Does Ram Air actually work?

[Slash]

I've heard a lot of yes and no's and a lot of other things like limited benefits and inducing drag for scoops but having large hp gains and the like. Reason being is that when I get my '86 Mustang GT I wanted to put in a fully functional Shaker scoop from an old Boss 302 but was wondering if it would be worth it.

 

[oopssorryy]

I've always heard that it's not very effective. I've been told a well designed CAI will do much better for power. My dad (a body man for 22 years, it's his "knowledge, take it as you will) said that vents in specific areas, like over the exhaust manifolds or over a supercharger, will benefit you more than a hood scoop because your getting hot air out of your engine bay. I'm not sure about that but it sounds good. He goes on to say that many scoops and ram air hoods are just there to accommodate a larger engine or supercharger.

I stress that I'm getting this info from my dad, he's not a car designer by any means, he's a body man. If this is all true or not, I don't know, its just what I've heard.

 

[Eric.]

Giving an intake fresh cool air is always good. It's why cold air intakes tend to stick the filter way down near the ground. A scoop is just awful for aerodynamics. More drag and lots of lift.

 

[speed junkie]

Yes ram air works (lol at some of the brand names that have emerged in the Ameican aftermarket) it is called forced induction. Lol but no, seriously now, "ram air intakes" were just a marketing scheme to sell aluminum tubing with fliters to ricers and truck owners. At the end of the day (and to make it, almost incorrectly, simple) an engine will be restricted by however much air can flow through the intake ports. Again, very simple statement for a topic that deserves more than that.

 

[Keef]

"Ram air" intakes like you might see on a Viper or Corvette or F1 car are functional and help to pressurize the intake manifold very slightly at speed.

 

[Exorcet]

Dynamic pressure = .5*air density*Velocity*Velocity.

Total pressure (a constant*) = ambient pressure + dynamic pressure.

Your car uses ambient pressure to make power, in order to maximize this pressure, you need to bring the air speed to zero (see the formulas above). However this already happens in the engine anyway.

The biggest benefit that you get from a good inlet is a lack of pressure loses from flow separation and turbulence.

This off the top of my head though.

*for the sake of this discussion

 

[Slash]

Well I figured it might help a little after I'm done swapping the motor. I kind of like want a "wow that's cool" kind of thing while not hindering performance as much as possible.

 

[Exorcet]

a "wow that's cool" kind of thing while not hindering performance as much as possible.

IMO, the coolest thing you can do is engineer a perfect part. But that's just me.

But anyway, you can get away with putting a scoop on your car without ruining its performance, a lot of manufacturers do it obviously. Just make sure that the air has somewhere to go if you care about drag. And don't direct the flow downward since that creates lift.

 

[Slash]

IMO, the coolest thing you can do is engineer a perfect part. But that's just me.

But anyway, you can get away with putting a scoop on your car without ruining its performance, a lot of manufacturers do it obviously. Just make sure that the air has somewhere to go if you care about drag. And don't direct the flow downward since that creates lift.

Well it probably won't be too big of an issue with a 400-450hp build so. IDK. I mean I don't need it but I thought it would be nice to have.

 

[SuBMWaru]

Well. The problem with CAI is they are affected by heat. And HP can be reduced. Depending on your locations climate, this could be a problem. As for the Ram Air stuff. All I know is some pontiacs had it a few years back.

 

[Slash]

Well. The problem with CAI is they are affected by heat. And HP can be reduced. Depending on your locations climate, this could be a problem. As for the Ram Air stuff. All I know is some pontiacs had it a few years back.

Most old Mustangs has it too. Hence where to scoop is coming from.

 

[savage388]

When engineered properly ram air works well. Suzuki used a ram air intake to create a passive supercharging effect at high speed on the original hayabusa. A ram air system can get larger amounts of cold air in the engine more effectively then even a cai when mounted on the hood. Drag and lift are only factors when speeds are very high and the ram air intake is something excessively large like something on an open wheel car. That is not to say that it works as advertised either. Many "intakes" are just that a arent sealed to properly use the small pressures created and even if they are the manifold and heads arent designed for such amounts of air. Then there is the factor of how fast you must be traveling to make use of the system, which is also rather excessive for a street car and is once again, best suited for open wheel applications like formula one and indy car. When applied in production cars the main use is marketing and aesthetics and has little performance use.
Specifically for your application slash, a shaker hood replica of an old Boss should function as good or marginally better than a good cai and wont pose any problems for performance, and it will have that racy look that you and designers go for.👍

 

[Slash]

The build isn't too out of league like my dad who goes crazy with building engines. I'm going to have to get an aftermarket hood anyways for the motor to even fit (built 302 EFI to built 351W carbed) so I figured I might as well do something fancy.

 

[Exorcet]

When engineered properly ram air works well. Suzuki used a ram air intake to create a passive supercharging effect at high speed on the original hayabusa. A ram air system can get larger amounts of cold air in the engine more effectively then even a cai when mounted on the hood.

Do you have any specific insight into this system? Just curious.

To increase mass flow (ignoring efficiency losses) you want to bump up density, which is equivalent to raising total pressure. This is impossible (or at the very least does not pay out very much) using the ram air effect until you reach about a third of the speed of sound. On a good day, that's still over 200 mph.

You can't raise total pressure without putting energy into the system (forced induction), so an intake with no moving parts can't do this.

Now, you can shrink the intake cross section to accelerate the air then slow it down again at some point to build up pressure. So I guess they would be doing this. I don't have enough experience with internal flow to say what kind of performance you could get out of this off the top of my head though. There would be limits on how quickly you could expand the flow before you start getting separation.

Drag and lift are only factors when speeds are very high and the ram air intake is something excessively large like something on an open wheel car.

Every bit counts. I don't think open wheel vs close wheel matters though

That is not to say that it works as advertised either. Many "intakes" are just that a arent sealed to properly use the small pressures created and even if they are the manifold and heads arent designed for such amounts of air.

I think the bigger issue would be making sure you pump enough fuel to keep up with the change in airflow, but that's something that cars should account for automatically these days.

Then there is the factor of how fast you must be traveling to make use of the system, which is also rather excessive for a street car

This makes sense to me, rough calculation seems to show that even under good conditions, benefiting from ram air won't happen on most road cars.

 

[Slash]

As for fuel flow I'm sure it'll get more than enough with the Holley pump on it so no biggie.

 

[savage388]

Do you have any specific insight into this system? Just curious.

Not really. It has been a while since I learned of this.
To increase mass flow (ignoring efficiency losses) you want to bump up density, which is equivalent to raising total pressure. This is impossible (or at the very least does not pay out very much) using the ram air effect until you reach about a third of the speed of sound. On a good day, that's still over 200 mph.

You can't raise total pressure without putting energy into the system (forced induction), so an intake with no moving parts can't do this.

Now, you can shrink the intake cross section to accelerate the air then slow it down again at some point to build up pressure. So I guess they would be doing this. I don't have enough experience with internal flow to say what kind of performance you could get out of this off the top of my head though. There would be limits on how quickly you could expand the flow before you start getting separation.

I'm not all to familiar with fluid dynamics yet, however I think that is how it would work. The air inlets would be smaller and the air would then be slowed down to build pressure. Just a theory though I'll look into it though.

Every bit counts. I don't think open wheel vs close wheel matters though

I was referring to the massive size of the intake above the cockpit.
Another though would be how does it work on top fuel cars? Its only a brief second but Id imagine the effects are quite something at 300 mph.

I think the bigger issue would be making sure you pump enough fuel to keep up with the change in airflow, but that's something that cars should account for automatically these days.

I honestly wouldn't think that any fuel modifications would have to be made to compensate for such minor gains in power, however without modern fuel injection maintaining air/fuel ratio would be an issue like an old mustang that slash is talking about.

This makes sense to me, rough calculation seems to show that even under good conditions, benefiting from ram air won't happen on most road cars.

The only place I can see real benefits is in the aerospace industry.

 

[sidney weese]

air induction works if you add air efficiently

 

[Cale]

 

[Space Dynamics]

Lol CAI.

 

[Adamgp]

That's a Hot Air Intake. Pretty common in the W-body community.

 

[Zenith]

If you're doing 190mph in your NASCAR around Talladega? Sure, you'll eke out a couple extra horses.

In your mostly stock Trans Am racing down highway 68? Nope.

 

[Tornado]

Do you have any specific insight into this system? Just curious.

To increase mass flow (ignoring efficiency losses) you want to bump up density, which is equivalent to raising total pressure. This is impossible (or at the very least does not pay out very much) using the ram air effect until you reach about a third of the speed of sound. On a good day, that's still over 200 mph.

You can't raise total pressure without putting energy into the system (forced induction), so an intake with no moving parts can't do this.

Isn't that what the idea between resonance supercharging/cross-ram induction was?

If you're doing 190mph in your NASCAR around Talladega? Sure, you'll eke out a couple extra horses.

In your mostly stock Trans Am racing down highway 68? Nope.

But Pontiac says my Grand Am has +5 horsepower because of that awesome hood.

 

[Slash]

I would think some setups woul be good for a few horsepower, specifically pointing at 1970 Boss 302s with the Shaker hood scoop. Air intake is limited to the carburetor by the size of the air duct off the otherwise sealed air cleaner. Not to mention the restriction from the filter itself. When you open the shaker, you bypass the cleaner and give it a lot more access to fresh air since theres more of an opening letting it in, and its being forced in when you're moving. Doing that is almost the equivalent of removing the entire air cleaner assembly which is common in drag cars to gain some power.

 

[bscar27]

I would think some setups woul be good for a few horsepower, specifically pointing at 1970 Boss 302s with the Shaker hood scoop. Air intake is limited to the carburetor by the size of the air duct off the otherwise sealed air cleaner. Not to mention the restriction from the filter itself. When you open the shaker, you bypass the cleaner and give it a lot more access to fresh air since theres more of an opening letting it in, and its being forced in when you're moving. Doing that is almost the equivalent of removing the entire air cleaner assembly which is common in drag cars to gain some power.

To back up @Slash's point about air cleaners, for a while I daily drove my car without and air cleaner, but when I changed the oil I decided to put it back on so everything would stay cleaner and it made a total dog out of the engine, hard to start and took a lot longer to get to proper operating temps

 

[Zenith]

Removing air filters and ram air are entirely different things.

Ram air is supposed to force air into the intake and cylinders. This makes no difference for most people.

Removing filters is freeing up flow and reducing parasitic loss during the intake stroke. This works if you don't mind bits of leaves and crap in your engine.

Also people, give actual useful data and reasoning besides "I took the thingy thing off my motor and my car feels faster."

 

[Slash]

Except with a scoop opened it is forcing air inside no different than any other Ram Air scoop, its just a filter bypass. Its only called Ram Air on certain vehicles but its effectively the same thing. I'm not talking about removing the assembly just opening the scoop vent.

 

[niky]

Sport Compact Car tested ram air.

http://www.modified.com/features/0208_technical_assistance_program/

Sort of.

-

Ram Air only truly works over a certain speed range, and even then, in best case scenarios, it's only worth a couple of hp... which can be easily swallowed up by the additional aerodynamic drag caused by the ram scoops.

 

[VXR]

My car has a small intake in the engine bay that brings in air through the grille. This can be switched for a bigger item from the next model up that helps breathing. Looks a lot neater than ram air, but the hood of the last Firebird is awesome.

I think I'll get on it and fit one.

 

[Exorcet]

Isn't that what the idea between resonance supercharging/cross-ram induction was?

That won't increase total pressure, it just captures more of it. Pressure builds up when air is trapped in the intake, but it's also quickly lost the longer it remains in there. The benefit comes from drawing in the pressurized air as quickly as possible.

 

[Space Dynamics]

That's a Hot Air Intake. Pretty common in the W-body community.

Yee We do it cause it's easy! - Also the more resistance you put into the intake, the hotter the supercharger makes it!

aaaand theres no intercooler so it's goanna be hot as heck anyways.