Looking at DNA air filter, claim 39% improvement in air flow. Believable?
Because @jsobell did't really fully explain it. When he wrote:If performance air filters do not perform any better than stock paper filters, why would all the race teams in auto, bike, boat, etc., insist on using them? Performance gain?
He was exactly correct and later explains why: a more porous membrane physically allows more air to pass through. Imagine a screened in porch on a breezy day. Now remove all the screens and put chain link fence in its place. Then imagine a third porch where the screens are made of coffee filter material.They give significantly less restrictive airflow, in the same way K&N do.
Well, no, this statement is contradictory to the previous one and should be understood to be false, all other things being equal. To use the porch metaphor again, the porch stays the same size and shape and retains all the same windows regardless of which screen material is used. And we'll grant that mother nature is providing a steady breeze that doesn't change much over time.If you think it will give your engine more airflow, it won't.
The inlet is a bottleneck indeed. The filter is yet another bottleneck. As to which one is more detrimental to flow, that is an engineering exercise you'll have to do for yourself. However, all things being equal (the inlet size does not change, but the filter material does) you should be able to deduce the net result on airflow.The inlet to the airbox is so small, that's the bottleneck, not the filter.
Note that it appears that the amount of actual "air filtering area" is larger with the DNA and the K&N, compared to stock.Oh, and as for which one? Well if you're hoping for extra airflow, the DNA rates the highest between K&N and DNA. There are no published figures for BMC.
I doubt we'd notice any difference between the three, but take your pick
They published a video of a full test of a Kawasaki filter on YouTube:
https://www.youtube.com/watch?v=pGSHtEjYIhc
TL;DR results:
• Kawasaki OEM 152 cfm @ 1.5 inH2O
• K&N Filters 161.6 cfm @ 1.5 inH2O
• DNA Filters 184.6 cfm @ 1.5 inH20
I'm not sure I did (or would) suggest that the 900 has more room for improvement than the 1200, but only time and testing will tell.As you say, I suspect there's more wriggle room for improvement on the 900 engine.