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Old 04-16-2008, 06:54 AM   #1 (permalink)
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Default Oil Filter Bypass Rating

I'm hoping someone with a Subaru Repair Manuel or racing background may know this:

What is the PSI (or equivalent RPM ) when the oil filter opens the bypass valve?

Here is why I'd like to know. I travel alot and there are certain parts of the interstate system lightly policed and therefore I will risk some extentend driving at 95+ mph. At that speed the engine is pushing 4000 rpms and I just want to make sure I'm not bypassing my oil filtration.

Thanks.
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Old 04-16-2008, 07:07 AM   #2 (permalink)
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bypass opens at 23 psi for the OEM not sure what the RPM's are though.
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Old 04-16-2008, 08:11 AM   #3 (permalink)
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Hmm, that's a really good question. 23PSI is pretty high, so I imagine it'd be closer to 5500RPM or so.

I'd also imagine that load has some small, maybe marginal, effect on oil pressure. Probably not worth noting for an N/A, but for a modified turbo engine it might be significant.
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Old 04-17-2008, 04:26 AM   #4 (permalink)
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Anyone running a gage in their car that can comfirm what RPM equals 23 PSI? Just don't blow the engine up trying to find out!
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Old 04-17-2008, 04:50 AM   #5 (permalink)
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Well, all I can say is. I've run at high speeds for extended times, not to mention high RPM's at the strip. My car has yet to blow up at 82K miles. My oil analysis says my motor is still in excellent shape. I think you are getting a case of what I like to call" analysis paralysis". Enjoy your car :)
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Old 04-17-2008, 12:28 PM   #6 (permalink)
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Quote:
Originally Posted by Korrie View Post
Anyone running a gage in their car that can comfirm what RPM equals 23 PSI? Just don't blow the engine up trying to find out!
Umm, 23 psi , you should be around 20 psi at idle , 30 or so at 2500 ...

I dont think the filter bypass will open unless it is plugged .....


Specification on an '02 is NO lower than 14 psi at 800RPM cold and no lower than 43 psi at 5000 rpm warm ....
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Old 04-17-2008, 12:47 PM   #7 (permalink)
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^^ I was thinking the same thing. The oil pressure gauge on MY03 reads 85-90 PSI when cold & drops to 20 PSI or less when at idle (freaky!). The oil pressure is rather odd on the boxer engine, since the pressure varies so much with the RPMs. It freaked me out when I first installed the oil pressure gauge. My son's 95 Neon Sport reads around 60-70 PSI cold & never drops as low as MY03.

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Old 04-18-2008, 07:21 AM   #8 (permalink)
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Thanks guys. That makes a bit more sense. Now that 23 PSI number has me mildly concerned

Here is my sad story to why I'm asking this. I owned a 2002 Chevy Prizm aka Toyota Corolla. It was a great little car that I racked tons of miles on. At one point I was driving it twice daily, 45 miles each way, while maintaining 90 mph. (don't tell the FHP they are probably still looking for me) At around 60K miles the engine started to sound like a diesel. Lots of valve clatter. After some heavy research it appeared that the oil filters would bypass around 3000-3500 rpm. Sustained driving at high speed leaves the oil unfiltered and since it was FL, I was pulling tiny sand particles through the intake. Needless to say the engine suffered a bit.

So if a similar situation occurs on the Subaru engines and filters then I will upgrade to an improved airfilter and perhaps install a bypass oil filter. Or just drive under 90 mph. Naaah.
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Old 04-18-2008, 07:59 AM   #9 (permalink)
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Paragraph 2:

http://www.fhi.co.jp/english/news/pr.../05_03_15e.pdf
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Old 04-18-2008, 08:12 AM   #10 (permalink)
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Whoah! How does a car go continuously for 62,000 miles at nearly 140 mph?
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Old 04-18-2008, 08:21 AM   #11 (permalink)
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Quote:
Originally Posted by Peaty View Post
I think you are getting a case of what I like to call" analysis paralysis". Enjoy your car :)
LOL. The power of paranoia created by car forums can sometimes be crippling.
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Old 04-18-2008, 08:23 AM   #12 (permalink)
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No. They didn't go continuously at 140mph.

They AVERAGED 140mph including rest stops and driver changes. Pitstops and driver changes every 2 hours and tire changes every 96 hours. The whole thing was just under 450 hours.

The motor used was an EJ20T, just like your motor with the exception of the location of the thrust bearing (and obviously the turbo). Mechanically, the two are almost identical.

So they were actually driving at just over 150 while they were moving.

As the article says, almost 20 years later that record stands.
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Old 04-19-2008, 06:05 AM   #13 (permalink)
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So them I'm good for speeds up to 140 mph. Awesome
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Old 04-25-2008, 06:46 PM   #14 (permalink)
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Default They bypass opens when filter restriction is 23 psi....

I'm sure that some of the posters understand this but I'll try to explain it anyway...

I am not sure what the normal "pressure restriction" is on an oil filter, but it's got to be fairly low. You could theoretically push a lot of oil through a filter at 100 psi, and so long as it all passes through the element without generating an internal pressure of 23 psi based on the element "holding back" the flow to the tune of 23 psi, you will have full filtration without anything going through the bypass.

If your filter is plugged with dirt or metal shavings, the restriction of the paper element will increase, and is more likely to open up the bypass valve when oil pressure of the car is high.

I'm new to this forum (just bought an '09 Forester 2.5X stripper with a stick yesterday), but know a ton of useless information, and a bit of useful info, hopefully.

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Old 06-01-2008, 05:36 AM   #15 (permalink)
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Hey I've just noticed this thread. I recently installed a B&M oil cooler which required the oil filter to be remotely located. I thought this was good as the original space by the filter is so tight that a sandwich plate with oil pressure sending units may not have fit. I am now rethinking this. The oil pressure when cold is reading 100psi and 40 at idle. I think this is too high. Has anyone managed to put a sandwich plate with oil temperature and pressure sending units in the space where the original filter goes? I am willing to do away with the cooler but want to keep the gauges.
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