physics to me . Guess that's where lots of schooling and computer modeling come into this.

Jordon is right none of us here are NASCAR or drag racers to the point that we need to concern ours with every last hp m if you feel so inclined to build yourself a ram air set up then do it chances are that you will not hurt the performance but, give you a mental edge. Oh and it can look cool if done right lol.

[HellPhish89]

I was just using the water pipe as a visual example so you could "see" what I'm trying to say.

10hp isn't something pro touring car guys usually worry about, if it does matter do a cam swap and make 50 more and be done lol.

Could always create boost via valve events >_> haha. I've read/heard that 3psi isn't impossible to see.

Using a water pipe analogy is a perfectly reasonable one. Air is a fluid.

[garvir]

nascar designs there inlet in the wind tunnel, differant for every track depending on speed they are tuning for. to big or to small you loose power. they do not divulge this info, highly secret. you know with nascar a few horsepower can make the differance between winning or losing.

[NOT A TA]

Related intake info written by F1 engineer aero guy Willem Toet. https://www.linkedin.com/pulse/air-ducts-down-earth-guide-motorsport-applications-willem-toet?trk=mp-reader-card