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dakota/marine
Dodge Dakota
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2/19/2003
09:25:00
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 Subject: 3.9L air intake
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Message:
I was wondering if anyone knew what the cubic feet per second was at idle, half way in the rpm range and redlined for my 1999 dakota 3.9L engine. If you could tell me the way you found out. I know you use the cylinder area and multiply some stuff. if you could take the time and let me know it would be a great help. thanks alot for kandahar, Afganistan,
Josh Shatto,
CPL USMC
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Jon
Dodge Dakota
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2/19/2003
12:26:07
| RE: 3.9L air intake
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Message:
Airflow = CID x RPM x .5 x Ev
divided by 1728
Ev is volumetric efficiency (assume 85%)
So for a 3.9L at idle (800 rpm):
239 x 800 x .5 x .85 / 1728 = 47CFM
Divide that by 60 for cubic feet per second which is about .8
The is the maximum airflow of your engine based on displacement. However in the real world the air flow is restricted by your throttle body. I'm not sure how much they flow, probably about 450 to 500 CFM max. Once you found the max airflow of your throttle body you could hook up a scan tool to your truck and look at a parameter called "Calc Load." That will tell you the airflow of your engine as a percentage of maximun airflow. At idle your engine will flow between 15% and 21% of max airflow and between 17% and 24% of max at 2500 RPM.
-Jon
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DakotaDan
*GenIII*
2/19/2003
12:37:15
| RE: 3.9L air intake
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Message:
Maybe something here will help you ?
http://www.csgnetwork.com/automotiveconverters.html
Dan
Next Time You Think You're Perfect
~~~~~Try Walking On Water~~~~~
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slopehead
Dodge Dakota
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2/19/2003
16:48:31
| RE: 3.9L air intake
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Message:
Jon has it pretty close but the 85% might be for full throttle not at idle when a high manifold vacumm is present. It is closer to 15% VE at idle.
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dakota/marine
Dodge Dakota
JOIN HERE
2/19/2003
22:01:36
| RE: 3.9L air intake
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Message:
Thank you for taking the time to answer my questions. The reason is i want to either turbo or supercharge my kota. So im going to get a turbo from vehical with the same CFM, about same rpm range and get a custom exhast manifold made for it. im also gonna have to get bigger injectors too, maybe a fuel pressure reg. Right now im in Kandahar, Afganland so all i can do is order parts either from ebay or other stores online and have them wait for me. right now im looking for the perfect turbo or supercharger. i wrote to kennbell and whipple, they are researching what would be the best to use for my truck. Does anyone know of some one putting a v8 supercharger on the 3.9? any and all help is great. Thanks again.
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dakota/marine
Dodge Dakota
JOIN HERE
2/20/2003
07:38:03
|  RE: 3.9L air intake
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Message:
That website is really helpful. Thanks again everyone.
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