ROADSTIR

I recently purchased a K&N air filter for my CDI and am having problems. The next day I was passing someone on the highway and when I put my foot down noting happened. I mean I floored it and the car kept tooling along at the current speed. I manually down shifted and that helped a bit but it keeps happening.


Then I took some CRC MAF cleaner and thoroughly cleaned the sensor. No luck. Finally, I said "what the hell" and popped the old air filter back in. Perfect! It was strong like bull. lol WTH?

Micah / AF1 Rac

If the filter is collapsing under high boost vacuum on the pre turbo side this sort of makes sense. Personally I don't think its easy to beat the stock air filter, other than for noise.

diesel2fast4u

^^what he says, you will not run out of air with your stock setup

boardboy330

K&N will let more dirt through with the air. The oil will also come through and coat the inside of your intake. Not worth any perceived performance IMO. If you want more air, pipe another line from outside to the intake box.

OM617.95

K&N has no benefit outside of a race track.
http://www.billswebspace.com/AirFilterTest.htm

Glyn M Ruck

Forget the K&N oiled filters. They don't filter very well. Diesels must always run excess air!

marc hanna

I've never had an issue with K&N's. I've been using them for years. In my OM642 I like them because you can extend the change interval compared to conventional filters. This is a benefit because replacing the filters is about an hour and half job.

Coating of the intake would only be caused if you improperly re-oiled them after cleaning. That myth has been thoroughly debunked.

Other than that, I agree, no useful performance gain for street driving. But then also, there's no useful performance gain on the street with performance brakes, suspension, pulleys, etc, but people like to buy them anyways.

OM617.95

That is absolutely wrong. K&N filters actually have a much shorter service interval because they have a very small filtering surface area and the oil is what does the fine filtering.
From my prior link: "Compared to the AC, the K&N “plugged up” nearly 3 times faster, passed 18 times more dirt and captured 37% less dirt."
Running a K&N for an excessive time without service (more than 5k miles) causes them to lose what little filtering ability they have as the oil is pulled out of the screen mesh by airflow.

That is also wrong. All of those provide a tangible daily benefit, especially supercharger pulleys.

Lets take a look at a your 08 R320 CDI.

K&N $76.
But you will also need a "recharge" kit. $19
Total: $95

Proper filters $41.50


Both claim to last 50k miles, but the K&N has to be cleaned every 5k miles in street use.
The K&N you have remove it, clean it, oil it and reinstall it. About 1 hour.
The proper paper filter you pull the old, toss it, install new. 30 minutes.
That means it will take you 114k miles to break even in cost, it will take 10x longer maintenance time, the K&N is letting more dirt into your engine 100% of the time, and the K&N is not increasing performance at all 99% of the time you are driving.

marc hanna

Your opinion is fine. I prefer evidence that isn't anecdotal. My experience is real-world.

Thanks anyway for the input.

OM617.95

Opinion? Anecdotal? WTF are you rambling about?

What part of "ISO 5011 test at Testand Corp of Rhode Island" is anecdotal to you?


Your opinion is fine. I prefer evidence that isn't anecdotal.

marc hanna

Anyone can post stuff up on the internet. I can make some fancy charts too. The very comments this article makes about debunking agendas kinda reveals its own agenda.

K&N filters are fine, and they don't plug up faster. The author clearly made the test to cause the result he wanted.

ISO doesn't mean a whole lot in the end, I deal with labs all the time, and despite using GLP they get vastly different results.

OM617.95

Ah, so you're just being a troll. I'll remember that fact about you.

Carsy

Glad to see you back .

You give good practical mechanical advice but leave it at that & we will all benefit including you.

Young John.

marc hanna

Back to the OP's original point. I've heard of people having similar issues with newer diesels when changing to a new air filter regardless of the brand. The computer needs to be reset to account for the new pressure. I think this can be done with both the start machine or by just disconnecting the main battery for a couple minutes, but I'm not certain on that.

I've never encountered this personally, and I use K&Ns on all my vehicles.

mersum1es

AFAIK there is no filter reset option in OM648. OM642 there is, and it's advised to use. And for some reason filter(s) of that model are very prone to collect all possible smaller than squirrel objects which you can see on the road...

I have also heard few cases where new filter has been causing troubles, and all fixed when filter brand changed. Personally I use Bosch in my OM648.

Glyn M Ruck

K&N oiled filters are known to achieve very poor filtration. They have been extensively tested & this is proven. Anybody that has any doubts about how little dirt it takes to ruin a diesel engine should watch the Cummins film "Operation Hourglass" It's old but as valid today as ever. K&N oiled screen filters are crap.

Glyn M Ruck

See ~ http://www.nicoclub.com/archives/kn-vs-oem-filter.html

I can confirm that our oil company labs & a certain very well known filter company's labs confirm this.

marc hanna

Yes, I saw the article in the link. It just looks very hokey to me. Without stating exactly how the tests were performed and the variables that impacted interpretation, the article states "This report shows, with empirical data and sound reasoning, why OEM filters perform better in a variety of areas." And secondly, it talks itself up with the cost of the equipment, as if that had some bearing on its integrity.

Honestly, I don't think there's any benefit in debating this - the test was clearly set up to debunk performance and efficacy under track conditions, and therefore is irrelevant for road applications.

One of the key claims it makes is that oiled filters will dirty your oil, however, my oil analysis after 18,000kms service on my oil, using a K&N filter, indicated that the oil was exceptionally clean. And based on owning several other vehicles and putting in excess of 300,000kms on them with no signs of unusual engine wear, I see from my personal real-world experience, no evidence of these poor filtration claims.

If I were to hazard a guess, I think AC Delco had some influence in those tests. But that's just speculation.

Glyn M Ruck

This forum's efforts are to try and provide the best possible advice to members. Ourselves & Donaldson have run extensive testing & I can confirm those findings are fine. Excellent results are also obtained with the likes of Mann + Hummel, Hengst, Donaldson etc. I have seen enough used oil samples in my life from dusty locations using K&N oiled screen filters with high wear resulting from high silica levels in the oil to know that these filters are junk. I cannot with a clear conscience recommend their use. They are nut & bolt catchers & I would not put them anywhere near my vehicles. They achieve nothing but are OK in racing where engine life is unimportant. No debate!

marc hanna

Fair enough. But we should also take all evidence into account. If these filter are so bad, then surely I would have encountered some noticeable detriment.

Glyn M Ruck

You are probably just lucky to operate your vehicles in low dust areas or don't expect them to do the kind of mileage that people are accustomed to from Benz vehicles in other countries.

marc hanna

I can respect that there are certainly other environments that are higher dust than here, but I typically put 300,000+ kms on my vehicles.

Glyn M Ruck

Mercedes Benz vehicles are the worlds taxis & hotel cars with major concentrations across Europe including Russia, Africa, Middle East & Asia Pacific. Life expectation without major repair is at least 1 million Km's. They are about 80% diesel. We run an S class & a couple of gasoline E Classes as airport cars from our Cape Town offices. Lowest mileage is at present 830,000 Km's. No major repairs. Lots of tyres & brake pads. Pretty typical. All these cars run their mileage quickly & much of the time fully warmed up.

OM617.95

Please stop feeding the troll (marc). Its obvious is mind is set and no amount of proof against his zealot beliefs will change it.

marc hanna

For those objective readers, I have provided my opinion supported by sound evidence. You don't have to agree with my opinion just as I don't have to agree with yours. Other people have provided there opinion and evidence to support it, and I respect that, because that's what fair and rational people do.