Measuring air box pressure?

[Tapio]

If you're trying to compare the two filters, is it really vital that the open end is reading ambient? As long as the test is conducted with the same parameters is that not enough?

Also, would you be better measuring the pressure drop across the filter? ie; the pressure immediately upstream and downstream for each filter?

No, it’s not. It’s just a bit worrisome that I’m so far off from what the readings should be. 490/1850 = 26 %.
It just struck me, as I’m writing this: maybe I should stick the open end of the hose down the induct instead. Then I’ll be measuring pressure drop across the filter, and nothing else. Ram effect is out of the equation.
I don’t like the idea of drilling holes in the induct.

[Corvus]

If you're trying to compare the two filters, is it really vital that the open end is reading ambient? As long as the test is conducted with the same parameters is that not enough?

Also, would you be better measuring the pressure drop across the filter? ie; the pressure immediately upstream and downstream for each filter?

No, it’s not. It’s just a bit worrisome that I’m so far off from what the readings should be. 490/1850 = 26 %.
It just struck me, as I’m writing this: maybe I should stick the open end of the hose down the induct instead. Then I’ll be measuring pressure drop across the filter, and nothing else. Ram effect is out of the equation.
I don’t like the idea of drilling holes in the induct.

Sounds like a plan.

Will the Bernoulli effect be the next headache, if it isn't already? But then again, the objective is a comparison of the two filters, so as long as the parameters are equal. No?

Several runs for each filter will check repeatability.

A test off the machine is also possible. I'm not sure a vacuum cleaner would provide the flow needed, but the intake to a decent air compressor might?

[Corvus]

Another thing occurred to me, although I'm not sure whether this is of any relevance. Presumably you'll have fitted some form of damping? To eliminate fluctuations?

If you haven't, should you? If you have, are they having an effect on "spot check" readings? I don't suppose you have that much time to devote to looking at the gauge!

[Tapio]

Sounds like a plan.

Will the Bernoulli effect be the next headache, if it isn't already? But then again, the objective is a comparison of the two filters, so as long as the parameters are equal. No?

Several runs for each filter will check repeatability.

A test off the machine is also possible. I'm not sure a vacuum cleaner would provide the flow needed, but the intake to a decent air compressor might?

Good point. Hadn’t thought of that. Damn that ram! And another thing: that hose end will probably not be content with sitting still, but will be whipping about like crazy, giving me readings all over the place.

Agree with you on the vacuum cleaner. I don’t think it’ll give enough airflow.

[Tapio]

Another thing occurred to me, although I'm not sure whether this is of any relevance. Presumably you'll have fitted some form of damping? To eliminate fluctuations?

If you haven't, should you? If you have, are they having an effect on "spot check" readings? I don't suppose you have that much time to devote to looking at the gauge!

Unless there are big transients, no problems with fluctuation. A bigger problem is waters’ surface tension. Water “clings” to manometer hose surface, and is reluctant to move. I plan on putting some detergent to water for next test. Whenever that’ll happen.

I tried to do this test at lower speed first. But as you have to have WOT, and be close to redline in order to see a difference, it was impossible. Looking at speed, tach, traffic, and maybe also where I’m going, and the manometer at that, was simply too much to handle.

[Corvus]

And capillary action causing parallax error.

There are big transients. They're sticking out each side. Ha ha.

[Corvus]

Another thing occurred to me, although I'm not sure whether this is of any relevance. Presumably you'll have fitted some form of damping? To eliminate fluctuations?

If you haven't, should you? If you have, are they having an effect on "spot check" readings? I don't suppose you have that much time to devote to looking at the gauge!

Unless there are big transients, no problems with fluctuation. A bigger problem is waters’ surface tension. Water “clings” to manometer hose surface, and is reluctant to move. I plan on putting some detergent to water for next test. Whenever that’ll happen.

I tried to do this test at lower speed first. But as you have to have WOT, and be close to redline in order to see a difference, it was impossible. Looking at speed, tach, traffic, and maybe also where I’m going, and the manometer at that, was simply too much to handle.

I'd already thought about using full throttle acceleration in the lower gears to apply load but not have high localised pressure differences. As you say, the drawback is it all happening so fast. ...... Video it.

[Tapio]

I can see what this looks like, from reading my postings on this thread, but before y’all put me off as an obsessed weirdo: no! I’m doing this out of curiosity, and because it amuses me.

On a more serious note: a lot of stuff is sold on the notion that they are “high performance” parts. Most of that stuff is just snake oil. I believe that the K&N filter is one of those.
Don’t get me wrong, I think K&N products are great. But this time they failed.

[Corvus]

I can see what this looks like, from reading my postings on this thread, but before y’all put me off as an obsessed weirdo: no! I’m doing this out of curiosity, and because it amuses me.

On a more serious note: a lot of stuff is sold on the notion that they are “high performance” parts. Most of that stuff is just snake oil. I believe that the K&N filter is one of those.
Don’t get me wrong, I think K&N products are great. But this time they failed.

Hey, of course you're a weirdo. You ride a bmw.

It beats watching soaps.

[nab 301]

I think this link was posted here before , it relates to cars and was really a comparison of paper media over foam and cotton gauze filters.
The conclusion was ( I think) that paper was the best filtering medium with marginally more pressure drop..
http://www.bobistheoilguy.com/airfilter/airtest1.htm

[Corvus]

I think this link was posted here before , it relates to cars and was really a comparison of paper media over foam and cotton gauze filters.
The conclusion was ( I think) that paper was the best filtering medium with marginally more pressure drop..
http://www.bobistheoilguy.com/airfilter/airtest1.htm

That's the thing with filters and efficiency. You can have efficiency of filtering particles or efficiency of flowing air. You can have both if you have the space.

There are cyclonic filters which use oil and centrifugal force to extract particles but these are usually larger still. The good news for motorcycles is that the airbox has become a "tuned" component in its own right and it's demands for volume in return for performance gains seem to be well worth it?

Will a filter shape interfere with the pressure pulses?

[Tapio]

I think this link was posted here before , it relates to cars and was really a comparison of paper media over foam and cotton gauze filters.
The conclusion was ( I think) that paper was the best filtering medium with marginally more pressure drop..
http://www.bobistheoilguy.com/airfilter/airtest1.htm

Great info there! Hats off for that man!
Yes, the differences were negligible, with K&N being the best. As he states:
“If you need the 0.14% better airflow, than the K&N is hands down the best filter.”
And remember, these filters were all the same size.

So, from reading that test and looking at the pic I posted above, I’d say that the K&N has a bigger pressure drop across it than the stock filter!

[Blackal]

I think this link was posted here before , it relates to cars and was really a comparison of paper media over foam and cotton gauze filters.
The conclusion was ( I think) that paper was the best filtering medium with marginally more pressure drop..
http://www.bobistheoilguy.com/airfilter/airtest1.htm

That's the thing with filters and efficiency. You can have efficiency of filtering particles or efficiency of flowing air. You can have both if you have the space.

There are cyclonic filters which use oil and centrifugal force to extract particles but these are usually larger still. The good news for motorcycles is that the airbox has become a "tuned" component in its own right and it's demands for volume in return for performance gains seem to be well worth it?

Will a filter shape interfere with the pressure pulses?

K&N type filters - do the job by adherence of the particles to the fillament which is coated with oil. As such - there is little or no progressive restriction by particulate.

Paper filters - do the job by nature of the holes in the filter being of lesser diameter than the particulate they are designed to stop. As time goes on - they become increasingly blocked to efficient air flow.

The use of a large "can-type" K&N filter (compared to the smaller "panel" type - on a bike like the R1100s - is better, but mostly - in the time between cleaning.

I say "mostly" because it may also prevent some larger debris from blocking the filter area, although to what extent - could be argued.

Some people may claim that leaves etc will lie accross the filter element on a panel-type filter whereas they will sit on the bottom of a can-type filter, and not block the element. I think in reality that leaves may be picked up off the bottom of the can, and end up deposited against the element, due to the turbulence in the filter. Wet leaves don't stay wet in such an air-flow.

Anyway - the above is my opinion, only - not based upon any scientific experimentation I have carried out.

From K&N



Al