increasing air pressure ( ram air scoops )

[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!

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.