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Nicholas
Dodge Dakota
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4/17/2002
16:18:03
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 Subject: Ram air or Cowl Induction?
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I have a 2001 4.7 Dak, Motorsports Edition. I called K&N yesterday and they arn't appearently coming out with an FIPK (cold air intake) until the end of summer 2002. If they do at all the girl said. So I was like, WTF! I am now thinking about either a Ram air, or Cowl Induction, but dont really know much about either, and which would be more functional. If someone could help me out, id appreciate it! thanks
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Dan Keller
Dodge Dakota
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4/17/2002
19:40:02
|  RE: Ram air or Cowl Induction?
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I found this little tidbit...
Air filter modifications are a typical performance upgrade for Dodge engines. The addition of a free-flowing cone filter is the most common. Considerable verbiage has been written on this subject but I feel confusion remains. This article addresses the perceived benefit of a "rammed air" intake system.
It is common knowledge that a car at speed can provide a ramming effect to the air entering a hood scoop. Common sense would suggest that this additional pressurization of the intake air reaching the air filter would result in increased engine performance, but is this added pressure really worth much? I have looked into this question and the short answer is no.
Engine power - pure and simple - is related to how much air-fuel mixture an engine can use and how high the compression ratio. Increase mass flow through the engine or increase the compression ratio and increased power output will result. The reason supercharging or turbocharging can dramatically increase engine power is because it in affect transforms a small-displacement low-compression engine into the equivalent of a large-displacement high-compression engine (yielding high mass flow / high effective compression ratio). But couldn't a "ram-air" intake yield some benefit? A poor man's supercharger so to speak? Let's investigate.
The ram-air pressure created by the forward motion of the car is proportional to inlet air density and the square of the velocity. Using conditions at 1000-ft elevation and 70F gives the following results:
Speed "ram pressure"
77-mph ( 0.1 psi )
109-mph ( 0.2 psi )
134-mph ( 0.3 psi )
155-mph ( 0.4 psi )
173-mph ( 0.5 psi )
Hence "legally" all one can expect to gain is a 0.1 psi increase in intake pressure (note this is a far cry from the 6-psi+ pressure increase that turbo's and superchargers produce). This increase in pressure is added to the ambient pressure of 14.17 psi raising it to 14.27 psi. But this is a less than a 1% increase in inlet pressure. This trivial increase in pressure would increase mass flow through the engine by a similar amount - yielding a 1.2-hp increase to a 170-hp engine. Not much of an increase and certainly not worth chopping up your Dodge's hood or front end to capture this "ram air" effect. Truth is the reason some air-filter mod's yield a discernible power increase is not due to intake air pressure but temperature. Intake air temperature has a much more dramatic impact on inlet air density (and hence mass flow through the engine) than small changes in inlet pressure. Here is an example.
Let's assume the factory airbox with its inlet in the fender draws in 70F air. A modified car with an exposed cone filter might breathe 110F warm air under the hood. Comparing the difference in air density with these two conditions reveals the warm air is 7.5% less dense than the cooler air and would consequently reduce engine power by a similar percentage - 158-hp vs 170-hp - a 12-hp reduction! In fact if we wanted to restore the density of the 110F air to that of the 70F stream, we would have to increase inlet pressure by 1.07-psi. So looked at in a reverse fashion, cooling the air 40-degrees is the equivalent of 1-psi of boost. Or another way, the cone filter would have to have 1-psi less pressure drop than the factory filter to yield equal power. Now 1-psi is a huge pressure drop for an air filter. I have never personally measured this but my best guess would be a value of around 1-inch-H2O ( 0.04 psi).
So the bottom line... Forget about "ram air". Use a low-pressure drop filter. But most importantly, duct or box off the filter so that it will draw in the coolest air possible. With this last point in mind, the area in the fender seems optimal (closer to the road surface would likely be warmer).
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dabigbossman
Dodge Dakota
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6/13/2003
13:47:59
|  RE: Ram air or Cowl Induction?
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Message:
I just finished reading you artical on Induction, very informative, I think you just saved me $300.00 bucks on buying "The Ultimate Air Ram System" Now, where can I find a Super or Turbo charger that will "Kick some serious A$$" for my Dodge Ram 2002 truck.
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Perry
Dodge Dakota
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4/01/2004
12:03:43
| RE: Ram air or Cowl Induction?
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I have a 1999 4WD Dakota w/ a 318. My question is this: Using the factory airbox with a high flow filter would it be beneficial to remove the airbox inlet that draws air from the fenderwell area and run a tube through the grill next to the radiator? I am in the process of fabricating an entire cold air system and until I'm finished I was curious if this "temp fix" was worth my time
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00R/T CC
Dodge Dakota
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4/01/2004
17:32:42
| RE: Ram air or Cowl Induction?
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That's how I've got mine. You have to tweak the A/C line that's in the way a bit, be carefull doing that.
Can't say that I noticed a difference, but that little elbow on the air box sure looks restrictive.
Whatever you run for ducting, be sure to cover it with foil dryer ducting for heat reflectivity. Some might say it looks ugly, but it's probably worth as much in performance as the drop in K&N, by keeping the incoming air cool.
While you're at it, cover the tube from the air box to the TB as well. Looks cool, is cool, stays cleaner, too.
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