RAM AIR CAI Available from RM Racing
- Thread starter slooper
- Start date
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Ok Ben, how do you explain what happens with this Audi from Autospeed.com where they are trying to elimnate negative pressure in the intake...Here is Part 1, Part 2, Part 3,
Part 4 and Part 5...
Now it has been a little while from reading these, however, where he sites his intake pipe, it sits in a high pressure area of the car, thus creating a "ram air" effect, right? Or am I reading it wrong...
Here is another thing about siting cold air intakes...All of these articles are courtesy of Autospeed.com.
Part 4 and Part 5...
Now it has been a little while from reading these, however, where he sites his intake pipe, it sits in a high pressure area of the car, thus creating a "ram air" effect, right? Or am I reading it wrong...
Here is another thing about siting cold air intakes...All of these articles are courtesy of Autospeed.com.
Here is what I will say about the pressure levels in the intke manifold of our cars. I still have my boost gauge hooked up to my car because I am too lazy to take it off. At idle, the manifold is at about 20vac. Guess what, at only half throttle, the manifold is at 0psi. So there is no need to try to make a ram air system. And, this one that RR-racing, is NOT ram air. I read that whole article from autospeed. The name of the article is "eliminating Negative Boost". Not "Attaining Ram Air". So what, he eliminated negative boost, our intake manifold is already at that point. But, you will not attain positive manifold pressure unless you are moving at 200mph with an intake tube at the front bumper leading STRAIGHT to the throttle body with little to NO bends. I'm sorry, it just wont be done.
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How did he eliminate the negative boost though??
All you need to do to eliminate negative air pressure, is to make the air box less restrictive. Which is what he did. The part that he is mistaken about is that he thinks that the reason he eliminated negative air pressure is because he made a path from the front air duct. That's wrong. He got rid of the negative air pressure because he made a more "clean" flow path into the air box. The positive air pressure at the front of the car has nothing to do with it.
Here is the main reason you can't get positive air pressure inside your manifold from a ram air setup.
All street driven cars have intake paths and intake manifolds that leak. They may just have very small leaks, but nonetheless, they still leak. The trick is to keep feeding pressurized air into the intake system to greatly overcome those leaks. A turbo can very easily defeat all the leaks. No ram air can. For ram air to work, it needs a big "mouth" to collect air. This is it's main and major downfall. That mouth will collect and pressurize that air, but here is the big flaw, it has no way of trapping and holding onto that pressurized air. Almost all air that is pressurized in the inlet will overflow around the edges of it. A turbo system has a sealed intake system. All the pipes after the turbo are sealed. The air can't escape unless the BOV lets it. Anytime there is fluid that is pressurized, it always has a tendancy to equalize it's pressure with the surrounding pressures. This is why you see planes with upturned winglets now. The pressure on the bottom of the wing wants to equal that pressure that is on the top of the wing. And some of that air pressure circles over the tip of the wing and then it pushes the wing down instead of up. When you see a plane fly through a cloud, and it makes the cloud make a swirly trail off the tip of the wing, you can see this happen with your own eyes. That winglet is a way of controlling that lost air pressure. This is also why planes with these winglets get better gas mileage. They don't need as much thrust to maintain altitude and speed.
That is about the easiest way to explain it. Now, ram air does work very good at very high speeds. This is why ram jets work. When you can pressurize the air so fast and so much that it doesn't have enough time to "spill" over the edges of its inlet, it will be pressurized and consumed before it has a chance to equalize with its surrounding pressure. But most cars aren't capable of enough speed to do this.
Here is the main reason you can't get positive air pressure inside your manifold from a ram air setup.
All street driven cars have intake paths and intake manifolds that leak. They may just have very small leaks, but nonetheless, they still leak. The trick is to keep feeding pressurized air into the intake system to greatly overcome those leaks. A turbo can very easily defeat all the leaks. No ram air can. For ram air to work, it needs a big "mouth" to collect air. This is it's main and major downfall. That mouth will collect and pressurize that air, but here is the big flaw, it has no way of trapping and holding onto that pressurized air. Almost all air that is pressurized in the inlet will overflow around the edges of it. A turbo system has a sealed intake system. All the pipes after the turbo are sealed. The air can't escape unless the BOV lets it. Anytime there is fluid that is pressurized, it always has a tendancy to equalize it's pressure with the surrounding pressures. This is why you see planes with upturned winglets now. The pressure on the bottom of the wing wants to equal that pressure that is on the top of the wing. And some of that air pressure circles over the tip of the wing and then it pushes the wing down instead of up. When you see a plane fly through a cloud, and it makes the cloud make a swirly trail off the tip of the wing, you can see this happen with your own eyes. That winglet is a way of controlling that lost air pressure. This is also why planes with these winglets get better gas mileage. They don't need as much thrust to maintain altitude and speed.
That is about the easiest way to explain it. Now, ram air does work very good at very high speeds. This is why ram jets work. When you can pressurize the air so fast and so much that it doesn't have enough time to "spill" over the edges of its inlet, it will be pressurized and consumed before it has a chance to equalize with its surrounding pressure. But most cars aren't capable of enough speed to do this.
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Some choice quotes from "Siting Cold Air Intakes" - AutoSpeed.com:
"So, even though the effect of ram air on performance isn't huge, there's a worthwhile gain that can be made.
But getting that pressure build-up in the duct requires that the mouth of the cold air intake be sited in an area of high pressure."
"At the front there must be a point above which the air goes over the car, and below which the air goes under the car. This is called the stagnation point, and it is here that there will be the greatest pressure developed on the front of the car as it moves forward."
"An extraordinarily sensitive switch, it is factory set to trigger at about 1 kPa (0.145 psi) and is perfect for this application.
...So at around 85 km/h there was enough pressure being generated at this location by the force of the airflow to trigger the switch."
"You'll certainly avoid making some of the glaring errors that we occasionally see... like drawing air straight from the wheel arch - a low-pressure area in many cars!"
For those who didn't follow the link...
"So, even though the effect of ram air on performance isn't huge, there's a worthwhile gain that can be made.
But getting that pressure build-up in the duct requires that the mouth of the cold air intake be sited in an area of high pressure."
"At the front there must be a point above which the air goes over the car, and below which the air goes under the car. This is called the stagnation point, and it is here that there will be the greatest pressure developed on the front of the car as it moves forward."
"An extraordinarily sensitive switch, it is factory set to trigger at about 1 kPa (0.145 psi) and is perfect for this application.
...So at around 85 km/h there was enough pressure being generated at this location by the force of the airflow to trigger the switch."
"You'll certainly avoid making some of the glaring errors that we occasionally see... like drawing air straight from the wheel arch - a low-pressure area in many cars!"
For those who didn't follow the link...
okay, since we have to justify our remarks, I was once an engineering student. Now that I've had my degree for several years, I might not be as bright as I used to be.
If you have two areas, one with a low pressure source and one with a high pressure source, then you are going to get flow between the two.. REGARDLESS of if the path is straight or not. That SHOULD be simple for an engineering student to understand..
As for calling it a "RAM AIR". You are the first person to provide the definition that a RAM AIR system has to push air straight into the throttle body. Does that mean that after the throttle body we don't care what happens to the air path? Are you suggesting that pressurized air can't turn corners... If that were truely the case, then there are NO true RAM AIR systems, as every intake system that I've ever seen has curves in it. Short of a set of throttle bodies hanging off of the head. Think about it, the throttle body doesn't care about the pressure of the air, the engine does. Oh yeah, RAM AIR is all about getting rid of negative boost. That is it's main purpose.
Next thing, have you ever watched a turbo car on a dyno. If you have ANY flex hoses in the intake path (ie. a stock eclipse), then you will see those hoses expand under boost. They still have pressure when they expand, so your arguement about the corrugated hose expanding and losing pressure is invalid.
Your formula's look good, but you don't take pressure into account in any of those formulas. Why not? Do you not agree that there will be a positive pressure at the scoop of the intake?
Open your flow book and read about fluid (or air in this case) taking the path of least resistance. Given the option of 0 psi, or -5psi, which way is the air going to flow.
Do you honestly not think that the air in front of a car is not pressurized while going 55mph? I suppose it just jumps out of the way then, and that car manufacturers are just wasting there money designing aerodynamic cars.
I do agree with your "semantics" arguement though. It's not a true CAI.
If you have two areas, one with a low pressure source and one with a high pressure source, then you are going to get flow between the two.. REGARDLESS of if the path is straight or not. That SHOULD be simple for an engineering student to understand..
As for calling it a "RAM AIR". You are the first person to provide the definition that a RAM AIR system has to push air straight into the throttle body. Does that mean that after the throttle body we don't care what happens to the air path? Are you suggesting that pressurized air can't turn corners... If that were truely the case, then there are NO true RAM AIR systems, as every intake system that I've ever seen has curves in it. Short of a set of throttle bodies hanging off of the head. Think about it, the throttle body doesn't care about the pressure of the air, the engine does. Oh yeah, RAM AIR is all about getting rid of negative boost. That is it's main purpose.
Next thing, have you ever watched a turbo car on a dyno. If you have ANY flex hoses in the intake path (ie. a stock eclipse), then you will see those hoses expand under boost. They still have pressure when they expand, so your arguement about the corrugated hose expanding and losing pressure is invalid.
Your formula's look good, but you don't take pressure into account in any of those formulas. Why not? Do you not agree that there will be a positive pressure at the scoop of the intake?
That statement would invalidate the usage of a turbo on a car with 0psi manifold pressure.
Open your flow book and read about fluid (or air in this case) taking the path of least resistance. Given the option of 0 psi, or -5psi, which way is the air going to flow.
Do you honestly not think that the air in front of a car is not pressurized while going 55mph? I suppose it just jumps out of the way then, and that car manufacturers are just wasting there money designing aerodynamic cars.
I do agree with your "semantics" arguement though. It's not a true CAI.
Good points, jmauld! In regards to "categorizing" this specific intake, I would say that it is both a CAI and a short ram intake. At high speeds, when the pressure from the front of the car has reached high enough levels (which I would wager does not have to be very high considering it only has to be greater than the pressure in the engine bay) then the intake pulls the majority of air from the scoop, which happens to be cold air. When the vehicle is at a stop and at low speeds, the path of least restriction is to pull a large amount of warm air from the engine compartment, which is what the short ram intake does. Therefore, depending on the vehicle speed, this intake acts as both a CAI and a short ram intake. Am I wrong in this?
sean
sean
No, you are right. But the air will never be pressurized by the time it reaches the intake manifold.
jmauld, yes, you are right about your points, but I think you misunderstood me also. Yes, you can still pressurize the air even if the intake system has curves in it, but then you will be bringing in head loss coeficients. A car has a hard enough time trying to pressurize the air without these headloss coefficients, what makes you think it will be successful after a bunch of curves.
And you truly cant compare air pressure from a turbo with air pressure from ram air.
And for the flexable corrugated hose. If used with a turbo system, yes, it would be fine because the intake tubing is sealed. But with ram air, it's not sealed and anything that has any give to it when the air is trying to pressurize will do nothing but hurt its chances of ever being pressurized.
jmauld, yes, you are right about your points, but I think you misunderstood me also. Yes, you can still pressurize the air even if the intake system has curves in it, but then you will be bringing in head loss coeficients. A car has a hard enough time trying to pressurize the air without these headloss coefficients, what makes you think it will be successful after a bunch of curves.
And you truly cant compare air pressure from a turbo with air pressure from ram air.
And for the flexable corrugated hose. If used with a turbo system, yes, it would be fine because the intake tubing is sealed. But with ram air, it's not sealed and anything that has any give to it when the air is trying to pressurize will do nothing but hurt its chances of ever being pressurized.
big_ben said:
I never claimed it would be. However, I don't think that you have enough evidence for this particular product to say that it won't be.
Thus, your accusations that people have wasted their money are premature.
What makes you think it won't be successful? It works for the RAM AIR camaros. (admittedly, their system is much more ideal then this one) Again, I'm NOT saying it will or won't work in this particular system. I'm simply pointing out that you don't have the evidence to say it won't work.
At what point are you referring to the car pressurizing the air? In the cylinders? I honestly don't see the point that you're trying to make.
Not taking into account heat, 1psi of pressure = 1psi of pressure. Regardless of the source.
True enough, (even for a turbo, that system is not perfect) but will it hurt it enough to completely negate it? Again, not enough evidence to say for certain one way or the other.
My whole point is that unless you have used this system, then there's no reason to completely blow it off. Give them time to test it and see what kind of effects it has. If they find it doesn't do anything, then you get say I told you so!
And hopefully, if this one doesn't work, they would do more research to produce a better productThese negative responses like this are not going to motivate shops to do this kind of testing for us.
big_ben said:
"Big difference" is relative. In some circles, ANY difference is still seen as a difference. And again, it's up to each person as to whether or not that difference is worth the cash.
My car modding background is mostly with turbo cars. You have NO idea how difficult it is for me to accept a mod that only provides 5hp increases... The majority of the mods on my car gave a minimum of 15hp. Including a simple K&N filter.
One good thing that this intake has going for it, is that it's safer then a true CAI system.
The main reason I am saying that it is a waste of money is because of the price. Have you looked at that factor? It's over $300! All it is, is a reactive short ram and some corrugated ducting. I' sure that you would agree that this is not worth over $250.
The only ram air system that might supply about 1/4 to 1/2psi above atmospheric is the ones introduced on the Camaros and Firebirds. But, how long were they on the market. The mysteriously came and left very quickly. Hmmmm, I wonder why. Maybe because they knew there were no positive effects with ram air at speeds that that car was capable of?
The only ram air system that might supply about 1/4 to 1/2psi above atmospheric is the ones introduced on the Camaros and Firebirds. But, how long were they on the market. The mysteriously came and left very quickly. Hmmmm, I wonder why. Maybe because they knew there were no positive effects with ram air at speeds that that car was capable of?
