Pro-design filter kit


30 replies to this topic
  • roylo

Posted July 29, 2009 - 12:50 AM

#21

Im not convinced they would get 5HP or anything near that. What I do think is removing the screen WILL increase throttle response and make a small gain in power, but probably too small to measure on a dyno accurately. I dont care for more power my 450 has plently but if I can gain some extra response then Im all for that.
The screen may be less of a restriction than the filter itself but it still IS a restriction and would affect the air flow. So, removing the screen combined with a much thinner and free-er flowing filter than standard would help even more I would say.

  • grayracer513

Posted July 29, 2009 - 06:19 AM

#22

The screen may be less of a restriction than the filter itself but it still IS a restriction and would affect the air flow. So, removing the screen combined with a much thinner and free-er flowing filter than standard would help even more I would say.

Again, the filters I use are freer flowing than the OEM filters. (not much; the stock element isn't as bad as you seem to think) With the filter in place in the assembled air boot, there is a measurable, albeit small, depression created across the filter. That is, with air flowing at a rate that exceeds the engine's potential, the pressure under the filter is lower than the outside air.

There was no such pressure drop on the carb side of the flame screen relative to the pressure between the screen and filter on the other side. This clearly demonstrates there is no significant impediment to flow caused by the screen.

But also again, believe what you like. The fact is that two big money racing teams (one a Supermoto team) have examined this question, and left the screen in place.

  • roylo

Posted July 29, 2009 - 07:43 AM

#23

[quote name='grayracer513']Again, the filters I use are freer flowing than the OEM filters. (not much; the stock element isn't as bad as you seem to think)

With the filter in place in the assembled air boot, there is a measurable, albeit small, depression created across the filter. That is, with air flowing at a rate that exceeds the engine's potential, the pressure under the filter is lower than the outside air.

There was no such pressure drop on the carb side of the flame screen relative to the pressure between the screen and filter on the other side. This clearly demonstrates there is no significant impediment to flow caused by the screen.
[QUOTE]

Ok. I understand what your saying about your testing showing no pressure drop from the screen. If its accurate then Ill believe it for sure. But just looking at the screen itself it sure looks like it would interupt the flow somewhat and I still say for now there are gains in throttle respose to be had by removing it.

In this test you performed, how did you simulate the great rush (speed) and volume of air the engine takes in when the throttle is suddenly cracked full open from an idle position?
How did you know or measure to reproduce in the test, the max air intake volume AND speed a YZ450 uses?

Remember, its no good blowing air through the filter and screen to test it because the engine sucks air through them, and a constant flow of air during the test would result in inaccurate readings aswell because this is not what the engine does. The air flow during idle would be very slow then you have to simulate a rush being sucked through when the throttle is pinned, (which would be the engines measured max or higher) and then measure the pressure drop.
I dont know if it can be accuratly done but if anyone can Id say you could do it haha. Anyway.

  • roylo

Posted July 29, 2009 - 07:59 AM

#24

The fact is that two big money racing teams (one a Supermoto team) have examined this question, and left the screen in place.



The fact is two teams against how many hundreds of big money teams that race without it?

  • grayracer513

Posted July 29, 2009 - 09:20 AM

#25

Double post sorry delete this.

Delete it yourself: click the Edit button at the right of your post.

In this test you performed, how did you simulate the great rush (speed) and volume of air the engine takes in when the throttle is suddenly cracked full open from an idle position?

There actually is no such "great rush" of air under that circumstance. At the moment the throttle is suddenly opened from idle at low speeds, air flow all but ceases due to the sudden drop in intake vacuum. That's what causes the stumble that occurs, and why the accelerator pump is needed to supply the fuel that would have been brought in by air flowing through the carb.

How did you know or measure to reproduce in the test, the max air intake volume AND speed a YZ450 uses?

Remember, its no good blowing air through the filter and screen to test it because the engine sucks air through them, and a constant flow of air during the test would result in inaccurate readings aswell because this is not what the engine does. The air flow during idle would be very slow then you have to simulate a rush being sucked through when the throttle is pinned, (which would be the engines measured max or higher) and then measure the pressure drop.

The test was done with the air box and filter assembled and off the bike, using a large "squirrel cage" fan to pull air through from the carb opening of the boot. Assuming 100% volumetric efficiency (which is quite unlikely to actually occur), a 450cc engine will move 65 CFM at 8000 rpm (roughly the power peak) and 85 at 10,500. The fan I used was rated 90 CFM.

Two slack tube manometers were set up with one tube in the air volume between the filter and screen, and the second entering at the boot between the screen and fan connection.

You are incorrect when you say that there is a difference between pulling or pushing air through such a system. There is not. Air moves in response to a pressure differential between the source (higher pressure) and the destination (lower pressure), and it matters not at all how the differential is created, whether by vacuum at the destination volume, or compression at the source. Air flows either way, and pressure drops across any obstructions encountered will occur regardless.

In point of fact, all air that moves is pushed, never pulled. The idea that a piston "sucks" air into an engine is technically false. The piston creates a depression within the cylinder by moving downward, and the higher atmospheric pressure outside the engine pushes air into the void in an attempt to balance the two pressure zones.

The fact is two teams against how many hundreds of big money teams that race without it?

In the first place, I really don't care how many run without the screens. Unless they are relying on actual tests that show some benefit, they are doing so without reason, based on intuition and myth.

It should also be pointed out that my tests, and those of the teams I cited were done on YZF's only, and the information learned from them does not necessarily apply to other brands. There is, for instance, apparently some evidence that CRF's do benefit to some degree from removing the screen, which, if true, could be due to differences in the screen density, or area of the screened opening on that bike.

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  • Ga426owner

Posted July 29, 2009 - 12:32 PM

#26

Grey my test on the Loudmouth was also very scientific also......:worthy:

This test took weeks of hard work and tons of energy, It is called the "Great Southern Redneck Air filter suck and blow test".......it was quite a site to see what I had to juryrig to seal and fill up that airbox and whew I almost passed out a few times out from the lack of oxygen, but geez I swear my bike is faster. I told you that Butt dyno is the ticket...... :thumbsup:

I called Loudmouth and for some strange reason they did not want to document my test either....hmmm go wonder.

  • grayracer513

Posted July 29, 2009 - 01:59 PM

#27

Grey my test on the Loudmouth was also very scientific also......:worthy:

You're on your pain meds again, aren't you? :thumbsup:

  • roylo

Posted July 29, 2009 - 03:01 PM

#28

There actually is no such "great rush" of air under that circumstance. At the moment the throttle is suddenly opened from idle at low speeds, air flow all but ceases due to the sudden drop in intake vacuum. That's what causes the stumble that occurs, and why the accelerator pump is needed to supply the fuel that would have been brought in by air flowing through the carb. .


Im talking about the stage where the engine is accelerating hard, throttle pinned. The air flow rate is also accelerating, not constant as in your testing.



The fan I used was rated 90 CFM. .



Was this fan flow measured and confirmed?

In anycase. You can do all this testing, but the fact is you put ANYTHING in the flow of air and it is going to disrupt the flow. Therefore the screen has to make a difference. You have to agree with that?

  • MuDPoUNdeR

Posted July 29, 2009 - 04:58 PM

#29

How about a basic test to see how much flow the screen is taking away?

Put the screen up to your face and inhale as fast as you can. Now take it away and see how fast you can inhale.

That's the difference you will notice on the bike. None...

(Make sure your sceen is clean haha)

  • grayracer513

Posted July 29, 2009 - 05:16 PM

#30

You have to agree with that?

No. I don't. Resistance to air flow increases exponentially with velocity, and at no point during the acceleration of either the engine or the air stream is the air resistance of any component going to be as great as at it's peak flow. If you do want to observe the stream accelerating, just watch while the fan is turned on. The results on the measuring equipment will not change.

At any rate, you are creating the impression in me that you don't understand the concepts you are attempting to argue, nor do you wish to, and that you are less interested in gathering information than in sustaining the argument for its own sake. Sorry if that seems harsh, but your question regarding the fan rating is an example of the latter. Owing to that, my discussion with you on this topic is ended.

Thanks for playing.

  • roylo

Posted July 29, 2009 - 07:42 PM

#31

Sorry if that seems harsh, but your question regarding the fan rating is an example of the latter. Owing to that, my discussion with you on this topic is ended.



Sorry but I think the fan having the correct flow in the test is extremely important. I dont see any harm in asking about it. You said the max flow of the bike 85CFM and the fan is rated at 90 so I assume from your reply you believed the fan manufacturers claim and went with that for the test. OK :thumbsup:





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