Originally Posted By: Phishin
Doesn't the basic laws of physics DEMAND that you can't have ultra fine filtration and ultra high flow rates?? ...
Use our air filters in our cars for example: when the filter is brand new, the flow rate is at it's highest, but this is when the filter efficiency is at its worst. As the filter gets dirty, the flow rate decreases, but the efficiency increases.
Because you are not using a proper definition to the application, nor understanding the limits as a whole.
What is "
fine filtration" in you context? Yes, there are some filters from Fram (and others) that have a very high efficiency (99% or there about). But at what particle size? 20um, generally. And the media (both the cellulose/glass TG and syn media FU) has MORE than enough ability to pass fluid; typically about 2x the volume that the pump is going to push. Most filters can flow around 10gpm or more; that's more than the pump will deliver. So, yes, if you understand how the situation is set up, then filters can be both "fine" and "high flow". Now, if you asked if they could be 99% at 2um, and flow 100gpm, given their current sizes, then you'd be out of luck there; no TG or FU is going to be able to do that.
When you consider true BP filter elements, they are designed for very high efficiency at very small particle size, with a concession to low flow. But if you desired, you can run 10 of them in parallel (10 x 10% flow for each for a total of 100% flow) and you'd have what you needed, although you'd struggle to find a place to mount them all under the hood!
So the difference is that a FF filter is "fine filtration" and "high volume" in context.
In your air filter example, you are generally correct. But what you fail to conceive, as do most folks, is where those criteria
start at, especially the former of flow rate. Most folks wrongly think that an air filter is sold in the box at a volumetric flow such that it's delivered to you at 100% of the design need when new.
THAT IS WRONG! An air filter is grossly over capacitized in terms of flow, so that as it ages and loads up, it still does not restrict flow below the "need" of the engine. Allow me to throw in some hypothetical numbers ...
Assume an engine needs a MAX of 750 cfm at WOT to produce the designed intent of max power. When they spec an air filter, they don't spec a filter that is 750-800cfm out of the box; they choose a filter that might provide 1200-1300 cfm out of the box. That way, even as it ages, the diminished flow capacity of the air filter due to ever increasing loading does not drop below the intended total max draw of the engine. It is a false presumption that most folks make. Even at the edge of it's intended FCI, the air filter probably would flow 900 cfm; well above the 750cfm required by the engine. So while you can see that the air filter lost 25% of it's "new" flow rate (from 1200 down to 900), it's still OVER the engine requirement by 20% (900 is > 750 by 20%). Again - these numbers are made up, but the CONCEPT is REAL!
Now, most assuredly, there are conditions that are going to send this upside down, but that is NOT by design intent, but rather neglect. If you ignore a filter change (air, oil, etc) to a point where you send the filter into a condition where it actually does grossly alter the flow, that is NOT the fault of the filter; it's YOUR fault for exceeding a design condition! There is no filter (air, oil, tranny, etc) that is under-capacitized from the OEM or aftermarket supplier. They are all grossly over-sized (in terms of performance to design spec, not "size") so there is a wide margin of error built into the product. There are conditions (total neglect; total abuse; total sludger; etc) that may exceed the ability of the filter, but that's not "normal" by any means.
This entire topic is actually about capacity; will the product have enough total ability to perform (both in flow capacity and contamination holding capacity, at the designed efficiency beta) such that the design intent is upheld? Filters are sold with a huge excess capacity in mind, so that as they age, they still are capable of providing the required flow and efficiency that the OEM had in mind. They will catch the intended size of particulate at the required efficiency, at well above the needed volumetric flow. They are designed in terms of efficiency and flow to exceed demand at worst case of the "normal" expectation.
I personally have run every-day filters such as the WCOD (white can of death; aka tearolator) for 10k miles and MC FL400S for 15k miles. Upon autopsy there was nothing horrid that happened inside; they were fine. I ran them for 2x and 3x the "recommended" distance, and they did their job well. The filter dissection was OK; the UOAs were great. I am NOT stating that this is smart for all people to do; you must understand the risks and benefits. But the reason I did it was to PROVE that there is a HUGE amount of excess capacity even in "normal" oils and filters. Therefore, those who run typical OCIs need not worry about the "need" for premium products. I did it to prove to folks that everyday lubes and filters are way more capable than your "normal" OCI will ever be able to stress their potential.
Whereas most folks in this thread have made decent points about syn media this and pump rate that, the concept comes down to one of capacity. I can assure you that most any product offered by an OEM or credible aftermarket can provide what is intended, and a whole lot more than your engine "needs".
The bottom line is this:
the products are sold "new in box" not at the max application need; they are sold well above that requirement so that as they age in service, they continue to have capacity above the max designed condition requirement. And then once you understand how your definition of "fine filtration" and "flow" fit into the equation, it all makes sense.
Quote:
This chemist, doesn't see how that's possible.
Being a chemist and not a mechanical engineer, you're forgiven.
Just kidding!