K & N air filter

[Patrol 1993]

Hi Guys,
I have a 1993 Patrol with 4.2 petrol with 200,000km on it.
What is the truth about K & N air filters?
Do they really give better economy / power?

Thanks.

Neil.

[MEGOMONSTER]

I have one in the GU, and I think it definitely makes a difference, getting more air faster.
Buy once, very easy to clean and re-oil.

[mudski]

I have one in the GU, and I think it definitely makes a difference, getting more air faster.
Buy once, very easy to clean and re-oil.

Me too. I have a second to swap over at service time to make things quicker.

[MEGOMONSTER]

Me too. I have a second to swap over at service time to make things quicker.

I do the same, keep one spare ready to go.

[megatexture]

Cheaper in the long run it just depends if your happy with slightly less filtration

[paulyg]

Is the slightly less filtration an issue? would it do any harm if you drive on very dusty roads?

[megatexture]

I can't really answer that but I know I would rather have longevity than a small increase in power but each to there own

[Ben-e-boy]

Cheaper in the long run it just depends if your happy with slightly less filtration

The difference is literally microns

[Parksy]

The trick to engine longevity is lack of filter maintenance. True story. The build up of dust and crap within the filter helps to improve its filtering and preserves engine life.

[Winnie]

From what I have read, the K&N filters better than a paper filter at high air speeds.

[MEGOMONSTER]

Is the slightly less filtration an issue? would it do any harm if you drive on very dusty roads?

You would just need to change filter more often.

[mudski]

I just do mine with every 5k oil change. Regardless of how dirty it is.

[megatexture]

Some good info here Pages 67-76 , and not just on filters

http://www.nissanpatrol.com.au/forums/showthread.php?89-Nissan-Patrol-Reference-Document

[nissannewby]

http://www.nissanpatrol.com.au/forums/showthread.php?27999-K-amp-N-air-filters/page3&highlight=filter

This thread explains why a k&n is better especially when used in the zd30 style airbox.

[megatexture]

While there are some good opinions in that thread there's nothing that would convince me to use one, I rather look at the stats in the comparison I posted, I would be more inclined to go off these then opinions but that's just me.
The main advantage that k&n have is the saving long term in maintenance

[nissannewby]

Can you post up a screen shot or something? Having trouble opening that link.

And they arent opinions it's logic plain and simple. Oldmav has done real world testing of this even using high end laboratory equipment for his results. Plus his qualification should be enough lol

[megatexture]

I'll try but there's a few pages lol

[nissannewby]

Once a paper element gets past 4m/sec its ability to filter is greatly diminished. A zd30 will easily see 12-14m/sec under acceleration and at this point the element inside the zd airbox can allow particles of up to 80 micron past. Now the k&n filters down to about 7 micron but will still do that at airspeeds of 14m/sec

[megatexture]

Let me know if you can see enough..1st 3 pages

[nissannewby]

That old chest nut lol. Have a look at the graphs and how they are setout. Even by those graphs every filter they tested was within 3% of each other. Then there is the fact the test was done by ac delco so of course its gonna reflect better on them. Have a look at how much restriction the ac delco has though compared to the rest. Like I said paper elements do work good but the need the right system to do so. That test doesnt really give you enough information to make a good decision. There are no air speeds posted. What happens when the filter restriction gets beyond 10in h20? I can gurantee you the zd airbox design will see above that much restriction for a lot of a zds driving cycle not to mention the air speeds being right up there as well. They also dont give you mention of the size of the particles that have been passed through the element.

You can have particles enter the engine if they are less than 10 micron and it wont cause any ill effects as it is so small it is lost in combustion. There really are so many more bases that the above test needed to cover to be informative

In a zd30 type induction system a k&n will filter better than any paper element.

[megatexture]

They do say 350cfm for the testing but Isn't this about the filter media filtration/airflow not the induction system? I wouldn't be changing the setup it would just be an easy replacement of the filter job so I'm more interested in the filter itself.
sure they are all within 3% in that one of 7 graphs I put up but what would that 3% add up to over 300-500,000km surely that would affect longevity?

[nissannewby]

They do say 350cfm for the testing but Isn't this about the filter media filtration/airflow not the induction system? I wouldn't be changing the setup it would just be an easy replacement of the filter job so I'm more interested in the filter itself.
sure they are all within 3% in that one of 7 graphs I put up but what would that 3% add up to over 300-500,000km surely that would affect longevity?

This is what im trying to say. You have more air requirement and restriction than what is in that test. So while the paper element in that test does well thats all they are testing is the element. So in an application like the zd30 and most airboxes fitted to a patrol k&n will filter better.

That 3% is only in those test conditions in real world with our zd box as an example the paper element will struggle to remove particles as small as the k&n will.

[megatexture]

I've been looking around just now and this fella has done a bit of real life testing that has me thinking also.
http://www.bobistheoilguy.com/airfilter/airtest1.htm

[megatexture]

Also I wouldn't have thought a zd30 would be that much higher than 350- 450 maybe. if a non turbo 2ltr 4cylinder uses around 141 cfm at 4000rpm (from the little reading I've done) I know at 15 psi would be compressing the air a bit but I've not looked at how dense it gets to work out the real volume but it can't be that much more.

[nissannewby]

I've been looking around just now and this fella has done a bit of real life testing that has me thinking also.
http://www.bobistheoilguy.com/airfilter/airtest1.htm

You have just found why the induction system makes a difference to a paper filters ability to filter.

[nissannewby]

Also I wouldn't have thought a zd30 would be that much higher than 350- 450 maybe. if a non turbo 2ltr 4cylinder uses around 141 cfm at 4000rpm (from the little reading I've done) I know at 15 psi would be compressing the air a bit but I've not looked at how dense it gets to work out the real volume but it can't be that much more.

A diesel of the same capacity requires twice as much air as a petrol and at far less rpm due to a diesel peak torque rpm. So your example of a 2 litre petrol requiring 141 would mean a diesel of the same size would require atleast 282cfm. Then more is required for a turbo. Not to mention the 142cfm is probably free flow or with very little to no restriction.

I dont doubt the paper elements in your examples offer better filtration at reduced flow but this is not in our application with a patrol.