any evidence of actual extra hp out of K&N or other filters?

[John390]

I ask because the stock filter appears large enough to flow more than enough power for our engines. I've seen similar sized filters for car engines. Even a little Kia engine is going to make at least double what ours can make even fully modded.

Anyone have good back to back dyno evidence of gains from K&N, DNA etc?

Now, that said, if so, is that DNA filter any good? I remember seeing a post somewhere that stated that it actually cost power because it interfered with the velocity stack?

I am going to be upgrading to the Gray Area complete airbox, and an upgraded injector.

Other mods in sig

thank you!

 

[Tom]

These little motors are strange. I don't have any empirical evidence to back this theory up with; but I think the gains from the K&N filter are from the way the filter element protrude into the airbox compared to the stock. Yes I realize the K&N flows higher in the mystery test they used to compare CFM to the stock unit (because K&N said so), but also there are posts that say a reversed K&N makes even more power. I would be curious to see how the stock filter compares to the K&N when both are installed with the filter element extending outside of the airbox.

 

[John390]

can we do a reversed filter on the RC390? I tried to put my stock filter in upside down and it didn't fit.

 

[RC390Brizzi]

I saw photos of an inverted K&N, if you take the top part off the airbox lid it should work.

Chad posted somewhere that he saw up 0.7hp difference doing that on a stock bike and even more on modified engines.

I'm a little annoyed by that because i found these posts after i ordered a DNA, which comes from Europe so sending it back will be an expensive hassle.
On the other hand i don't race mine, all the mods are just for fun.

 

[John390]

I have a fully open airbox. I completely cut the top part off and carefully trimmed it down to bare minimum. I tried to flip the filter and the lid didn't really seem to fit the filter.

 

[MadnessWithout]

I never even thought or heard about reversing the air filters to get more power. This really works? (I can't seem to open the link to where Chad saw a 0.7HP difference)

Sent from my XT1650 using Tapatalk

 

[CDN Duke]

There's a historical reference here: https://www.rc390-forum.com/forum/electronics/1033-ecu-flash-post18861.html#post18861

Just realized that

RC390Brizzi ​

linked the same above.

 

[MadnessWithout]

There's a historical reference here: https://www.rc390-forum.com/forum/electronics/1033-ecu-flash-post18861.html#post18861

Just realized that

RC390Brizzi ​

linked the same above.

Yeah I was trying to click his link but it wasn't working. Seems your link works though!

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[Tom]

I actually just did the reverse filter mod last night. The cone shaped polishing bit that comes with dremel kits seems to cut the perfect amount of material when using the inward protruding lip as a guide on the underside of the filter cover.

Upon cranking the bike, I noticed my AFR values at idle leaned out from a rough 13.6 to a steady 13.8. I havent had a chance to ride yet, but going off of how the idle became leaner, it looks like inverting the filter does infact feed more air into the motor.

I think this has more to do with the way the intake air stream has more area to flow through, than the increased volume of the airbox. With the pleats facing up, the stream is less impeded by the filter element. Fluid dynamics states that liquids (or air in this case) tend to stick to the surfaces of the flow's pathway. For example, the pressure at the inside walls of a free flowing pipe will be higher than pressures measured in the middle of the flow within the pipe. I think that by inverting the filter, you are giving less area within the flow of the air for it to stick to.

I think this is also why it's been proven the DNA filters produce such a measurable power loss when compared to the K&N. The DNA filter clearly presents more filter area for air to initially pass through, but the deep protrusion into the flow of the intake air's stream gives it substantially more area to stick to, impeding the free flow. I think if someone ran a dyno back to back, with an inverted K&N vs inverted DNA, you would see the DNA filter produces more power.