So then, the stock carb configuration is tuned around the fact that the stock filter media limits air flow, correct?
No. Unless, you clog the filter up with dust. The stock carb settings are tuned to the intact tract and the air filter pressure drop.
I know, the air box also smooths air flow, bonus... How can it possibly be a good thing to limit or restrict air flow?
It doesn't, for the stock engine, it's just a fictional point you made up.
The math I have always seen indicates that more air (oxygen particularly) in addition to the correct ratio of fuel produces more power. In addition, the ability for an engine to more readily fill the chambers with that air/fuel mix increases volumetric efficiency, which is good from both an economy and power stand point. So it seems to me, that the stock carb tuning was not the optimal configuration, but rather a patch job to deal with a crappy filter media that was the only thing available at the time...
Yes, more air and fuel of the proper ratio into the cylinder makes more power. You are not going to get that with the stock engine and by simply changing the induction pressure drop.
I don't know why you don't just toss the filter altogether? Why filter at all? In our quest for power, do we even need to prevent the dust, dirt and bugs, from sand blasting the cylinders? Do we mind rebuilding the engine after every time or every few times it's run? (Depends on where it is run)
Ignoring the GI "ladies stockings" trick of WW2. Also seems to me that we should be overjoyed at the ability to retune the carbs to work with a more free flowing filter that creates less of a pressure differential at the media. Let the thing BREATHE. And we should be doing so in a manner that creates a suitably clean, smooth flow... And should allow for a hardtail or Konged frame, and not look like a big black box.
Free flowing it rather a myth often used as sales pitch. The stock clean filter flows plenty for the stock engine to make power at red line RPMs. Most of street driving is nowhere near any "flow limits" for the stock engine or stock air filter.
If you don't care how long the engine lasts, then let it breath without a filter. Stacks look better in a hardtail or konged frame and who cares how long the engine lasts? Do you really need a hardtail or konged frame bike to last 100,000 miles?
I have read TT's very fine posts, and do understand why there is a big plastic box. My point is, that while the stock filter assembly is very well thought out, and very well engineered, it is not the ultimate solution.
It was for it's era, I think. And it works well as delivered. Today, no, probably not ultimate. Go to modern bikes if you want an ultimate solution, along with fuel injection, Ox sensors, and closed loop fuel metering with a computer. Heck, add a pressure sensor too, to compensate for altitude changes.
Paper filters are still used the world over primarily due to cost considerations.
Yes, both cost and the very small particle size it allows through to the cylinder walls.
There are a multitude of other filter designs that perform far better (including less pressure differential across the filter media) in both filtration and flow, excluding oiled cotton filters.
I'd like you to elaborate on that. Please, name brands and filter specs. We could all benefit from that data!
Even though I use K&N clones on most everything, except my Jeeps, they got real K&N's... due to shape constraints, otherwise I would have gone cheap-o.
You know that "cheapo" does have a quality implication.
Ultimately, what I was saying is that there IS a better way to do it. Pods, unfortunately are not it.
I expect there is, today. We have already talked about a much larger air plenum, and much larger filter area.
The real question is WHY you feel the need to do it. Do you expect to get power levels from the engine comparable to modern bikes? How much money do you wish to put into a 30 year engine design? I suspect, that since hardtails and Konged frames seem to be what you favor, you are just looking to change things, and the filter box is just another object to change. But, I'm just guessing Perhaps you have other ideas.
I DO understand the limitations of the pod design, I DO understand turbulence and flow. I have an extensive library dedicated to all things gearhead oriented. Including several books on carburetors, one for every type I own (excluding these...) and a very good general one called Carburetors, and another dedicated to intake design. Do not talk down to those you do not know, unless they state something that is factually untrue.
Which you did about the flow issue. Do I now have permission?
Speaking of which, whether or not there is a honking big filter, if there is a pressure differential (which TT has time and again stated is necessary for proper tuning) created across the filter media then the filter is not flowing as much as the engine can ingest.
Science does not support that statement, I'm afraid. It does consume more energy to maintain the same air flow. But, the pressure drop alone does not freely equate to reduced flow.
If the flow rate of the filter was sufficient, then there would be no vaccum created.
Huh?? The vacuum is created at the falling piston (and at the venturi). And science does not support your flow rate theory, sorry.
Did you mean to say pressure drop?
Granted, all filters create a impedance to flow.
Agreed, related to air velocity.
The trick is to find the one that creates the least impedance.
Not so tricky, unless you include a requirement for the same particle size block capability.
And yes an aftermarket filter in the stock assembly does fit the bill. However, that still leaves the issues of size, location, and style to be addressed.
Well, we've had the style argument already. For some, that trumps everything else including science and ideal function.
Cheers,
