The "myth" of ram air.. does it WORK in cars/trucks?

FACT or FICTION: Would be interested in hearing your guys opinions.

It's not a matter of opinion if it works or not.

It's a matter of fact, it either works or it does not, no opinion involved.

My opinion, done right, there is no downside. Doing it right, is not always easy or obvious.

I also suspect most reports of gains, are more from getting a cooler air inlet source, rather then any 'ram' effect.

Cold air is better than warm air

Fiction.

You can "ram" as much air in there as you like, but it won't make fart in the wind difference: there's a thing called an air filter standing in the way.

So after 100? years of racing,rearward facing "ram" scoops should be rather common if indeed its a myth, even in race cars without filters?

Some of the homebuilt airplane guys that use a special shaped inlet for their engines, even with an air filter say that it will give a extra inch of manifold pressure.

cold(er) air & I think there'd have to be some pressure increase. It'd have to have some bennie, maybe alot. No actual back to back testing done here tho

My 64 ran 145 with a scoop, 147 with the same scoop sealed to the hood.
Doug

Much R&D went into the development of this hood...


It ain't an ornament...

Ram air works great! The problem is figuring out the correct carburetor mixture from idle to the speed where the ram air works the best without being too rich at idle to that point and when too much air will lean it out!

Grab some air

Absolutely works. I've made my own from junk many times... the car always picks up.

Problem with the examples given in this thread is that most, if not all, of the improvements are due to not using warm under hood air and are not due to ram air effect. NASA did some testing and it really isn't until you hit 100 mph that any noticeable effect is seen. Of course design (getting above the boundary layer)is important and I don't see any of the pictured scoops designed to do that. I suspect that the mixture issues mentioned are due more to turbulence of the airflow through the carb than a pressure increase in general, after all that is what makes a carb work.

For a street cars, it's for looks. A race car may see ram air effects at the top end of the run.

Old post for geeks getting into the facts of ram air
=====
Page 415 of the Bosch Automotive Handbook, 5th edition

has the two equations you need
to see how horsepower and torque change
when either temperature or pressure change.

For temperature the offical equation
used by Americans (SAE) Europeans (ISO) and Japanese (JIN)
is:

{ Temperature Before + 460/Temperature After +460} raised to exponent 0.6

you need a scientific calculator to do this
but there is one built into every Windows computer
under Start...Accessories

As an example,
say that your re-locate your air inlet to a spot where the air temperature
drops to 80 degrees
when before the air coming in had been 100 degrees.

{100 +460 divided by 80 + 460} raised to exponent 0.6

={560/540} raised to exponent 0.6

= {1.037} raised to exponent 0.6

= 1.022

You mulitply this number times your horsepower or torque
so if your engine.
If your engine makes 230 hp at peak
1.022 times 230 = 235 horsepower with the 20 degree lower air temperature.

You may have heard the 'Rule of Thumb' that each 10 degree F reduction in air
temperature improves horsepower by 'about' 1% and the equation above is where
that comes from, but is more accurate

For corrections when the pressure changes
the following equation is used:

{absolute pressure after/absolute pressure before} raised to exponent 1.2

As an example
say that the weather is changing where you live
and one day the weatherman says the pressure is
29.5 inches of Mercury as a stormy "Low" passes over
then the next day a clear sky "High Pressure Area" passes over
and the pressure rises to 30 inches of Mercury

{30/29.5} raised to exponent 1.2
{1.0169} raised to exponent 1.2
= 1.0204

It is important to realize
that built right into your engine
are IAT (intake air temperature)
and MAP (manifold air pressure)
sensors.

Your IAT and MAP sensor outputs can tell you whether an aftermarket air intake
has helped or hurt your power output. You can read these sensors
yourself by using an OBD-II scanner, or a cheap electrical multimeter.

You are correct to suspect that most CAI's
only make more noise and have flashy colored parts.

Want confirmation about this from a CAI manufacturer?

Well right now KN Filters is running an advertisement in the various hot rod
magazine saying that a typical paper air filter from the factory creates a
restriction of about 2.8 inches of water....and when this filter gets really
dirty the restriction rises to about 12 inches of water restriction. The KN
advertisement has a dyno graph showing that this can cause about 11 hp power
loss on a high horsepower engine.

The pressure of the air around us is about 404 inches of water
so KN Filter is saying that the pressure is changing from
404 - 2.8 = 401.2
to a new pressure of
404 - 12 = 392 inches of water

Play around with the equations above
and you can find out what the actual horsepower of the engine KN was using
was....and then confirm it by looking at the dyno graph in the advertisement.
=======
Heard of the 'Ram Air' effect where the speed of the air hitting the vehicle
builds up pressure in a forward facing air duct and helps 'supercharge' your
engine a bit. ?

Well, at 'typical' street speeds the effect is very very small.

The formula for that is:

Inches of water pressure from Ram Air = (mph) times (mph) divided by 2025.

So at 70 mph the ram air effect is:
(70 mph) times (70 mph) divided by 2025 = 2.4 inches of water.

So the very best possible air inlet tube designed for Ram Air would actually
have a positive pressure of 2.4 inches of water.

How much pressure is an inch of water ?

One psi of pressure is equal to about 28 inches of water.

You can get this by dividing the cubic inches in one cubic foot ( 12 x 12 x
12 ) by the weight of one cubic foot of water ( 62.4 lbs).

The air pressure around us is averages about 14.5 psi at typical heights above
sea level.

So another way of looking at it is that the air pressure around us is about
400 inches of water. ( 14.5 x 28).

So the best Ram Air system at 70 mph gives you a boost of about 2/400 or one
half of one percent. Small.

Ram air started in airplanes where it means more. An airplane going 300 mph
gets a boost of:

300 x 300 divided by 2025 = 44 inches

This is a percentage boost of 44/400 or about 11%

Want a challenge?
Consider your tires.
Some strange facts:
At 70 mph the center of your tire is moving 70 mph.
The bottom of your tire where it 'grabs' the pavement is moving at 0.1 mph
The top of your tire is moving forward at 140 mph.
If you could put a 'Ram Air' inlet right at the top of the tires (where it is
horribly dirty and wet) you could get a significant air pressure boost.....

Supercuda beat me to it. The challenger t/a hood looks engineered to clear the boundary layer, AAR cuda hood looks like a crude NACA duct, and the old superstock scoops look "engineered" to clear tall manifolds or velocity stacks rather than a ram effect.

Cool air = better than hot air. In fact I'm surprised that after all these years of hotrodding, the standard open element 4 barrel air cleaner sucking in hot under hood air is still the gold standard.

As far as any ram effect goes, even IF you did get a smidge of pressure off it, at best it would help to overcome the resistance of the air filter. The carb is not going to see pressure.

Did a lot of work on this in the old Comp car. Figuring the area of the scoop inlet and where the tipping point was as far as at what speed the scoop was travelling vs the engines inlet demands. At that velocity and higher the engine sees a positive pressure in the scoop. Ram air as it were.

"Some strange facts:
At 70 mph the center of your tire is moving 70 mph.
The bottom of your tire where it 'grabs' the pavement is moving at 0.1 mph
The top of your tire is moving forward at 140 mph."

That point was made here in 2011 with an explanation of Weldon's Vegas Indy car fatality, nobody got it then either.

I have wondered about that too.

When a gasoline engine is idling,
Does it use less gallons in an hour
With hot air?

At idle
Intake side pumping losses are high
Because the throttle is nearly closed.

Hot air has less oxygen per cubic foot than cold air,
So the throttle has to open a bit more
And idle vacuum has to drop,
Therefore more atmospheric pressure is available
To push the piston downward on the intake stroke.
This reduces intake pumping loss.

My 1995 Magnum 5.9 V8 seems to have a complicated fender side air inlet system that sucks hot engine compartment air at idle,
but when the truck is moving gets cooler air from a passage in the fender that has its inlet up by the passenger side headlight.

It is so complicated that it has to be designed that way on purpose.

Since they are using the fender sheet metal as an air passage,
Why didn't the designers get the engine air from a vent high up on the passenger side A pillar. This "snorkle" inlet would have other advantages.

Ram air busted: because it does not exist, for the following reasons:
- Air is incompressible at any automobile speed (I.e. speeds less than Mach 0.3).
meaning that the kinetic energy of the air cannot be used to compress the air and
raise the static pressure.
- The “ram air” nozzles commonly employed on automobiles tend to be the wrong
shape. A divergent nozzle is required for ram air. Straight-profile scoops cannot
provide a ram air effect.
Select one of the two types of intakes, warm air, or cold air. Beyond that its just about
looks."
Reference https://www.physicsforums.com

Intake air temps: The rule of thumb with the average V-8 is 1 hp for every 10 degree (F)
drop in intake air temp. That works out to about 1% for 30 degrees.

Cold air kits: Busted (sorta)
https://youtu.be/gCi2yo4UqPI

Most interesting was no air filter made no power gain vs using an standard factory air filter.
Makes you think twice about those K&N claims we all seen. Fascinating stuff.

Yet these guys dyno tested a ~400hp mopar big block and found a 14hp difference between a generic 3" paper air filter in an open element air cleaner versus open carb. Clearly these results would vary with engine air intake demands as well as the efficiency of your existing air cleaner, but the filter they used for their dyno testing was pretty standard in the hot rod community.

http://www.hotrod.com/how-to/engine/1307-mopar-engines-power-vs-luxury/

My 95 5.2 magnum in a jeep grand cherokee just had a generic factory cold air intake just like you would see on any other modern vehicle. IIRC air was drawn in from the headlight bucket area.

My memory is a bit fuzzy,
but on the Spitfire airplanes "reverse ram air" was applied to the engine exhaust manifolds and a worthwhile gain in airspeed resulted.

It should be remembered that if two otherwise identical cars
capable of 100+ mph terminal speeds in the quarter
drag race repeatedly,
with the two drivers swapping vehicles after each race,
if one car gets fitted with an air intake that gets 2% gain from cooler air and 2% gain from ram air,
you would expect that car to win more than 50% of ten or more races.

There's something else at foot there. We did that at the track too. Difference in ET was statistically insignificant with a 400 big block in a 74 Satellite Sebring Plus. I believe the ET's were a consistent 14.2 give or take a hundreth.

Meredith effect

Air cleaner tests are no good with out carb mixture changes too. This rings true with any induction side testing you do.

We must have a failure to communicate here. I wonder if those egg heads are getting hung up on the street meaning of "ram", to me in our application, it only means raising the general air pressure in the vicinity that feeds the carb or whatever, anything that does that in our hobby qualifies to me as "ram", if we aren't splitting hairs. We raise the inlet pressure all the time, sometimes lower it un-intentionally, hence all the comments as to the carb needs tuning for fair comparisons. I pretty much lost interest at the "Incompressibility" at less then mach 3 comment.

You get cold air in either case - scoop sealed to the base plate/carb or not - but you pick up power by having a PROPERLY designed scoop sealed to the carb. A poor design can actually SUCK air OUT of the scoop.

On my car in C/SA back in the 70's going 115 or in SS/GA going 125 - hooking up the scoop to the air cleaner baseplate has always produced more power - shown in lower ET and higher MPH.

In fact John Baumman (Chrysler carb expert) jumped in my case when I ran slower at a Milan Test Day after a change in manifolds from the old factory six pack to the STR. When I took the hood off the car and he saw no baseplate he said "there is your problem". I had to "modify" that OE 69-1/2 baseplate with a hacksaw - added some sponge to the outer portion to seal it to the hood - and picked up a solid tenth and 1-1/2 mph. But don't believe any one person - do a base line test - if you have a scoop - attach a sealed base plate to the scoop and make a couple passes then take it off. See what happens. Don't give up because some people offer up invalid assumptions and opinions - TRY IT FOR YOURSELF.

.(point)3 mach. Around 230mph.

This is true of people. However the science of fluid dynamics doesn't lie. Great conversation though, interesting opinions

They may not lie - but they are subject to interpretation. If all else fails - use scientific instruments. Hook up a manometer to the scoop - like Chrysler did back in the day. Yes - the primary purpose of the street scoops were for fresh (colder) air - the race packages were tested and proven to provide "ram air".

(Don't waste yer time...


He's already made-up his mind...)


'Ram Air' is a myth...

FD trumps all...

I think it stands to reason that without a carb to hood seal, between the speed you put on and the fan turning 5000rpm, the engine bay is enough of a high pressure zone to overpower your tiny scoop.

Lets not forget that cars fun faster at lower elevations, proving that the slight difference in air density does make a difference.

I wonder why the old pro stock cars had that giant air scoop on their cars,not real aero are they?

There is a lot in the design ov the air cleaner itself. The difference between running a stub stack atop the carb without anything else and running various air cleaners, from stock design to cheap aftermarket design, from 3x10" to 2x14" to 5x14", from paper to K&N were notable enough for me to ditch the thing altogether and risk sucking whoknowswhat down an open stub stack. One ov the many 'tricks' on that car... though you'd probably be mad to daily drive a car with essentially an open carb on any engine you had real money into. Had i been really gambling, i'd have found a way to 'flow' the hole in the hood into the stub stack and then be only sucking in cold air on top ov all else... but that would be literally asking for trouble with an open carb. Maybe for track only...

Now a days the manometer has been changed out for a map sensor mounted in the scoop/carb plate area. Makes it very easy to see if the pressure is above or below atmospheric. If you haven't done this you're just not as dedicated as some other racers. It's always easy to talk theory, results speak for themselves.
Doug

A map sensor doesn't show flow turbulence though. turbulent air thru the carb is not optimal. I might need to make one.

Chrysler seems to have dedicated more money to designing and building long runner intake manifolds, than on ram air/cold air inlets ahead of the throttle blades.

In the end everyone's budget and time is limited.

Getting a high flow rate 25 to 28 inch long runner intake manifold that also feeds all eight cylinders equally appears to provide more bang for the buck for street driving.

there is a saying...

"spare me your technical BS and show me your time slip"

Science and theory is great, but i'll take real world track numbers anyday.

There are horsepower dividends to be found here.

My builder uses those contoured plastic stub stacks on some of his hydroplane engines. Good for several HP (less than 10) on a 2.5 litre engine.

The theory is they straighten out the airflow into the carb.

If you race with no air filter, leaving the filter base on depending on how it's shaped is supposed to help for similar reasons.

Not knowing the correct engineering speak but it's either aero or fluid dynamics (Maybe both?) at work I believe.

Kevin

This guy got ALOT of power.

myth or not, atmospheric presser + 1 is boost, turbo, sc, or ram air.

richard petty used a cowl induction setup that worked---there is a pressurized area there at the leading edge of the windshield--when he did it it was called legal cheating because the rule had not been formulated---also wind tunnel tests show a dead layer of air at the front and top of the car--if your scoop sticks up 2-3 inches it is looking cute--but isnt that effective

Cold air intakes have been proven to work over and over again. Physics says that you engine will produce more power with a higher inlet pressure. You might be able to say that a particular design doesn't work but to say the ram air never works at all, especially on the basis of an internet physics forum, is ridiculous.

Air is incompressible at speeds below 230mph. And what the difference between an online forum and some guy writing it out on a chalkboard in the 1930's?

Ice, explain this:




I believe you will find a similar device on every NASCAR vehicle in competition, including those tracks where speeds seldom exceed 120 mph.

underhood = lower pressure
near the windshield = higher pressure

the higher pressure air just moves into the area of lower pressure.

Considering most NASCAR noses are completely blocked off from incoming air and no scoops allowed, drawing air from the cowl is the most convenient spot I would think. But I ain't no engineer lol.

"But I ain't no engineer"

We agree. LOL

Spend some more time re reading Wiki:

"Compressible aerodynamics[edit]
Main article: Compressible flow
According to the theory of aerodynamics, a flow is considered to be compressible if its change in density with respect to pressure is non-zero along a streamline. This means that - unlike incompressible flow - changes in density must be considered. In general, this is the case where the Mach number in part or all of the flow exceeds 0.3. The Mach .3 value is rather arbitrary, but it is used because gas flows with a Mach number below that value demonstrate changes in density with respect to the change in pressure of less than 5%. Furthermore, that maximum 5% density change occurs at the stagnation point of an object immersed in the gas flow and the density changes around the rest of the object will be significantly lower. Transonic, supersonic, and hypersonic flows are all compressible."

The word "arbitrary" stands out above, and the "compressibility" expressed is in terms mainly of aircraft aerodynamics, engine nlet intakes are much more responsive/sensitive to very low pressure changes relating to the original question posed, "fact or fiction", not "worth it or Not"

IIRC, some years back one of the car mags did extensive testing of cold-air induction systems. I do recall one thing they mentioned was boundary layer air and the need to raise most scoops higher above the hood line to realize a true gain.
"Ram Air" is somewhat of a misnomer as related to automobiles and seems to really be confusing some folks who are trying to take it literally.



Tim

id you ever stick your hand out the window while running at 60 mph? What did it do, just sit there? I think not.
Doug

This has GOT to be a record-breaking troll thread...

Troll thread? Then I suggest you hit the notify button and give a reason to the moderators. Thanks.

The trolling began with this post. You are not interested in hearing our "opinions", you are interested in trying to prove a point and therefore making yourself appear knowledgeable.

I don't think it worked.

I'm not trying to prove a point.It's called counter arguments. That why I said I'm interested in all opinions. Had my mind sorta made up.. but not really. But whatevs dude.

Ram air isn't a myth, it just isn't worth much power for a street car since it is only a small amount of pressure at freeway speeds. A fast drag car can make use of ram air though. Pro Stock cars build a significant amount of pressure in the scoop going thru the lights.

Chevrolet did that with the '63 impala Z-11 cars.

You really mean "Smokey"?

The guy writing on a chalkboard would be a known expert with a Phd paid to train students. The guy on the internet forum could be you.
Higher pressure = compressed. Air is in fact compressible.

They all had them. Maybe smokey came up with the idea, but it was standard on all the Z11 cars, even Ronnie Sox's....
http://www.streetlegaltv.com/news/muscle-cars-you-should-know-63-chevrolet-z11-impala-427/

The auto manufacturers sure have wasted a lot of money with hood scoops and ram air setups over the years.

ok then. Red line is normal atmospheric pressure.where's the boost from ram air?

We have a different benchmark I guess for what makes a fact vs a myth then. All I see is colored graphs.

So, ram air works, eh?

In that sense, you're sure right buddy!

Exactly, a couple of graphs with no explanation of what they are does not prove or disprove anything.

If you want to see ram air in action then call a Pro Stock team and ask them for a pressure reading from the air box during a 1/4 mile run. Or call up a NASCAR team and ask them the same info. Or to make it simple call Dave Braswell and ask him how much air pressure a Pro Stock carb sees in the lights and how it changes the AF ratio.

if you have contactinfo i'd call! i'd be curious to see exactly whats going on. Thanks good Sir.

Depending on scoop inlet area, as soon as the vehicle sees a specific velocity that creates a flow volume greater than the engines need at its specific RPM you will, from that point and accelerating further, have a positive pressure situation.

What is the bottom value (X axis) and why are the graphs so different?

Basically what this is saying is that +.34 Psi @ 14.21 psi = + 17hp difference IN FAVOR of ram air. Which is good. However air is incompressible at speeds below 230mph IE: 14.7psi @ sea level + xx value.

So the ram air does work at bringing the PSI close to atmospheric pressure of 14.7, but will not cross that threshold until ground or airspeed reaches at least 230mph.

So myth confirmed, to a point. My apologies, as I should have said ram air to create boost, as boost is defined as 14.7psi + xx.

Exactly, you don't necessarily need boost to create more power, more flow will do that. However there are plenty of MAP readings out there showing above and below atmospheric pressure depending of configuration of the inlet. Do you think a knowledgeable racer would sacrifice aerodynamics of a protruding hood scoop if it slowed the car down? I think not. Do you think none of these teams test?
Doug

BS

Thats it? Then what's your insight? Cause BS is the answer of a prepubescent teen.

Something is wrong with your basic assumption that air is incompressible at speeds below 230mph. That statement is false, air is compressible at any speed. So that original statement needs to be run down and understood. I think it is causing all of your confusion.

It is vey easy to hook up a pressure gauge in an air box and drive down the road and you'll see positive pressure well before 230 mph. So someone just made a basic error when they wrote that statement.

So, who said it created positive manifold pressure at common race speeds?

If it reduces the amount of vacuum in an intake then it has been successful. It does not require pressures above barometric.

Air inlets of different shapes and sizes will create different pressures. Combine that with different air demands of different engine/chassis/speed combos and you're all over the board.


As for JCC, don't try to make him think something he doesn't want to think. He has his own little ways of fighting for his preconceived notions. That's why I have him on ignore.

Agree with this statement, although it's been a long time since I got my ME degree. To the OP, please identify the source of your info? Seems to me there may be some confusion there since air absolutely is compressible, but in calculating line losses in fluid flow it was acceptable to treat air as "incompressible" within a small range. If the pressure drop (hence the change in density/volume) was too great you would you would have to break the system into smaller segments to do the calculations.

Of course, that was back in the day when YOU actually did the calculations, and not just feed info into a computer that spits out a number.

https://en.wikipedia.org/wiki/Compressible_flow

Just hook up a manometer to an air box and you'll see that it generates positive pressure even at highway speeds. That is all the proof that you need.

From your source:

"the Mach number (the ratio of the speed of the flow to the speed of sound) must be greater than about 0.3 (since the density change is greater than 5% in that case) before significant compressibility occurs."

Key word: significant. It does not say it is not compressible, just not significant. So what everyone has been saying is correct, and there absolutely is a pressure change and a potential performance gain possible from ram air.

Also, look up velocity pressure or dynamic pressure, since that is the physical phenomenon that comes into play in this situation. You will see, that for relatively low velocities, (less than 0.3M above) the equations converge for compressible and incompressible flow. So you could use the equation:

q = 1/2 pv*2

to calculate the pressure gain.

You've drawn the wrong conclusion. Go look up how a pitot tube works and you'll see that there is something called dynamic pressure. A hood scoop creates dynamic pressure at any speed. There is nothing magic about 230 mph. An Indy car creates down force well before 230 mph. Small airplanes fly at speeds lower than 230 mph.

Well, nothing else seemed to be working.

And you asked for opinions, 3 or 4 times I have already given reasons contrary to your thinking, among others who have also, and you keep making statements with out any backup, and now are using charts referencing aircraft design considerations, which have little bearing on this forum or topic, and you continue to ignore those concerns voiced by many, and in deference to feets, they have yet gotten to the point of simply call a spade a spade, or as I succinctly stated, "BS", which seems still pretty accurate.

"Feets" taking a shot at me about my comments here. when you have me on "ignore", bizarre

Somebody Quote me please

Best of Moparts?

And people wonder why we can't get a good government in place.

Stir the pot. You hit it there buddy.

I think it clearly explains that the is a marginal PSI increase up to 14.7psi. .25psi .30psi whatever. Now that example of a 17hp increase was was an example for 200hp engine. On a 1000hp engine it would be around 85 hp increase from a .25psi gain. Obviously it doesn't take the cooler air into consideration because it'll be more yet. No BOOST yet. From what I read, you'll make BOOST after 230mph from ram air. 15.5psi, 15.7psi 16psi. In other words 1psi above atmospheric pressure increase per xxmph above 230. K? K.

Why are you so hung up on 230 mph? The air molecules don't know how fast the hood scoop is going. It isn't like they look at a car and say "it is only going 210 mph so we're not jumping in".

The pressure in a hood scoop will increase with the square of the velocity starting from zero. It isn't a light switch that turns on at 230 mph. There will be positive pressure (greater than 14.7 psi) at any speed above zero. The equation was posted back on page one of this thread.

When you can back up your claims, with actual TRACK TIMES, instead of just "theory", then report back. K?

Why did IE go from "The "myth" of ram air.. does it WORK in cars/trucks?" to "boost"?

Ram air works, even if it does nothing more than allow the engine to get cooler air. I suspect that was the intent of most air grabber type systems.

Well it's just the fluid dynamics theory. That's all. Show me the contrary proof that ram air can give positive pressure. Again, great conversation (some notable exceptions however).

Where is that dead horse thingy?

Just being honest here, "Idiocracy meets Moparts" thread

This has been a fun waste of time.

Show me the contrary proof that ram air can give positive pressure

As I said in an earlier post:
Depending on scoop inlet area, as soon as the vehicle sees a specific velocity that creates a flow volume greater than the engines need at its specific RPM you will, from that point and accelerating further, have a positive pressure situation.

This theory you have with those graphs are for clean flow situations like air passing over an aircrafts wing. They have no bearing here.
Now for the above:
Lets take an engine with an air consumption rate of 1000cfm.
Now the vehicle has a scoop with an inlet area of 30in^ or .21ft^
We know Q=VA, where Q is volume fluid flow in this case in CFM.
V= the vehicle velocity.
A= the area of the scoop.
Simple algebra V=Q/A
1000/.21=4761.9 FT/Min or 54.1MPH
At that velocity and above pressure will start to increase. More air entering than the engine normally consumes so the unused air compresses and builds pressure within the scoop. How much is hard to calculate as there are turbulence issues in the scoop. We actually had a scoop on the Comp car that created enough reversion above the carb that it sucked fuel out of the vent tubes at a certain speed. Took a while to figure that one out. I am now out on this subject.

so the RAMCHARGERS were correct all along!!!!

That has been done several times on this thread. You seem to have your brain locked on something and won't let it go.

Positive is defined as an increase.

If a container has 12 inches of vacuum and you raise the pressure to 3 inches of vacuum that is considered a positive increase in pressure. While still a vacuum, the pressure is higher than before.

You seem to be the only one fixated with pressures above barometric.







Sadly, the primary exception seems to be the OP.

That can't work. It's way too obvious and simple of an answer!

You don't understand fluid dynamics. You read a Wiki article and didn't understand it and now it appears that your brain has locked up. If you understood fluid dynamics then you would understand the concept of dynamic pressure and how to calculate it. You would look at how a pitot tube works and you would understand that it is the same principle as a hood scoop. If you had any sense at all you would type a few search terms into Google and come up with stuff like this thread:

http://www.yellowbullet.com/forum/showthread.php?t=366312

I've been in cars with no hood, and no air cleaner, and fuel getting sucked from the carb, onto the windshield...

I also assume all racecars with brake cooling ducts are just for looks, as air can't possibly be rammed in and be affective....

Here is the graph of dynamic pressure relative to speed. A well design air scoop should be able to capture most of this pressure. I think this chart comes from Moparts member Mark W.

I spent some time talking to a guy that raced 68 W31's (ramrod 350) for Oldsmobile. The 68 cars used two ducts routed to scoops under the front bumper. He did a good bit of testing and reported that this was worth significant ET and MPH improvement. He did mention that the scoop-under the bumper design on the 68 cars where more effective than the sealed hood scoop design used on the 70 cars.

Also, aside from any increased intake pressure effect, we know a cooler intake charge is beneficial.

Is the shaker hood on a Cuda fully sealed to the carb or is it vented?

Leaf blowers are unbelievably cheap now days.
Gasoline generators,
Kw-hr meters,
hand held wind speed meters and
other test equipment
have never been as affordable as now.

These things can be tested yourself, in the style of Mythbusters.

Should i be encouraged that people have strong feelings on these subjects,
Or discouraged that
the typical high school physics classes of today
appear to be very ineffective?

Past threads about tailgate up or down
Have sadly gone down the path of this one.

What if you leave the tailgate down on your treadmill?

My hand didn't do a thing till about 230 mph, then oh yeah, felt the boost. Just did it, nothing before that though, strange???

Ram air is indeed beneficial all over in all engine related performance builds, across all, industries.

I'll bet 99% of forum members already knew that hood scoops and cool air ducts improve performance by only a small amount in real world driving.

Since lots of people think scoops look sexy, they aren't going away anytime soon, which will no doubt keep discussions like this one going.

Every NASCAR car that I have seen up close was getting intake air from the bottom of the windshield by way of a carbon fiber air box from the firewall to the carb. I'm pretty sure each and every NASCAR car has these air boxes that feed the carb cool air and supposedly higher pressure air that piles up at the bottom of the windshield at high speeds.

Hood scoops slow them down, stick your hand out the window at 60 mph, now at 200, still got a hand? Benefit of scoops are less than the drag it produces, so they use the cowl, no drag and good results. NASCAR from day one said they where not allowed.

You are implying exactly what?
And are you going to share your idea of why from the get go (1959?) why Nascar has never allowed hood scoops on "stock" cars?
Or why NHRA has recently restricted them on Pro Stocks?
I agree, this never ending thread needs to be renamed "Moparts Mythbusters".

Wow.. this is turning into the "can a propeller plane take off from a conveyer belt" fiasco.

Maybe Mythbusters can say confirmed/busted lol. Oh but they ain't on the air anymore..

"And are you going to share your idea"

Nah, look it up, I did

Some don't look anything up. Some need to get a fluid mechanics textbook.

Every airplane in the world uses a Pitot tube which is ram air to move a gauge. You are using aerodynamic concepts for compressibility in front of an airfoil. Wrong use of application, but hey what do I know? I have only worked on everything from a 747 to an F-15 to a UH-1 to a super cub.....

http://www.luizmonteiro.com/Article_Pitot_Static_Blockages_02.aspx

actually it can. coming from someone who landed on a moving freight train...

The complete question was "And are you going to share your idea of why from the get go (1959?) why Nascar has never allowed hood scoops on "stock" cars?"

Then care to share what you looked up, and what you discovered, and your source, like a grown up?

You likely will find that "Nascar" adhered to the philosophy of maintaining a stock appearing car like the paying spectator drove in the late 50's, and hood scoops were not part of that look, I suspect the tradition took hold thru till today on hood scoops. Aero concerns of turbulence of air scoops was not on the radar back then in stock car racing. The cowl intake solution was a clever successful later work around.

According to Chevrolet, they couldn't figure out why there Chevrolets were slowing down as the race wore on and the Pontiacs were faster with 25 less horsepower. It was determined that the Pontiacs engine bays were running 20-30* cooler than the Chevrolets. After some experimentation at Daytona speedweek, the NASCAR cowl induction was born.

Just so happens Popular Hot Rodding magazine did a test with a NASCAR style cowl induction:

"One thing to keep in mind is that this sort of induction doesn’t really offer any true ram effect, and, in fact, most ram-air-style systems don’t either until very high speeds—and even then the pressure increase is pretty negligible. Since cooler air is denser air, and denser air makes more power, the real goal is to provide the engine with an easy source of the coolest air possible."

Well, it's clear astjp2 won the thread with an actual graph of pressure vs. airspeed.

Be careful with that conclusion, there have been graphs shown by parties here with opposing views, interpreting the graphs is the key. I'll try to find the graph of protagonist "certainty" vs intelligence.

PS read my sig link.

So you are saying that every aircraft that uses an airspeed indicator is wrong? Or that my graphic is bad data? That is where those numbers come from. The size of the opening does not change the pressure either, a 1/4" pitot and a 3" have the same pressure, the larger one has more overall force because of the cross section but the pressure inside is the same. Tim

No, what I saying is, blind faith in graphs(?) is what started this train wreck, blind faith is the problem, not the graphs.

The equation for that graph was provided back on page one of the thread so the answer was here the whole time. The OP just had "wiki induced brain freeze" which is a relatively new disease. Didn't exist when I was a kid.

Your just not getting it

SHOW ME BOOST! On a car, not a plane, boat, ship, jet, ufo, mosquito after taco night, a bad night of explosive diarrhea but a car travelling at 100mph, or even 200mph, with ram air induction showing BOOST.

Pretty simple request.

RE:

I think YOU'RE (not your) not getting it.

You want boost?

Look inside the pitot tube. There is your boost. Even if you stick one on a car.

ANY increase in pressure is technically boost.
Raising a vacuum 1" closer to atmospheric pressure is boost.

If you want to see 14.8 psi inside an engine on a 14.7 ambient day without going stupid fast then you're going to need mechanical assistance.

There.

Are you happy?

See I didn't have to show anything.

I make a real concerted effort to not let these things go personal.

But The Pontiac/Chevrolet tidbit above has me raising my eyebrows, again, because I have never heard that explanation before, there is no obvious explanation for his conclusion, no quoted source/reference, the author who is connecting the dots, and the author's track record here on this thread, already connecting unrelated dots. Just my opinion before it gets written in stone.

Sport440
{Why would ram air boost stop at 14.7???} Answer, It doesn't.

It increases from whatever the starting atmospheric pressure is currently at.



BUT, It WILL, still be Boost, A Increase in PSI with a Working Ram air Effect. ANY Increase is BOOST by definition.


[/quote]



Sport440,
Okay Now you changed your original question,

From,...{ The Myth of ram air...does it WORK in cars/trucks}

TO;{{ Boost is defined as 14.7psi + xx}}


Ram air boost can start at any MPH from zero and increase from there. There have been formulas and charts posted to prove that.

It takes 70 millibars to achieve 1 psi of boost.

Ram air systems, for most of us will be below this level, but still capable of .50 psi around 150 MPH .25 psi around 100 MPH .125 around 80 MPH

So pick your MPH from any of the above for your {Boost is defined as 14.7psi + xx} and add that. 14.7 + .25/100 MPH = BOOST

Ram air is{ No myth}. CONFIRMED

Probably the best apples to apples comparison offered. This car is a 1994 SLP firehawk (Ed Hamberger's company.) The only changes done between this car and the 1994 V8 firebird is the "ram air" induction... The standard V8 firebird made a rated 275 crank hp the firehawk made a rated 300 crank hp. Same heads,cam, exhaust (the optional exhaust added 15more) same throttle body. Ect. There was a tune change required and a map location change required but nothing crazy because the car still had to pass cal emissions... Basically, Just the hood which is sealed to and feeds directly into the throttle body. Now you could say "oh its marketing" but time slips don't lie. The std V8 FB was no match for the same year Vette in 0-60 or 1/4 mile...But the Firehawk easily beat the Vette which btw also used the same LT1 engine with a different cam. So, Ram air > camshaft in power gain. Yes there's suspension changes, and vette sized wheels and tires. No gear changes. Please explain this any other way.

R70 - you answered yourself - they tuned it, put a lighter bonnet on, changed to possibly? lighter wheels, better suspension and better exhaust - how much came from ram air - un-answered. The firehawk was still 200lbs heavier than a c4 though, go figure on the 1/4 times - obviously a better thought out/engineered package.

Not going to knock ram air though, an 1/8th of a psi is an 1/8th of a psi, as stated above the temp difference would be where its at for major performance changes vs under bonnet air

Arguably you would be better off using the cowl air routed to behind the front wheels to help reduce the aero CD

You got your answer in the first few posts. It's about fresh or cold air. A scoop that isolates the intake to the air outside the engine compartment will get you colder, denser air. A scoop above the boundary area is going to get you more cold, dense air no matter what speed you're traveling. I've been told this is good. Ram Air is a name Pontiac concocted, as did dodge with Ramcharger. It all works to get you fresh air, which is exactly why Chrysler referred to N96 as the... Fresh Air package and not the Forced Air package. The last four pages of forced air debate is off topic. Ram air works, my friend, and lucky for you, the 1969 1/2 A12 cars have the best production scoops ever produced. Go now. Celebrate.

Everyone is going to have an opinion ranging from their seat of the pants feel, to the highly educated and scientific, so I will skip an opinion and give my personal "i did this" report. For years on my Dart drag car I ran just a flat hood with with a 14" x 3" air filter, then after a time I decided to try a dual ram air set up just to see if it would net anything. I used flex dryer duct from the air cleaner down next to the radiator and attached to the underside of the bumper, just about a foot off the ground. After running that set up for about a year and having torn it off a couple of times loading it onto my trailer I decided it was time to lose that and go with a hood scoop. Before to ditched the ram air set up completely, I wanted to test all 3 set ups to see the difference between them. Keep in mind that the air cleaner used with the ram air dual inlet had no air filter, I just used a 3" wide piece of sheet metal shaped to the same circumference as the filter, cut 2 oval shaped holes in it for the snorkel fittings and put a lid on it. I didn't want the filter to be a restriction. Here are the results for the test, all on the same day, all within an hour of each other in like conditions...
Run 1, 14" x 3" air cleaner with filter, no ram air-11.57 ET
Run 2, 14" x 3" air cleaner assy without filter with dual inlet ram air-11.42 ET
Run 3, ram air assy removed including filter assy, carb sealed to underside of hood with foam, with the scoop in my sig pic-11.27 ET.
Point of interest and probably disagreement, there are those that will say the gain from run 1 to run 2 (adding ram air) was only from introducing cooler air, but on the hottest of days, with the ram air inlet only about 12" off the pavement, that air isn't going to be to cool, not as cool as the underhood air temp once the car was making speed, and the car on any given day was always about a tenth and a half quicker with the ram air. I do believe its a combination of both, and the fact that I had to jet up the carb 2 jet sizes tells me that more air IS being forced into the engine. A LOT of air moves into and out of the engine compartment through the grill opening at speed. I believe the even bigger pick up with the sealed hood scoop was a combination of a shorter, more direct path to the carb and the air being forced downward, and a cooler charge of air given it was coming in through a much higher opening, never coming in contact with the underhood heat at any point. Whichever you believe is the correct answer, the FACT is, it works!