K&N air filter makes whining noises?

[r4robert]

I have just fitted a pair of K&N air filters to my SL350. They were a straight swap for the standard filters.

Apart from hearing the change in engine revs more easily when the engine changes down gears with the auto box, there is a high pitched whine, almost like you hear when the wind blows very hard, when I accelerate.

At first I thought it might be the road surface and tyres, but after several miles it’s not.

Any ideas what this whining noise is?

Also the exhaust has a tad more 'growl' to it, together with a little more bass.

All I did was change the blinking filters, now the car sounds very different!

Can anyone explain?

Many thanks
Rob

[kso524]

Hi mate i used to work for K&N There filters in my view and many race teams are that they are the Best you can buy. the noise you are hearing is the Air that is being sucked in as these filters Breath 10000s of times better than the standard air filters you have had before, this will help your motor breath better,engine run better & should give you more mpg. nothing to worry about at all. if you have any issues you should call K&N Ltd they are at John street Warrington Cheshire Google number and ask for Technical and im sure they will put your mind at rest.
cheers paul

[r4robert]

Thanks Kso524 :-)

It was the whining noise that had me 'spooked'.

Induction noises, and I suppose a tad more exhaust noise is probably to be expected as more air in = more air out.

But how do you explain the whining noise, it’s quite disconcerting?

[anonymous-user]

What are the downsides to fitting K & N air filters?

I ask as surely there must be some?

Mercedes Benz are a huge company that spend millions developing cars, if they could get more power, better mpg and efficiency simply by changing something as relatively cheap as the air filters, surely they'd do it from the factory?

Is it a case that more air in is because they aren't doing what they are designed to, that is they aren't filtering as well?

Just curious.

[HumbleJim]

[r129sl]

Ten thousand times better? Really?

Interesting: http://www.autoblog.com/2005/09/07/how-well-do-k-n...

Edited by r129sl on Tuesday 18th February 11:05

[SilverPhoenix]

From memory the noises/sounds you're experiencing are normal, although I’ve not changed a standard filter for a performance filter for a long long time.

I did consider K&N when I got my C32, but I was guided towards BMC by a Mercedes technician. Never got round to changing them from standard in the end. Still rocking paper filters!

[anonymous-user]

yellowbentines said:

What are the downsides to fitting K & N air filters?

I ask as surely there must be some?

Mercedes Benz are a huge company that spend millions developing cars, if they could get more power, better mpg and efficiency simply by changing something as relatively cheap as the air filters, surely they'd do it from the factory?

Is it a case that more air in is because they aren't doing what they are designed to, that is they aren't filtering as well?

Just curious.

I would, suggest that they don't filter as well. I can't see how they can let more air through without letting more dirt through.

I am sure they're OK if kept very clean and oiled but doubt that they could safely be left for the mileages that the manufacturers specify.

[BGarside]

If they are not kept clean they will tend to plug up with dirt and could become more restrictive than a standard filter.

In most cases I think the filter element is not the most restrictive part of the average induction system anyway and so you might not see any detectable power gains from using K&N elements.

[r129sl]

The quick research I did suggests caution:

(1) they let more dust in,
(2) the extra air they allow through does not significantly increase power (<0.5%),
(3) if over-oiled they can contaminate the MAF.

I guess you can add:

(4) they make an irritating noise.

The weight of evidence was that they may be appropriate on a high performance engine which is used in short, high performance applications (like a racing car) but for a high mileage daily driver, they are worse than pointless.

[r4robert]

Thanks to everyone for your input.

I took the airbox off and discovered that one of the filters was poorly seated, allowing a seepage of air, and hence the ‘whining sound’.

Just re-seated the filters and finished a test drive and the whine is gone!

Not sure I like the increased induction noise or extra ‘growl’ from the exhaust, but I have the OEM filters at hand....!

As for performance, my understanding is that the ECU has to 're-learn' the airflow, so that will happen gradually.

(Point taken about racing engines vs regular car engines.)

Many thanks guys :-)

Robert