Finding the Oil Bypass PSI number

[pedaltothemetal]

On a cold start my late model GM engine sees 60psi max even at low rpms. It stays there until the oil warms up enough to drop the psi down to 25psi at low rpms and will climb to 40psi at higher rpms. Is it safe to say, 60psi is the bypass level, cause it never gets higher than that no matter the rpms when the engine is cold. Am I also safe to say, 40psi when the oil is hot is always in the non bypass. If this is so, then during my longer drain intervals, I will keep an eye on my max hot oil psi. If it starts to creep to the 60psi max, then I will have to change the oil filter cause it will be clogged and causeing bypass. If not, then will go the full 10,000 miles extended oil change interval without a oil filter change. I'm running 15w40 Royal Purple and the Delco OEM PF44 filter.

Leo

 

[Ken2]

Your oil pressure is controlled by the oil pressure control valve, not by the oil filter bypass valve. The bypass valve only looks at the difference between the inlet side of the filter and the outlet side and opens to limit the maximum differential pressure, maybe 8 psid or 10 psid, or whatever it's set at.

Your GM engine has the oil filter bypass valve built into the engine, not the filter. It has no effect on your engine's oil pressure. Oil will get to the parts of your engine with a one or two psi drop through the filter when the oil is hot and the filter clean, and it will have the maximum drop allowed by the bypass setting when the oil is cold, what?...8 psi.

I know of no way to determine when the oil filter bypass valve is open or closed. Well, one way, but it won't be effective. If your engine mounted filter bypass valve wasn't letting any oil get to your filter, the filter would stay cold when the oil was warm. But, part of your oil will continue to filter, so the filter can will get warm.


Ken

 

[pedaltothemetal]

On GM engines is the bypass valve parallel to the filter, and only opens gradually when the pressure is sufficint enough to start opening this bypass valve?

Leo

 

[Mike_dup1]

quote:

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Originally posted by pedaltothemetal:
On GM engines is the bypass valve parallel to the filter, and only opens gradually when the pressure is sufficint enough to start opening this bypass valve?

Leo

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Looking in my 2002 LS1 service manual its show there is a pressure relief valve in the oil pump and a bypass valve mounted in the oil filter housing. This would be the same for the late model trucks as they are based on the LS1 engine design. If you take off the filter, and look up you will see the bypass valve off center of the oil filter fitting.

I am still looking for spec's on these in the manual but have not found them. Does not appear to be there. But I did find a definition of excessive oil comsumption

quote:

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Excessive oil consumption, not due to leaks, is the use of 1 quart or more of engine oil within 1,500 miles

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It also goes on to state that improper oil viscosity can be the casue of excessive oil consumption.

[ February 09, 2003, 05:47 PM: Message edited by: Mike ]

 

[Ken2]

quote:

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Originally posted by pedaltothemetal:
On GM engines is the bypass valve parallel to the filter, and only opens gradually when the pressure is sufficint enough to start opening this bypass valve?

Leo

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The oil filter bypass valve begins opening when the pressure difference between the inlet of the oil filter and the outlet of the filter exceeds the valve's set point. The bypass valve doesn't know nor care if the oil pressure is 10 psi or 100 psi. It only knows about the differential of pressure across the filter. Yes, in parallel with the filter.


Ken

 

[Patman]

FWIW, my LS1 Formula behaved like that, and my LT1 Formula goes to about 50psi and stays there for a while after a cold start, even at idle.

As far as the oil consumption on LS1s, since a lot of guys report that mixing in 2qts of 15w50 actually stops their oil consumption, I think these engines would do best with a very high 10w30 (like Amsoil) or a thinner 10w40 (like Redline, Royal Purple or Amsoil)

[ February 09, 2003, 07:59 PM: Message edited by: Patman ]

 

[pedaltothemetal]

OK.
So oil pressure is the restriction of the myriad of small orifices the oil pump has to pump against and thru. These small orifices are the main restrictions, and not the oil filter. The filter is just sitting in the main artery of oil flow, and a bypass will open if the oil filter becomes a restriction with a pressure differential between it and the oil capillaries. Sounds about right!

Leo

 

[Mike_dup1]

More fuel for the fire.

quote:

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Bulletin No.: 00-06-01-025A
Date: September, 2001
INFORMATION
Subject:
Correct Oil Viscosity and Oil Filter Usage for the Duramax 6600 Diesel Engine (RPO LB7)
Models:
2001-2002 Chevrolet Silverado and GMC Sierra 2500 HD and 3500 Models with 6.6L Engine (VIN 1 - RPO LB7)
This bulletin is being revised to add the AC Delco oil filter part number and add the 2002 Model Year. Please discard Corporate Bulletin Number 00-06-01-025 (Section 06 - Engine/Propulsion System).
Important :The Duramax 6600 diesel engine can produce oil pressures over 690 kPa (100 psi) during a cold start condition and the oil pressure gauge may remain near 552 kPa (80 psi) while driving. Because of these oil pressures, it is important that the correct oil filter is used and torqued properly and the proper oil viscosity is used for the ambient temperatures.
Oil Filter
The correct oil filter for use on the Duramax 6600 engine is the AC PF2232 or the production oil filter, GM P/N 97214983. This filter was designed specifically for use on the Duramax 6600 engine and incorporates improved filtering capabilities as well as an integral oil pressure relief valve. The oil filter should be torqued to 24 N.m (18 lb ft) to prevent leaks under high pressure conditions.
Oil Viscosity for Cold Weather Operation
SAE 5W-40 viscosity oil designated as API CH-4 or CG-4 should be used if the ambient temperature falls below -18°C (0°F) to prevent excessive oil pressure on a cold start. Refer to the Owner's Manual diesel supplement for additional information on proper oil usage for other operating conditions.

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[Ken2]

No fuel, no fire.

The valve inside the D-max filter is doing just what we're talking about. If the oil is cold and thick the resistance of that thick oil trying to flow through the filter will become excessive creating excessive pressure differential within the filter. That pressure differential will be relieved by the filter's internal valve.

We're talking about the same thing. There is more than one way to describe what's happening.


Ken

 

[pedaltothemetal]

Does anybody know if the pressure goes down or up on a late model GM car when a filter gets clogged. I guess it depends where the pressure sensor is located. I want to keep my eye on my pressure gage during my long drain interval.

Leo

 

[JohnnyG]

But what about oil shear? If the oil gets thinner during use as M1 does initially,(posted elswhere on this board) how would you know what to attribute the pressure changes to? And to what degree? I knew a guy once that would change his oil when the pressure went down. of course this was 30 years ago and oils were a little different back then. Seemed to work on that Red/White '62 Ford Galaxy 500 Convertible!