oil filter pressure bypass, remote mount flow?

[Hubert]

What are the oil bypass pressures for the 6.5?
I was reading thread

http://***********.com/forum/showthread.php?t=58756

and others generally about oil pressure and oil temperature etc.

I ran accross this doing a google on it.

http://www.speedwake.com/upload/showthread/t-28021.html

I looked in my helm manual and it shows location of oil cooler bypass and oil filter bypass but they don't give P/N or pressures. It only tells me 10 psi minimum oil pressure at idle warm.

I know of lots of posts on remote mount oil filters and some (a few of my posts too) recommend some over others due to pipe fittings size etc. But never seen one recommending changing oil filter pressure bypass when using remote mount???

I thought I have read somewhere it was low like 15 psi but now I can't find it. The 2nd link says factory big block gas bypasses at 11 psi. I figure 15W-40 the bypass would be higher anyone know?

I figure cold our oil coolers and remote oil filters are getting bypassed a fair bit which is fine but what about at warmer oil temps and considerations for longer remote mount lines and pipping losses?

[Hubert]

uh ohh ******'s guess that was a bad idea. Just trying to learn and spread knowledge to the right people.

[JoeyD]

The bypass is looking for a pressure difference between the pump output to the filter. If a filter became clogged or blocked it would bypass it same as the oil cooler.

[Hubert]

Joey,

I am not so sure about that. Please say your reasoning a different way.

As I understand it...

The oil pump can and will supply 80 psi(according to my '97 book). Why we don't measure 80 psi on guage is the flow is not restricted enough to build 80 psi at the guage you get leakage through all the oil passages (bearings) before the pressure guage and there is not enough restriction after to build pressure it just recirculates.

Not so at the oil pump it will build pressure to what ever restriction it sees up to the 80 psi or flow oil first.

The first place oil goes is to cooler. In cold weather the oil will be thick and slow to move quick enough to keep 80 psi from pressurising the cooler and you don't want flow restricted to bearings so it bypasses some (I think this a simple spring type pressure bypass) Same thing happens at the oil filter. Oil filters will blow out at too much pressure and most have internal bypasses too.

I would think the bypass in the block would be set a little lower than the filter pressure so that when cold oil goes directly to lubrication. Some will still circulate to the filter to warm filter and start it flowing so it can filter all the oil. Othewise once the internal oilfilter bypass is exceeded you are going to get really dirty oil circulating and you don't want that.

In the link it says GM has at least 2 bypass pressure settings for the oilfilter. Remote mount and standard (at least for big block gassers). 30 psi and 11 psi bypass pressure respectively.

Sounds like its to accomidate piping losses in the remote lines. From a couple of posts the piping losses sound fairly significant if the remote location is farther away.

I'd like to know what kind of numbers are involved for the 6.5.

[Bnave95]

I have notice that after my Bypass install that the psi will drop to around 25 during idle once Eng. is warm. Comes back up to 40 off idle.

[Hubert]

It theoretically should not really change the oil pressure at the OE pressure guage because the guage does not care where the oil comes from bypassed or through filter.

However, if its remote mounted and the filter is not absorbing heat from exhaust manifold it may be a bit cooler and increase pressure some. ???? Thats my theory. I have touched on this before but I don't remember anyone commenting on it.

Related:
I have thought about it a little and kind of read some related stuff but never actually posted. In a cool to warm engine (cool oil) normal operating temps but not HOT. When you romp on accelerator, doesn't the oil pressure peak at the pump and blow by these bypasses to keep from stressing the oil cooler and filter element? Hot I think the oil fill flow much easier.

I use to think minimum oil temp was 212F (at normal operating temp) but after several post and more reading I think its approximately 180F-200F ideal temperature.

[ 02-20-2006, 05:44 AM: Message edited by: Hubert ]

[tommac95]

There is a pressure relief valve in oil pump to limit max pressure, as at/after starting cold. There is a bypass valve in each oil filter cartridge, to allow flow to bypass the filter when it becomes clogged [before puncturing filter medium and spilling all accumulated crud through bearings/galleries].
There is a bypass valve in block/filter pad assy vicinity, which allows most flow to avoid cooler when the oil is cold/thick, and pressure is above what cooler likes (and oil needs to heat before lubing effectively).
Helm manual describes refitting the valve assembly in oil filter pad .Usually a shim beneath a spring would change pressure. A couple members have recorded failure of the pressure relief valve in old oil pumps, causing system pressure to fall off.

[Hubert]

There is a pressure relief valve in oil pump to limit max pressure, as at/after starting cold. There is a bypass valve in each oil filter cartridge, to allow flow to bypass the filter when it becomes clogged [before puncturing filter medium and spilling all accumulated crud through bearings/galleries].

Yes the oil pump is regulated at 80 psi. Thats a lot of pressure. More than enough to damage an oil filter.

I see the bit in the manual about refitting the bypasses. But it does not give bypass pressure or exactly what the operation function is of the oil filter bypass valve.

Yes, oil filters have a bypass mechanism internal but I think its only a fail safe to keep element from rupture???. I would think the bypass in filter pad would be set a little less than the filter's internal pop off pressure mechanism. This would ensure flow when cold and would allow a little "flex" with oil flow surges ie rpm changes and oil pump flowrate with out washing crud out of the filter through the pressure pop off internal to the filter.

Anyone know what the bypass pressure is for GM part number 25014006. Its the oil filter pressure bypass valve for a 97-98 CK 6.5 (L56 6.5S,L65/6.5F).

I am concerned as I mounted my remote filter a little farther away from engine with gentle bends in hose ~ approximately 6-7 ft of lines each way. The additional flow friction may be allowing more oil to bypass the remote oil filter and filtering less oil than the OE filter if the oil filter bypass valve is relatively weak.

[Hubert]

OK I have some numbers for the bypass valve and theories on how it actually works but don't have all the numbers or time to post right now.

It took approximately 1.1 - 1.2 lbs force to open valve.

It took approximately 1.7 lbs to fully open the valve (depress spring fully).

Piston area while closed is 0.068 sqin.

So at cold start up this valve will open at approximately 16-17.6 psi

As soon as the valve opens the cross sectional area of piston is 0.148 sqin. This is hard to explain but the piston comes up the sealing surface and this surface has a hole of .294 dia. Thats all the oil sees while its closed. Once open and piston is pushed back the oil sees entire face of piston at approx. 0.435 dia.

Theortically it only takes 9.6 psi to hold this valve half way open once open cold.

OK i know these are perfect world numbers but it gets interesting stay tuned if you have a remote mount set up with close to or more than a couple of feet between the new remote mount location and the OE filter position.

Its really a rather difficult calculation and I am still thinking about proper assumptions for flow numbers and what really happens to valve.

In OE filter mount configuration I think it opens when cold then shuts shortly after and probably won't reopen unless the filter plugs. But with longer remote mount I am not so sure what happens.

[Hubert]

Here are some of my findings and info for comment I welcome better real world numbers, and/or some truths about oil flow. I realize these are some crude calculations and I don