I understand the Blitz air filter removes particles down to 150 microns in size. The K&N website says that their filter elements remove particiles in the 10-20 micron range which they claim are the most damaging to the engine.

It seems as though the Blitz filter is useless, might as well go without. What filters actually meet desireable FD specifications?

 

A lot of members, including me, use the the K&N filters for whatever type intake they have. I have not heard of anyone complaining about K&N quality.

 

That is the million dollar question (and I have the feeling that this will turn into another "synthetic vs. dino oil" style debate). The facts are: a gauze filter element (like K&N) will always flow more air than a foam filter element (mostly because the gauze element can be "pleated" for more surface area, which can't be done with a foam element). But, "dual stage" foam elements perform much better in the filtration department, i.e., trapping smaller particles that would otherwise get through a gauze element (many "single-stage" foam elements use a coarser grade of foam in order to get enough flow, but they suffer on the filtration side). So it's a tradeoff; if you feel you need to get every single micron of dirt particles out of the airstream, then a dual-stage foam filter would probably be your choice. However IMO, you're going to be impeding airflow, no matter what some manufacturer websites say, because two turbos (or one big one) spinning at XX,000 rpm create one hell of a vacuum. If maximum airflow is your goal, then a gauze filter (like a K&N) would be the better choice.

Mahjik was telling me that foam filters outflow all others when the filters get dirty, but I haven't found any truly convincing data yet.

 

I have the HKS and they really SUCK! The intake pipings were full of dirt last time i cleaned them and i change the foam every 3000km. I will change them into Apexi intake which i beleive they are the best.

 

Ive read that the difference between airflow of foam and gauze is less than one HP. So honestly I would choose only on quality and endurance.

 

It may have been a hoax, but I remember a maillist post floating around a year or two ago about a supposed article, or informal study, on K&N filters. The writer worked for some co. that used numerous heavy gasoline powered equip... don't remember exactly. But he thought he'd save the money the co. was sinking into air filters by using the cleanable K&N's. Following this change, the equipment started mechanically f'ing up all over the place due to particulates being sucked into the intake.

I'm not sure if it was ever discredited, but I thought I'd thow that out.

 

the new Accel Kool blue are supposed to be really good, plus they are way better looking than the Apexi or K&N.

 

i trust K&N

 

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I believe that first and foremost a street driven car needs an filter element that removes harmful particulates. Secondly, for maximum performance, it should allow a sufficiently high air flow.

Kento: Does the particulate which is trapped by the dual stage filter but passed by the K&N filter damage the engine? I doubt it because the OEM air filter is a pleated gauze type and I would think any filtration capability above stock would be overkill.

 

http://www.mkiv.com/techarticles/filters_test/2/

 

Bio-Weapon:

Very interesting article. I have hunted for information that compares/reviews the performance of different air filter products but have not found anything. We need access to more of this kind of information.

 

Yep, that's the same trash that everyone refers to... Make sure to read the end:

"It is questionable how accurate the original source of data is, as HKS are proven to sell more induction kits than any one of the others featured in the test, and yet there induction kit rates as the worst kit in the test. This suggests that either HKS rely upon their brand name to sell their 'poorly' manufactured air filters, or that the original Japanese test was nothing more than a PR stunt to promote the lesser known equipment. HKS and Blitz continue to be the best selling induction kits in the UK, and are used by Middlehursts, Hiteq and Abbey Motorsport as their first choice when the induction kit modification is carried out."

As they state, no one really knows who created the original data (since they didn't do the test themselves). Without other tests to validate or invalidate this data, it's not much use.

 

If the apexi filters can never be cleaned and they are supposed to be "lifetime" use, then what do you do when they get dirty?

 

Mahjik:

Are you aware of any reliable data or are we selecting filters on the basis of sales brochures and gimmicks.

 

A few years ago when I was looking to purchase an intake, there seemed to be much more info available on the web. Now, it seems people just get whatever "brand" they like best.

Honestly, I don't think it matters what intake you get. I do agree that foam filters probably do not filter as well as non-foam filters. However, I have yet to see anyone have a turbo/engine failure and directly relate it to a foam filter. All filters require maintenance (whether cleaning or replacing). If you aren't replacing/cleaning your filters, then it isn't filtering anything.

Running the turbos out of their efficiency range will kill them a lot quicker than having some microscopic dirt particles get thru.

Food for thought: There are many people with large single turbos that don't run filters at all. Not something I would recommend, but they don't ever seem to have problems.

That being said, for the stock twins, the Blitz intake looks sweet under the hood.

 

Negative, the OEM Mazda filter is a pleated paper element, not a gauze type. The filtration properties of paper fiber elements are far superior to gauze or foam, but again, their flow suffers because of it. The manufacturers, however, expect their engines to be lasting beyond 100K (cue FD engine lifespan wisecracks...), which is why they specify paper elements for OEM fitment.

Will the dirt that passes through a gauze filter damage your engine? Sure, but to what extent is, again, the million dollar question. Since many FD owners look at their car's engine life span as less than 70K, to them it's kind of a moot point. The rotary engine is probably less susceptible to dirt in the intake mixture than a two-stroke motorcycle (whose roller crank bearings depend on oil supply from the intake mixture) or perhaps even a conventional piston engine (which has a constant oil bath from the sump).

Like most, I'd go toward the flow side of the compromise, and use K&N. I'm not a big fan of the single foam filter elements.