Ram Air Intake

[Hate_Camel]

A long time ago I was told that ram air does not make a big difference in performance until you're reaching speeds of 140mph+

It seems like it would make more sense for aircraft but can anyone confirm this?

[FordGT90Concept]

Makes sense to me. Turbochargers and superchargers are better. They'll get extra air into the engine no matter the vehicle speed.

Ram air intakes are better than nothing though.

[Steevo]

Also depends greatly on the location and the rest of the intake configuration.


For example, interfooler style ram's work well enough, but they are prone to diminishing returns if you can't keep a large enough intake tube to the throttle body/MAF sensor.

Cutouts that are flush do almost nothing.

Raised hood scoops work as long as they don't create a swirl effect in the intake, which causes centrifugal forces on the airstream actually harming efficiency.


The best solution is usually the simplest, short arm intake, with a open supply of cool air.

[JC316]

Here is the thing, in a naturally aspirated engine, there is no way the flow of air from forward movement alone can exceed what the engine is already pulling in. Ram air is a gimmick, pure and simple. Any gains are coming from it being less restrictive, not from additional air being forced in by the movement of the car.

Originally Posted by Steevo

Raised hood scoops work as long as they don't create a swirl effect in the intake, which causes centrifugal forces on the airstream actually harming efficiency.

Centrifugal force can actually help under the right circumstances. See the B head on the 4.6L DOHC, it's designed for the air to swirl into the combustion chamber, but it takes a lot of RPM to make it work.

[Bundy]

I am firmly of the belief that ram air makes very little difference due to the negligible pressure increase achievable. On the other hand, a temperature difference of just a degree can contibute to a measurable improvement in density and therefore oxygen delivery. It's colder air you need for performance.

I therefore think intake location matters more than intake orientation.

[1Kurgan1]

Originally Posted by JC316

Here is the thing, in a naturally aspirated engine, there is no way the flow of air from forward movement alone can exceed what the engine is already pulling in. Ram air is a gimmick, pure and simple. Any gains are coming from it being less restrictive, not from additional air being forced in by the movement of the car.

Centrifugal force can actually help under the right circumstances. See the B head on the 4.6L DOHC, it's designed for the air to swirl into the combustion chamber, but it takes a lot of RPM to make it work.

I think the "gimmick" of Ram Air is more the fact that since it's on the hood, it's pulling in cool air, rather than hot air. Rather than it being about the air speed increasing power. And the cooler air does make more power, nothing crazy, but there will be small gains.

[FordGT90Concept]

They're also in the slip stream so it does have higher pressure than ambient air around the engine. Not much, but enough to be measurable.

My brother's old T-bird had ram air intakes and a turbo on an I-4:
http://en.wikipedia.org/wiki/Ford_Pi...a_OHC_.28LL.29

[Steevo]

Originally Posted by JC316

Here is the thing, in a naturally aspirated engine, there is no way the flow of air from forward movement alone can exceed what the engine is already pulling in. Ram air is a gimmick, pure and simple. Any gains are coming from it being less restrictive, not from additional air being forced in by the movement of the car.




Centrifugal force can actually help under the right circumstances. See the B head on the 4.6L DOHC, it's designed for the air to swirl into the combustion chamber, but it takes a lot of RPM to make it work.

I will refer you to the "intake tornado" "Intake Vortex" or many other Bullshit devices.


Air at velocity flows like a liquid.

http://en.wikipedia.org/wiki/Cyclonic_separation


Air flowing in a vortex takes a longer path and picks up more heat, and has a much lower chance of reaching a resonant wave that will help compress air into the cylinder. The whole idea of crossover and variable length intakes is to allow a resonant standing wave formation to help increase volumetric efficiency. The problem with any variation in the air density is one cylinder will run lean while the next runs rich, and when you are sitting on the side of the road with a hold in a piston you will be wondering why.

[WhiteNoise]

I have RAM AIR on my ZX7R and it doesn't engage until I hit a little over 100 mph. Infact I can hear it working at 110. It makes a sweet sucking sound.