Oil Filter Bypass or Not + Oil Pump Relief Valve
06-26-2015, 01:16 AM
#16
Here:
06-26-2015, 11:38 AM
#17
Race Director
[QUOTE=gpjli2;12386634]
Yes, the rationale for a filter pressure bypass is to continue to supply oil to the engine in the event the filter becomes clogged.
The problem is the filter doesn't become clogged unless or perhaps if one simply chooses runs the filter way beyond any reasonable amount of time/miles.
Another problem is the filter bypass doesn't work until the pressure is very high. I'm not sure how effectively this would allow oil to flow to the engine with a plugged filter. There is the question too of whether sufficient oil volume could flow through the bypass to supply the engine with enough oil under all operating conditions.
And how I wonder would the driver know this filter plugging condition was present? I would have to believe if the driver elected to leave the filter in service to the point the filter became plugged that he would continue to drive the car until the engine gave out for if not lack of oil from having severely degraded oil.
I suspect I'll be in the minority on this but a filter bypass is a solution to a non-existent problem. I think the pump bypass makes more sense. The engine never receives unfiltered oil. 'course, this requires one change the oil filter at reasonable intervals, to guard against a plugged filter but this gives one a lot (a lot) of room.
For instance, if Porsche believes a Boxster engine could go 30K miles on a filter then it could probably go way beyond 30K miles.
When I asked about this bypass business I was told the bypass routes high pressure oil back to the pump somewhere. There is no bypass for the filter.
As I understand it, should the filter be clogged/blocked for whatever the reason, the bypass will flow oil to the motor. This is ugly but preferable to the alternative ie an engine running with no oil.
In another thread on the subject someone indicated that the correct filter to use in the LN mod has a bypass valve built in to avoid the catastrophic "no oil flow" scenario.
As I understand it, should the filter be clogged/blocked for whatever the reason, the bypass will flow oil to the motor. This is ugly but preferable to the alternative ie an engine running with no oil.
In another thread on the subject someone indicated that the correct filter to use in the LN mod has a bypass valve built in to avoid the catastrophic "no oil flow" scenario.
The problem is the filter doesn't become clogged unless or perhaps if one simply chooses runs the filter way beyond any reasonable amount of time/miles.
Another problem is the filter bypass doesn't work until the pressure is very high. I'm not sure how effectively this would allow oil to flow to the engine with a plugged filter. There is the question too of whether sufficient oil volume could flow through the bypass to supply the engine with enough oil under all operating conditions.
And how I wonder would the driver know this filter plugging condition was present? I would have to believe if the driver elected to leave the filter in service to the point the filter became plugged that he would continue to drive the car until the engine gave out for if not lack of oil from having severely degraded oil.
I suspect I'll be in the minority on this but a filter bypass is a solution to a non-existent problem. I think the pump bypass makes more sense. The engine never receives unfiltered oil. 'course, this requires one change the oil filter at reasonable intervals, to guard against a plugged filter but this gives one a lot (a lot) of room.
For instance, if Porsche believes a Boxster engine could go 30K miles on a filter then it could probably go way beyond 30K miles.
06-26-2015, 01:11 PM
#18
Burning Brakes
Thread Starter
Porsche does call the filter a full flow oil filter in the oil circuit layout (diagram in the After Sales Training 911-Boxster 2002-2007 document), page 28.
So that being the normal mode, the bypass at the bottom of the filter may come into play when starting at below freezing temps, with 5 bar pressure at idle, with a filter at end-of-life, possibly then the pressure drop forcing the oil through the filter membrane can be high enough (until warm-up) to overcome the spring at the bottom of the canister that forces the poppet down, and a portion of the oil supply heading up the oil delivery pipe directly. This would balance out flow pressure drops (across the filter paper) and across the poppet, with some % of oil heading each way until oil viscosity dropped to the point where the EOM canister bypass closed again.
Macster-for your high mile engine (Boxster ?) did you buy it new, what are your oil change intervals, and current mileage ?
Thanks
So that being the normal mode, the bypass at the bottom of the filter may come into play when starting at below freezing temps, with 5 bar pressure at idle, with a filter at end-of-life, possibly then the pressure drop forcing the oil through the filter membrane can be high enough (until warm-up) to overcome the spring at the bottom of the canister that forces the poppet down, and a portion of the oil supply heading up the oil delivery pipe directly. This would balance out flow pressure drops (across the filter paper) and across the poppet, with some % of oil heading each way until oil viscosity dropped to the point where the EOM canister bypass closed again.
Macster-for your high mile engine (Boxster ?) did you buy it new, what are your oil change intervals, and current mileage ?
Thanks
06-26-2015, 03:13 PM
#19
Instructor
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I'm pretty sure he's mentioned 5k intervals, and I believe he uses Mobil1.
01-09-2017, 12:55 PM
#20
02 C4S 63k miles. (sorry, wrong forum, but I think we have same oil canisters)
I bought a new filter with canister for $28. I used some needle nose pliers on the spring at the bottom of the old canister and it seemed to have a good amount of spring tension. Not sure if that was the original oil canister. I change oil every few months as I do about 20k miles a year. Not much chance for my oil to get any where near sludgy.
I am not a fluids engineer but it seems that the bypass would not open all that often. Even on a cold morning, it seems that the pressure drop across a quality high flow filter would not be so high that the bypass would open. I agree that it might open if the filter was used for too long and was starting to resist flow. I am thinking that the bypass in the canister would not open anymore than any other spin filter. If in fact there is no bypass on the Napa 1042 then I start to wonder if that is a good idea. If we start our cars in sub freezing weather, does that mean that oil will just flow very slowly as it struggles to pass through a non bypass filter? Or do we just not drive unless it's warm outside, lol. Not me, I drive it in the snow.
I bought a new filter with canister for $28. I used some needle nose pliers on the spring at the bottom of the old canister and it seemed to have a good amount of spring tension. Not sure if that was the original oil canister. I change oil every few months as I do about 20k miles a year. Not much chance for my oil to get any where near sludgy.
I am not a fluids engineer but it seems that the bypass would not open all that often. Even on a cold morning, it seems that the pressure drop across a quality high flow filter would not be so high that the bypass would open. I agree that it might open if the filter was used for too long and was starting to resist flow. I am thinking that the bypass in the canister would not open anymore than any other spin filter. If in fact there is no bypass on the Napa 1042 then I start to wonder if that is a good idea. If we start our cars in sub freezing weather, does that mean that oil will just flow very slowly as it struggles to pass through a non bypass filter? Or do we just not drive unless it's warm outside, lol. Not me, I drive it in the snow.
Last edited by USNA1970; 02-08-2017 at 10:41 AM.
04-03-2017, 11:41 PM
#21
**** question about oil pressure reading at 5k rpm
The manual says oil pressure should be "at least" 3.5 bar at 5000 rpm. Doesn't say at what oil temp.
I have new 5-40 Mobil 1 with new filter and with oil temp just above 200 I got just 3.5 bar. This is in the garage but not a super hot day and not a super high oil temp.
My 993 used to exceed the recommended pressure readings. I haven't tested my 997 at lower temps.
The 997 showed 2.5 bar at 3000 rpm.
Should the oil pressure read above 3.5 bar if the engine is totally cherry? I have 40k miles. I know this is ****, but just wondering.
Charlie
I have new 5-40 Mobil 1 with new filter and with oil temp just above 200 I got just 3.5 bar. This is in the garage but not a super hot day and not a super high oil temp.
My 993 used to exceed the recommended pressure readings. I haven't tested my 997 at lower temps.
The 997 showed 2.5 bar at 3000 rpm.
Should the oil pressure read above 3.5 bar if the engine is totally cherry? I have 40k miles. I know this is ****, but just wondering.
Charlie