The Ram Air Myth is the most mythical of them all. It differs from the other myths, in that the other myths are misinterpretations of physical phenomena, whereas ram air simply does not exist.

MYTH: Use of a scoop on the front of the vehicle to collect intake air, or provide “ram air” can raise engine performance.

TRUTH: At automobile velocities, there is no ram air effect.

SIMPLE EXPLANATION

The "Truth" statement says it all. How much simpler can it be? The Ram Air effect is a total myth because it simply does not exist. “But Pontiac uses it on the Trans Am, and they know more than you do.” To those who offer this, tsk tsk. Careful reading of Pontiac’s statements on the matter reveal that the HP increase of the WS6 package are a result of a less restrictive intake, and a freer-flowing exhaust, NOT any ram air effect.

So why does Pontiac use Ram Air? Easy! To make people buy their cars! And they are quite effective with this strategy.

DEEPER EXPLANATION

Of all of the applied sciences, fluid mechanics is among the most difficult for many people to comprehend. It is a relatively youthful applied science as well, meaning that it has not had two or three centuries of work to mature into an applied science on par, with say, chemical combustion. To make matters worse, it is mathematically defined almost entirely by experimentally-determined mathematics.

This last point is the true differentiator between those who only understand concepts, and those who can quantify what they are discussing. Truly, quantification is the real skill of the engineer. It is one thing to speak about qualitative issues (the “what” of the physical sciences); it is entirely another to quantify them (the “how much” and “to what extent” of the same). In grade school, students are first taught about “closed form mathematics” and then that these mathematics are typical of scientific expression. A good example of this is Newton’s famed “law of action and reaction”, the mathematical expression of which is a succinct F=MA. So straightforward. So simple. Three variables in perfectly-defined harmony. Given any two of them, the third is easy to nail down.

Unfortunately, a vast, vast majority of the mathematics used in engineering are NOT closed form. Instead, they are multi-variable correlations valid only for a narrow set of circumstances. Deviate from those narrow circumstances, and a new expression must be experimentally derived. Fluid mechanics is almost entirely defined by these experimentally-determined expressions, further muddying an applied science not well understood.

And if there ever were an applied science for which common sense is wholly inappropriate, it is fluid mechanics. Virtually nothing obeys the “common sense” rules of observation, explaining why those who believe in ram air have extreme difficulty in believing that is simply does not exist.

The Deeper Explanation begins with a basic explanation of engine principles. Air and fuel must be combusted at a specific ratio, namely, 14.7 parts air to 1 part fuel (this is a chemical ratio). Stuffing more fuel into the cylinders without increasing the amount of air they also swallow will get no gain whatsoever. So the hot rodder’s adage “more air = more power” is proven correct. Figure out a way to stuff more air into the cylinder at any given RPM and throttle setting, and you can burn more fuel. Since burning fuel is what makes power, more air truly does create more power.

The amount of air which is inducted into a cylinder is a function of the air’s density. As the air flows through the intake tract, it loses pressure, and as the pressure decreases, so does the air’s density. (Denisty is mass divided by volume. Since cylinders are a fixed volume, increasing the density will also increase the mass of the air in the cylinder.) There are two ways to increase the pressure and density of the air inducted into the cylinders:

- Decrease the pressure drop from the throttle plate to the cylinders

- Increase the starting pressure at the throttle plate.

Ram air is an attempt to do the second. Under normal circumstances, the air at the throttle plate is at atmospheric pressure, and this pressure drops until the air reaches the cylinders. Ram air would start the process at some pressure higher than atmospheric, and even though the drop is the same, the cylinder pressure is higher because of the increase at the start.

Just how would this increase in pressure at the throttle plate occur? The oft-wrong “common sense” says, “If a scoop is placed in the airstream flowing around the vehicle, the velocity of the air ‘rams’ the air into the scoop, thus increasing the pressure.”

Why is this incorrect? There are two types of pressure: static and dynamic. Placing of one’s hand in front of a fan, or out of a moving car’s window, clearly exerts a force on the hand as the air diverts its path to flow around it. Most people would say “See? This is a clear indication that ram air works. Clearly there is pressure from the velocity of the air.” Well, this is correct, but only to a point. This is an example of dynamic pressure, or the force any moving fluid exerts upon obstacles in its path as the gas is diverted around the obstacle.

What an engine needs is static pressure. This is the pressure the same fluid exerts on any vessel containing it at rest. For those who were physics/chemistry geeks, it is the pressure caused by the force of the molecules bouncing off of the walls of the container. The key to understanding the difference between static and dynamic pressure lies in the velocity of the gas. Dynamic pressure is only a momentum effect due to the bulk motion of the fluid around an obstacle. Static pressure is an intrinsic property of a gas or fluid just because the molecules of the fluid are moving around. Any fluid which is moving can have BOTH dynamic and static pressure, but a fluid at rest only has static pressure.

The point of ram air would be to increase the static pressure, which would correspond to an increase in the in-cylinder air density, and of course, more air. Superchargers and turbochargers do what the mythical ram air purports to do. A supercharger trades the power of the belt and uses it to compress the air in the intake tract. This energy trade-off results in an increase in intake air pressure, more air in the cylinders, more fuel burned, and more power. A turbocharger trades the power of the hot gases and uses it to compress the air in the intake. The overall effect is the same – an increase in intake static pressure.

For ram air to work, it would have to trade the energy of the air’s velocity (as the vehicle moves through the air) for an increase in static pressure (since static pressure is a part of a gas’s internal energy, we see this is TRULY a trade in kinetic energy for an increase in internal energy). Now for the true reasons why ram air is a myth:

- The way for air velocity to be traded for an increase in static pressure is to actually SLOW IT DOWN in a nozzle of some sort. This is easily the MOST counterintuitive part of fluid mechanics for most people. The “common sense” mind says “In order to increase the pressure of the intake, the velocity of the air needs to be increased, just as increasing the speed of a fan exerts more force upon the hand.” Not only does this confuse dynamic with static pressure, but is also misses the point, which is to trade the kinetic energy of the gas for an increase in internal energy. How can this trade occur if the kinetic energy of the gas is increased? It cannot, and in fact, the only way to trade it is to use the velocity of the gas to compress itself – by slowing it down.

- Below about Mach 0.5 (or about half the speed of sound), air is considered “incompressible”. That is, even if the correct nozzle is selected, and the air is slowed down (the official term is “stagnated”) there will be zero trade. No kinetic energy will be traded in as work capable of compressing the air. The reasons for this are not discussed here; the reader may consult any reputable fluid mechanics textbook for confirmation of this fact. In plain English, a car is just too slow for ram air to work.

Still not enough evidence? Here is a little test. For ram air to work, the nozzle must be of a specific shape. The “Holley Scoop” for the Fiero is the wrong shape, by the way. The fact that it has no net shape at all immediately means it cannot effect any kind of energy trade off, so it cannot possibly create ram air. This is also true for the hood scoops on the Pontiac Firebird WS6 package as well, by the way.

What shape must it be? There are two kinds of nozzles. Pick one:

- Converging. This nozzle gets smaller as the air flows through it. It has a smaller exit than entrance. If the nozzle were a cone, the fat end is where the air would enter, and the narrow end is where it would exit.

- Diverging. This nozzle is opposite the other; it gets bigger as the air flows through it. With a larger exit than entrance, the narrow end of the cone is where the air would enter, and the fat end is where it would exit.

So, which is it?

Without hesitation, most of the “common sense” crowd will answer “Converging.” BZZZZT! Thank you for playing anyway! We have some lovely parting gifts for you! Bill, tell ‘em what they’ve won….

The answer is “divergent”. Yes, the nozzle would have to shaped so that the skinny end is pointed into the air stream, and the fat end connects to the throttle plate. How can this be right? Remember, to increase the static pressure of the intake air (which is the true “ram air” effect), the kinetic energy of the air must be traded to compress the air. This is done by slowing the air down, or stagnating it, and the only way to do this is with a diverging nozzle. Ah, but since air is incompressible at automobile speeds, it doesn’t matter any way.

Conclusion

Ram air is a myth because it does not exist, for the following reasons:

- Air is incompressible at any automobile speed., 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 such as the Holley scoop for the Fiero cannot provide a ram air effect.

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85 F-40 Replica (unfinished)
88 GT 5-speed
02 Millennium Yellow C5

You are correct. Ram Air does not exist in the automotive world. However, I will suggest that the "Ram Air" setups used on cars provide more power than a traditional air cleaner setup on the same engine. Simply because it offers a free flow of cooler air. No Ram Air effect, but it's a very efficient cold air induction system.

True, Formula88.

Thanks! Very informative and helpful. It certainly clears up a lot of issues.

I still think my Holley scoop "looks" good!!

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REDHOTT88 - Steve
'88 FORMULA

The problem is that the article you got that from refers ro "Ram Air" in the aeronautical sense. If you go back and read Pontiac's description of "Ram Air" as it was originally stated back in the late 60's, They refer to Ram Air hoods as the same thing as "Cold Air Induction". (Cold Air Induction was already being used by someone else, but I don't remember who) The "Ram Air" Engines were referring to the high flow of the intake and heads. The person who wrote that may understand the dynamics he talks about, but saying that Ram Air on a car doesn't work without understanding how it was defined originally is ignorant.

In aeronautical terms a "wing" is used to provide "lift" in auto terms it used to increase "down force". In aeronautical terms the Fiero doesn't have a "wing" It has a "Slat".

[This message has been edited by Oreif (edited 10-08-2002).]

Next he will be telling us that there is no Easter bunny, tooth fairy, or Santa Claus.

Pontiac knew in 1964 when air scoops were first installed on GTO's but figuired it to improve sales.---alf

Excellent read. Mind if I copy and paste for future reference?

godalex, are you about a month into your new semester at college?

Sounds like someones a little too excited about their texbooks (hehe)

so, from this says, it would be no problem to the intake pointing backwards out the back of the car? I will agree the "ram air" as a form of creating boost is not gonna happen. But placement of the intake where it can easily grab the air it needs is benificial. Like cowl induction, putting the intake on the body wheres theres alot of positive pressure.

Good article.

To add more fuel to the argument, the reason ram air does not work as everyone believes is basically the same reason why a ramjet does not work well at speeds below Mach 1. An aircraft with a ramjet actually requires some type of "low speed" engine to get the craft up to the necessary speed. In many experimental aircraft, this was accomplished by combining both types of engines into a single unit (called a turbo-ramjet), which is basically a turbine engine which changes into "ramjet mode" at a certain predetermined speed. A good example is the SR71 spy/recon aircraft.

Tsk, tsk, tsk . . . credit where credit is due . . .

http://www.vetteguru.com/ramair/

Thought that looked familiar . . .

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Mid Atlantic Fiero Owners Association
New England Fiero Association
Keystone State Chapter, P.O.C.I.
P.O.C.I.

Excellent article, now if I could only get my 14 year old son who has been sold on the got to have a "ram scoop" marketing campaign to believe it.

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Alan

The actual pressure increase is pretty much negligable, true. (nearly all the gains come from cooler air TEMP. And yes, actually, discounting turbulance, an intake will work nearly just as well placed backwards.(talking a few tenths of once percent at automotive speeds.)

Take a look at the inlet cone in an SR-71, now there's a ram-air 'hood'!

Best!
Ben.

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Ben Cannon
88 Formula, T-top, Metalic Red. (2:13.138 at Sears Point) "Every Man Dies, not every man really Lives"
88 Formula, Northstar, Silver, In-Progreess. -Mel Gibson, "Braveheart"

Now that we've seen you can cut and paste, how about some thought in answereing a question.

If "ram air" is ineffective at velocities below about mach .5, how can Mooneys and other aircraft equipped with an air cleaner by-pass/ ram air set-up pick up about 1 to 2 inches of manifold pressure? Look that up on the Lycoming or Continental engine charts and see if it doesn't give you some extra performance. And I can assure you that these aircraft are flying at much less than ".5 mach". Try less than 200 knots.

An engine doesn't give one rat's hind a$$ about anything but absolute manifold pressure and temperature. That determines the corrected absolute manifold pressure. Period. End of discussion. ANYTHING that you can do to 1) decrease the temperature of the charge just before it goes into the cylinder and/or 2) increase the manifold pressure will result in increases in horsepower. And it's a damn near linear relationship.

That said, does ram air work? As it's applied on the old T/A's with the rear facing hood, not much, but some. As it's applied on other applications, say a pro/stock car, yes, it works. As well as a turbo or blower? No. Better than sucking hot air through a restrictive labyrinth of ducting? Yes.

Your statement that the Holley style Fiero scoop results in no ram air effect is also false. I put a challenge to you. Cut a hole in the side of your car. Put an aircraft airspeed indicator pitot in the hole, facing out. go drive it 70 mph. Tell me what it shows. Now put on the holley scoop and change nothing else. Tell me what it shows. There will be an increase in pressure. A lot? No. Some? Yes. Beneficial? Yes, to a slight degree. But proving your statement wrong, certainly.

How do I know this? Look at an airplane cabin window. Most small planes have a small door cut in the plastic. It simply opens in and leaves a hole when it's opened. It will create not any pressure, but actually a vacuum. The make a little add on that is a small scoop (not unlike the holley). It will now blow the cap off your head.

BTW, a diverging nozzle is NOT required to trade energy, but it is the most efficient. But being the most efficient is not a requirement, only an ideal.

Next time, spend more time with such texts as "theory of wing sections" and "computational fluid dynamics".

John Stricker

quote Originally posted by jstricker: ...Now put on the holley scoop and change nothing else. Tell me what it shows. There will be an increase in pressure. A lot? No. Some? Yes. Beneficial? Yes, to a slight degree. But proving your statement wrong, certainly... John Stricker

It should read: There will be an increase in pressure. A lot? No. Some? Maybe. Beneficial? NO.
*Measure the pressure AT the TB not at the vent opening. That increase (if any) would be nominal at best. A performance add-on? Hardly.
It would be the equivalent of somebody going on a diet, lossing 5 lbs, and then saying the weight savings are "performance enhancing".
OUT>

Explain to me how an increase in pressure, however slight, would not reflect at the throttle body.

Remember, I said "to a slight degree". Not unlike underdrive pulleys and a host of other items that are treated as the holy grail. Do they make a difference? Some do. Enough to matter? Usually not. Enough to MEASURE? Sure, if you use sensitive enough instruments.

My point was this. The claim was that the Holley scoop by nature of it's design could not increase Absolute Pressure at the inlet. That claim is false.

John Stricker

quote Originally posted by G-Nasty: It should read: There will be an increase in pressure. A lot? No. Some? Maybe. Beneficial? NO. *Measure the pressure AT the TB not at the vent opening. That increase (if any) would be nominal at best. A performance add-on? Hardly. It would be the equivalent of somebody going on a diet, lossing 5 lbs, and then saying the weight savings are "performance enhancing". OUT>

I read once in a sport bike magazine that the "ram air" scoops out the front of a Honda CBR600 F4 did nothing until around 130MPH or maybe 150MPH, I can't remember. I am now doubting this is true.

I do believe that the automotive idea to gather cooler air with the external scoop is a good one. That an usually by doing an aftermarket setup you can reduce some of the restriction in the intake tube and get rid of all the muffleing devices.

And for anyone who is saying why the hell would you do 150MPH on a bike, I usually climb closer to 170-180MPH when roadracing. Brainard International Raceway in MN has the fastest first turn in North America. You basically go down the 1/4 mile drag straight away and go wide open through the first turn, only the reduction in tire diameter(leaning the bike) to slow you down.

Talk about a rush. I am really going to try to get my fiero out there this coming summer.

Thanks for passing on the info.

MOBILE

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Member MN Fieros Forever 1986 GT. Self Installed SC3800/getrag almost everything performance wise is modified/upgraded, inside and out. Over 10 years in Car Audio and Car Electronics Experiance P.S. GOT 19"s??(all the way around)

last time i check it was called ram air, not forced induction. air is being rammed into the scoop. Case and point. My brother's 68 GTO has the raim air 2 hood. On his air filter its always really dirty in the two spots where the scoops lead to. instead of the engine searching for air under the hood its can grab it easier by it being right there. Now when your travling at say 90mph at 4,000 RPM, the engine needs more air. and the air thats going 90mph is going into it. Its not any pressure but the engine breaths a sh!t load easier. Stick your hand slighty out the window at highway speeds, you can feel the force of the air against it. Now that same force it going into the engine. Put your lips in a whistling type position and suck in, its hard right? now open your mouth wide and suck in, its eay and your lungs fill up faster. Now in the wistling position thats a normal car at 4,000rpm with the air intake running into the fender. with your mouth wide open thats the engine at 4,000rpm with a Ram Air set up.

That article says that Ram Air was claiming to be a forced induction set up. Pontiac never called it forced induction and nobody except the people who write that crap think it to be a type of forced induction. Its Ram Air! its ramming air into the scoops. You dont call a turbo or a blower ram air do you? No, because it's forced induction. If you (universal you) think ram air is forced induction, buy a moped

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--Adam--
1987 Blue GT 5-speed
IM AOL: GTFiero
What oil leak? That puddle under the car is just sweat from all that horsepower.

Kind of off topic, but in the same ballpark - you say a cowl induction scoop uses pressure (or lack thereof) to draw fresh air in.

So this...

A.) Allows hot air generated by the engine to be expelled, and produces more downforce by drawing air from the bottom of the vehicle, through the engine bay, out the vents?

B.) Pulls air via "cowl induction" into the engine bay, expells it under the vehicle, and generates lift?

I have always wondered about this, because the area behind the cockpit of the Fiero is already low pressure correct?

Thanks

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--Will | ironwill2000@hotmail.com

You're all missing the point. Ram Air as defined in engineering terms doesn't exist in an automovtive environment. Ram Air as an marketing term is what Pontiac uses on some of it's cars. Does the Ram Air intake provide a performance increase? Yes. Is it from a Ram Air effect? No.

Like he tried to say, it's all about fluid mechanics. It doesn't have to be intuitive. If you doubt it, go ask a Fluid Mechanics professor at your nearby Engineering College.

In the picture you post, there is no "cowl induction". Cowl induction worked (supposedly) by tapping into the high pressure area and flow reversal at the point the windshield meets the hood. That is a significant high pressure area. The problem was that as it was designed by GM, the area was so small that there was more suction going on there than there was high pressure. It may have helped slightly by allowing cooler air in, but not significantly. In the picture you posted, there is no windshield to cause the high pressure/flow reversal area and very little airflow coming there to begin with.

In the picture you posted, there would either be negative pressure or possibly even stagnant air there due to the fact that there is a lot of airflow disturbance from the roof area of the car. The flow would drop down (gravity works on air too) but it would be a toss up as to how much negative air you have there. What you do certainly have is an outlet to let out any high pressure air that might be in the engine compartment and openings up high to let convection draw the heat out of the engine compartment.

So the answer to your question is that air is moving out of the scoop in the picture and definitely not in it. And possibly more by convective activity than any actual airflow action.

John Stricker

quote Originally posted by Will-Martin: Kind of off topic, but in the same ballpark - you say a cowl induction scoop uses pressure (or lack thereof) to draw fresh air in. So this... A.) Allows hot air generated by the engine to be expelled, and produces more downforce by drawing air from the bottom of the vehicle, through the engine bay, out the vents? B.) Pulls air via "cowl induction" into the engine bay, expells it under the vehicle, and generates lift? I have always wondered about this, because the area behind the cockpit of the Fiero is already low pressure correct? Thanks

Thanks......thoroughly enjoyed the post! I still like the way scoops look though.

Phil

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If you find my replies helpful, please take the time to give me a positive rating. Thanks.
GTDude
OVER 25 years GM experience

Redhott88: Your scoup does look good!

Oreif: Cold air is a good thing; I frequently here people talk locally about the "Ram Air" magically forcing more air in... I see it referenced here too. I always liked that article, so I just posted it for those who may not have known the difference. Since we are involved in using technical knowledge to enhance performance, I am of a mind that good information (correct info) is a necessity. (if we want real world results for our investment) If we all understand the physics and mechanics of our interest, then we can make sound decisions in mods and choices. (Avoiding snake oil) With out the technical background, many people buy into 20HP chips for the fiero, tornado's that magically add HP and milage, 20 HP timing mods on ebay, expensive headers that often hurt performance, etc, etc ,etc. I think with the right back ground info, and there is an abundant supply of it here, we can all accomplish amazing feats of performance on our little Fiero's.

Sorry avengador: There is an Eastern Bunny, Santa Clause and a Tooth fairy.

Wipeout: cut and paste away. Here is the original link:
http://www.gemair.com/~phorine/Articles-Ram%20Air%20Myth.html

lateFormula: Nah (I'm 37)... College was quite a while ago. I have been studying a lot lately to bring my certifications current. MSCE, and MCSA. Not as much fun as car stuff.

Pyrthian: A nice free flowing cold air supply is always preffered.

Blacktree: Goodpoint. Gotta love the SR71! Where else can you find a plane that requires leaky fuel cells and special fuel because it gets so hot at speed (skin gets something like 400F) that seals would melt, and the fuel would ignite! (the wings actually heat up and swell to seal the tanks in flight)

Good Luck Alan! If he is a smart kid, he may beleive it after doing a little research. It is interesting that on the firebirds without ram air, if you simply set up a cold air induction package you will get similar HP.

[This message has been edited by godalex (edited 10-09-2002).]

As defined in engineering terms? You mean like this:

"ram air
Air entering an airscoop or air inlet as a result of the high-speed forward movement of a vehicle. "

From DICTIONARY OF TECHNICAL TERMS FOR AEROSPACE USE collected from 1965 NASA paper text version by Daniel R. Glover, Jr. with assistance from others at the NASA Glenn Research Center, Cleveland, Ohio.

Is that what you mean?

Or how about this:

airscoop
A hood or open end of an air duct or a similar structure, projecting into the airstream about a vehicle in such a way as to utilize the motion of the vehicle in capturing air to be conducted to an engine, a ventilator, etc.

I'd say that qualifies as well.

High speed is a relative term and you have to know as it applies to what. There is a significant and measurable amount of pressure at low speeds. There is even a significant amount of pressure right now in your A/C or heating ducts in your home caused by air movement.

At a speed of about 20 mph, there is an air pressure increase of about .2" of water. That's not a lot, but it's measurable. I agree that the ram air scoop on the Trans Am's that faced rearward were useless from a ram air standpoint, only from a cold air inlet standpoint. But a blanket statement that there's no such thing as any kind of a ram air effect in automotive applications is quite simply false.

Ram Air can and does exist in the automotive world. A common USEFUL example is ram air into a radiator. You know, the reason your cooling fans don't generally run when you're on the highway? It works there, why would it magically disappear when used in an induction system? Because it doesn't.

It exists. It's real. It's measurable. If done correctly, it can be a real benefit. If done incorrectly all you get is a gee whiz look.

BTW, I have asked several professors in fluid dynamics and even have some time at the Beech wind tunnel down at Wichita State.

John Stricker

quote Originally posted by Formula88: You're all missing the point. Ram Air as defined in engineering terms doesn't exist in an automovtive environment. Ram Air as an marketing term is what Pontiac uses on some of it's cars. Does the Ram Air intake provide a performance increase? Yes. Is it from a Ram Air effect? No. Like he tried to say, it's all about fluid mechanics. It doesn't have to be intuitive. If you doubt it, go ask a Fluid Mechanics professor at your nearby Engineering College.

GTDude, hey I love the look of the Ram Air scoop too... just looks mean.

See my point for posting it here? A lot of us don't get the straight scoop (pun intended) when it comes to stuff about cars. If we beleived every manufacturers HP claims, by the time you are done bolting on all that stuff you could have 900 HP! Woo hoo! But as was mistakenly stated by Will about cowl induction (cowl induction has to be over the cowl) we can now see a cowl induction hood scoup mounted any where else (rear, side, etc) becomes just a scoop (or a vent), as pointed out by Jstricker.

Now whether you beleive it or not, well, you can always look into it yourself. I myself spend copius hours researching some topics to death. I prefer to get things right the first time, I hate wasting money and time, and I read virtually every post here on this forum before I ever joined it, just seeking info. (Same on a few other forums too) So take it as it was intended, even if it was cut and paste. The forum is for sharing info, and I shared it. Cut & paste is convenient, I could have just plastered the link here, but I myself prefer it when I open a thread and the info or picture is there, and not elsewhere. (it seemed implied that I tried to sneak it by like I wrote it, which wasn't my intention. Just saving people a step)

I've got to weigh in here. The info posted by GODALEX is about 90% correct, while JSTRICKER is 100% correct.

Ten or fifteen years ago I designed and prototyped an electronic airspeed indicator for aircraft use. From my foggy memory it seems that the dynamic pressure at 200 mph is about 1.5 psi. (This assumes 100% pressure recovery; most real-world diffusers achieve about 80% max.) Since dynamic pressure is proportional to the square of speed, the maximum dynamic pressure available at 70 mph would be about 0.17 psi ... only a little more than 1% "boost" over static conditions, even assuming 100% pressure recovery.

For GODALEX, JSTRICKER, and all who responded ... keep it coming.

Some experiments on the effects of "Ram Air" systems on motorcycles here

I knew I read that sportbike article somewhere!

Thanks,

MOBILE

Plagerism is plagerism, whether you adknowledge it after the fact or not.

Too Bad.

John Force/Austin Coil/Bernie Fedderly

Michael Schumacher/Every F1-IRL-Cart teams

Tell me these guys have it all wrong.

I work for a Tier 1 supplier to the Big 3 and I have seen documents stating "Ram Air option for perceived customer benefit." That is straight from the manufactuer.

Matt
3.4l DOHC Turbo

quote Originally posted by Matt Hawkins: I work for a Tier 1 supplier to the Big 3 and I have seen documents stating "Ram Air option for perceived customer benefit." That is straight from the manufactuer. Matt 3.4l DOHC Turbo

Perceived Benefit??? What manufacturer?
That is funny because the 3400 in a Grand Am is 160hp, The "Ram Air" engine is 180hp. (Cam and head flow make the difference not hood scoops) So the Ram Air Grand Ams only have a perceived 20hp?? Even the "Ram Air" Trans Am's have a horsepower gain. Again this is due to other changes not hood scoops. Pontiac has always had anything tagged "Ram Air" as having more HP than the normal version. It doesn't matter what was changed, (Cam, head flow, carb/throttle body size, etc) It was always a gain.

Who died and left this guy in charge of physics? What a crock. If ram air didn't exist, certain types of jet engines would not exist.

I'll grant the effect is minimal at normal highway speeds, but if the scoop is of the right shape and in the right location, it can and does increase performance at high speeds.

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Yes I was refering to GM. 99% of the HP gains are from exhaust flow and engine calibration. Spark tables are modified for more power, but you must run better fuel (in most cases premium). Not trying to burst anyones bubble, but Ram Air is bunk on street cars. It is all marketing. Read any fluid dynamics book and then you will understand.

Matt
3.4l DOHC Turbo

Cowl induction was called that because it inducted air from the cowl. It was originally used on C2 Corvettes. The relatively steep windshield on those cars creates a high pressure area at the base of the windshield as the direction of flow changes.

Without a steep windshield behind it a backward facing scoop is just a backward facing scoop. It doesn't even take much advantage of Bernoulli's principle.

It's not a matter of whether or not the ram effect exists at highway speeds. It does, else the airspeed needle in the T34 I fly wouldn't come off the peg at 40 knots. What matters is the extent of the effect at highway speeds, which isn't much.

Fluid dynamics equations are just reduced shorthand for discreet flow equations in the limit of an infinite number of particles.

If you think about fluid behaviour from the molecular point of view, you'll never go wrong.

quote Originally posted by DaveL: Who died and left this guy in charge of physics? What a crock. If ram air didn't exist, certain types of jet engines would not exist.

You didn't read the entire first post. He goes on to say it doesn't exist at automotive speeds. Yes, it exists for aircraft, at higher speeds. I haven't seen any 0.5 Mach street cars.

I maintain that the Ram Air intakes do help performance in a street car, but not because of a ram air effect. It's just an efficient cold air induction setup. For it to be actual Ram Air, as a Ram Jet would use, then you'd have to increase the static pressure of the air as it enters the engine. So, how much does the Manifold Absolute Pressure increase in your engine with Ram Air? Is it pressurized and showing boost? Or are you still running an engine with a vacuum?

Check the MAP sensor output with and without a Ram Air intake and see if you can tell a difference. Remember Ram Air is an effect that pressurizes the air and forces it into the engine. This is how a Ram Jet works. But even a Ram Jet has to have alternate means to get to speed so the Ram effect can take over.

Oh, and the 3400SFI in Grand Ams is rated at 170HP in the SE and 175HP in the GT with Ram Air. The engines are identical, except for the air intake and the muffler. Same heads and cam. That same engine is rated 185HP in the Montana, so that just confuses things more.

A little knowledge is a dangerous thing. Reading a definition of Ram Air in an engineering book gives you a little knowledge. Great, now you know just enough to be dangerous. Do some more research.

And I'll say once more, yes, the types of intakes used in race cars, and on cars touting "Ram Air" do help - it's just not a true Ram Air effect in the Aeronautical sense. And that's all the hair I'm gonna split on this one.

Check this out, Pontiac markets the entire package (WS6) together. Pontiac doesn't say that the Ram Air hood increases horsepower. It says that the Ram Air Package (WS6) increases horsepower. The Ram Air hood is for looks, and I'd take the Ram Air hood on the TA (or the new Grand Ams for that mattter) over the stock hood 'cuz I like the way it looks. Yes, it leads to very little if any actual performance increase on regular roads. But boy does it look good

My $.02

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Nick
AIM: Naskie182010 www.naskie18.com