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Joined: Thu Feb 26, 2009 11:00 pm
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Location: Melbourne

Post Posted: Thu Aug 18, 2016 8:25 pm 
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Velocity is decided by the rate that the cylinders are pulling the air in to the engine (or a turbo is sucking it). More revs=more velocity.
If the filter presents a restriction, it will slow ultimate velocity for a given engine speed. less velocity=less power
Less restriction= more power. That bit isn't hard to work out.

The (apparently) harder bit is that to maintain filtration with increased air moving into the engine, you need a filter with more surface area. You want the air moving through the filter slower, not faster. More available area for the air to move though, means the air is moving slower.

What can happen with low restriction filters is that they increase turbulence at the air flow meter. This can upset their readings and cause poor response during transients.

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az supporter
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Post Posted: Sat Sep 10, 2016 10:11 pm 
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Marko_SJ wrote:
greenzook89 wrote:

And don't get me started about changing Dirtbike Foam Filters


Please start. My opinion got me crucified by many on Thumpertalk. Interested to hear yours. :mrgreen:



Haha. I learnt long ago dirtbike forums are mostly stuck in in the dark ages. Examples. You must run your 2 stroke at 25:1. You must clean your filter before every comp. Same as spark plugs. Then we get to my personal favourite, carby jetting Armsup .

But nah, my opinions dont matter, my bikes were never touched by a so called "professional", they were all built/tuned at home yet I still managed to win 7 state titles and place in the Top 3 in Australia various times. Oh and I never blew up a motor even though the experts told me "they wont last"

Anyways, I digress. Back to K&N flyscreens :thefinger:

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Makes me want something similar

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Joined: Sat Dec 19, 2015 8:19 pm
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Vehicle: Suzuki Vitara SWB 1992

Post Posted: Thu Sep 22, 2016 9:51 pm 
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to all that believe in foam / cotton filters (have a look inside the air box of a bull dozer or excavator) they are build for the dust and they all use paper with a donnaldson pre cleaner

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Location: Darwin, NT
Vehicle: WT sierra, GU CRD

Post Posted: Tue Sep 27, 2016 2:21 pm 
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greenzook89 wrote:
Marko_SJ wrote:
greenzook89 wrote:

And don't get me started about changing Dirtbike Foam Filters


Please start. My opinion got me crucified by many on Thumpertalk. Interested to hear yours. :mrgreen:



Haha. I learnt long ago dirtbike forums are mostly stuck in in the dark ages. Examples. You must run your 2 stroke at 25:1. You must clean your filter before every comp. Same as spark plugs. Then we get to my personal favourite, carby jetting Armsup .

But nah, my opinions dont matter, my bikes were never touched by a so called "professional", they were all built/tuned at home yet I still managed to win 7 state titles and place in the Top 3 in Australia various times. Oh and I never blew up a motor even though the experts told me "they wont last"

Anyways, I digress. Back to K&N flyscreens :thefinger:


yours is similar to mine and I know EXACTLY where you come from in that assessment of the situation. Apparently I was lazy and had a pathetic maintenance schedule because I dont clean filters every ride, I clean them when they are dirty.

It upset some of them more when I said the only benefit of removing a clean-ish filter is the chance of getting dirt in the airboot. The concept of a blocked filter filtering better was lost on many also.

I also said I'd rather check my sprocket bolts or check spokes, triple clamp bolts or clean the fork wipers rather than waste time cleaning a clean filter. Apparently I make excuses for my poor airfilter habits too.

I enjoyed that thread greatly. 8) 8)

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az supporter
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Post Posted: Tue Sep 27, 2016 9:57 pm 
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Clean them when they are dirty. What wizardry is this?

I suppose if you havent checked the triple clamp bolts and the forks start slipping it wont matter as you have a clean filter. Priorities!

It also used to amuse me with the vintage blokes that used to run little K&N pods off the end of their carbies. Every time they dropped it there was a little ring of dirt on the carby slide :lol:

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Makes me want something similar

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Joined: Wed May 14, 2014 9:12 pm
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Vehicle: Suzuki Vitara JLX

Post Posted: Wed Oct 05, 2016 7:47 pm 
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I only ever blew up a motor when my sponsor said 'run this new oil at 50:1 instead of 25:1 with your other oil'
seized the bigend on lap 2 of a hare n hound - back to the old Castrol after that!
Spent more time tuning the suspension and making sure I had good tyres
Although there was an enduro we would do out Kogan way that would seriously dirty up a filter

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Post Posted: Mon Feb 27, 2017 8:15 pm 
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Steve, can you tell me the dimensions of the Hiace box?
Thanks.

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Post Posted: Tue Feb 28, 2017 7:59 am 
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It's not handy at the moment. Circa 400x180 I reckon.

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Post Posted: Tue Feb 28, 2017 2:44 pm 
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That'll do, thanks

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