I will be updating my PCV line oil trapping article, soon, but in the meantime, here's more info about my favorite coalescing filter:

As some of you know, I measured PCV line flow and pressure at idle and under higher RPM conditions. Flow was approx. 36-39 LPM and vacuum at about 20 inches of mercury (equivalent to about 10 psi vacuum). The coalescing filter I chose contains tightly wound borisilicate glass fiber that is dense enough to trap all oil aerosols, while still allowing up to 8 CFM of flow (at 100 psi). Recently, Watts published additional data and I thought I'd share the details.

1) At an inlet pressure of 10 psi (pressure or vacuum) allows a flow-though of 1.7 CFM (48.1 LPM), plenty more than what our cars are generating.

2) A grade 6 (0.3-micron) filter is 99.97% efficient, allows just .008 PPM (parts per million) of oil carryover, and filters particulates to .01 microns.

3) A grade 10 (0.6-micron) filter is 95% efficient, allows .85 PPM oil carryover, and filters particulates to 0.7 microns.

Needless to say, this Watts filter "cleans up" oil better than anything I've ever seen that is used as an oil trap in C5s.

Thus far, my filter has over 1500 miles of easy to very hard use and it is still filtering like a champ!

Original article: http://www.conceptualpolymer.com/PCV...oval%20101.pdf

Dave

 

Flow across a filter is usually defined in terms of pressure drop.
It sounds like your filter flows 48.1 LPM at a 10 psi pressure drop, which would significantly reduce flow compared to no filter and no pressure drop.

I like your idea and would like to have one of these, but I'd still like to know flow with and without the filter.
Can I talk you into taking a regulated compressed air supply at 10 psi, and seeing how long it takes to inflate something like a garbage bag THROUGH THE PCV VALVE without the filter, and then with a used, oil impregnated filter added?

Oh, about how much oil have you removed from the reservoir in the 1500 miles?

 

 

Actually, I measured pressure drop across my filter as 0.1 psi. That is insignificant, in my book. More info to follow.......

 

Are these (Watts filters)available at Graingers?

 

No, they are available through most Watts distributors:

http://www.wattsfluidair.com/Distributor.html

Getting back to Warp factor's questions - If you have a measured flow without any restrictions and then place a filter in-line with the direction of flow, that filter is generally considered "clogged" if the pressure drop across it is approx. 10% of the pressure without the filter. So, for a line that "sees" 10 psi of pressure or vacuum, a 1 psi pressure drop may be cause for concern.
Keep in mind that I measured a 0.1 psi pressure drop after subjecting the Watts filter to more than 1000 miles of driving. How much oil you trap is directly related to the amount of blowby your engine piston rings allow, so one engine may provide much more oil to trap, compared to another. I sized my extended housing so that I shouldn't have to empty it for about one year (5000 miles). However, if it starts filling up at a faster rate, or if it slows down, further investigation may be necessary. When it comes to filtering oil, flow/pressure variation, filter density, and pressure drop should all be considered before selecting a coalescing filter.

Dave

 

thanks for the updat dave. i cant wait to get my car on the road to see how it works out with yr can and the amw can

 

Pat,

I think I can safely say that after using a filter that allows only .008 PPM of oil carryover, your intake will be MUCH less oily, especially when compared to using just a common, low-tech catch can.

Dave

 

So pressure drop was .1 psi at 30-something LPM? If so, that's impressive, especially with an oiled filter.

I still can't figure out what Watt's specs mean:
"At an inlet pressure of 10 psi (pressure or vacuum) allows a flow-though of 1.7 CFM (48.1 LPM), plenty more than what our cars are generating."

Usually if they mention supply pressure and don't mention pressure drop, the other end is atmospheric. That would be a 10 psi pressure drop.

 

They do list a chart of pressure drops, but those numbers are for filters that "see" 100 psi. It's not really relevant to our conditions. This is why I mentioned that for a typical 100 psi and high-flow application, a 10 psi pressure drop (differential) across the filter is reason to replace the element itself. What would be interesting to find out is what kind of flow change occurs when GM's new PCV valve replacement, a simple oriface, is installed. My guess is that the oriface restricts flow and hence, the amount of oil that flows to the intake, whether in liquid, aerosol, or both forms.

 

You guys must have way too much time on your hands....