"Ram Air": Truly functional...or a gimmick?

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K

Kit Sullivan

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My factory Ram-Air is awesome...I would never dream of owning a Mustang with a NASA hood without a functioning ram-air system.

But...I have often wondered if it is truly effective. has anyone ever done some actual definitive testing one oway or the other?

I have run my with and without the system "hooked up", and have felt absolutely no difference from seat-of-the-pants driving. Of course, that doesn't mean it doesn't work...just that it may not be measurable from behind the wheel.

Some repetated 1/4 mile runs with and without would probably give the answer. has anybody done this? Any magazine ever tested this?

Just wondering...

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HP might improve from cold air even if there is no ram effect so performance may not answer the question of does a ram air hood really ram air. I think some sort of pressure measurment is needed to decide if any measured gains are from cold air or pressure (or both). I'm betting that most gain would be from cooler air not true ram air pressure.

 
I'd say it helps a little but looks VERY cool!

Ray
+1

I read somewhere that there were no HP gains but definitely has the cool factor. I was wondering though if you removed the block off plates for non Ram air cars if it would aide in reducing the under hood heat. I am thinking it would but I would prefer the RA system.

 
I was wondering though if you removed the block off plates for non Ram air cars if it would aide in reducing the under hood heat. I am thinking it would but I would prefer the RA system.
I run non ram air and no block off plates. Near as I can tell all it does is help get the engine dirty. ;)

 
I was wondering though if you removed the block off plates for non Ram air cars if it would aide in reducing the under hood heat. I am thinking it would but I would prefer the RA system.
I run non ram air and no block off plates. Near as I can tell all it does is help get the engine dirty. ;)
Lol, I remember at one point that I had them off but reinstalled them, probably for that same reason.

 
I remember reading somewhere that it was a 15 hp gain. I could be wrong. It wouldn't be the first time. Just ask my wife.

 
I'd say it helps a little but looks VERY cool!

Ray
I have functional ram-air on mine and highly suspect the cool factor is bigger than the actual performance gain. It gets more attention than anything on my car followed by the 8-Track radio. I would think anything that brings in cool air from outside of the engine compartment does help to some degree.

Jim

 
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If bringing in cool air is what really helps then some of the 73's are already set up with that.

They have the fresh air ducting that brings in cool air from the grill area directly into the air filter.

20p7tad.jpg


 
I would suggest Cool air nets the biggest gain. The huge scoop on pro stock cars only provide positive pressure above 54mph and I am told then add 3_17hp dependent on air quality. These are some of the planets most impressive atmo engines so I would say for a street driven pony the ram effect would be minimal

 
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Ok, I have a flat hood but I have observed that water drops hardly move on the hood surface while driving which means that there is no real pressure build up that would force air into the inlets on the hood. Otherwise the drops would move towards the windshield. They do but only very slowly so, not like there was much force applied to them.

I've even read somewhere that on some cars the hood surface is very low pressure area which means that a setup in which the air has to be sucked through a scoop in that area would even have the adverse effect as the engine would have to "suck harder" to overcome the lack of atmospheric pressure. That means you have less pressure than without any ram air setup at all.

I dunno if that applies to our cars too but the water drops show that there is at least no increased pressure.

Now cowl induction is a different story as the bottom of the windshield is a high pressure area that would force air into an inlet. That's how the air vents in the foot well are fed.

 
Performance gain, zero. But it did make my car experience vapor lock problems ever since as the air cleaner retains lots more heat.

 
Ok, I have a flat hood but I have observed that water drops hardly move on the hood surface while driving which means that there is no real pressure build up that would force air into the inlets on the hood. Otherwise the drops would move towards the windshield. They do but only very slowly so, not like there was much force applied to them.
That is the exact reason for the invention of the NACA duct! The flat surface of the hood is basically under ambient pressure due to the laminar airflow across its surface. The NACA duct introduces a lower-pressure zone under the laminar area...higher pressure air ALWAYS flows into low pressure air. This creates an almost vacuum-like effect of pulling air into the duct.

Thats the theory, anyway. Who knows if our hoods were properly designed aerodynamically to actually work that way...

 
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Ok, I have a flat hood but I have observed that water drops hardly move on the hood surface while driving which means that there is no real pressure build up that would force air into the inlets on the hood. Otherwise the drops would move towards the windshield. They do but only very slowly so, not like there was much force applied to them.

I've even read somewhere that on some cars the hood surface is very low pressure area which means that a setup in which the air has to be sucked through a scoop in that area would even have the adverse effect as the engine would have to "suck harder" to overcome the lack of atmospheric pressure. That means you have less pressure than without any ram air setup at all.

I dunno if that applies to our cars too but the water drops show that there is at least no increased pressure.

Now cowl induction is a different story as the bottom of the windshield is a high pressure area that would force air into an inlet. That's how the air vents in the foot well are fed.

Ok, lets step into it a bit. The real gremlin here is called "boundary layer". It's why the scoops and collectors on old school airplanes and drag cars were always set out above the skin surface. It's probably why the pillar scoops on a Shelby stick out somewhat disproportionately. If you don't collect air above the boundary layer you significantly reduce the volume taken in (assuming the inlets and duct runners are of the same size.) Here's a better explanation that kinda explains why most factory scoops on cars are little more than aesthetics and your raindrops don't move. Keep in mind that there are many more factors against the functionality of scoops like temp, turbulence, humidity, relative wind, etc.

http://www.grc.nasa.gov/WWW/k-12/airplane/boundlay.html

 
The boundry layer IS the lamainar airflow layer. Yes, you want to get above that layer, into the turbulent air...hence the wild snorkels on some Chryslers back in the day. However, those scoops induced significant drag. The NACA duct was designed to get air to flow into a scoop FROM the boundry (non-moving) air layer, without inducing any scoop-created drag.

 
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