Ram Air

[joe4speed]

I have a cervini stormin norman "ram air" hood. I love it, I love the looks and I love the sound. Have noticed no extra power, but I love it!

(the headlight, and foglight covers are gone now.)

I have a cervini stormin norman "ram air" hood. I love it, I love the looks and I love the sound. Have noticed no extra power, but I love it!


Joe4speed what does it sound like refering to the sound you like

[srv1]

i thought "ram air" only works as it says at really high speeds like 190+(roughly) mph. is that true?

[jim_howard_pdx]

D a m n,

here I go again gettin techie on ya'll, and then out will come those jim bashers sayin I'm a know it all.

I don't know it all. I learn new stuff every day. I break everything I have ever raced. I build stuff at the edge of the envelope and I drive it like it will last forever....

Ram air.

Actually, hold you hand out the window of your car as you drive down the road. For every 17 mile per hour the temperature of the air compresses against your hand and drops 5 degrees f.

That is why a jet traveling 475 mph has an outside temperature of -30 degrees f to -60 degrees f. (the friction of the air warms the aluminum skin, but the compressed air cools it down and the temps above are what remains.

So at 17 mph your engine will love having denser, compressed, cool air. At 70 mph the air is really streaming in. At 120 when you go through the speed trap of your drag strip, the air is super cold, super dense, and tightly compacted. This is why ram air is so effective. It is free horsepower, but remember you will need to rejet your carb or you will go leaner as you go faster. This is disastrous. A speed density EFI might want some recalibration. A MAS EFI will make the corrections as part of its normal function.

Hope this helps.

Now try to stand on top of your car while it goes 70 mph. The wind blast will make you slip and slide, at 100 mph you could not remain on the car without tether straps.

[srv1]

what i meant Jim was for actual "ram air" to be affective the most, high speeds is where it is more useful. correct me if am wrong know it all!

[PKRWUD]

Originally posted by srv1
what i meant Jim was for actual "ram air" to be affective the most, high speeds is where it is more useful. correct me if am wrong know it all!

There will always be negative pressure, or a vacuum, between the carb and the "ram air". The ram air can not and will not exceed the amount of air the engine is asking for.

James, don't get confused, it's cold air induction, period. Same rules apply.

[gofastmercury]

Air flow over an object will exchang heat more quickly the faster it moves, know as wind chill factor, but the temp of the air does not change, or its density. I'm also sure the air is cold at 10000 feet, at any speed.

BUT, The point is, non under hood air is better than under hood air. The chevy cowl hood, is a good example this, not a pressure thing, just cool uside air.

[PKRWUD]

Originally posted by gofastmercury
BUT, The point is, non under hood air is better than under hood air. The chevy cowl hood, is a good example this, not a pressure thing, just cool uside air.

Exactly. Very well put.

Take care,
~Chris

[srv1]

Originally posted by PKRWUD
There will always be negative pressure, or a vacuum, between the carb and the "ram air". The ram air can not and will not exceed the amount of air the engine is asking for.

James, don't get confused, it's cold air induction, period. Same rules apply.

not even at 240 mph? seriously, it never changes it state from cold air to somewhat of forced induction at a REALLY high speed? i use 240 cause the McClaren F1 can do that.

Better yet, the Z06 Vette. rated at 405(right?) can do 200 mph, so if i had a ram air, you mean to tell me at 200 MPH that engine is sucking the air in rather the air forcing itself in?

[fiveohpatrol]

by the Ideal Gas Law--> Pressure*volume=density*constant*Temp.

I dont see velocity in there, so the density does not change.

[Agent_4573]

by the Ideal Gas Law--> Pressure*volume=density*constant*Temp.

By definition pressure= area*velocity

so area*velocity*volume=density*constant*temp

However everyone on here is correct when they say that even at 200 miles an hours the engine is still sucking air in rather than having it forced in.

[fiveohpatrol]

By definition pressure= area*velocity

what make you think this is true?

pressure's units are: force pre unit area (ie Newtons/meter^2)

how does this equal (m^2) * m/sec ???
or for you english units people: lbs/inch^2 does NOT equal
(in^2)*ft/sec

[joe4speed]

The sound is cool... I can't really explain it... It makes a low growl when you first floor it, coming from the ram air holes in the hood. The deep intake noise... I can't explain it!!! LOL

[PKRWUD]

I agree with you Joe, I have had hood scoops on 4 of my last 10 cars, and I have a functional cold air kit on my truck that I have affectionately called Ram Air.

James-
Does the air that enters a jet engine ever pushed in faster than it's sucked in? Even at 1500 mph? No. If it was, the jet would stop accelerating. Unless of course it's got the engines killed, and is in freefall.

In an automotive application, the more direct the source is, the better, but it will never be forced. It's nothing more than a cool sounding name for cold air induction.

Kinda like blower vs. supercharger. lol

Take care,
~Chris

[jim_howard_pdx]

fiveohpatrol wins my first award for finding one of my flaws.

Obviously the air does not become denser as it compresses--only colder. However the air fuel charge IS a much denser "charge". You get extra cylinder pressure when the denser air/fuel mixture heats up under the compression stroke. This is where the extra horsepower of ram air is created.

No......The air being pulled through your manifold is over 500 mph. You would have to exceed mach 1 in order to pressurize the carburetor or FI system. Do you see this?????

FiveOhPatrol! Awesome!!! Good catch, I did not expect anyone to call me on this one. This is like post grad level internal combustion engineering!!!!

YOU ROCK!

By the way, some gases will become more dense as they pressurize and will change states from gas to liquid. Liquid Hydrogen, Nitrogen, and Oxygen are several gasses that do become "dense" as a function of their compression. In physics we like to say it is not dense but just a change of state from liquid to gas and back, but a "chaos" theory mathemetician would dispute the physics instructor from now till the end of time.....

I guess I fall somewhere between the two pencil necks. Gotta love those of us who refuse to pick sides......



MOST EXCELLENT.

[fiveohpatrol]

you are an odd odd man

[Agent_4573]

ok I was wrong with my first equation but let me correct myself. Let me start with this

Obviously the air does not become denser as it compresses

I'm not understanding this because if you compress air you make it more dense. Also if you compress a gas it heats up, it doesn't cool down. Think about a nitrous bottle. When you shoot the juice you decompress the bottle by letting liquid nitrogen escape. This is what makes the bottle so cold.

Now as for the pressure being dictated by velocity, I was originally wrong with my equation. If you look at the equation of continuity and bernoulli's equation, you get two things, a1v1=a1v1 and that work is equal to the difference of two pressures time the volume of liquid(air) to pass over a section. putting these two equations together and substituting back in, ,you get pressure change*volume=.5*mass*velocity at point 2 squared + .5*mass*velocity at point 1 squared. This means that velocity and pressure are related.

Think of it this way. You have a garden hose. You put your thumb over the end of the hose and the water squirts out faster. You decreased the area of the end of the hose and that made the water move faster. But in order for the water to move faster, you must increase the pressure. Thats why the more of the hose end you cover, the harder it is to keep your thumb over the hose. if you think im wrong doublecheck me in "Serway and Beichner's Physics for scientist and engineers" volume 1 fifth edition pages 470-472

[Agent_4573]

and its not post grad engineering, its freshman physics.

[srv1]

Originally posted by PKRWUD
James-
Does the air that enters a jet engine ever pushed in faster than it's sucked in? Even at 1500 mph? No. If it was, the jet would stop accelerating. Unless of course it's got the engines killed, and is in freefall.

In an automotive application, the more direct the source is, the better, but it will never be forced. It's nothing more than a cool sounding name for cold air induction.

Kinda like blower vs. supercharger. lol

Take care,
~Chris

basically your saying demand is higher than supply, right? i see what you are saying now. what happens if you put a venturi in the tract of the "ram air"(not the carb)? at 200 mph? i would be curious to know.

thanks Chris

[Agent_4573]

There is an engine called a RAM JET engine which actually uses speed and the "ram air" effect. At speeds over mach one, around 700 mph, planes create a shockwave, basically waves of super-compressed air. The engine is designed to direct these shockwaves into the engine to produce forward thrust. At speeds of over mach 3, the "engine" itselft just gets in the way of the compressed air effect. So there are instances in which the air is actually pushed into an engine faster than being sucked in, but it was only really used in the "Blackbird", an air force recon plane. The only problem is this kind of engine is only effective at speeds greater than mach one, so a standard jet-turbine engine must be incorporated in to get the plane going at least that fast before the ramjet can take over... GO here for a more detailed description of how this works: http://www.grc.nasa.gov/WWW/K-12/airplane/ramth.html