Dave Vizard explains how the K&N filters works

Bendy toy

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He's tested K&N filters against paper elements on a gas flow bench. he says K&N clean down to microns even when covered in dirt and they flow almost as well as having no filter installed.

The filter stuff starts about 3 minutes in.

 
well. live n learn..i now know how a k and n works. years ago i built a 1380 mini engine using Davids book, how to tune a mini. it was faster than a 2 litre injection s sierra at the time, it went like stink.
 
I ran an FJR with either stock or K&N filters exclusively between oil changes.
I noted that the oil came out filthy when running the K&N whem compared to the stock item so I stopped using them.
I used the K&N cleaning / oiling kit to look after it too.
 
All the other comparisons I've seen between K&N filters and others state that OEM filters perform just as well. From memory these were referring to supposed BHP increases.
 
Well the shite i've seen on customers bikes downstream of a K&N filter obviously haven't listened to what he has to say.
 
Well the shite i've seen on customers bikes downstream of a K&N filter obviously haven't listened to what he has to say.

do you mean to say that a lot of shyte has got past the filter?, due to poor cleaning? or a poor fit? or are you saying k and n doesnt filter well?
 
Very interesting indeed. Good find - K&N stuff starts at 4.25 through to 14.30.
 
Vizard is famous for tuning cylinder heads with a flow bench. He was getting huge performance gains from the old 5 port mini 1275 even with a single SU carb.
He tested the K&N for flow and dirt trapping. Flow was better than paper especially when dirty.
I ran a Montego diesel for 140,000 with K&N filter. It was scrapped when turbo failed. Engine was fine but body was full of tin worm.
 
Very interesting indeed. Good find - K&N stuff starts at 4.25 through to 14.30.

The whole video is worth the time. Especially the bit about cylinder pressure when the exhaust valve opens and how the Mini tends to run the inner cylinders weak.
 
I’ll bet the BMW does not feed both inlet valves equally. The angled port will favour the lower valve. But it’s all one pot so not a buggy unless after ultimate power.
 
do you mean to say that a lot of shyte has got past the filter?, due to poor cleaning? or a poor fit? or are you saying k and n doesnt filter well?

I'm saying what I've seen on bikes that come in for servicing...... I'll add that not one of the bikes had been tuned in any way whatsoever so I can't comment on Daves tuning tips.
 
The OEM filter is more than good enough and we know it stops the dirt. A K&N will also stop the dirt when its cleaned at the correct intervals and when its treated with the correct sticky oil. Use the wrong oil, abuse the fabric, lose it's wafty fibres and you might as well "install" an old sock.
 
As well as not filtering very well it’s easy to over-oil a K&N then the bike doesn’t run well at all, huge power loss. I know, I’ve done it.
 
As well as not filtering very well it’s easy to over-oil a K&N then the bike doesn’t run well at all, huge power loss. I know, I’ve done it.

They filter fine but as you say too much oil is bad. It’s even worse when there’s a hot wire mass air flow meter sitting just behind.
 


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