mambodoc

I keep my paper elements clean and change them when recommended. I considered these as well as K&N for awhile but decided that ny C4S performs exceptionally well with the Porsche engineered OEM filters.

L_perm

For those who are under the impression (as I was) that the BMC's higher air flow necessarily means less efficient particle arrest, the official specs on the BMC show particle arrest down to 7 microns. The usual paper filter targets 10 microns, which is the common requirement for an engine. I don't have the actual specs on the Porsche air filter, but, given this information, there is good reason to believe that particulate filtering efficiency is actually better with the BMC--or at least not worse.

It is my understanding that the primary benefit of the BMC is that it doesn't lose its air flow rate as quickly as the stock filter. (Similar to the Dyson marketing.) I've been told that the initial air flow rate of both filters is similar when new, but the gap grows as the filters are used.

As far as MAF fouling goes, that generally happens after owners re-oil their filters with too much oil. Not a significant issue otherwise. This I've gathered from talking with many tuners and racing organizations.

LP

speed21

I would agree user opinions will always run thick and fast on the subject of which offers the better air filtration, performance etc....

Here's an interesting account:
http://forums.audiworld.com/archive/...t-2678036.html

Bottom line: If an air filter dependant upon an oil substrate doesn't do anything other than cost more money, require maintenance and in that process leave the user exposed to potential risks, then why bother? But if it makes one feel warm and fuzzy then by all means...

L_perm

First, I am not a user of any AM air filter. I simply researched the options a while back. Second, there are always exceptions to every rule. The fact that someone on the internet is telling a story that appears to contradict my info is not a surprise. Third, if you don't understand how maintaining initial air flow rate is beneficial, then I understand your need to belittle me.

You made an incorrect assumption, followed with an implicit argument based on one data point that can't possibly be considered random, and demonstrated a willingness to ignore obvious benefits in order to do what? Insult me.

Talk about things that make people feel "warm and fuzzy"...

LP

speed21

Please don't take it too much to heart and apologies if I've upset you. I was never suggesting you had a BMC, and my intention was not to belittle more so provide some tangible information from an obvious credible source. The warm fuzzy remark was not for you personally but a general comment. The "argument" you speak of was also not based on one data point at all for me. Being a major supplier of certain very well known OEM filters i have my own sources of information anyway but i put that link up as it was evidently from someone directly in the filtration industry making his own elaborations for those questioning the efficiency of the K&N/BMC arrangements..... saying things I've heard stated previously. I think if anyone wants a BMC that's fine by me, and if they think it is actually doing something then thats terrific! The placebo effect is an amazing thing lol. For me the ultimate proof of any pudding is in the scientific testing supported by real numbers and the manufacturers spend enough time doing that to keep on top of the game. Alex's testing of the GT3 engine was also great myth buster, which he provided for the general members who had expressed doubts and questions of their own. How can anyone argue his dyno report? But again no one is mandating what to do or not to do. Anyway have a great day. It's only a silly filter....not worth fighting over

L_perm

Agreed. Thanks for the apology. I wouoldn't say I was upset as much as I was just disappointed to receive what seemed like thinly-veiled sarcasm in response to what I thought was an innocuous post providing information I had picked up in my search. As I mentioned, I had been under the same impression as many--it's intuitive that a filter that passes more air would pass more particulates. The fact of the matter is I don't know what to believe regarding the different filter mediums, which is why I haven't changed from OE.

Just to give some more of my own insight, which everyone should take for whatever they deem it's worth, the GT3 test appears consistent with the idea that the primary benefit of an AM filter is the maintenance of initial air flow rate, as opposed to any additional air flow. If the engine can't use the additional air flow--that is, if it's able to get all it needs through the OE filter--then any additional air flow offered by the AM filter is useless.

The information out there on particulate efficiency is spotty, at best. One has to ask why? I quoted the 7 micron figure for the BMC, but the fact is that we don't know what percentage of the 7 micron particles are arrested. BMC states, "containment of all impurities is guaranteed as far as 7 microns..." Really? 100% of all particles 7 microns or bigger are always blocked by the filter? I would like to believe this, but it seems a stretch. How much of a stretch I don't know, and really have no way of verifying.

K&N and BMC both quote efficiency measures relative to ISO-5011 tests. BMC quotes 98.5%, for example. K&N targets 96% to 99%. The tests basically amount to pouring dirt into the filters until they clog. (This is a gross simplification, as you know.) But, for example, BMC's 98.5% doesn't distinguish which test--there is a "coarse dust" and a "fine dust" test.

The problem with the coarse dust test, just from my layman's standpoint, is that the dirt consists largely of particles that are too large, unless you're driving in a thick dust storm--only 36% of the particles in the coarse dust test are 20 microns or below. So, when you see 98.5% efficiency on the ISO-5011 test, you still don't know how good the filter is at catching the really small stuff, because the 1.5% of particles that got by could all be 1 micron, 180 microns, or any combination of particles in between. In the fine dust test, 74% of the particles are 20 microns or below, so it would seem the more useful test, but neither K&N or BMC specifically represents an efficiency measure for this test.

Still, let's look at what BMC gives us--98.5% ISO-5011 efficiency and guaranteed 100% efficiency down to 7 microns. Since, they don't specifically name the "fine dust" test, which it presumably would be in their interest to do, I assume the 98.5% is on the coarse dust test. Taking this information on its face, the BMC misses approximately 9.4% (1.5% / 16%) of the particles below 7 microns. (I'm assuming approximately 16% of the particles in the test are below 7 microns based on the fact that 10.5% are 1-5 microns and 11.5% are 5-10 microns. Obviously, I have to extrapolate something from the latter figure, so I'm assuming that a little less than half--5.5% of the 11.5%--of the particles in the latter category are less than 7 microns.)

So, is this good, or bad? We don't know unless we have the same info for the OE filter.

Also, we have to ask the question: is the filtering efficiency of the BMC affected by the coarser dust in the test? That is, if a vehicle is unlikely to encounter much of the coarser stuff, and yet the coarser stuff gets in the filter and diminishes efficiency filtering the smaller particles, then we see why the "coarse dust" test is flawed for use with passenger vehicles that stay on paved roads. Why aren't the AM manufacturers quoting the efficiency results of the "fine dust" test? Is it because 95.8% efficiency doesn't sound as good as 98.5%? (If you translate my figures above, a 98.5% on the coarse dust test--under the assumption that all particles 7 microns or larger are arrested--becomes approximately 95.8% on the fine dust test.)

Actually, 98.5% rounds to 99%, and 95.8% rounds to 96%. Could this be the range that K&N targets. Who knows?

Bottom line is that we have some information with which we can derive efficiency estimates under certain assumptions. But, the biggest missing piece is the information on the OE filter. I don't know where to find that. Do we know who manufactures the OE filters for Porsche?

LP

phillipj

LP,

Mahle is the air filter manufacturer for Porsche..

speed21

Yep. Agree totally. And if a GT3 engine can't find any power out of one of these then what other Porsche engine would?? I did read a thread where another brand of engine found @1 hp at the very top end of the rpm range though lol. I bet the driver could really feel that extra surge of power

It is also note worthy for those using these types of filters to consider that the particulate removal efficiency of any air filter is also effected by its actual position in the car. As most would be aware, 99% of cars have the filter at/in the very front, which is subject to the cleanest air path...well away from all the dust being stirred up by the wheels and the body of the car as it passes over the ground. A Porsche on the other hand has its air filter in the very rear of the main body behind the engine, and behind all the wheels, which is precisely the point why you would want the best possible air filtration system working for you. Has anyone ever had their rear bar off or rear tail lights out? The fine particulate that can be found is a tell all. The rear end of any car is the worst possible place where all the debris is kicked up and swirled back and around the rear end....up and around everything. Also, while on the subject of these types of filters, how prey tell does a layperson know exactly when the fitter is due cleaning and re oiling least of all know the job has been done correctly? For a very expensive piece of equipment like a Porsche engine it sure seems to me like one heck of a lot of risk and fiddling about for the sake of psychologically convincing oneself the filter is actually doing something that is actually noticeably better performance wise.

Edit.Just saw this doozy and had to show: (check out photo 10 and 11) Some things never cease to amaze... Imagine the filtration going on back there with those two small hiflow cones ...and all the hype surrounding the justification of the spend.
http://www.6speedonline.com/forums/9...t-h-r-etc.html I wonder what the dyno report will show this one as producing
But the funniest thing is a 991 doesn't even have a rear lid to show it all off. I mean.. why would anyone bother? But I'm sure after all that $pend this mod definitely does something. I'm sure the wallet feels the difference

speed21

Mahle products are No 1. So the OE filter is high qual.

Porsche would have undoubtedly done their homework with the filtration and flow requirements for the engine/car. We are talking Porsche here. Engine longevity and reliability is a key hallmark for the Porsche brand. Performance without reliability and longevity isn't a great result.

So to summarise for the OP;
1) Zero HP or Torque gains (re GT3 dyno report)
2) Higher unit purchase cost.
3) Regular maintenance requirements which are subject to a degree of expertise.
4) Unknown factor of when to actually maintain/service.
4) Potential for decreased engine life/increased component wear, particularly given the location of the filtration system.

phillipj

I have to agree.. I have swapped back and forth with the BMC and the Mahle.. I certainly didn't dyno the reults but I can't see (or feel) any performance benefit whatsoever.

jhbrennan

Does anyone know if you can get an OEM type paper filter without the foam front. It''s put there for sound reasons and I don't think it can be removed easily.

L_perm

I think it's also there to help keep water running into the air box off the paper. I conjured this in my head, so I could be completely wrong. But, I have noticed after washing the car that the foam will have captured some water and effectively keeps it from the paper.

LP

speed21

Read posts #7,#8,#9. http://www.6speedonline.com/forums/9...er-filter.html
....seems this topic has been discussed so many times lol. Why can't folks just be convinced their money has been well spent?...and all that extra HP materialised in the process lol. It also appears the paper flows better anyway... and if it gets dirty then thats good because its actually doing its job! And, when it blocks up with dirt then replace it! Cheap insurance for the engine!

"Cleaner Air".
http://www.mahle.com/MAHLE/en/Produc...s/Air-cleaners

http://www.mahle.com/MAHLE/en/Produc...intake-systems
It's not just the filter, it's an entire system designed for the car to do more than just filter the air.

Aftermarket "Cold air intake system" is another one.....how many of you heard this snake oil?

I guess the carbon fibre has a "refrigerator" in it somewhere

Proof that some people believe anything is possible if it looks pretty and they pay enough for it.

phillipj

I guess the carbon fibre has a "refrigerator" in it somewhere


That is sooo awesome ......

jhbrennan

Porsche literature describes the foam in place for sound reasons.