LOL.. Having read your post, prior to this edit, which noted the addition of the coma for clarification, I then understood where you were coming from. Having recalled your input from previous vehicle aerodynamic discussions, it did strike me odd, that you would state something goofy like that, (prior to understanding your post with the clarification) in this thread.

 

I know this is an old thread, but it's 4 in the morn, and I don't have any thing better to do than read these threads.

IMO C.A.I. pretty much says it all, it's a cold air intake, the delta T across the outside and inside air is the only thing that improves performance.

An airplane with a ram jet engine having the same surface area opening as a TPI 48mm Throttle body will need to reach speeds of >225mph before it will begin to produce any pressure at the exhaust, mind you, it hangs entirely in the air, and is designed to scoop air, so if you really believe your car is ramming air, look up, and make sure you're not strapped to the underside of a 747.

 

I've been thinking about this one for a few days and I have arrived at this thought: It's not about compressing air at all. A normally aspirated engine has to suck air in and any means of reducing intake manifold vacuum by supplying more air lessens the power loss resulting from the pistons working against intake manifold vacuum as well as increasing the amount of air/fuel mixture in the cylinder.
With that thought in mind I would have to say that the idea of ram air is entirely valid and the only requirement is placement of the ram air intake at a point of high air pressure, and making it large enough to maximize its effectiveness.

 

I assume that what you are pointing out is the perpendicular (to velocity) component of pressure, or the the Bernoulli effect. Higher velocity produces lower perpendicular pressure. But it would appear to me that "ram air" effect would be measured using the pressure parallel to the direction of flow, as would be done using a pitot tube.

 

Cold air is one of the benefits but it is the ramming of air that is largely responsible for increasing power. Before I installed FTRA I had the cold air factory SS hood and the FTRA made a big difference OVER the cold air. That is undesputable evidence ram air works IMO.

 

Actually Fred, I was implying pressure measured parallel to the direction of the flow. As you stated, this would appear to be more appropriate for measuring the ram air effect. This (making this more complicated than it should) high pressure/low velocity scenario, as you are aware, has the ram air inlet attached to a vehicle cutting through the air stream, typical of a real/practical situation. IOW, the high velocity air is halted/slowed by the body panel, as well as the ram air opening itself, that is attached to the body panel. If we were to monitor a probe that was far enuf removed from the vehicle body, IOW, in clean undisturbed air flow, also parallel to flow, person might not agree that scenario still applies. But in order to take a measurement, the air flow is again slowed at the probe opening. Agree? I believe I succeeded in making this reply as confusing as possible.

 

Not necessarily....as was mentioned before...the velocity can be measured by a pitot tube which, if you've seen one, isn't much of a restriction at all as the size of the tube and the diameter itself is really negligible to the disruption of flow to the intake.

I believe it's 7:30 in the morning and I still haven't slept yet so hopefully my response was not as confusing as possible.

 

I agree that the whole concept of Ram Air has become more of a "stylists" concept than an engineer's concept. The aerodynamics of the body panels are going to have a lot more affect on the pressure at the air inlet than the simple fact that someone cut a couple slots in the hood - I think that's what Arnie said in much more technical terms????. It really needs to be reviewed for each specific application. Obviously the the hood scoop on the 4th Gen Camaro SS is not as effective as the one on Kurt Johnson's Pro Stock body.

I think people who throw around claims of "CAI is better than ram air" and vice-versa have never taken the time to look at the flow of air around (and under) the body to determine if there is any real benefit of one vs. the other. Might be an interesting "project" for a budding engineering student.... measuring air pressure at the TB for a specific configuration... e.g. LT1 WS6.

 

First, the ‘ram air’ intakes that we’re talking about don’t make it past the boundary layer of air on the surface of the hood.

Second, what’s better, air 6” from the pavement that is heated >20* over ambient by the sun heating the asphalt, or air taken from 2’ above the pavement pretty close to ambient temp?

 

My boss (at the engineering firm I work for) told me that cowl induction is better then Ram Air....he drew something on a light pole (we were in a parking lot leaving work)....showed how as air is forced into the "ram air" opening...that something called "packing factors" make it useless....that it doesnt' really "force" air in....and that the only thing you can do is make the air colder for a denser charge....I mean...is the arguement about the "ram" effect or the temperature...

 

F-body owners who doubt ram air works need to try FTRA. It is one of the best mods I have! The gain is very noticeable OVER cold air which I had previously. The car pulls harder and harder the faster you go. It is well known FTRA is good for 2 miles per hour in the quarter. What more proof do you need! : )

FTRA forces large quantities of pressurized air from the bottom of the car and the LS1 really responds.

 

How much of that is just due to cleaner cold air? You can't use a dyno to prove that, and you can't use ETs because of driver inconsistency...there is no real way to prove it works except a bunch of people spending 150$ and saying it does....when the physics and dynamics behind it says that it doesn't do anything.

 

Cleaner cold air? Did you read my post? I said I had COLD AIR previously and ram air made a difference OVER cold air.

So basically what you're saying is you don't believe a bunch of people who say FTRA works. Isn't that what these boards are for? To learn from others with real world experiences? It's not like I would come on here and lie. If FTRA didn't help I wouldn't hesitate to blast it just like I did about the SLP MAF which is now sitting in a box.

Yes you are correct...you won't see the gains on the dyno. After installing FTRA I immediately noticed how the car pulled harder and harder the faster you go. It was as if the torque curve became steeper.

 

Are you using your "butt-o-meter" to measure these results or have you quantified them? You mention MPH increases in the 1/4, did those increases come with the same DA, temp, humidity, etc?

 

Take a deep breath...a step back and re-read this entire post. May I suggest reading both of Injuneer's posts and Ultra_Dog's as well.

Congratulations that your butt is telling you that your FTRA has a steeper torque curve than your CAI.....but sorry chap, it just isn't so. You can preach on all you want about your butt-o-meter and what other "people" say about FTRA, that still won't change the facts.

I can convince everyone on this board that the conservation of lateral momentum is totally false but that doesn't make it any less true.

Sorry to burst your bubble I would give you a nice big hug right now if I could.

You may want to read this article once more: http://www.vetteguru.com/ramair/ and tell me why your butt should override fluid dynamics.

Ah what the heck...here's another link:

http://www.snowgoercanada.com/tech_ram_air.shtml

Yes...in the end you will get SOME gain but not anything near advertised and the speeds needed for the advertised gain aren't all that practical.