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Discussion Starter #1
so im up for a service on my old gq which takes the 3ltr gu air filter as the airbox has been modified..anyway i seen a add for the k&n reusable air filter and am wondering if they are a worthwhile investment as apparently you also need to buy their filter cleaner and their filter oil?or i can go down to sprints and get a paper filter for 16dollars...what do you all think about these reusable filters..they also claim more power and god knows i can sure use every last drop of power i can get out of the old girl..thanks fellas
 

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Some people hate them some like them they have been around for a long time and if they caused premature motor wear like some people say then they wouldn't be still operating. I've had a couple of them in different vehicles a petrol/lpg GQ set up with an open air filter just like people use to do to their V8 holden motor on top of the carby and it did seem to be a little bit more responsive and better on fuel when tuned correctly. Also In a 12HT 60 ser cruiser with similar results don't expect big changes you may not even notice any at all it's a case of trying it to find out. I will eventually get one for my GU airbox as well. I've never had any problems with them I have always used K&N's own brand of filter cleaner and oil just follow the instructions and don't be too shy when re oiling it you won't have a problem but you have to be prepared to take the time to wash and re oil it occasionally. Finer filter has a replacement air filter which is apparently very good as well.
 

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here in the phil. knn cost around $120 usd and cleaning kit $20 usd (good for 3 cleanings). an original nissan filter cost $45-50 usd. so in a handfull of years your knn is actually cheaper.

I've had the knn filter on my gq for the past 3 year and i clean it twice a year. so the cleaning kit will last me 1.5 years or so. very happy with it :D
 

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K&n flows much better than a factory oiled filter a filters much better than a factory paper filter. I think they are worthwhile if you can be bothered with the maintenance.
 

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Y2KGUII ZD Wgn
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I was not a believer in the K&N, preferring the genuine, but I gave it a go early last year and changed my mind, I have a section on the K&N in my build thread, yes it will make the engine breath better, I paid $80 something for mine and $20 something for the cleaning kit.

Due to my ECUTalk I can see changes in MAF readings, on the first clean I over oiled which saw a drop in MAF, so I learned a lesson from that, the second clean was fine, with 1,000,000 miles the K&N target I'll get my money back no worries. The difference on mine between the std air filter and a perfectly cleaned K&N is 0.4v at the MAF, be warned, this will bring any old limp issues you may have had previously back to the forefront.

I always have a spare air filter in the back, one thing I've learned is that if I was going to be doing a trip where I was constantly in dust I would remove the K&N and fit a genuine air filter for those parts, but around town and normal playing I thoroughly recommend them.
 

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Mate,

I used K&N on my old petrol gq and again on my diesel gu.....I never had a problem and felt it definately breathed better. I did a couple of back to back tests k/n vs paper and seat of pants definate improvement with k/n. Now running 4inch airbox with a oiled type pod filter....I will stick with these filters for the rest of my driving days.
 

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Discussion Starter #7
thankyou fellas,so ive got the rb30 motor with the vl commodore efi conversion and strait outve my airbox is my airflow sensor,is this what you mean when you talk about a maf readings?
 

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Y2KGUII ZD Wgn
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thankyou fellas,so ive got the rb30 motor with the vl commodore efi conversion and strait outve my airbox is my airflow sensor,is this what you mean when you talk about a maf readings?
Yes that would be it, they have a few different names with manufacturers but we call them MAF (mass air flow meter/sensor).
 

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I was going to get uni filter. They are a foam filter and can be washed with turps I think it is. Lots of motorbike guys run them, the added bonus over the kn is drying time.
I think you can get an extra sleve to put over it if you want to extend life or for dusty conditions.
The company is based in gosford I think and will make any dimension you want.
So I was going to get one slightly narrower for the Zd30 airbox. But as always its just ideas for now.
 

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I was going to get uni filter. They are a foam filter and can be washed with turps I think it is. Lots of motorbike guys run them, the added bonus over the kn is drying time.
I think you can get an extra sleve to put over it if you want to extend life or for dusty conditions.
The company is based in gosford I think and will make any dimension you want.
So I was going to get one slightly narrower for the Zd30 airbox. But as always its just ideas for now.
Benny, the K&N is also slightly smaller diameter to give more flow around the filter. I think the Uni filter for the ZD30 airbox is also smaller but not when you fit the outer extra cover sleeve.

I use a unifilter cover sock thing over the snorkel head when in really dusty conditions. It also stops bees and locusts from blocking up the snorkel when in country areas during the bad time of the year for locusts.
 

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I've had a K&N for about 3 years now and I recommend them. As GU2 says carry a spare paper filter for dusty(convoy) conditions because it's far easier to clean a paper filter out the bush.
 

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I've used a stock filter, a UNI filter and a K&N in the GQ. I'm terms of flow stock is good, UNI is better, K&N is better again. In terms of ease of cleaning UNI is awesome. But I run a K&N because of the flow. I picked up 2 psi boost just with the filter change, which says a lot.
 

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Some reusable filters and ive hard K&N, dont filter particulalrly well IMO. Fine dust retention can be lower.
Might be ok on road vehicles
Oiled reusables need much more regular servicing, and are a little more restrictive but can work ok.
Original oily types work well and are cheaper.
Watch out for excess oil gettng over MAF sensor and stuffing it.
 

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From what I had searched previously all this has been covered before on this forum. Just my reasons for leaning towards the uni filter is the option to have one made to suit and ease of cleaning.
Please note this is only from research and not actually personal experience.
As most people have read some of oldmav's posts regarding air filtration setups on the td42, the Zd30 airbox is a major fail as for air speed and filtration abilities of paper filters, i wouldn't expect a high flowing filter to do much better in the zd airbox unless the filter was smaller and airflow somehow distributed better over the filter surface
 

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Y2KGUII ZD Wgn
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From what I had searched previously all this has been covered before on this forum. Just my reasons for leaning towards the uni filter is the option to have one made to suit and ease of cleaning.
Please note this is only from research and not actually personal experience.
As most people have read some of oldmav's posts regarding air filtration setups on the td42, the Zd30 airbox is a major fail as for air speed and filtration abilities of paper filters, i wouldn't expect a high flowing filter to do much better in the zd airbox unless the filter was smaller and airflow somehow distributed better over the filter surface
From one of my posts in my build thread in 2013, this was before I modified the airbox opening to give a 38% increase in area, after that the "ring" I speak of was much larger covering the full height of the aircleaner:

Have been a staunch supporter of the std Nissan air filter for many years (I have tried aftermarket filters and experienced a range of issues). Ive used aftermarket on other vehicles with out problem but maybe my experience with the ZD30 makes me more clinical in decision making.

In all honesty I have never tried K&N on a DI, so in the interests of research I bought one, recent threads on filtration and air flow, etc, grabbed my attention.

I bought a direct replacement K&N # E-9267, costing $85 over the counter (could have gotten it cheaper on e-bay but it wasn't all that different when you added freight and I couldn't be bothered waiting).

The dimensions in rounded numbers are:
Std = 180w x 143h (x 43t) This takes up an area inside the housing of 808cc.
K&N = 163w x 144h (x 35t) area inside housing of 737cc.
The K&N has a lip seal at both ends (identical) so there is no argument which way is up and it gives a snug seal fit, I can't complain about that.

The area around the outside of the filter in the housing:
Std = 176cc
K&N = 247cc

From the above we know that there is an increase of 71cc (4.3ci) in area and that is a 28% increase over std.

One argument I've seen was the ring that appears on the std filter may be an indication of air flow restriction to one area, well after a family emergency 660km round trip down to Lismore yesterday in traffic straight after fitting, today I have the same ring on the K&N even with 28% more area available, seeing as my snorkel has been on since almost new I have nothing to compare with, do non snorkeled vehicles get the same ring, in such a short period of time??????????

Expectations:

I. More air flow should see my MAFv change, and it did, I have my JayCar unit tuned just below the critical point of my 2 limp areas by around 0.01v, my 2450rpm limp returned with a reading of 3.94v, well above the 3.88v I previously would have to hold for several seconds before limp occurred. So more air is being ingested at some points.

2. Performance variation. I must say the vehicle feels a bit stronger at 2000rpm and may be a little better up further, an upcoming dyno will give a definitive answer to that.

3. Fuel eco improvement. My fuel eco didn't change, I achieved 10.7L/100 and that is in the "normal" range for a trip like that.

As mentioned I will be putting the old girl on the dyno in a month or so for something else but will do a back to back between the std and the K&N to get solid data. In the meantime I will monitor what happens and particularly monitor the MAF for cleanliness.
 

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Well off topic, but when I fitted a pancake K&N filter to my BMW K100RS I immediately noticed that most of the vibration that came through the foot pegs disappeared. When I sold the bike I sold the filter to another bloke and he noticed the same effect with his bike.

Interesting....
 

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If you do a lot of driving in very dusty regions then I wouldn't use the K&N's. Yes they improve the performance by a knats tadger over standard paper filters but even with the 'sticky oil' they allow finer particles into the engine.
I've done a few dyno runs with & without the K&N's just to see for myself what they can do. Yes the HP was up by a few and the pick-up was noticeably quicker.
The Orange plot is with a K&N and the Blue was with Genuine Paper filter...a difference of about 4-5hp.

The sticky oil can also damage MAF sensors, especially those with 'Hot Wire' sensors.

Back in my days with Land Rover we fitted K&N's to a number of our rally cars but once we opened them up and found the fine grit sludge in the sump we stopped using them.

I'll only ever use genuine paper filters now and change them regularly.
 

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Put a K&N in my 4.2 GQ a week ago and the motor feels like it can rev easier it wants to pull harder it can idle down lower in gear without labouring it's made a bigger difference than it did when I had one in a 60ser cruiser there well worth the money.
 

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Have always run a k&n on every car I have owned,been using the k&n Apollo CAI since they became available.I put an oiled sock in snorkel head for dusty conditions.My oil barely changes colour between services .
 

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Batt's...of course the engine will rev easier....it's getting more air.....& ultra-fine dust particles along with it!

Bigger holes in the K&N filter allow more air through...the oil is supposed to trap the fine dust before it passes through but it doesn't stop as much as it should and then you have fine sandy sludge in your sump.
This is called a 'Trade Off in Performance'...no such thing as a free lunch when it comes to getting more HP from an engine.
 
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