Article topic: Does ram air work?

I think by this time GRM should see that this would be a very well read article and besides that it would be fun to experiment.

Brett_Murphy wrote: For our next argument, which is faster, a turbo or a supercharger? (yes, I said faster, not more efficient at a given RPM, etc)

Definitely a Chevy!

Brett_Murphy wrote: For our next argument, which is faster, a turbo or a supercharger? (yes, I said faster, not more efficient at a given RPM, etc)

a turbo is a supercharger..

the way to test it would be to have a "ram" with a reversible scoop. So it's drawing the SAME temperature of air in either position. POint it forward to see if the "ram" effect works, and then point it backwards where it would just be sucking regular air rather than "ram"

novaderrik wrote: only because someone doesn't know that "vacuum" and "pressure" are two sides of the same coin..

I think we all agree on that, its pretty common sense, i think the question is how you define it, IF we wanna say that decreasing vac @ specific RPM/GEAR/SPEED/LOAD is the goal then ALOT of mods do this, does that make a larger TB ram air?

So i guess the real debate is what does ram air claim to do, if it is simply to increase HP/TQ then most ram air kits work just on better airflow and cooler air, but a CAI does that as well... does that make a CAI ram air?

For ME ram air to be truly ram air would need to see a pressure above ambient, otherwise in my book, it is just a very efficient and well designed intake... but thats opinion and your definition may vary....

I have never heard or seen anywhere that Ram Air would produce boost... nor that it claimed to

SVreX wrote:

bravenrace wrote: Why not? Positive pressure does provide a greater volume of air, which if used correctly will increase power. The real question is how much?

Because the potential positive pressure increase that could be caused by the forward movement of the vehicle does not exceed the negative pressure created by the sucking of the engine whether or not the car is moving, so there is not a gain in pressure. Ever put your hand over the intake of a running car? It does, however, make more fresh air available for the engine to pull in, as I noted earlier.

As far as the engine is concerned, merely reducing the vacuum would constitute a ram air effect. IE, if the engine pulls .5psi vacuum at full throttle without a ram but .3psi at 100 mph, that's still a useful ram effect.

We discussed this in class one day. The professor started with the basic equation for dynamic pressure:

And everyone agreed they understood how that worked. So then he had a student come up to the board and work out the pressure at various speeds. The punchline is you have to go 170mph to get half a psi of pressure. Yes, this is just for non-compressible fluid, but the basic magnitude is there.

unevolved wrote: We discussed this in class one day. The professor started with the basic equation for dynamic pressure: And everyone agreed they understood how that worked. So then he had a student come up to the board and work out the pressure at various speeds. The punchline is you have to go 170mph to get half a psi of pressure. Yes, this is just for non-compressible fluid, but the basic magnitude is there.

This sounds inline with a friend who works for NASA telling me you would need to go about 350mph to get 3psi of "boost"

Yeah.

Here's this equation:

at 60F and sea level:

Or, in short, "why I don't believe in ram air intakes."

irish44j wrote: the way to test it would be to have a "ram" with a reversible scoop. So it's drawing the SAME temperature of air in either position. POint it forward to see if the "ram" effect works, and then point it backwards where it would just be sucking regular air rather than "ram"

the problem with this idea is that depending where the scoop is placed, you might actually be sucking air out of the intake tract as the air flows over it or even getting into the high pressure area at the base of the windshield and still getting a sort of a "ram air" effect..

unevolved wrote: Yeah. Here's this equation: at 60F and sea level: Or, in short, "why I don't believe in ram air intakes."

I have a physics and engineering degree, so I understand the math. I understand what you are saying, but you're probably wrong because you only looked at one small equation and omitted the rest of the system. First off the velocity of air near the car is probably not equal to the velocity of the car. Secondly, the pressure near the car is not atmospheric. Simple math, sure, but your assumptions are wrong.

tuna55 wrote: I have a physics and engineering degree, so I understand the math. I understand what you are saying, but you're probably wrong because you only looked at one small equation and omitted the rest of the system. First off the velocity of air near the car is probably not equal to the velocity of the car. Secondly, the pressure near the car is not atmospheric. Simple math, sure, but your assumptions are wrong.

I'm well aware it's not 100% accurate, it's just meant to give an illustration of how dynamic pressure actually happens. Reasonable variations in temperature or ambient pressure aren't going to change the overall magnitude of the curve. It still rises really slow, which is all I was pointing out.

What type of duct does that graph represent? Volume of air it's affecting?

/thread

Javelin wrote: What type of duct does that graph represent? Volume of air it's affecting?

No, just pressure. It's just a small part of the overall problem.

Does ram air work? If by 'work' you mean 'measurable increase in pressure in the intake tract' then the answer is yes it CAN work.

sportrider caption said: KAWASAKI ZRX1100: As a test control, we fitted the Pi System to a non-ram-air-equipped motorcycle. If you think figures like 17mb seem insignificant, take a look at how much vacuum is present in a regular airbox and you'll realize even that amount of positive pressure can make a huge difference. With a pressure of -27mb, it's obvious that power gains can be realized by converting that vacuum into positive pressure. Read more: http://www.sportrider.com/tech/146_9910_ram/photo_12.html#ixzz1tcC01mzq

sportrider caption said: KAWASAKI ZX-9R: Another impressive showing by a ram-air-equipped Kawasaki. Even though the intake ducts are smaller than the ZX-7R's, the Nine's airbox pressure builds quickly (albeit a tad rougher than the 7R), peaking at 28mb. It's also interesting to note that the Nine's slimmer ram-air ducts run over the frame spars, while the 7R's ducts run through the frame spars; yet the Nine's airbox pressure builds much quicker and higher. It makes you wonder what kind of pressure the new ZX-12 is going to make. Read more: http://www.sportrider.com/tech/146_9910_ram/photo_10.html#ixzz1tcCL8ux8

28 mb (millibar) is approximately 0.4 psi. Not quite turbo territory but positive pressure is positive pressure.

neon4891 wrote: /thread

Jeremy Clarkson is always confused, he just doesn't always know it.

How about installing some sort of gauge just before the throttle that would read vacum/pressure. ?

Looking at all those motorcycle graphs on the linked page and applying this to a car, to my way of thinking a larger volume area of RAMMED AIR would smooth out those swings in power especially on the 2 cylinder engine or the large displacement car engine. I'm thinking an extra chamber rather than larger diameter tubing or bigger scoops.

The larger volume area would act as a reservoir to average out the drops in pressure due when the intake valves open and in the analogy of the soda bottle move that turbulence and overfill much further upstream to give a smoother air flow where it matters.

I know what I mean, but I'm not sure exactly how to explain it, but in my mind it's just like on a radiator that is more effective if you can give it an area ahead of the actual radiator for the air to accumulate and a place for the air flow to "change" from more turbulent state to a flow pattern that will more effectively cool the radiator.

The bottleneck would have to be the air filter.

But by anyone's definition RAM air works. When it takes the vacuum numbers from a rather large negative value to a smaller number & in some cases a positive number that's working. It is not a turbo or SC and short of a Bussard Ramjet engine (http://www.nasa.gov/centers/glenn/technology/warp/ideaknow_prt.htm#ram) we will never reach the speeds or scoop sizes to give a huge power add, BUT adding anything to the horsepower to me is a win. Even if it's only at speeds above X mph. If it's free, why not do it?

This thread has some awesome graphs, equations and theories. I enjoyed reading it, but it definitely reminded me why I went to school for business instead of engineering! haha

Remember the glorious days of American Iron V8 engines with a 4 barrel carburetor and an intake snorkel about the diameter of a quarter? Back when simply flipping your air filter lid could gain you like a full second on a quarter mile time?

In that era of "fine engineering", even the worse of ram air systems would generate a heck of a performance gain. Not from magical pressure, just from unstrangling the air flow to the carburetor.

I suspect a whole lot of those who see gains with these setups (as well cold air intakes) are gaining simply from this scenario.

My beloved Spitfire is a great example of this sort of terrible design. The carburetors face right into the fender well, minimizing filter depth. They live right over the exhaust manifold, so they can bake nicely. Cool air for them is the hot air coming through the radiator. In thick summer traffic, the temperatures around the carburetors can get so high that they percolate gasoline faster than the fuel pump can supply, and the engine slowly dies in an eye searing cloud of fumes.

In this case, a cold air intake / ram setup works wonderfully, and gives huge increases in power. Having absolutely nothing to do with air pressure.

foxtrapper wrote: Remember the glorious days of American Iron V8 engines with a 4 barrel carburetor and an intake snorkel about the diameter of a quarter? Back when simply flipping your air filter lid could gain you like a full second on a quarter mile time? In that era of "fine engineering", even the worse of ram air systems would generate a heck of a performance gain. Not from magical pressure, just from unstrangling the air flow to the carburetor.

I am always explaining to friends of mine that want to mod their cars and are not really THAT into motorsports that most modern cars had millions of hours and dollars spent designing their parts. A perfect example of this is most intake systems which have a lot of thought and work put into them. Sure you can "perfect" an OEM airbox with a lot of thought and ingenuity but slapping on an ebay "cold air" intake on your car will likely decrease your power...

Sure, there are some parts they put on a car that decreases performance to net an increase in comfort...but many things are best left along on modern cars. Especially modern performance cars, I remember when the s2000 came out watching people try and squeeze more power out of it N/A...it has 120hp/liter! The only way to make a notable power gain is forced induction and those engines have a super high compression ratio...which usually calls for new internals, etc. Ok I am ranting now.

I do have the same concern about the frs/brz twins. They have what, 100hp/liter? Makes me wonder whats left on the table.

Of course you can still gain power on modern cars, its just more difficult and expensive...unfortunately its no longer 1992 and a trip to the aquarium store and home depot to get "parts" won't make your DSM run 11's! haha!

It takes something like 100 mph to generate 0.2 psi.

I visited a ram-air site that makes them for the pontiac G8 and they claimed 35+ hp over stock.... and they tested it on a stationary dyno. There was no "ramming" at all. All of the gains had to be from cooler air and reduced restriction.

foxtrapper talking about restricted air cleaners takes me back to my SAAB 96 special. I took the air cleaner off and added stacks to the three carbs. wouldn't run over 3000 rpm. After rejetting the carbs, every thing was fine.