Sounds like a Pontiac hater. "there is no ram air effect at any automotive speed" how about 140mph? might not be much but should be some. Ford has a scoop on the Mustang. I think the term "Ram Air" is a Pontaic trademark....My opinion....Paul
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09:24 AM
Marvin McInnis Member
Posts: 11599 From: ~ Kansas City, USA Registered: Apr 2002
The "ram air" effect is not quite a myth ... it is just highly overrated, and insignificant at automobile speeds. The term "Ram Air" (with capital letters), as used by Pontiac, means nothing; it's just a marketing gimmick.
If you do the math (dynamic pressure: P = density * V squared), you will find that the pressure boost from "ram air" will gain you a theoretical maximum of less than 2% at 200 mph ... and even that assumes a properly designed, 100% efficient intake system.
Conversely, the gains from using cool intake air rather than heated air from the engine compartment are considerable and easy to obtain. Again, if you do the math, you will find that you can gain up to 10% simply by reducing the intake air temperature from 160 degrees F (typical engine compartment air) to 80 degrees F (typical outside air). PV=nRT ... it's not just a good idea, it's the law!
The issue of intake air temperature is worth pondering for those of you who have replaced the stock Fiero cold-air intake with a cool-looking K&N filter located in the engine compartment. No flames, please. It's your car and you can do with it whatever makes you happy.
------------------ '88 Formula Project Testostarossa "Anything worth doing is worth overdoing."
[This message has been edited by Marvin McInnis (edited 11-21-2003).]
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09:51 AM
naskie18 Member
Posts: 6258 From: Commerce Twp, MI, USA Registered: Jun 2002
Sounds like a Pontiac hater. "there is no ram air effect at any automotive speed" how about 140mph? might not be much but should be some. Ford has a scoop on the Mustang. I think the term "Ram Air" is a Pontaic trademark....My opinion....Paul
Unless they've changed it recently, the scoop on the Mustang is full of plastic, no air gets it through it, its appearance only.
And I believe you're correct about the "Ram Air" phrase/system being a Pontiac trademark/copyright
The site is technically correct. Ram Air as used by Pontiac is simply an advertising term. Ram Air as applied in fluid mechanics does not take place at the relatively slow speed a car can achieve. Even 200-300 mph is insufficient to achieve an actual Ram Air effect.
The key is: Below about Mach 0.5 (or about half the speed of sound), air is considered “incompressible”.
So unless your car is travelling faster than Mach 0.5, there is no Ram Air effect.
Ram Air is still a valid marketing tool, but does not accurately describe what the intake does.
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10:02 AM
Pyrthian Member
Posts: 29569 From: Detroit, MI Registered: Jul 2002
Ram Air can/does work. But, so what. I'm sure thats why all intakes on race cars point forward. Take the air where its under the most pressure. But, I'm also sure it creates no boost/pressure. it just helps to avoid air flow restriction. Now, for some fun - this may work: air tight passenger cabin. roof scoop, about 2 inches high, 14 inches wide, ducted straight into the cabin. and, the cold air intake run into the cabin. I think at over 40 MPH, the cabin will be above 1 atmosphere pressure. The key to ram air is to have a pressure chamber.
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10:27 AM
Oreif Member
Posts: 16460 From: Schaumburg, IL Registered: Jan 2000
The problem is the article uses the term of "Ram Air" as the original aerospace definition which is a way of creating boost. Which is true that a car cannot go fast enough to create "boost" by ram air. Pontiac uses the term to mean it rams cool air into the intake. Basically "Ram Air" means "Cold Air Intake" in terms of how Pontiac uses it. There is no "myth" about it. It's just the way the term is used. If you look at the cars that Pontiac calls "Ram Air", The usually have the air cleaner sealed to the forward facing scoop. The "Ram Air" engines were designated when they used large, less restrictive, free flowing intake/exhaust manifolds.
The article states that the Pontiac "Ram Air" designation provides no performance gains. Well that is incorrect. Everyone knows that cooler air provides more power. So there is a gain. They just look at "Ram Air" from a boost point of view when Pontiac uses it as a term for Cold Air intake.
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10:32 AM
Formula88 Member
Posts: 53788 From: Raleigh NC Registered: Jan 2001
Originally posted by Pyrthian: I think at over 40 MPH, the cabin will be above 1 atmosphere pressure. The key to ram air is to have a pressure chamber.
Did you read the entire article? It explains why this is wrong, even though it sounds correct. Fluid has both a static and dyncamic pressure. While you would feel the air rushing in through the scoop (dynamic pressure), the atmospheric pressure inside the pressure chamber, but outside the flow of air would still be 1 atmosphere (static pressure).
A lot about Fluid Mechanics is not intuitive. The article is referring to the scientific definition of Ram Air, which has nothing to do with why Pontiac uses it as a marketing term.
Case in point: Mach III Turbo razors. Are they turbocharged? Are they supersonic? Nope. Good razors, though.
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11:10 AM
naskie18 Member
Posts: 6258 From: Commerce Twp, MI, USA Registered: Jun 2002
Originally posted by Formula88: Case in point: Mach III Turbo razors. Are they turbocharged? Are they supersonic? Nope. Good razors, though.
Yeah they are. Definately a quicker and better shave than the Mach 2 or Mach 3 or whatever they had sent me before 'course, maybe thats 'cuz I hadn't changed the blades on the old one....
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11:14 AM
Pyrthian Member
Posts: 29569 From: Detroit, MI Registered: Jul 2002
Will a scoop create "ram air" boost? Doubtful at normal automotive speeds. However, if you creat a funnel for the air, you can accelerate the air through it and you will gain a positive effect. The trick is to make the funnel grab enough air without creating too much drag (thereby negating any horsepower gain). That's the reason why most scoop openings are larger than the throttle opening.
NASCAR makes use of the area if high pressure at the base of the windshield to assist the pump (that is - motor) at high speeds. So, it utilizes both the cooler ambiant air temperatures and the high pressure area to "create" more horsepower. It may be only a small gain but a gain none the less.
But at sub Mach 0.5 speeds, air in incompressible and therefore it won't compress.
You've said this twice, so an important clarification is in order:
Air doesn't abruptly become compressible at around Mach 0.5, it's just that the compressibility at low speeds is so small that it can be ignored in many aerodynamics and gas dynamics calculations.
By the same laws of physics and gas dynamics, your car is subject to aerodynamic heating even at 60 mph, but the temperature rise is so small that you can (and probably do) ignore it.
This is the only disagreement I have with Dave Rodabaugh and his otherwise excellent treatise. There's a big difference between saying that something doesn't exist and saying that it's insignificant under normal circumstances.
[This message has been edited by Marvin McInnis (edited 11-21-2003).]
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03:01 PM
sardonyx247 Member
Posts: 5032 From: Nevada, USA Registered: Jun 2003
However, if you creat a funnel for the air, you can accelerate the air through it and you will gain a positive effect. The trick is to make the funnel grab enough air without creating too much drag (thereby negating any horsepower gain). That's the reason why most scoop openings are larger than the throttle opening.
The funnel would have to be backwards. But not at Fiero speeds. Like the F1 cars, if you look at the intakes and vent it is a V shape. It starts out small then gets bigger. That is also F1 at over 200mph and lots of $$$ in design
