AIR FILTER EFFICENCY

[twinrat]

Hi all my first post,i have been considering changing my air filter  to a different type K and N etc ,but before i do i thought i would take a vacuum reading of the airbox with moter revving up to high revs  and get a reading to see if there was a lower vacuum if i changed filters . guess what no vacuum reading .i would have expected there to be at least some vacuum if the standard air filter didn't flow well .can anybody shed light on this or is the standard filter extremely good ??




Do it your self be sure its done right.

[mister]

Hi all my first post,

Um... you sure of that. I see 47 next to your post count. And they all weren't posted after this one.

Michael

[the mole]

If you want to check the vacuum across the air filter, you don't just need high rpm, you also need the throttle wide open, ie. the motor must be under load. You need a dyno, or you need to set up your vacuum gauge on the bike and go for a high speed run.
This is because it doesn't take much horsepower to spin the engine at high rpm in neutral, so there's not much air flow.

[Suzuki Stevo]

The point where you want to attach your gauge to tell you what you want to know is between the carb and filter....but you could actually plug you vacuum gauge in the end of the filter (same thing) and that will tell you what you need to know. I'm a painter and that is how we know when to change our filters on our paint booths. A low reading would be clean efficient filter, a high reading would be clogged or inefficient filter. I'm not really sure if a dyno would be required, load or no load, 6000 Rpm moves the same CFM with a load as without     

[the mole]

No, the CFM changes with load. If you're revving at 6000 rpm in neutral the throttles are only open a little above idle so there's high manifold vacuum due to the restriction in the carb throats, and much less airflow than at the same rpm at WOT. (unless its a diesel!)

[Suzuki Stevo]

No, the CFM changes with load. If you're revving at 6000 rpm in neutral the throttles are only open a little above idle so there's high manifold vacuum due to the restriction in the carb throats, and much less airflow than at the same rpm at WOT. (unless its a diesel!)

Your measuring CFM (more or less), the load has no bearing on the situation, the engine is a fuel/air pump.  Hint...your not measuring manifold vacuum 

EDIT: Your not really measuring CFM, your measuring the restriction of the air cleaner. But CFM is required for you to do that.

[crzydood17]

No, the CFM changes with load. If you're revving at 6000 rpm in neutral the throttles are only open a little above idle so there's high manifold vacuum due to the restriction in the carb throats, and much less airflow than at the same rpm at WOT. (unless its a diesel!)

Your measuring CFM (more or less), the load has no bearing on the situation, the engine is a fuel/air pump.  Hint...your not measuring manifold vacuum 

EDIT: Your not really measuring CFM, your measuring the restriction of the air cleaner. But CFM is required for you to do that.

your wrong hes right lol, At low load but high RPM the engine is sucking in air but the cylinders aren't filling up completely, they still move the same distance up and down clearly but are not fully filled with fuel/air mixture(they hold a vacuum). Though even at full load at 11k there can still be vacuum from inefficient intake system... The only way to truly test what he is trying to do is to take the bike out with a vacuum gauge that keeps the highest vacuum reading. Then take it up to 2nd gear WOT and then read the gauge after he stops.

[Suzuki Stevo]

No, the CFM changes with load. If you're revving at 6000 rpm in neutral the throttles are only open a little above idle so there's high manifold vacuum due to the restriction in the carb throats, and much less airflow than at the same rpm at WOT. (unless its a diesel!)

Your measuring CFM (more or less), the load has no bearing on the situation, the engine is a fuel/air pump.  Hint...your not measuring manifold vacuum 

EDIT: Your not really measuring CFM, your measuring the restriction of the air cleaner. But CFM is required for you to do that.

your wrong hes right lol, At low load but high RPM the engine is sucking in air but the cylinders aren't filling up completely, they still move the same distance up and down clearly but are not fully filled with fuel/air mixture(they hold a vacuum). Though even at full load at 11k there can still be vacuum from inefficient intake system... The only way to truly test what he is trying to do is to take the bike out with a vacuum gauge that keeps the highest vacuum reading. Then take it up to 2nd gear WOT and then read the gauge after he stops.

You clearly don't understand the CFM aspect of an engine running either....

[Suzuki Stevo]

You guys are over thinking it, this is basic science class 101 stuff if you understand what you are trying to accomplish...
"Can you put a vacuum gauge between a carb and air filter and measure the vacuum differences between 2 different kind of air filters to determine what filter flowed better?"
Yes you can!
"But you need to put the bike under a load to make the slide open up on the carb to let in air!"
No you DON'T...load or no load. First and foremost all internal combustion engines are basically fuel/air pumps. 480cc's displaces 480cc @ X Rpm= Y (CFM), load or no load the CFM you are moving is determined by the RPM.

Now see....you made me go all scienceclassnshit     

[crzydood17]

you aren't understanding how with the throttle plates partially closed there is a negative VACUUM in the cylinder where less than 14.7 PSI of air/fuel is inside the chamber before the piston starts going up. Even without the cylinder full you can rev it because of the small amount of power it takes to turn the rotating mass. This is the same reason your choke revs the engine because even with the throttle plate at a minimum and your vacuum maxed out the extra fuel is allowing the engine to make slightly more power and rev till the power/load is equal. CFM is reduced because of the vacuum (less than ambient pressure, 14.7psi, in the engine) STICK THAT IN YO JUICE BOX AND SUCK IT!

[Suzuki Stevo]

you aren't understanding how with the throttle plates partially closed there is a negative VACUUM in the cylinder where less than 14.7 PSI of air/fuel is inside the chamber before the piston starts going up. Even without the cylinder full you can rev it because of the small amount of power it takes to turn the rotating mass. This is the same reason your choke revs the engine because even with the throttle plate at a minimum and your vacuum maxed out the extra fuel is allowing the engine to make slightly more power and rev till the power/load is equal. CFM is reduced because of the vacuum (less than ambient pressure, 14.7psi, in the engine) STICK THAT IN YO JUICE BOX AND SUCK IT!

Your mistake is you measuring the vacuum at a point between the throttle plates and the pistons. The volume displaced buy the pistons drawing in the fuel/air mixture remains constant, regardless of the throttle position. That's why it's called DISPLACEMENT, yes the throttle plates/slide regulate the flow, but...whatever the displacement of the piston, that is the volume it gets when it goes down on the intake stroke 

Take your readings from the other side of the throttle plates and all vacuum readings are driven by the resistance of the air filter, displacement of the pistons and the RPM, it's the law of physics, you can't get around it 

[crzydood17]

if i put my finger over the end of a syringe and pull what happens inside lthe tube? the plunger moves but no air is sucked in, if i release the plunger, it sucks up... no air in pulled into the cylinder, The same exact thing happens in a engine, if the throttle body (your finger) is covering the intake then even when that piston is at the bottom of the stroke it cannot pull in any more air. Think of this, if the bike pumps as much air at no load and just a cracked throttle then why do we need to open the throttle any more than it takes to rev the bike to 11k rpm at no load, clearly it is flowing the same amount of air if your presumption is correct.

[Suzuki Stevo]

if i put my finger over the end of a syringe and pull what happens inside lthe tube? the plunger moves but no air is sucked in, if i release the plunger, it sucks up... no air in pulled into the cylinder, The same exact thing happens in a engine, if the throttle body (your finger) is covering the intake then even when that piston is at the bottom of the stroke it cannot pull in any more air. Think of this, if the bike pumps as much air at no load and just a cracked throttle then why do we need to open the throttle any more than it takes to rev the bike to 11k rpm at no load, clearly it is flowing the same amount of air if your presumption is correct.

Running with a load, clearly takes more right hand to maintain the same Rpm...and your not forcing fuel/air into the cylinder...it's taking it, by virtue of displacement. (see above)

[Suzuki Stevo]

Well this has been actually pretty entertaining. Seeing that I have never actually tested my above statments in a real world environment and even though they a based on my knowledge of basic fundamental internal combustion principles, let's just call it my hypothesis for now.   

(hī-pŏth'ĭ-sĭs) pronunciation
n., pl., -ses (-sēz').

   1. A tentative explanation for an observation, phenomenon, or scientific problem that can be tested by further investigation.
   2. Something taken to be true for the purpose of argument or investigation; an assumption.
   3. The antecedent of a conditional statement.


So in my best Stewie Griffin voice imagine a long drawn out "D-I-S-P-L-A-C-E-M-E-N-T" followed by a long awkward silence, right before the credits roll 

[twinrat]

gee this looks like an interesting post .Have wound throttle round suddenly to 9000 rpm  slides had to open even momenterly but did not register any vacuum on my Morgan tune gauge .Took my hook up point off airbox where all the patent or manufacture numbers are  on the right side .Will try again this weekend on the road in the lower gears throttle wide open and gauge mounted on the screen.After ive got this sorted im going to test the exhaust for backpressure by welding a fitting in exhaust pipe about 6"before the start of the muffler unless some one has already done this..
                                                                         

do it yourself be sure its done right.

[the mole]

Stevo, what you say is true if you are talking about a diesel engine (or an air compressor) but not a petrol (gas) engine.

In the diesel the amount of air ingested in a given time is dependant on rpm but not on throttle setting because in a diesel there is no restriction in the intake apart from the air filter. Adjusting the throttle of a diesel simply changes the amount of fuel being injected, so that at low throttle a diesel is ingesting a lot of air that does not take part in the combustion process, as only a small amount of the O2 is used to burn the small amount of fuel. In petrol engine terms it is running a very lean mixture. At WOT most of the O2 is being burnt as a lot more fuel is being injected.

In a petrol (gas) engine, the mixture of fuel/air has to be kept close to the ideal (stoichiometric) mixture, so to vary the power output a variable restrictor (the throttle valve) is placed in the intake. This valve's purpose is to adjust the volume of air being ingested in to the engine, and the rest of the carburettor is designed to admit the appropriate amount of fuel to match the air flowing through.

If you are running your bike down the highway at 70 mph, the engine is ingesting a certain amount of air (CFM), when you close the throttle the amount of incoming air is reduced (the carb reduces fuel intake proportionately to maintain mixture) and the amount of power being produced decreases, so you slow down.

If, as you suggest, the amount of air being ingested is independant of throttle setting, then how on earth do you not spend your entire riding time doing about 105mph?

And please, have a chat to someone like a mechanic who has a good working knowledge of the ICE before you come back on here and tell me how wrong I am.

Even better, don't talk to anyone, tell me how much you want to bet on this (I could raise about $6k at short notice) and we'll take it from there. I'd be happy to forward the $ to any well known forum member not known personally by either of us to hold. 

[the mole]

Crzydood, thanks, and hey sledge we could use your BS filter, where are you?

[twocool]

My local auto parts store used to have a cool display case, clear plastic, with a K&N filter in there and a brand x filter in there....they were connected to some air source (don't remember if it was vacuum or pressure....and some fancy gauges.......it showed that the K&N was passing more air (pun intended)...

I'm not sure where the guages were inserted or what they were measuring....pretty sure they were measuring air flow...not vacuum......the whole idea of a high effeciency filter is to allow more air to pass........and still filter out small particles......it is hard to do both at the same time....

But if I were trying to make a test rig.....I would try to measure air flow thru the filter, rather than vacuum on one side of it......

Just my 2 c....

Cookie

[twocool]

http://www.bobistheoilguy.com/airfilter/airtest2.htm

The above website really goes over all of what you are looking for..both flow effeciency, and filtering ability....

Bottom line is it doesn't really matter much....maybe only in race cars/bikes....

Differences in filters is so small as to be insignificant!

I like K&N because of the long life...( used in my airplanes and some cars) you clean, oil and re use.........I just use suzuki in my suzuki...

Cookie

[crzydood17]

i love me some AEM dry flow, those things are beasts, run some water into it and clean it up every 3000-5000 miles, shake it out let it air dry a bit and throw it on... screw all that oiling crap, too bad aem doesn't make a lunchbox