Ram air system
#1
I have read some documents about Ram Air System, they say that increases power by mean of using cold air from atmosphere instead hot air from motor compartment.
I decided to do some numbers:

Calculated difference in amount of air between 86°F (30°C) and 194°F (90°C)
My Mustang is 351 in3 (5.75 lt), 8 cylinders
From general gas law, ideal gas law
PV = nRT
Where
P is atmosphere pressure = 1 atm
V is volume = 5.75 lt
n number of moles or grams
R is gas constant = 0.0821 atm lt / mol K
T is temperature in °K
For T1 of 30°C = 303°K
n1 = PV / RT = 1 * 5.75 / 0.0821 * 303 = 0.231 moles of air at 86°F
n2= PV / RT = 1 * 5.75 / 0.0821 * 363 = 0.193 moles of air at 194°F
Difference = 0.231 – 0.193 = 0.037 moles of air
Meaning a 16% less air at 194°F
So in that way we can run engine richer and have more power

What do you think?
Has somebody tested?
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#2
Me thinks the math is not necessary. A cooler, denser air/fuel charge will typically produce an increase in horsepower, however, the increase in all likelihood will not be noticeable. The air funneled into those hood scoops is negligible compared the rush of air blasting through the grille and over the lower front valance at speed. Grabbing cooler ambient air through those scoops can't hurt, and yeah it looks cool, but any "ramcharging" effect is nill.
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#3
Yes, good point.

By the way, my Mustang is not Ram air.

Best regards.

Mario
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#4
Over the years, I have run my car at 1/4 mile dragstrips (mostly OCIR and Riverside) with and without the ram-air hooked up.
There has never been a noticeable difference either way.

But...it is cool!
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#5
Yes, I think that there is Math defference but not noticeable like you say.

Best regards
Mario
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#6
As I remember My father who was in the Air Force, always said that the ram air effect didn't really begin to have much effect on things of this nature until about 80 mph. After that, the ram air effect started to overcome the CFM the engine was already pulling in by itself. I'm not quite sure about the accuracy of the numbers but it makes pretty good common sense. If the theory is true, it would explain why Ram Air doesn't effect our Mach1's much if any, as You don't reach 80 mph till about 3/4 track, by then the extra power would be virtually useless. A Pro Stocker on the other hand, Hits 80 mph in about the first 100' and has a huge scoop to maximize the Ram Air effect, plus it runs out near 200 mph. so there is a lot more air movement to work with. I wonder if any of the Pro Stock teams have ever done any research on this??? Just a few more thoughts on the subject. JTS 71 Mach1
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#7
Yes make sense, maybe sombody from Pro Stock teams can tell us.

Best regards.
Mario
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#8
I guess we'd be comparing apples to blueberries. Pro Stock car - tunnel ram intake with 2 1050 CFM Dominator Holleys, no air filters, huge aerodynamic air scoop to suck in as much air as possible. Outside of intake is packed with dry ice or liberally sprayed with R134 refrigerant before a run. Our cars - Well, not so much.
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#9
Several factors prevent the ram-air system on our cars from being noticeably advantageous...beginning with the simple fact that the shape of the "NASA scoops" ( Ford's words...) are not shaped correctly, like a true "NACA duct" ( the actual name) and therefore provide very little...if any...actual "ram" effect.
Certainly there is some amount of cold air induction going on, but since the stock system ALWAYS draws warmer underhood air into the carb, any outside cooler air is always blended with the warm air being drawn in underhood.
The closest and most direct air source will be drawn in before any air sourced from further downstream, and I suspect the underhood snorkel feeds air more directly than the hood scoops do...although I might be wrong on that point.
I was determined for years to get some exhaustive and significant results of ram-air vs non ram-air performance, and I could never get any conclusive ond way or the other. Many, many 1/4 runs and no discernable difference.
Much more noticeable improvement with dry-ice packs on the manofold between runs.
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#10
Excellent points!, Thanks, every day one can learn.

Best regards
Mario.
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