Discussion in 'Tuning, Styling and Performance.' started by sus, Feb 16, 2017.
Agree with Crash1, stick to standard OEM filters
They are odd as in the filter is fixed in the housing and comes as 1 part, there are 2 (left and right)
ordered new standard now thanks
You know it makes sense
It's the only choice
Just my 2p, I replaced my standard MB filter with a K&N one 2 years ago and I only had it in a week before selling it on. No increase in power, I actually experienced an increase in fuel consumption and a decrease in torque, once I got a new standard filter and put it back in my car was back to normal.
I've replaced standard paper filters with "High Performance" versions on several cars - not the Merc, like the OP says there isn't one for the newer 350's it seems.
Using the filter on my Impreza as an example:
- It provides better filtration, more "bits" get stopped by the filter, less chance of crap getting sucked in. Can't be a bad thing.
- It's MUCH better build quality, less chance of it flexing in the air box and not sealing properly & allowing crap to be sucked in. I've seen paper filters get bent / split due to being quite weak - my filter is strengthened with a wire mesh.
- Air filter can be re-used after a quick clean, potentially saving a little money. I've had the same Greenstuff filter in my Impreza for many years now, still going strong.... though Impreza paper filters aren't the most expensive if I'm honest lol.
- Air does flow better through it, meaning the engine wastes a fraction less power pulling air in. Negligible, especially if boosted, however...
- While peak numbers on a dyno don't appear to change - at least not outside a possible margin of error for the most part - the initial throttle response can seem improved and slightly more crisp.
A quality air-filter - so better filtering and flow properties - is often just a small part of lots of other tweaks. I've seen modded cars running poorly after just replacing an after-market filter with a standard paper one, as it was part of the overall package so to speak. Doing just a filter - either swapping to or from an aftermarket - would likely make little difference alone. Like any hardware mod, combined with tweaks to the map, even just a filter can make a difference to how a car feels, if not give the "20bhp just from a filter" that some might claim
As an aside, I've done a fair bit of mapping - not for a couple of years though -and you can often see measurable differences after relatively small hardware changes. A friend and I actually fitted an after market top-mount intercooler to his Impreza. We were told I'd not make a difference, we needed a front-mount etc. but we changed a fair few peoples minds with the measurable improvements we got from this relatively straight-forward mod.
Anyway, sorry, I can ramble on about this stuff...
Do you think your experience and level of detail in measurements exceed those of the design and development teams at the OEM..?
Seriously we get asked this all the time. The only way "performance" air filters improve volumetric efficiency is by reducing the vacuum barrier they present to the intake manifold. That's it. That means less filtration. There are no two ways about it. In addition, cars not remapped and modified to require much greater mass air flow cannot take any advantage of the reduced vacuum barrier.
Aftermarket 'performance' filters do not filter better.
There are numerous independent tests proving this. Paper element filters still provide some of the best filtration available.
The only way to increase flow without sacrificing filtration (like for like physical is to increase the surface area and the only way to do that is increase the size of the air box.
The 'performance' filters industry is built on some of the most successful snake oil marketing on the planet.
Guys come down to me and i will take you for a ride in my CLK430 which runs a few little tweeks nothing you cant carry out yourselfs , but i do run green filters and have been for 2 years now, i get 28 mpg on a run even at 80 mph and as the 430 is known to be sluggish on pull away and power this car is only 4cars behind an M3 and still gaining pace
Means nothing in isolation. You need to do back to back blind testing and test filtration on a proper test rig.
You could argue how come a simple remap can make a car more powerful while also giving improved driveability, response and general economy if the OEM's are so good. Not going to get into it, but there's a lot of room for improvement over OEM, as a very successful aftermarket and mapping industry shows.
On filters, I read fairly comprehensive reports back in the day showing certain aftermarket filter brands providing improved filtering and flow over OEM - though this was always with a remap in the picture too, never just an air filter. I'd not have gotten a Greenstuff back in the day if it compromised protection (filtration) over flow. I don't blindly follow "common knowledge" or pub talk on these things, I do my research and make up my own mind.
It may well be that OEM filters today are much better than those fitted to my '99 Impreza - well, I'd hope that to be the case at least - but back then it made a measurable difference. Additionally, if you're going after big power - as with my friends Impreza - the OEM filter, air box and tubing become a major limiting factor. Like I said, in isolation an air filter might not make any discernable difference, but as part of a set of mods it might be critical.
To be clear, I have direct experience of a relatively lightly modded vehicle running a performance air filter, switching back to OEM and it caused the car to run poorly. I also worked on my friends big power build, his car would have been choked with the standard filter. We ended up fitting a full cone filter set up, along with a "cold box" insulated surround with cold air feed to avoid pulling in engine head. We placed thermal sensors in various places to monitor temps, as well as what the car (aftermarket ECU) gave us. Fun project.
Oh, and while mapping is fairly crucial to get the most out of any physical mods, many standard ECU's can adapt to a degree - the maps are not set in stone, but are based on many parameters measured by the engine. Again, I've done a fair bit of this over the years - though not recently - mostly on Imprezas.
Before changing air filters it's worth looking @ the science, it's actually quite straight forward.
This page is from a well respected engine builder. Using the maths I made an air filter box and filter for an old classic (previously fitted fairly restrictive "sports" pancake filters)
Made a big difference to the top end.
Ok. OEM engine maps are designed to take account of fuel and environmental conditions over a very wide geographical range. Especially Japanese built cars homologated for the Euro market, as they simply do not understand that our cars can operate from -20C and 6000' ASL down to +35C and -30' ASL, with fuel ranging +/-15% from the quality baseline. If lucky there will be 4 or 5 maps per engine variant/ model available for Europe, usually two but in many cases just one. VAG for example run just one very conservative map from plant.
So with all of that, there is huge scope for improving the power output of the engine.
Remember also that the engine is not designed for sale at Power(max), it is developed to output a wide range. Example, the VAG 1.9 TDi Pumpe Duse. That was released in 95, 105, 130, 150 and 170PS variants with no difference between them other than the ECU's program. Now the engine is physically capable of 340PS the last time I checked but at that level it won't meet its quality targets for durability, NVH and the rest. My point is that engine power is just one of the very many variables that OEMs have to juggle in order to deliver a desirable product to the market. Not everyone, in point of fact most people prefer specific fuel economy, smoothness, quietness, reduced tax and increased powertrain reliability over raw engine power.
So, all the aftermarket performance mods directly move the car away from its homologated condition. That condition is the one that the OEM has had between one and three thousand highly qualified, highly experienced, hard working, under appreciated, generally very good looking and manly design engineers working for 3-4 years on, to develop the absolutely best product range to fill the market opportunity they have spotted- and to meet all the regulatory issues that are required in doing so. That is why a car's engine power can be increased.
Now we have a really good open source study of this in the form of the Rolls Royce Merlin. Through development it went from naturally aspirated 900hp to forced aspiration 2200hp over 5 years, incorporating increasing fuel octane ratings (87-130) and boost pressures (5-22psi). And that was an engine treated as throwaway part (few did more than 600 hours before being shot out or shot down)- and it was an engine that was required for Power(max) condition... interestingly the first big performance improvement was a completely revised intake manifold. And one of the biggest problems they had was adequately filtering the air volume to prevent ring wear and carbon fouling...
So on an unmodded car a "performance" filter will achieve diddly squat. On a modded car a greater air mass volume may be required and a "performance" filter may well allow that, along with improvements to the air flow in the intake (which is still a black art btw no matter the FEA and CAE used). But all of that will only have a negative effect on the life of the engine and increase its maintenance requirements, and chances of catastrophic failure.
......and on a lighter note , there are some great YouTube video of cars with modded (assuming poorly done) engines blowing up on the dyno.
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