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Discussion Starter #1

Always knew they were shite, and seriously detrimental to the engine. Would wager the DNA are the same.
 

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I wouldn't trust anything that bloke on the video says, I only watched the first 10 seconds and when I spotted it was that idiot I could not watch anymore. He carries out stupid experiments like making a con-rod for a lawn mower engine out of drinking straws just to see how long it lasts, the bloke is a knob!
 

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I have read some gumph which stated that K+N filters need pulsating air to be flowing through them before they work properly, they do not work well with a constant air flow, it is something to do with vibrating the cotton strands so that they trap the particles. Whether is true or not I have no idea. I can say that Fram oil filters are total crap, I build V8 engines as a hobby and I would rather use an old sock over a Fram oil filter!
 

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I don't see how you could pulse air into the box. It comes in straight into the pipe, as is.
I always suspected those cotton filters were crap after I fitted one to my car donkeys years ago. When I went to clean it, the box had dust on the wrong side of the filter, whereas it was clean with the paper one.
The onlyway they can logically let more air through, is if they're less restrictive (more porous = bigger holes = more air)
 

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I don't see how you could pulse air into the box. It comes in straight into the pipe, as is.
I always suspected those cotton filters were crap after I fitted one to my car donkeys years ago. When I went to clean it, the box had dust on the wrong side of the filter, whereas it was clean with the paper one.
The onlyway they can logically let more air through, is if they're less restrictive (more porous = bigger holes = more air)
Over the years I’ve read all the tech stuff from K+N re filtration, how the oil attracts the dirt etc. At the end of the day if you look through a brand new filter towards the light you can see light through the pinholes all over the panel! Enough said. I prefer clean cylinders and inlet tract, I won’t miss the extra 2 bhp anyway.
 

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I don't see how you could pulse air into the box. It comes in straight into the pipe, as is.
I always suspected those cotton filters were crap after I fitted one to my car donkeys years ago. When I went to clean it, the box had dust on the wrong side of the filter, whereas it was clean with the paper one.
The onlyway they can logically let more air through, is if they're less restrictive (more porous = bigger holes = more air)
When an engine is pulling air through an air box the engine will create pulse waves in the airbox as each cylinder inhales on its intake stroke, it is not a constant stream of air, I guess a gas turbine would be an engine that creates a constant stream of intake air.
 

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Discussion Starter #7
When an engine is pulling air through an air box the engine will create pulse waves in the airbox as each cylinder inhales on its intake stroke, it is not a constant stream of air, I guess a gas turbine would be an engine that creates a constant stream of intake air.
Either way, I don't see how a K&N would stop crap getting in. You can literally see daylight through them. And as the video shows, they let so much crap through. Other videos on there showing cylinder walls scratched to buggery.
Better to just stick a paper filter in. Even the poorest performing one out performed the K&N. Is it really worth it for 2hp?
 

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It makes perfect sense that a finer filter will reduce flow but another consideration is the more it filters the quicker it will block.
I appreciated this fact and have used quite a lot of K&N filters without any issues but have done so knowing that particles smaller than 2.5 microns will definitely get through and above 5 microns is where they really start to filter.

A particle of smoke is typically around 1 micron and human hair is over 50 microns. I think this is the basis for EGR systems on diesel engines but it is obvious that the build up of carbon particles means that there is a lot more danger of internal damage to cylinder bores by this than external air.

So from that video it would tend to point to using a paper filter but changing it regularly but my only concern is that a low quality air filter is more likely to have manufacturing defects and could let very large particles through or even the filter particles itself could breakdown and enter the intake.
Also quality doesn't have much correlation with price so I wish I hadn't started thinking about it now :)
 

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It makes perfect sense that a finer filter will reduce flow but another consideration is the more it filters the quicker it will block.
I appreciated this fact and have used quite a lot of K&N filters without any issues but have done so knowing that particles smaller than 2.5 microns will definitely get through and above 5 microns is where they really start to filter.

A particle of smoke is typically around 1 micron and human hair is over 50 microns. I think this is the basis for EGR systems on diesel engines but it is obvious that the build up of carbon particles means that there is a lot more danger of internal damage to cylinder bores by this than external air.

So from that video it would tend to point to using a paper filter but changing it regularly but my only concern is that a low quality air filter is more likely to have manufacturing defects and could let very large particles through or even the filter particles itself could breakdown and enter the intake.
Also quality doesn't have much correlation with price so I wish I hadn't started thinking about it now :)
It makes perfect sense that a finer filter will reduce flow but another consideration is the more it filters the quicker it will block.
I appreciated this fact and have used quite a lot of K&N filters without any issues but have done so knowing that particles smaller than 2.5 microns will definitely get through and above 5 microns is where they really start to filter.

A particle of smoke is typically around 1 micron and human hair is over 50 microns. I think this is the basis for EGR systems on diesel engines but it is obvious that the build up of carbon particles means that there is a lot more danger of internal damage to cylinder bores by this than external air.

So from that video it would tend to point to using a paper filter but changing it regularly but my only concern is that a low quality air filter is more likely to have manufacturing defects and could let very large particles through or even the filter particles itself could breakdown and enter the intake.
Also quality doesn't have much correlation with price so I wish I hadn't started thinking about it now :)
Oiled 2 stage foam is the way to go.
 

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Has anyone mentioned that these filters need to be oiled? Does that not catch the dirt?
The K+N certainly needs oil as does any foam filter, you can not oil a paper filter because it will fall to pieces and get eaten by the engine. (water will do the same thing to a paper filter). The K+N would have been pre-oiled in the test. I've read about other tests where a K+N out performs all other filters but its each to their own I guess. The bloke that made the vid does loads of other 'tests' which are dubious to say the least! (Running lawn mower engines on alternate fuels but then having to choke the air intake to get the engine to run, he then concludes some how or other that the engine made less power whilst ignoring the fact that he had 'throttled' the engine).
 

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I like some of his vids but this time I think he's got his test a bit wrong. Sprinkling the powder on the filter with no airflow is not a real world simulation. Oiled filters work by the oil trapping some particles and then soaking them with oil. They then become a part of the filter which can then trap other particles. Dumping so much on at once will not allow that to happen.

Paper (or cellulose) are the best filters in normal operation. If there is a likelyhood of water getting in then an oiled filter is better.

Foam filters are cheap, oiled and washable which is why they are used in "dirt" applications. They probably also filter better that cotton.

Cotton type oiled filters are the worst at filtering but they aren't as bad as he's made out. Normal road environments don't have so many particles in the air... well not unless you are stuck behind a lorry on a narrow country road. They kick up all the dust and grit from the gutters so I drop back when that starts happening.

However - If there was a paper alternative for my motohooligans K&N then I'd have bought it. Once I get around to checking the one in my 1190 I just might put the standard filter back in (the bike came with a K&N that was dealer fitted).
 

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Discussion Starter #13
I like some of his vids but this time I think he's got his test a bit wrong. Sprinkling the powder on the filter with no airflow is not a real world simulation. Oiled filters work by the oil trapping some particles and then soaking them with oil. They then become a part of the filter which can then trap other particles. Dumping so much on at once will not allow that to happen.

Paper (or cellulose) are the best filters in normal operation. If there is a likelyhood of water getting in then an oiled filter is better.

Foam filters are cheap, oiled and washable which is why they are used in "dirt" applications. They probably also filter better that cotton.

Cotton type oiled filters are the worst at filtering but they aren't as bad as he's made out. Normal road environments don't have so many particles in the air... well not unless you are stuck behind a lorry on a narrow country road. They kick up all the dust and grit from the gutters so I drop back when that starts happening.

However - If there was a paper alternative for my motohooligans K&N then I'd have bought it. Once I get around to checking the one in my 1190 I just might put the standard filter back in (the bike came with a K&N that was dealer fitted).
Yeah good points. I think I'd agree on the foam filters being best overall. I've used them a lot in the past, and the wrong side of the filter has always been almost spotless. I'm thinking of replacing my 690 paper with the same.
Would be interesting to see what they use in the Dakar or WRC. Though driving from Ruthin to Manchester is far from comparable :D
 

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When Lyndon did the Dakar he was using pre-oiled foam in his 450 (and throwing them away afterwards:eek:).

I have never seen dust on the inlet boot on my trail bike (with oiled foam) but I'm pretty sure I saw some bits on the inlet trumpets inside my motohooligan.

I do think we can get a little over concerned about inlet cleanliness though, especially as motorcycles general don't do high mileage. Just look at all the carbon crap that is in your exhaust pipe.. where do you think that came from. :oops:
 
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