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-   -   Bypass effectiveness BMK13 vs. BMK11 (http://www.peachparts.com/shopforum/tech-help/34397-bypass-effectiveness-bmk13-vs-bmk11.html)

adamrei 03-24-2002 02:39 PM

Bypass effectiveness BMK13 vs. BMK11
 
Seems I am still looking for an informed mind on this. The BMK13 setup looks attractive for maintenance purposes but I still have an unanswered previously posted concern (reply):


Thanks for yor reply. I was referring to the BMK-13 diagram shown by ck42 (a reply to bypass filtration post by LightMan)and applicable to those of us that have spin on oil filters. It seems to me from the picture (BMK-13 diagram) that since the bypass and full flow filters operate in parallel in this set up, and the intake and exit pressures differ by the pressure drop across the lines, then the effective pressure across the bypass filter seems to be rather small. An electric analogy may work here, if you have a small resistor (full flow) in parallel with a large resistor (bypass) the current division states that most wil flow through the full flow with the voltage drop (pressure differential) being the same across the two elements. So, when compared with the set-up of outlet return to the sump (The BMK-11 setup) I think that the effective pressure is the oil pressure minus crankcase pressure. This effective pressure seems to be significantly higher than the BMK-13 set up, and since the bypass offer significant restriction to flow due to its arrestance rating (1 micron?) it would seem to me that it would work/flow better and clean faster with a higher effective pressure. Can somebody shed some light on this observation please? Thanks.

so, BMK-13 looks attractive but when compared to the BMK-11 it seems to be way behind in flow/effectivenes/speed of contaminant removal since all are directly proportional to the pressure across the bypass filter element. Please comment. Thank you.

LightMan 03-24-2002 03:16 PM

both about the same
 
they both work at about the same efficiency. You're right on with your thinking, aside from the fact that the Bmk-11 has a resistor installed in the return line. I think this is done because they don't want to divert TOO much oil away from the full flow system which protects your engine, but i'm not totally sure on that.

Just a note- many tap the return line into the valve cover instead of the sump, this may be easier for you, I dunno.

LightMan 03-24-2002 03:17 PM

more effectiveness
 
if you want more filtration, try to fit the biggest bypass filter you can, they are offered in a few different sizes.

adamrei 03-24-2002 04:08 PM

Hi LightMan. Thanks for your reply and for starting an interesting thread!. Yes, there is an orifice restriction to limit the volume diverted, However, it still seems to me that even if restricted, volume is only restricted since hydraulically, about the same pressure exists.....we are back to the issue of pressure across the element and its effectivenes. So, the question is how effective is the BMK13? or in other words, you need extra hardware to properly bypass.......there are no shortcuts.......or BMK13 is marginal when compared to the more hardware intensive BMK11 with lines going to the sump(another issue, you may not want to return to the top of the engine on account of flooding??) or the statement is : the only way to safely and properly bypas the oil is : restrict the volume (orifice), apply maximum pressure across the element, and return to the sump (to avoid flooding on top during high RPM on account of different engine architecture plans?) PLease comment. Thank you all for your great input.


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