I wouldn't use those filters, period. Take off one of the filters and put a dab of bearing grease about four inches into the intake tube. Then put the filter back on and drive the car about three hundrend miles and see how much dirt and grit gets by that filter.

You will get rid of those filters after this little test.

 

why oil when you can get a brand new filter element and it will look shiny and new again. Thats what I do. I got the HKS Racing Suction too, but I have a 91 Turbo. I would change filter elements every year. Its only $20-25. You also get to pick your own color. The yellow is alright, but I personally like the green one.

http://www.hksusa.com/products/?id=787

 

Because without oil, the things don't filter worth a damn!

 

With oiled filters, that test doesn't produce the effect you might think.

Why oil the filters? The oil is what traps dirt particles. The filter element is just a means to hold the oil in place. There is no real filtration without oil.

When I had the HKS, I used a motorcycle oil for foam filters by PJ1:

http://www.jpcycles.com/productgroup...A-923374F0EE55

 

That's true with K&N as well. Pretty much all filters which aren't the older paper based ones require oil to properly filter.

 

Apexi's filters don't have oil and filter pretty well. But HKS has two different filter elements. If you go to their website, look at both the super mega flow and racing intake kit. The super mega flow kit talks about a triple density dry filter element. The Race intake talks about double density wet filter. Even in the filter list, they have "wet" and "dry" filters.

 

Yes, I didn't mean to imply that HKS filter were the only ones that required this. That is why K&N dyes their oil pink, so you can verify the entire filter has been treated.

 

Just because they don't come oiled, doesn't mean they aren't supposed to be..

Yes, HKS sells some filters which are pre-oiled. However, ANY foam filter needs to be oiled for use regardless of the brand. Its a basic concept from lawnmowers, motorcycles, cars, etc. The oil is what does the filtration, the mesh is just what the oil sits on to get in the way of the particles.

 

No problem. I wasn't trying to attack you. There just seems to be a misconception on the forum that having to oil HKS or Greddy filters is bad, but having to oil K&N filters isn't a problem (or that K&N filters don't require oil just like the others).

 

I know....we're on the same page.

 

Apexi filters are made by K&N. the pink color is the oil, or else it'll be plain white cloth. Same as Knightsports or any filter that looks like K&N, they're all K&N with pink oil added to the filter before packaging.

I remember quite a few years back Weapon R used to make different color oils for their different color K&N knock-offs.. but i can't find them anymore.

 

The older (up to about two years ago) HKS SMF filters where a dual layer wet filter. The really old ones from the 90's used a different type of foam and had the tendency to chuck after extreme prolonged use.

The current ones are a triple layer/density dry type. From my knowledge the filtration was just as good or possibly better than the older types..... especially considering that HKS supplies intake/filter assemblies for Subaru's SPT and Saturn's Saturn-sport lines which have to meet certain OEM criteria of filtration.

I've used all of them for years on my past cars ranging from 160rwhp to 604rwhp, and havent hand an issue.

Just my $0.02

 

Apex'i filters are not made by K&N. Apex'i is owned by the parent corporation Apexera in Fuji Japan, which is where their factories are, which has no ties to K&N Engineering Inc. Knightsports I'm not sure about, since you can't get a good look at their filter element from their webpage, since they make they're own intake boxes and cones out of carbon fiber.

As far as dry filtering goes, AEM has just come out with the first fully synthetic dry filter that filters up to one micron, which is pretty damn good.

 

i believe that the Apexi air filters are known to be the best providing flow and filter at the break event point... get all sort of power but not sacrificing the ability to filter...

Apexi filters are meant to be dry... if u get a chance to wet the whole thing, you'll realise the filtering actually becomes better.... but you'll be sacrificing the performance and air flow...

why ? this is because the old dirt trapped in the filter touches with water, it became a layer of clay moulded on the surface of the filter instead of just capture and hang on the filter and pressure air can just blow it away...

i tried that before my boost pressure will drop after i wet it... and it tot that it will give a higher humidity entering the engine. but realise the twin infernos are too hot and it doesn't make a difference but the water causing boost drop by 3 to 5 %.

after while it became so dirty that i have no choice but chuck it away...

so my experience is... other than those wet filters.... keep away from water or oil.

 

Go to a MC shop that sells dirt bike stuff the best oil is UNI filter oil for foam filters. The also have a cleaning kit where you soak them for a few hours in the biodegradeable foam filter cleaner. That **** works great, the filters come out looking new.

 

I was implying that the filter elements sold seperately are pre-oiled. The one I bought a year ago, was pre-oiled. Therefore, you don't need to oil the dirty filter when you can buy a brand new filter element that is already pre-oiled. That beats washing out an old dirty filter element and then oiling it and in some cases where people over-oil the filter element and screw up there engine. It only costs $20-25 for a filter element which should be changed every year or so. If you can't afford that then I don't think you should be messing with a Rx-7. It's also easier to do. The new super mega flow reloaded version is a dry 3 layer filter element. I have not tried it myself, because I got the HKS RS which is a 2 layer wet filter.

 

My friend we did the test many times with well oiled filters.

 

Well, I can tell you from personal experience running HKS filters with real foam filter oil (PJ1), my intake tubes were clean each time they were removed (which unfortunately was quite often). Even when I had oil shooting in there from track usage, it was just oil, not dirt.

However, I did run them for a while without oil when I first got the kit (as I didn't know any better at the time) and the tubes were coated with dust at that time.

What type of oil did you use? The PJ1 filter oil is basically like an extremely thick glue. If you had a thinner oil, it might not have worked as well.

 

See, that kind of thing makes no sense to me. If you have to use oil that's like thick glue, what's the point in the first place?

 

Then why not go back to older paper style filters where you don't need any oil at all? The motorcycle guys have been using foam filters with the "glue" type oil for years and continue to do it. You would think if it was a "bad" thing they would have abandoned it years ago.

 

I replaced the HKS filters with K&N cone filters. So, if that's in your budget, you could do the same.

I needed the reduced diameter of the cones vs. the mushrooms to fit with my Knight V-mount kit. I also didn't have the fancy bracket bridging the two pipes. That's what I get for getting the kit used.

 

PJ1 Foam Air Filter Oil is that way aslo...

http://www.transworldmotocross.com/m...663485,00.html

 

do the lower filter replace the stock plastic 90 deg bend to the turbo??

 

Yeah, the primary turbo intake pipe in the kit bolts directly to the compressor.

 

Oh, I wasn't saying that it was a "bad" thing, I just don't think they flow as well as regular cotton filters. And actually, I don't know anybody who has a foam filter on their bike. Everyone around here who rides uses BMC filters, which is a cotton filter. The BMC's entry level use a lightly oiled cotton filter, while their race filters are strictly plain cotton. I have heard that if you leave in a somewhat dusty region, like near lots of farmlands or out in the deserts, not to use the race filters as they don't filter as well. I guess there's always a compromise.