Ram Air

[TheEdgeofSanity]

ok. some Grand Am's have ram air. I know the whole idea is to pick up air from the front of the car as it moves to somewhat pressurize it as it goes into the engine. But really, does it increase performance? how much of a PITA would it be to do on an alero? has it been done before and just called something else?

[AJules]

wouldn't work, we don't have the front air dam that grand ams have

and if you would go with a setup like their stock ones it would be pointless because you could just get a cold air intake and it would be much better.

grand am gt ram air really isn't ramming any air anywhere if you take a look at it.

[TheEdgeofSanity]

k, thanks.. I was just wondering after seeing my gf's grand am has ram air.

i'm getting the impression that it was a sales gimmik

[AJules]

Originally Posted by TheEdgeofSanity

k, thanks.. I was just wondering after seeing my gf's grand am has ram air.

i'm getting the impression that it was a sales gimmik

that's exactly what it was

If i remember correctly though, It wasn't when they made their old trans ams. But that was different because their throttle body was facing the front of the car, allowing it to actually be ram air.

but yeah, CAIs are better than the grand am's "ram air"

[yoslvr442]

you could design a setup with an eclosed box around your cone filter and have a scoop that feeds right into that box. that would be a ram air as well. but most people dont want to have a scoop on the side of their hood or custom make a tunnel system under the hood running from the front to that box.

[TheMeaningOfLife]

Soon im going to build on of those but it will pick up air from the bottom of the car. Im going to build like a scoop on the plastic part that holds the bumper and fender on the bottom. Ill run some sort of duct up to a marine battery box then put the end of the intake and cone in that.

[AJules]

so basically a cold air box?

[TheMeaningOfLife]

Yeah, if that what its called.

[yoslvr442]

no thats basically a ram air induction system. the fact that you will have a sealed system running directly to the filter is a ram air induction.

[Vinalero]

As 442 said, a Ram air doesnt pressurize the air. Its only a scoop in the hood where fresh gets to a sealed box where the air filter is located. Fresher air makes a difference. I believe a GAGT with the ram air have 5 more hp.

[AJules]

Originally Posted by Vinalero

I believe a GAGT with the ram air have 5 more hp.

lol i highly doubt that

next time you get a chance, take a look at a gagt ram air setup
no way it could be worth 5hp

[TheMeaningOfLife]

Well when im done ill let youa ll know if itsd any differnt.

[[ion] C2]

Sorry about the old post bump, but I found a writeup about ram air systems that explains how they don't work, thought some might find it interesting.

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 cannot provide a ram air effect.

Select one of the two types of intakes, warm air, or cold air. Beyond that its just about looks."

[lonnie]

^^nough said!

[[ion] C2]

Some guy on j-body is saying that bikes can get like 2 PSI of boost at around 85MPH using ram air, lol.

[joserivas19]

it doesnt give you anymore hp. its just for looks as well as the speedometer reading 150mph instead of 140mph like the regular models. like some of the guys said, a cai is much better, i have one and it works great.

[-Alero-]

i always just aw it as something that allowed the engine to work a little less to inhale its air it wants, my bike has ram air, and the ram air just benefits by making it easier for the motor to inhale when moving, and plus it lowers combustion temps due to the moving air

[CiscoPath]

I had this mounted on my car last year. Sounded good, little extra pull at highway speeds. Too bad I didn't secure it properly and got flattened in traffic

[CiscoPath]

Pics of it mounted. Like I said, never bothered to secure it

http://www.pbase.com/ciscopath/fmi

[xXManwhoreXx]

Thats awesome! I've never seen one of those! wtf how much HP does that add omg! bang bang skeet skeet!