Not sure if anyone cares but I've asked some questions of K&N regarding max CFM and the point of diminishing returns as far as air volume increases are concerned. Bottom line is that max CFM is 451 @ 6000 RPM, while the higher flow filter can provide 592.4 CFM the stock air box creates a 240 CFM bottleneck. I'm all about real data so yeah here ya go.
Thank you for your interest in K&N products. A stock engine usually has a volumetric efficiency in the high 70% to mid 80% range which would put the CFM of your motor at 451 CFM at 6000 RPM. That is the maximum amount of air that your engine car draw in so, even if your use a filter that can flow 800 CFM, your engine will still max out at 451 CFM and there won’t be any performance gain.
The CFM of a filter is based on its surface area and our 4 layer cotton filters flow around 6 CFM per square inch. Horsepower gains from the intake system are primarily from designing a more efficient and smoother intake tract. As you can see from our air flow test data, our panel filter can flow 592.4 CFM on its own, but in the stock, restrictive airbox, it can only flow 240 CFM.
http://www.knfilters.com/dynocharts/33-2334.pdf
By eliminating the airbox and using a smoother intake tube, the efficiency increases and the CFM capability of the system is greater than the requirements of the engine.
The only benefit of using a filter that flows more CFM than your motor needs is that it extends the service life because there is more surface area to draw air through before the filter becomes clogged. With that being said, a twin intake will provide no performance gain and will only be for aesthetic purposes.
