Wix 57002 quality

[ZeeOSix]

What got me initially interested was this site. It was the best description of the differences between the two mazda filters I had seen.

https://artsautomotive.com/art-icle...mazda-oil-filters-1wpe-14-302-vs-1wpy-14-302/

While it didn't provide specific valve opening pressures, the spring test they conducted indicated a significant difference in spring rate. I then did the customary online/google search. For the NA filter most numbers I quoted came from Mazda forums like Miata.net which I have found credible. For the turbo filter I actually found some numbers in a thread here on BITOG. The number (or range) I quoted was also found on some other mazda forums including a Mazda cx5 forum. I can only assume these numbers are reasonably correct/accurate.

Reading the info in that link, all he did was measure the spring rate of the bypass valve spring. He never calculated what PSI would start opening the valves. As you said, all he found was one spring was stiffer than the other. He needed to measure the active area of the valve, then calculate the PSI based on the area and how much force it took to crack open the valve. Maybe you saw that kind of info someplace else - ??

From the linked article, it said:
"The 1WPY’s spring is 3300 grams @ 1mm of compression. The 1WPE’s spring is 2200 grams @ 1mm of compression. This is a pretty big difference."

Those are pretty stiff springs, as 2200 grams is 4.85 lbs and 3300 grams is 7.28 lbs. That much force to compress the springs only 1 mm means they are pretty stiff. But again, the PSI opening pressure would depend on the pressure area of the valve.