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I just installed a K&N cold air intake and now when ever I shut off the car I hear a exhale noise comming from the intake. Any ideas why or is this normal?
 

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normal
 

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Discussion Starter #5
Thanks!!
Exactly! decompression sound. How does it damage the MAF? Where is it so I know to be careful when cleaning.
 

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If you follow the directions for cleaning, you'll be fine. I've had mine for 3 years now with no problems. I've cleaned and re-oiled it at least 6 times. Oh, and as stated, the sound is normal.
 

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Just Nuts
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Sorry for a noob question. What is the effect of the K&N filter ? They claim to offer better MPG. Is there any truth to this ?

I prefer no change in engine noise, but more MPG or power. Will a K&N filter be good for this ?
 

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K&N is know for damaging BMW MAF meters so be carefull when you clean it .
that would be an improper oiling, nothing to do with the name brand, i never oil mine to be honest
 

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that would be an improper oiling, nothing to do with the name brand, i never oil mine to be honest
I don't think the filter works properly without oil.

I clean the MAF whenever I clean and oil the filter.
 

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are the stock filters oiled? i know what they tell you, they also sell an oiling "kit" ive had filters for years on my bikes etc, i oil maybe every 15,000 and very lightly if that
 

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are the stock filters oiled? i know what they tell you, they also sell an oiling "kit" ive had filters for years on my bikes etc, i oil maybe every 15,000 and very lightly if that
They are said to need oil because they are more permeable (and thus more particles can get through) than regular panel/dry filters. The oil aids in filling the some of the voids and traps particulates in the filter.

A dirty dry filter will limit the amount of air that passes through, but with a filter that needs to be oiled because it has become dry also has the potential to pass greater amounts of particulates into the engine.
 

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Just Nuts
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Having searched around, I am getting the impression that these filters aren't all that useful other than to give a louder engine noise. As I am more into UFO-tech - super fast and complete silence, these filters will do me no good.

It's curious there are claims that the filters would give better MPG and 10% more HP. Seems quite outrageous.
 

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10% HP is probably optimistic. I've used K&N drop-in filters in several cars over the years and they probably add a few HP and 1-2MPG at best.

Obviously, a CAI is going to provide better results than the drop-in filter, due to better airflow dynamics, provided it's properly shielded from engine heat.
 

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Just Nuts
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Even a few HP increase is impressive given the relative low cost of the filter. But I wonder if the impression is just from the louder engine noise ? It would be interesting to see someone's dyno charts for a stock car with just a new drop in filter.

Even with a 1 mpg improvment, I think the filter would pay for itself in 6 months of my short distance driving, and therefore is worthwhile. Has anyone else noticed improved milage ?
 
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