K&N Air filters

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Dec 13, 2015
Esher, Surrey
Mercedes SL 280 R129
Just prepping for a long trip, do K&N filters make a difference aka are they worth the money.
Research has proved time and again that they offer no significant advantages.........
They provide deep growling induction sound which some like.

They are also reusable which (in theory) means that in the long run they are more economic to run and more environmentally friendly.

In terms of any BHP or torque increase, an air filter upgrade will only make any noticeable difference if the engines breathing and air flow are improved throughout, i.e. induction manifold, turbo/super charger (if fitted), valves, and exhaust manifold and rear box. But in isolation, a 'free flow' air filter will make little or no difference to engine performance.
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experience has shown that if used on an engine with air flow meters/MAF sensors, oil from the filter element can be drawn onto the hot wire causing premature failure.
My take on the likes of K&N is this from some limited experience.

K&N drop in panel filters, no advantage. Depending on the particular car maybe a slightly nicer induction growl, they are expensive and need cleaning & oiling. I wouldn't bother, just stick to an ordinary paper filter from a respected manufacturer.

K&N cone filters married to their induction system (i.e. replacing the complete original intake system, with a 57i kit) could be worthwhile and will offer power gains depending on the car. Also the induction noise may not be to everybody's liking. Downsides, there's no guarantee of a power gain and it's expensive. The only unmodified engine I'd consider fitting the complete induction kit is a very high rev'er, with an excess of c.7000 rpm.

I would probably advocate using the likes of the 57i kit when the original engine has been modified and is producing maybe 25%(?) more power than standard.

As for the oil affecting MAF's, I think that's a myth as I never had the issue and I don't know of anybody else who did either, bar when the filters are over oiled after cleaning.

That's my 2p's worth anyway.
The K&N sticker looks really cool stuck on the air box - friends will think you have a hot car:thumb:

Don't waste your money, just stick to a good quality OEM paper filter.
I'm new to Mercs, although I have extensively used K&N and 3A Racing (AAA - Australian Auto Accessories) Pod Filters and panel filters on classic 900 Saabs. Overall my experiences support the advice given by John Jones Jr.

Generally, I did notice that the cars became more responsive with a Pod filter, whereas the panel filters offered a very subtle increase in response. The advantage of using a panel filter is that they work with the existing OEM induction systems, whereas a pod filter requires the existing air filter box to be removed along with possible alterations in the pipework layout. My main motive for using pod filters was to improve the throttle response rather than add more gee gees under the bonnet.

Does the increased responsiveness of a pod filter mean that it has added more horse power? Not necessarily. The engine power could be the same, but you are accessing more of that power. Thus the increased throttle response may give a false impression that the pod filter has 'increased' the hp. It is a bit like people who lose weight claiming that they now have "more energy", when in truth after losing weight they have less weight to carry around, which feels easier than before, thus giving them the feeling that they now have more energy.

The induction noise of the K&N Pod made the cars sound "Boy Racer", hence I switched to the quieter 3A Racing pod as I did not fancy being cop bait!

Mounting the pod filter directly onto the Air Mass Meter made a slight improvement in response over mounting it at the end of a long pipe connecting the pod to the air mass meter. This may be because the air has less distance and less pipework to travel through when mounting directly onto your AMM. Placement of the pod filter is important too. If you mount it in front of the engine, like say where the existing air filter box is/was in the CLK320 W208 behind the driver side headlamp assembly, then cool air hits pod filter. If the pod filter is mounted behind or on the engine then the air going into the pod filter and induction system is heated by the engine, resulting in less dense air so a weaker combustion.

In all honesty, I found the Pod filter to be more noticeable upgrade than the panel filter both in terms of induction noise and throttle response. Therefore if you do want to use a filter upgrade and don't mind removing your air filter box, I would also suggest the pod filter option like the K&N 57i kit. If however you wanted to keep your existing induction system and use a panel filter, then it is harder to justify the cost over the minimalist gains in responsiveness.

Talking with friends and family in the automotive industry and motorsport, the consensus is that to notice any significant increase in hp would require a combination of modifying the engine portings, re-routing the induction flow, remapping the ecu, and upgrading the fuel delivery system in addition to using a pod filter. So unless you are racing or a die hard petrol head, is it worth all the extra outlay? At the end of the day would any of us notice if the power output had increased by a meagre 7 hp from 218 hp to 225 hhp during our everyday drive?
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As for the oil affecting MAF's, I think that's a myth as I never had the issue and I don't know of anybody else who did either, bar when the filters are over oiled after cleaning.

That's my 2p's worth anyway.

Only time I have ever seen this happen is when some idiot has reoiled the wrong side of the filter :doh:
Just remove old air filter and superglue a 99p jumbo car wash sponge in there - same results.

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