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Discussion Starter #1
I believe the equation for optimum intake CFM is:

((Max RPM) x (Engine Displacement in CI) / 3456 ) x .85 = CFM

According to this equation, assuming it is correct, the Challenger R/T 345CI engine only requires ~500 CFM at Max RPM of ~5850

Our stock air filter is rated at ~720 Max CFM. Well above the 500 required.

How does a more free flowing intake increase power? Is there something preventing the intake system from reaching 500 CFM?
 

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You said the stock air filter is rated at 720 MAX CFM. Is that specifically just the air filter or the intake system as a whole?

Has there been any tests that confirm that the stock filter flows 500 CFM at 5800rpm? The max of the filter flow can be 720 but I dont take that as solid proof that at 5800 rpm it is allowing 500.

Im not saying I know the answer to your question but I think it is interesting.

Another factor is the temperatures. I have tested and proven that the LMI fender intake runs significantly cooler than the stock set up.
http://www.challengertalk.com/forums/f18/lmi-fender-pull-v2-temp-averages-102139/
 

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Discussion Starter #3
You said the stock air filter is rated at 720 MAX CFM. Is that specifically just the air filter or the intake system as a whole?

Has there been any tests that confirm that the stock filter flows 500 CFM at 5800rpm? The max of the filter flow can be 720 but I dont take that as solid proof that at 5800 rpm it is allowing 500.

Im not saying I know the answer to your question but I think it is interesting.

Another factor is the temperatures. I have tested and proven that the LMI fender intake runs significantly cooler than the stock set up.
http://www.challengertalk.com/forums/f18/lmi-fender-pull-v2-temp-averages-102139/
The filter is rated at 720 Max CFM. I do not know what the Max CFM of the intake system is.

Interesting info on the LMI. Thanks for the data.
 

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It increases the rate and velocity of the incoming air charge. Fuel injected engines want air as fast as they can get it. CAI's and high flow filters help more air arrive to the engine sooner improving responsiveness and acceleration. Fuel injected can use more air than carbureted ones. The restriction in most CAI's is the filter.
On another mopar vehicle that made about 300 hp, the following mods each improved power and acceleration over the previous one.
Stock
Drop in replacement air filter
14 x 3 inch [email protected] ffilter
ported throttle body
14 x 3 inch [email protected] filter plus a [email protected] x-streme filter lid
ported intake manifold
I was especially surprised how much better the vehicle accelerated after the addition of the x- streme lid myself. I thought the 14 x 3 inch [email protected] would provide all the air it would need and want but I was wrong.
In my mind, there is no way one intake tube and one round filter is feeding these hemis all the air they could use and want.
 

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Ya that brings up a good point.

The piston is pulling the air in so ANY restriction at all would reduce output. Its more about the velocity of the air coming in. The stock filter may flow 700 CFM Max but how much effort does it take to pull that air through at those CFM's?
 

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Every part in the induction system has a flow rating and a pressure drop number where that flow rating occurs. The problem is they tell you the flow rating number but rarely tell you at what pressure drop number (sort of like giving a hp rating w/o the rpm). If you were able to acquire the flow rating of each part, all at the same pressure drop condition, then you would know which part has the headroom and which is the bottleneck.

To answer more directly to the topic title, an upgraded air intake with a higher rating may or may not be any help at all. If the original intake already flows everything the engine could ever need, then the new intake isn't going to flow any more than that (because it is actually the engine that is the limiting factor). If the new intake has a higher flow rate at a specific pressure drop than the original intake at the same pressure drop, then the new intake will flow more (assuming the engine can use that extra flowrate).
 

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I believe the equation for optimum intake CFM is:

((Max RPM) x (Engine Displacement in CI) / 3456 ) x .85 = CFM

According to this equation, assuming it is correct, the Challenger R/T 345CI engine only requires ~500 CFM at Max RPM of ~5850

Our stock air filter is rated at ~720 Max CFM. Well above the 500 required.

How does a more free flowing intake increase power? Is there something preventing the intake system from reaching 500 CFM?
valve size, lift and duration also factor into what the intake system can actually flow
 
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