K&N Air Filters

Originally Posted by emimix

OEM stuff are not optimal so you keep getting back for replacements


the filter is not about power, but better ventilation and air flow ...it's also more $$ than the OEM, and you dont' need to change it for life

Just realized this was a 2 year old post...

But BMW covers the replacements for the first 4 years or 40,000 miles.???

I get that you want to change your filter, and good for you it is after all your car - but don't make the argument that BMW cheaps out on air filters or that "Use it for life" saves you money.

(BTW - Agree with the post - if you don't know where its at - maybe you shouldn't change it yourself. Also be careful that when you take your car in for scheduled maintenance they don't check the air filter and ding you for non-oem)

Now can can anyone tell this guy where he can find the air filter?

This is a bit long but is from a "formulator" (lubrication engineer). The whole thread is on the BITOG forum under air filters - http://www.bobistheoilguy.com/forums...Number=2886504.


Metro, I can't point you to anything specific with regards to warranties but I can point out some facts of life.

An oiled cotton gauze filter (OCG), and K&N is only one manufacturer of them, is at the low end of the efficiency scale amongst the available filters, both OEM and aftermarket (excluding offshore, noname junk) . It doesn't fall below the "industry standard" of about 97 percent on coarse test dust (in fact most OCG will show about 98+). It's likely a K&N (which is probably the best of the OCG filters out there) would meet the minimum standard for efficiency required by most vehicle and engine manufacturers, outside of commercial agricultural and heavy duty applications. Remember... minimum standard.

So yes, you can safely say OCG filters are "adequate" in the efficiency department but they are nowhere near the top of the food chain there. In general, they are chosen for their high flow rates and longevity. This is why they are synonymous with performance engines. Performance engines are usually operated in fairly clean environments, because they are fun vehicles rather than daily drivers or workers, or they are used where the rigors of racing will overcome the engine long before the increased wear from less-than-stellar filtration efficiency. And if a vehicle operates in what is largely a clean-air venue, air filter efficiency is less an issue.

IMO, OCG filters are a legacy product from the days when OE air filter efficiency was generally low, flow rates were abysmal (it was the housing design as much as the elements) and when you used the old filters in dusty environments, they plugged up quickly. A K&N was a Godsend in that situation. You got an air filter that let your engine actually BREATHE, it held a lot of dirt, plus the efficiency was about the same as the filter you replaced and often better. What was not to like! You were an idiot not to glom on!

Air filter technology has marched well past those days. The OEM are largely designing filter systems that have adequate if not superior airflow to more than meet the engine's needs (there are exceptions, of course). Average efficiency is 96-97% plus on FINE test dust (99+ on coarse) and capacity has doubled or tripled versus the olden days. In that environment, it's harder for a OCG filter to compete based on the facts but legend and lore are carrying them beyond their era a bit.

With any engine, cleaner air is best from the wear standpoint as the dirt that comes in from the intake is the worst for the engine and it can begin a chain reaction of wear... wear begets wear. And you want a filter that gets out a lot of the fines because the fines are the bits that get between the rings and cylinder the easiest, causes damage there and then gets into the oil and because these fines (1-20 um) are usually too small to be caught by the oil filter in large numbers, so they continue to circulate and cause wear.

In the past decade or so, air filter rating has been standardized to the ISO 5011 protocol but remember one important fact... the test allows the use of EITHER coarse or fine test dust. In evaluating filters, you need to know which. A filter that shows 98 percent on coarse will show 92-94 percent on fine. If you see a rating and it doesn't specify which, assume coarse because those are the best braggin' numbers. And yes, you can find filters that will produce 99+ percent on FINE and those are the best choices for engine longevity. Remember that a finer filter may have a shorter service life, but the modern synthetic media filters can combine high capacity with high efficiency. Short service life is more an issue with high efficiency cellulose media filters but even then, this can be accounted for by an increase in media (more pleats) or a larger filter (if the package size will permit... i.e. more underhood room for a larger filter).

So, I guess the question you have to ask yourself... and I won't call you a punk like DIrty Harry might... what is it you want to achieve? If it's a stock vehicle used as transportation, what's the advantage to likely taking a hit in the efficiency department? If it's a high performance car and you are considering an improvement for performance sake, the OCG choice is nearer the mark but consider that many of the dry aftermarket elements, like the one you mentioned, usually have efficiency superior to OCG but with virtually equal flow rates per square inch of media and if they don't, they just engineer MORE media in the filter to make it so. I could quote chapter and verse on some of the media I've looked at, but since I've done all that before, I'll suggest you just look back at my past posts.

Final thoughts here. I was given a chart by an engineer at Parker filtration that illustrates very well the effects of low vs high efficiency air filtration.

Code:
For Every 10 Pounds of Dust Drawn Into the Air Filter Inlet:

EFFICIENCY OF FILTER DUST INTO ENGINE

99.95% 0.005 lbs.
99% 0.10 lbs.
95% 0.50 lbs.
90% 1.0 lbs.



Edited by Jim Allen (Today at 08:01 AM)

Good inputs here. "Air filter upgrades" are all pretty much scams.

But a perfect money maker at that.... just look at all the companies vying for your $$$.

Here is some real data on K&N: http://www.billswebspace.com/AirFilterTest.htm

Unfortunately for the "My brother swears by it crowd" it likely requires WAY too much critical thinking....

Wow those are some interesting graphs and results, thanks for posting !!!

Originally Posted by Griffin 27

Wow those are some interesting graphs and results, thanks for posting !!!

This has been around for quite a few years. Actually, it was so damaging to the aftermarket filter vendors that they felt the need to 'counter' this in their marketing- hence you began to see "ISO 5011 Testing" data on their websites over the last few years- of course, the critical fact is that they only present very select pieces of data.

When you look at an ISO 5011 done by a test house, typically they require that the entire report be published. Whereas filter vendors just run their in house tests, maybe don't specify media size, and publish whatever they need to deflect criticism.

People like to think there is some 'magic' solution to 'flow/vs/filtration. there really isn't. Yes, you can deflect the curve one way or the other, just a bit, but not appreciably, and not for 10k, 20k, 50k miles. (ie 'lifetime'). And remember, race cars are rebuilt every year- don't buy a filter because they use them on race cars....

m6pwr and ard,

Thank you guys for the detailed information that you've given us. I will remove my K&N filter today. For years I've been under the impression that the K&N filters were one of the best filters in the market and I was terribly wrong.

Thanks again

Almost fell out of me chair!




Dont often get that kind of response.


Here is a thought:

As you can see from filter performance curves, the resistance of a filter goes up as it loads with dirt- hence, over a lifetime, your airflow is very good when new, and drops until you finally replace it.

My recommendation to people who are seeking the best airflow, would be to just replace the air filter more often! I do oil filters at 2x the BMW rate, and replace the air filter every other oil change. Easy Peasy. You'll always be on the 'good half' of the dirt loading curve!

A

+1. I'm taking out my K and N as well. I don't want it to mess up the air sensor with its oil either. Good thing I kept the original. :-)


Thanks again for the info.

Originally Posted by m6pwr

By the way, BMW does recognize DINAN. Many BMW dealers are also DINAN dealers and DINAN warranties their mods/software. If the dealer updates your factory software/ecu when you have the car in for service (which they do all the time and which will wipe your DINAN), and if they're a DINAN dealer, they will reload whatever DINAN performance stage you have at no charge - - it's part of the DINAN warranty. Don't think other mod houses do this.

But the financial Warranty is the responsibility of DINAN, no? It's not like BMW as an OEM will replace, free of charge, components that fail as a result of a DINAN tune or, and this is the tricky part, that are suspected to have failed as a result of a DINAN tune. Mind you, I assume the tunes do not cause serious failures, but time will tell.

Dinan only warrants consequent failures caused by the Dinan performance remap (let the arguments begin). For example, an auto tranny that appears to fail because of the significant increase in torque produced by the tune (let the arguments begin). The Dinan warranty mirrors the BMW as far as time/miles: 4yrs, 50k mi. I'm not familiar with other aftermarket tuners, but do any of them warrant consequent failures caused by their mods?

Originally Posted by m6pwr

Dinan only warrants consequent failures caused by the Dinan performance remap (let the arguments begin). The Dinan warranty mirrors the BMW as far as time/miles: 4yrs, 50k mi. I'm not familiar with other aftermarket tuners, but do any of them warrant consequent failures caused by their mods?

Not that I know of. The price difference would give an indication of the value proposition of a warranty. I've always a assumed that if it is a serious or catastrophic claim, a number of issues come up that could even invalidate DINANS warranty, or BMW's for that matter. Racing comes to mind. Also does a BMW failure, cause a bigger problem because the car is tuned and that has increased the stress on some components. For instance, you are driving your tuned car with an additional 100 hp over stock. The water pump fails and then...who knows what else goes. I'm sure they get sorted out, but there has to be some disputes. Can't be that easy.