k&N filters

[Dave779]

I have an SL350 2003 which has previosly been re-mapped and a performance back box about 12 months ago. I did some research on changing the filters and found differing oppinions, but added them to the car this week. To say I was impressed is an understatement it seems to be the missing performance part of the jigsaw. A lot more smooth power and a good increase in mpg also, just thought I would post my findings.

 

[Craiglxviii]

The one thing they do is add a very far profit margin to K&N's shareholders.

I'll say again. We have benchmarked these against identical form-factor and mass airflow- rated OEM paper filters.

The paper filters perform either at parity or several percent BETTER than K&N across the whole speed range.

That is for straight test- rig, controlled test results. Anything different you find on your car is either due to something else you've done, or placebo effect.

 

[LostKiwi]

All a K&N does (apart from make money for the company) is make more noise which will probably make you think they are 'better' as Craig said - placebo effect.

Think about this logically...
To get more power you need more air but to get a noticeable improvement you need to gain around 10% or more. To get 10% more power you need 10% more air.
Even K&N don't claim their filter flows 10% better!
Now just getting a potential flow increase of 10% will not be evident until the filter flows it's maximum rate - i.e full throttle and maximum RPM.
Now taking into account real world tests on flow benches show there is in most cases zero improvement in flow draw your own conclusions.
Let's also remember modern engines are tuned for maximum economy. From an air flow perspective this means minimal resistance to flow - exactly the same thing you want for power!
So given the manufacturer will already have tuned the inlet tract for minimal resistance to flow and spent millions doing so do you really think a little tin pot third party company producing filters for hundreds of different cars from different manufacturers is going to do better?
Finally K&N filters use an oiled cause. If you don't oil the gauze correctly it can leak onto the MAF and you'll soon be in a world of pain....

 

[turbopete]

as above. and if further proof were needed, these things have been dyno tested here

 

[Dave779]

Thanks for the replies but there are also several independent dyno runs online stating and showing the opposite. I appreciate you like to keep mercedes parts on your cars, but linked to my remap (which is the most important thing) and exhaust mod there is definitely more smooth power. However if you have had the above mods carried out on your car also and can factually prove me wrong then I am afraid we are going to have to 'beg to differ' on this point.

 

[John Laidlaw]

Dave, like all these things there are specific cases which can prove good or bad for each individual.
I had K & Ns on my 500 - which had an exhaust mod too, like you I felt the power delivery was a little smoother, maybe placebo who knows, but it did do something...for sure the car was louder!
Enjoy!

 

[Dave779]

Thank you John.

 

[peterws1957]

The one thing they do is add a very far profit margin to K&N's shareholders.

I'll say again. We have benchmarked these against identical form-factor and mass airflow- rated OEM paper filters.

The paper filters perform either at parity or several percent BETTER than K&N across the whole speed range.

That is for straight test- rig, controlled test results. Anything different you find on your car is either due to something else you've done, or placebo effect.

Coincidentally I have been looking at air filter materials this week but the specifications quoted totally defeat me. Is there a simple way of understanding the figures in terms of flow rates ,application etc ?

 

[LostKiwi]

Thanks for the replies but there are also several independent dyno runs online stating and showing the opposite. I appreciate you like to keep mercedes parts on your cars, but linked to my remap (which is the most important thing) and exhaust mod there is definitely more smooth power. However if you have had the above mods carried out on your car also and can factually prove me wrong then I am afraid we are going to have to 'beg to differ' on this point.

You still can't beat physics.
What is subjectively felt cannot counteract the pure physics that determines how power is made.
To get 10% more power (the minimum improvement required to make it able to be felt) you would have to flow 10% more.
That 10% will only be noticeable at full throttle and max RPM.
K&N filters do NOT flow 10% more than standard filters therefore subjectively it would be difficult (read impossible) to feel any true difference. The effect you notice is down to more noise making you think its going faster so therefore it must be better.

Put your car on a dyno with the K&N fitted. Then swap back to the original and run it up again. I'll bet there is sod all difference other than a K&N filter has lightened your wallet (which may be why you think your car is quicker).

K&N is a very successful marketing company and thats it. Snake oil for filters.

 

[Steve@Avantgarde]

The only time a larger performance filter will make any benefit is running on a engine which is fuelled by a carb.

Modern electronic fuel injection with preset and limited fuel maps will make little or no difference as the MAF hot film system has a metered tolerance which works inside of a specific operating range.

 

[Craiglxviii]

Thanks for the replies but there are also several independent dyno runs online stating and showing the opposite. I appreciate you like to keep mercedes parts on your cars, but linked to my remap (which is the most important thing) and exhaust mod there is definitely more smooth power. However if you have had the above mods carried out on your car also and can factually prove me wrong then I am afraid we are going to have to 'beg to differ' on this point.

You can beg to differ all you like, but you're wrong. The straight physics and fluid dynamics are against you. The engineering benchmarking tests run by the team of overworked-but-cheerful, rugged-yet-handsome engineers to which I belong all demonstrate exactly the point that I made. A K&N filter does not allow for any real increase in mass airflow at all over an identical form-factor paper filter. When I say "real", this needs some clarification. Mass airflow depends on the relative speed of the air hitting the intake as well as the suction of the engine drawing air in. So creating speed ranges (0-10, 11-20, 21-35, 36-55, 56-70, 71-100mph etc) one can see that at one speed range the K&N filter might have a few % greater airflow (actually, lower airflow impedance) than the paper filter, at another one the paper filter may have a lower impedance. But across the standard operating speed range of the car the paper filter outperforms the K&N filter n mass airflow (and, more importantly, actually filters the incoming air better). Plus they're 10% of the cost of a K&N filter.

What we find when people are totally, utterly sure that some performance increase is caused by X... is that, typically, several other changes have been made as well. These changes can be psychological as well as physical. A really good example is the 95 vs 98RON issue; many people maintain that they get better, snappier performance and better fuel efficiency from 98RON. Well, I've seen some blind tests done that show different. Fill a car up with 95RON and tell the owner it's 98, and they drive slightly more cautiously (and their mpg actually improves). Fill up with 98 and tell them it's 98, ditto. Fill up with 95 and tell them it's 95, they drive like normal and the apparent mpg drops. The point here being that one can make a much greater increase in fuel efficiency by driving carefully than by slightly increasing the anti-knock rating of a fuel. One could summarise this as "Only looking for the evidence to prove one's point", or in other words confirmation bias.

Nothing against using "Mercedes" parts on my car (Mercedes make very few parts except for engine castings and body panels, by the way- their supply chains make the rest and in many cases fit them to the car too)- MB air filters are chosen from a big fat book of standard form-factor air filters, all sized to allow for different mass airflow rates and speed ranges, then a custom airbox is created to supply smoothest, least turbulent airflow going into them. Simple as that.

 

[Craiglxviii]

By the way, K&N Engineering Inc. posted record revenues of $128m for FY2015; the figures before this were $87m, $75m, $70m then a series of near insolvency years. To put that into context, for a number that I've been able to find in the public domain Toyota spent around $800m to develop the Avensis. So, the profits one could expect from a manufacturing company- let's be generous- are around 10% nett. That's tops, $13m a year, to backwards-engineer many different parts into a whole range of engines from a whole range of manufacturers and do it better than those manufacturers could, given they own their own performance data.

 

[Droverunner]

>>>These changes can be psychological as well as physical.

Bit of a soapbox thing for me....

I'm a very strong believer in the psychological aspect of how we perceive a car's performance and driving pleasure. It's part of human nature and if feeling good about a car makes us believe it's going well than that's all part of motoring pleasure.

Over the years I've looked after many cars for relatives and friends. Often after a visit to me for a service or whatever they will text/mail saying thanks and that it runs so much better. I know in reality I haven't done anything that will make a discernible difference to the way it goes. But I may have washed it, leathered the dirty windows inside or vacuumed the interior... and that's what makes them feel better about it.

In a different way similar can be true after collecting from a dealer service for folks that use them... the combination of the car being washed... ambience of the dealership... and mentally justifying the invoice... all combines to make it drive better when you leave.

 

[00slk]

Interesting read here, I too think that the K&N filters are just for show, although I have raced cars for many years and have found on the dynamo's that there has been a slight improvement over the standard filters that are factory fitted, not much but enough to measure up on the scale. However these engines were not stock and have had major reworking that increased HP and Torque and were all carburettors. I have raced two fuel injected cars and one benefited hugely by removing the entire air filter and box and replaced this with a one piece air ducting tube from the front of the car to the intake with just a fine mesh over the end to stop and stones or rubber pieces getting sucked into the intake. This worked extremely well on the 280SE.
The other was highly modified old hat Lucas injection fitted car and although very quick, it did make a nice induction roar and made it feel faster. Interestingly I force fed this car too like I did with the Mercedes and the only noticeable difference was at top end revs.
So I'm guessing if you want your cars to perform a little quicker/faster run without the filters and filter box...........As usual these are my own opinions and should be taken with a pinch of salt

Peter

 

[Dave779]

Dyno Results: G37 Stock vs KN Panel Filter - Motorvate's Garage Ep. 1

Stillen Cat Back Dyno: G37 Sport Sedan - Motorvate's DIY Garage Ep. 11

The above dyno results on youtube state with the greatest respect that'you are wrong' Craig. Both show performance gains in both bhp and torque. Unless of course the dyno was suffering from the 'placebo effect' also, and my oppinion is that a 'dyno' test is more credible than some random tests conducted, and also it is a fact that all companies will cut costs to give an overall better result for the mass (ie paper filters are cheap). Also if K&N made 1 Billion dollars last year good look to them.

 

[LostKiwi]

Dyno Results: G37 Stock vs KN Panel Filter - Motorvate's Garage Ep. 1

Stillen Cat Back Dyno: G37 Sport Sedan - Motorvate's DIY Garage Ep. 11

The above dyno results on youtube state with the greatest respect that'you are wrong' Craig. Both show performance gains in both bhp and torque. Unless of course the dyno was suffering from the 'placebo effect' also, and my oppinion is that a 'dyno' test is more credible than some random tests conducted, and also it is a fact that all companies will cut costs to give an overall better result for the mass (ie paper filters are cheap). Also if K&N made 1 Billion dollars last year good look to them.

And TurboPete's results posted show exactly the opposite.

Craig isn't involved in 'random tests' - he works for a major motor vehicle manufacturer.

So I'll ask you given you are so adamant in your statements... how do the physics work that gives this 'extra power' that you can feel (given it takes a 10% increse in power before most people will notice it)?

 

[Dave779]

Exhaust Flow in an Automobile

The engine is like an air pump; the more air that is allowed to flow through it, the more horsepower that you get out of it. In other words, if you have a free-flowing air intake and exhaust system in your average vehicle, you’ll get more horsepower because of the efficient flow of air into and out of the engine. Fuel requires air to burn and thus to produce energy. The more air that is available for combustion will also improve efficiency otherwise known as gas mileage.
No matter how much additional air is forced into the engine, no additional HP will be made unless additional fuel is also added (IE remapped engine). The energy that makes HP in an engine comes from the combustion of the fuel, not only the air. In general, every two HP produced requires one pound of fuel per hour. When modifications are performed that increase airflow into the engine, more air is available for the combustion of fuel. The combustion of the additional fuel is what translates into additional HP. Air is not allowed to flow too freely because of restrictions in the form of the catalytic converter, the resonator, and the muffler. However, these components are necessary by regulations to maintain safe exhaust gas emissions and minimal sound levels (noise suppression). Also, in part, it takes time and money to design an excellent performing and free flowing exhaust system; something that car manufacturers just can’t afford to waste resources on. This is where aftermarket companies come in to create cost effective options for performance minded car owners. Of course, a free flowing exhaust would be expected to make more noise than a normal one. But a good manufactured system has a deep throaty tone, while yielding increases in horse power and also passing emission tests.

Maybe I have not got an extra 10% more power which I never stated, just that I could feel a noticeable difference in the cars performance which i had passed on to fellow members should it interest them..

 

[umblecumbuz]

At least, you

Dyno Results: G37 Stock vs KN Panel Filter - Motorvate's Garage Ep. 1

Stillen Cat Back Dyno: G37 Sport Sedan - Motorvate's DIY Garage Ep. 11

The above dyno results on youtube state with the greatest respect that'you are wrong' Craig. Both show performance gains in both bhp and torque. Unless of course the dyno was suffering from the 'placebo effect' also, and my oppinion is that a 'dyno' test is more credible than some random tests conducted, and also it is a fact that all companies will cut costs to give an overall better result for the mass (ie paper filters are cheap). Also if K&N made 1 Billion dollars last year good look to them.

PLEASE DON'T SHOUT!

 

[Craiglxviii]

OK. LK's point is that to feel a difference, due to the logarithmic response to stimuli for the human nervous system, you would need to make around 10% change in the level of that stimulus. That's not a rectal extraction figure either, it's fairly consistent across a broad swathe of criteria.

MIRA, Millbrook, JLR, A-M and BSI Labs' dynos would beg to differ with Motorvate. And with the greatest respect to them, they aren't the official body charged with testing standards.

I'll say it again. I do this sort of thing (amongst a few others) for a living, that is to say benchmarking of performance of various levels of parts to systems. What we see with specifically K&N Engineering's air filters of the oiled film/ gauze type is that they show no noticeable performance advantage over a bog standard OEM paper filter of the same form factor across engine speeds ranging from 0-160kph. Those are tests done under closely controlled conditions with kit calibrated to meet international test and homologation requirements.

if you find different then there are several conclusions:

1. The kit being used has not been calibrated;
2. The tests are not controlled e.g. like for like.
3. Other change factors have been introduced from one test to the other.

This is all pretty elementary stuff. I can give you a real world example. Take the air filter out of the car and run the engine. Do you see a 10% performance improvement? No, you don't (and you rapidly score the cylinder liners to death too). To get that level of improvement one needs to reconfigure the airbox/ intake. This was a serious problem for the RAF in 1940-1; R-R ended up having to completely redesign the air intake to the supercharger to improve engine performance. Also, by the way, in the same time frame they had to introduce various extra-big air filters to prevent the Desert Air Force's machines from getting chewed up by sand. These gave a serious performance loss (35mph) solely down to the aerodynamics (big and bulky) until the Vokes filter was adopted, which was a much cleaner shape. So, an engine that consumed the equivalent air volume of a double decker bus while on tickover didn't notice any performance loss (and here, where performance was literally The Sole National Interest) when using a filter of supposedly greater MAF impedance.

 

[Craiglxviii]

Exhaust Flow in an Automobile

The engine is like an air pump; the more air that is allowed to flow through it, the more horsepower that you get out of it. In other words, if you have a free-flowing air intake and exhaust system in your average vehicle, you’ll get more horsepower because of the efficient flow of air into and out of the engine. Fuel requires air to burn and thus to produce energy. The more air that is available for combustion will also improve efficiency otherwise known as gas mileage.
No matter how much additional air is forced into the engine, no additional HP will be made unless additional fuel is also added (IE remapped engine). The energy that makes HP in an engine comes from the combustion of the fuel, not only the air. In general, every two HP produced requires one pound of fuel per hour. When modifications are performed that increase airflow into the engine, more air is available for the combustion of fuel. The combustion of the additional fuel is what translates into additional HP. Air is not allowed to flow too freely because of restrictions in the form of the catalytic converter, the resonator, and the muffler. However, these components are necessary by regulations to maintain safe exhaust gas emissions and minimal sound levels (noise suppression). Also, in part, it takes time and money to design an excellent performing and free flowing exhaust system; something that car manufacturers just can’t afford to waste resources on. This is where aftermarket companies come in to create cost effective options for performance minded car owners. Of course, a free flowing exhaust would be expected to make more noise than a normal one. But a good manufactured system has a deep throaty tone, while yielding increases in horse power and also passing emission tests.

Maybe I have not got an extra 10% more power which I never stated, just that I could feel a noticeable difference in the cars performance which i had passed on to fellow members should it interest them..

That's a highly simplistic view. More air and more fuel into a given cylinder volume and given crank throw will only go so far. Remove the fuel/ air restriction and to gain power in an internal combustion piston engine one needs to do either one or both of two things:

1. Increase cylinder volume.
2. Add more cylinders.

One then also needs to endure that the cylinder head is optimized for improved (greater, less turbulent) airflow and that exhausts are optimized for tuned peak backpressure and no more (please don't ask me about exhausts though, I only know about aeroengines here).

However, your original point paraphrased was "I get better performance because I have K&N filters. Oh, and I've remapped it and modded the exhausts too". That could be phrased more accurately as, "I get better performance due to my remap and exhaust mod; I believe the K&N hype so that must make it even better".

I'm fully convinced that your performance improvements come from the modding. Just NOT the K&N part of it.