Please clarify these terms and their specific meaning. (Air filter test)

[WB9K]

I'm finally getting around to doing the A/B road test of the K&N vs Mann paper air filters. The parameters I measured for comparison were MAF specified, MAF actual, Absolute pressure, and RPM. There were some other things too, but I don't believe they'll say anything relevant. I didn't find the block that shows boost in the short time I had this morning to set up the VAG-com. Hopefully that won't doom my experiment; I'm hoping absolute pressure and MAF actual together can give a picture of what's happening with boost. Can any of the gurus chime in with details on these four parameters and how they work together? I'll be watching mileage in the next few weeks as well to see if there's any real difference there. After staring at the graphs I came up with in Excel, I think I understand what I'm looking at OK, but want to make sure before I put a presentation together on what I found.

Just as a teaser, I will say that there were definite measureable differences between the two filters. However, that may well be irrelevant....

I look forward to learning.

dh

[2004STARWARSTDI]

Are you aware that an oiled air filter such as the K&N will damage your MAF!

[WB9K]

Originally Posted by 2004STARWARSTDI

Are you aware that an oiled air filter such as the K&N will damage your MAF!

I'm aware that many here say it will. Mine was in for just under 5,000 miles and the MAF is just fine. This test is the result of a couple testy threads here just a couple months ago. Thanks for your concern, though.

[Lex4TDI4Life]

If I knew how to put one of those popcorn eating fellers in here, I would do so...

This should be entertaining if nothing else.

[davebugs]

I have a 2001 Golf TDI auto. Ran VW air filters up to 14k - VW had replaced the MAF by then. At 14k I started running a K&N. I ran it with regular cleanings (20-40k depending on mood, weather, travel habits) until recently at 142k. At that time the K&N was very dirty and when cleaning it my 'soft' bristle brush wasn't soft enough and poked holes in it. Rather than wait on another K&N I jumped in another car and went to my local dealer and installed a VW air filter.

I personally think K&N's are fine and have them in several cars and trucks and have run them for years. VW MAF's appear wimpy on their own.

I'm planning on ordering another K&N even though the car doesn't get as many miles as in the past. I'll be very interested in the results that you find and perhaps that will influence my decision.

Be prepared to be picked apart. But atleast some of us will appreciate it.

Thanks for taking the initiative.

Dave

[DieselOx]

...got my popcorn too...

[alphaseinor]

[WB9K]

Well, I was hoping this would be more than merely entertaining. Can someone at least verify or shoot down the idea that MAF actual and absolute pressure taken together can in fact give a pretty clear picture of boost level?

[Drivbiwire]

Just the other day the proud owner of another K&N filter showed up...That is until we opened his airbox and found this:



Yes the filter seal was working and no migration was found. The dirt was coming up thru the filter media.

The BRAND NEW filter was installed 10,000 mile prior at the last service interval and it was oiled by K&N. The filter itself appeared clean on the inlet side! The box was completely coated by fine dust that was puring thru the K&N media...Needless to say the MAF was coated with dirt as well.

In my opinion they are junk and should never be used in applications where filtration if CRITICAL!

DB

[Drivbiwire]

Originally Posted by WB9K

The parameters I measured for comparison were MAF specified, MAF actual, Absolute pressure, and RPM.

Won't work.

You need to install a filter AFTER the K&N so you can see the dirt it does not catch similar to what the guy did in this experiment:


Then you need to instal one of these to determine actual restriction in inches of water:


You are making the same mistake everybody seems to make when first getting into diesel tuning...The turbo eliminates the effects of filter restriction! This is forced induction not naturally aspirated! You are confusing the two and seem to not understand they are completely unrelated.

The only true way to measure the effects of a filter would be the N75 duty cycle at full load and max boost pressure. Even then the fact that the OEM filter will outflow the K&N will come into play! Yes the OEM filter will outflow and outfilter a K&N filter at the 15 micron range on any given day and operating conditions...It's called "area" that makes all the difference.

DB

[DieselOx]

I'll do my best. The way I see is (and I could easily be wrong) is boost is the variable. If you change the amount of air coming in, the boost will be changed by the ecu so the intake mainifold pressure will be whatever the ecu wants for those conditions.

Boost is shown in "mbar" in vag-com. I can't tell you anything about whether you can infer boost from what you've measured, I don't think so though.

Run it again logging boost and see what happens.

But I think you'll only need MAF, MAP, throttle position (wide open) and speed and what gear you were in (just tell us, I think you only can log 4 things)) to make or break your point.

As I see it, different filters may change MAF a little bit, but the ecu will compensate, and MAP will always be the same, or nearly, given the exact same conditions (wide open runs in same gear on same stretch of road).

All of the above is my best guess and loosley held opinion; I've only learned about these cars since last April. I only state this so I can be corrected if necessary by those more knowledgeable to help us newbies learn something.

I still won't ever let a K and N filter anywhere near any car of mine, regardless of the outcome here. (but my brother's made several filters for helicopter intakes with k and n medium, and they're extending the life of the turbines by a factor of 100? over no filter or just a particle separator).

[nutdriver]

WB9K - The advice on this topic to not use a K&N filter on these engines is spot on. Here is one study that might save you some trouble.

http://home.stny.rr.com/jbplock/ISO5011/SPICER.htm

[Drivbiwire]

I think you hit the proverbial nail on the head, the ECU commands the turbo to make a "specified" amount of MAP (Manifold Air Pressure) for a given set of conditions which are not absolute (they vary depending on a host of other factors and conditions).

If you run without a filter boost pressure will always equal X, install a restrictive filter and the boost pressure will still equal X. The difference is that the turbo will simply be commanded by the ECU to decrease back pressure (with the more restrictive filter) thus moving more volume more efficiently accross the turbine to achieve a higher "flow" thru the engine translated boost pressure will STILL equal X!

The only thing running a K&N will achieve is a SEVERE reduction in filtering efficiency without ANY resulting benefit in power or performance.

As for the turbine [aircraft], all turbines for the most part run without any filtration thus the problems with "FOD" and the requirements for cleanliness on the airport ramps. Helicopters due to operations in areas not normally used for aircraft operations require particle seperators. The problem is that since these remove some of the compressed air that is used for combustion in the turbine you lose power when they are in use. Hot and high conditions require judicial use of the seperators. Even small turbo-prop fixed wing aircraft have them and those too suffer from reduced power when in use.

Our TDI's never run anywhere near 100% of their potential, the turbo is throttled back by the ECU when driving down the highway to probably 25% of it's rated output. Even when helping the motor pump out 90Hp at sea level it's probably only tapping 75% of it's rated potential, the other 25% is in reserve to prevent the turbo from overboosting the engine or getting into "surge", in other words the stock turbo at sea-level can outflow the motor to the point that the compressor will surge/stall and grenade due to flow reversals as a result of the over supply of air that is being pumped into the intake.

DB

[WB9K]

Nutdriver, very interesting link. I haven't read it TOO in depth yet, but I gist is hard to miss. Thanks for posting that.

Unless I'm missing something, MAP (called "absolute pressure" in VAG-com) is a function of MAF actual and boost combined. My version of VAG-com in my vehicle allows me to log up to three engine measuring blocks simultaneously, which is actually up to 12 parameters. Graphing in Excel is quite easy.

The test was done on a single day where temperature, road conditions, and fuel were all the same. All data was taken with the engine at full operating temperature. The filters were a K&N which had been in the car for just under 5,000 miles followed by a brand new Mann filter (not the cold climate version.) Here's the Reader's Digest version of what I found:

1. Removing the K&N, a very clear oblong pattern of dust was collected on the "dirty" side of the filter. This proves beyond a doubt that air does not flow evenly through the entire surface of the filter, but at different rates in different areas. The pattern on my Buick's K&N was equally irregular when I serviced it recently, but different from that in the Jetta. I feel this confirms my previous point that turbulence inflicted by the airbox can and will affect the way air and particles move through the filter. This may cause variation in filtering efficiency of the same filter from one model vehicle to another. This is really just a side note--this experiment was about testing differences in flow, not filtration. I can post photos of both of the K&N filters if anyone is interested.-

2. The K&N and Mann filters do not flow identically. Comparing MAF specified with MAF actual, it is clear that the K&N flows better than the MANN despite the greater area of the paper Mann filter. The K&N responds to the engine's demand for air faster AND in greater quantities than the Mann does. It is possible that there is a VERY slight performance edge early in acceleration with the K&N as it allows more air to flow before the turbo can DEMAND more air by force. However, the turbo's response is very fast, and any gain here is negligible for all but the most competitive race drivers. I certainly did not feel the kind of difference I have with most gassers I've used K&Ns in. The greatest differences in the recorded data was on the highway, especially during hard acceleration. I can post the Excel graphs that show this if anyone is interested.

3. Here's where everyone can say "I told you so." MAP never gets any higher with the K&N than it does with the MANN. It appears that the airbox/turbo combination are in fact more than adequate for the engine's needs even with a paper filter. After the previous discussions on the subject here, this is what I expected to find. It could be possible that MAP builds a bit faster with the K&N, but my driving patterns were not nearly controlled enough to show that one way or the other. This tells me that mileage gains with the K&N are going to be at or near zero for my TDI--and mileage gain is the only reason I personally use these filters to begin with. I will be watching mileage over the next few weeks just to verify that expectation. I want to reiterate here that this is NOT what I have observed in several gassers over the years, but those cars are obviously different. Live and learn. The K&N in my Buick Regal and Ford Ranger are staying put. I'll probably sell the one for the VW to a gasser guy.

I have not yet pulled the MAF out again to check it for oil or dirt contamination. I pulled it once after about 500 or 1,000 miles with the K&N and it was bone dry with just a hint of very fine dust on the leading edge. I'll post what I find when I pull it, probably on Monday. The MAF actual readings I got with both filters plainly prove that my MAF is not failing. My feeling on this is that K&N filters do pose a somewhat higher risk of MAF failure. This could be due to a lot of things, among them improper filter maintainence, over-oiling, poor oil quantity control at K&N, and the fact that the K&N's will indeed pass at least a little more debris than a paper filter. Many here have seen failed MAFs with K&Ns, while several others have not. Many have also seen failed MAFs with paper filters. This is not a scenario of absolutes.

Again, if anyone actually cares to see any of my data or pictures, I'll post them. The graphed parameters are RPM, MAP ("absolute pressure"), MAF specified, and MAF actual.

I hope everyone is enjoying their popcorn.

[DieselOx]

Thanks for having an open mind and allowing the facts to influence your views but also not giving up too easily. It took a lot of work on your part, and those other threads really got out of hand, but you stuck with it. I think it's healthy for widely held opinions to be tested around here once in a while, just to keep this place honest.

I think you should post the graphs, so future doubters can be pointed to them quickly and avoid the drawn out arguing.

...putting away the popcorn, nothing to see here...