What By-pass pressure should I look for?

[TrentMiller]

Hi guys, My normal oil pressure is 25-37 psi (warm)

I usually idle around 25 psi, and cruise at normal/high temps around 30-35. (1750 rpm at 65 mph) At higher rpms 2200-3000 i see a warm 70, hot 50, rare that i go past 2000 rpm though.

I've run m1 0-40 (speced) pre t6 Rotella 5-40, t6, Delvac 1, and tdt. and they pretty much have the same pressure at warm/hot temps.


Now the problem, i've used oem, m1-301, and recently wix 1516
They all seem to have the bypass set to 8-11 psi.

This is significantly lower than my lowest oil pressure, in fact the FSM for my vehicle stats the minimum oil pressure is in fact, 12 psi at hot idle. I've never seen anything below 24 psi.

Should i be looking for a filter with a higher by pass? Something in the 35 psi range maybe?

On "cold (san diego)" starts i always peg the pressure gauge at 100 psi idle for 1-5 minutes depending on temps.

My gauge is an after market, self installed gauge, verified it with a physical test gauge manufactured by caterpillar.

Vehicle is a 2006 Jeep liberty crd with the turbo diesel i4 2.8L

I have about 5 UOA's 4-9k oci. and they always show insolubles of .3, and i have egr blocked.
Oil is always very sooty. I have considered Centrifugal filters or a secondary bypass setup, have limited physical room, would like to get this sorted.

Thank you for your comments.

 

[chevrofreak]

You are misunderstanding what the bypass PSI setting means. It is not absolute pressure, but pressure differential. It is the pressure difference between the inlet side of the filter and the outlet side. It is to allow enough oil to flow into the engine if the filter media is being too restrictive (either plugged, or the oil is cold).

 

[widman]

As said, it is differential. It should be what your engine requires. Engines and pumps are different.

 

[TrentMiller]

Thanks guys.

I should have thought about that one.
I cant believe i..

Anyway, thanks.

 

[FZ1]

What is the oem oil weight spec?

 

[daman]

When i cross i look for the filter with a high BP rating that way you know a little more oil is going through the filter media vs the BP upon cold starts,etc....

 

[Gary Allan]

Quote:
On "cold (san diego)" starts i always peg the pressure gauge at 100 psi idle for 1-5 minutes depending on temps.


If this is your peak stable pressure (not "pushed" to that level), this is where you're at peak PSID across the media. Outside of loading (not usually a big factor) this is the principle time a filter bypass valve MAY be shunting flow. It's when the pump is in relief.

No relief event from the pump, VERY little (virtually NONE) PSID.

That's the way it works.

 

[widman]

Originally Posted By: daman
When i cross i look for the filter with a high BP rating that way you know a little more oil is going through the filter media vs the BP upon cold starts,etc....


This is exactly what you don't want.On startup you want the oil to get to the engine parts as fast as possible. Remember it is filtered every few seconds that the engine is running. Every few seconds that it runs dry wears bearing and valve train.

Quote:
On "cold (san diego)" starts i always peg the pressure gauge at 100 psi idle for 1-5 minutes depending on temps.


Are you saying you hold the accelerator down to max out the pressure to 100 psi? Remember pressure is inverse to flow. High pressure means reduced flow and heart attack for human or engine. You want it to run lower than 1700 rpm or so until the temp gauge starts moving up. Only then is the oil thin enough to properly circulate.

 

[daman]

Originally Posted By: widman

This is exactly what you don't want.On startup you want the oil to get to the engine parts as fast as possible. Remember it is filtered every few seconds that the engine is running. Every few seconds that it runs dry wears bearing and valve train.

Not a issue...between what your media is flowing and what the BP is flowing your going to get PLENTY of oil supply,just more is forced through the media vs the BP..they both still flow and nothing ever runs dry.

let you in on a little secret...i have a '83 5.7 with the BP closed OFF!,100% filtered oil,instant oil pressure upon start up,and the engine runs fine been like that for thousands of miles run a NG on that beast.