Just curious as to when an oil filter would go into bypass mode?
Bypass Mode? When does it happen?
- Thread starter bustednutz
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If it is plugged. It's better to go into bypass to let unfiltered oil through than to let no oil at all through.
Oil pressure is higher than the filter's bypass is set to flow, to lower restriction.
Say you are running a cold engine under high load so the oil is still pretty thick and doesn't want to flow well, the filter will bypass to eliminate the restriction of the filter to keep the flow up.
Say you are running a cold engine under high load so the oil is still pretty thick and doesn't want to flow well, the filter will bypass to eliminate the restriction of the filter to keep the flow up.
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Whenever your oil pump is in relief there's a potential for bypass valve action. Otherwise, it can also potentially occur if severe loading is present. Otherwise, outside of some transitioning event (shifting @ 7000 rpm where inertia trumps mechanicals) rarely. Cold starting, where the pressure generated exceeds the relief valve setting on the pump is the most likely time for this to occur. The oil mass may not be able to get to speed fast enough, the oil pump does a burn out until it "hooks up" moving the heavy load ..the train starts moving ...blablabla.
When ever the pressure on the inlet side has enough difference from the pressure on the outlet side to overcome the spring pressure on the bypass valve. "differential pressure"
I too am curious about the filter going into bypass. For example, on my 07 Altima 3.5SE, the filter goes into bypass at 8-11 PSI. Using the formula that A.E. Haas used in his paper "Motor Oil 105", i.e., 10 PSI per 1000 RPM, I am lead to believe that any RPM over 2000 (2000 RPM equals 20 PSI oil pressure) would result in the filter going into bypass, and no filtration occurs. Am I correct? Does this mean that the oil is only filtered when the oil is at or near normal operating temperature, and the engine is at a low enough RPM to have less oil pressure than the maximum oil filter bypass setting? What am I missing here? Am I thinking too much--or not enough?
I don't know why people worry about their oil filter needing to go into bypass operation when the engine requirements need it too. The only scenario I can think of that would be harmfull to the engine by going into bypass is if the oil filter wasn't cleaning the insolubles out of the oil while not bypassing the filter element under normal operation. But in that case, nothing's going well for the engine anyways.
Originally Posted By: cookieman214
I too am curious about the filter going into bypass. For example, on my 07 Altima 3.5SE, the filter goes into bypass at 8-11 PSI. Using the formula that A.E. Haas used in his paper "Motor Oil 105", i.e., 10 PSI per 1000 RPM, I am lead to believe that any RPM over 2000 (2000 RPM equals 20 PSI oil pressure) would result in the filter going into bypass, and no filtration occurs. Am I correct? Does this mean that the oil is only filtered when the oil is at or near normal operating temperature, and the engine is at a low enough RPM to have less oil pressure than the maximum oil filter bypass setting? What am I missing here? Am I thinking too much--or not enough?
I think you are confusing oil system pressure with ingress/egress oil filter differential pressure. The filter will go into bypass once 8-11 psi difference of the pressure going into the filter from the pressure going out of the filter. Does that make sense?
I too am curious about the filter going into bypass. For example, on my 07 Altima 3.5SE, the filter goes into bypass at 8-11 PSI. Using the formula that A.E. Haas used in his paper "Motor Oil 105", i.e., 10 PSI per 1000 RPM, I am lead to believe that any RPM over 2000 (2000 RPM equals 20 PSI oil pressure) would result in the filter going into bypass, and no filtration occurs. Am I correct? Does this mean that the oil is only filtered when the oil is at or near normal operating temperature, and the engine is at a low enough RPM to have less oil pressure than the maximum oil filter bypass setting? What am I missing here? Am I thinking too much--or not enough?
I think you are confusing oil system pressure with ingress/egress oil filter differential pressure. The filter will go into bypass once 8-11 psi difference of the pressure going into the filter from the pressure going out of the filter. Does that make sense?
Originally Posted By: INDYMAC
I don't know why people worry about their oil filter needing to go into bypass operation when the engine requirements need it too. The only scenario I can think of that would be harmfull to the engine by going into bypass is if the oil filter wasn't cleaning the insolubles out of the oil while not bypassing the filter element under normal operation. But in that case, nothing's going well for the engine anyways.
The other thing that usually gets overlooked is that when a filter is in bypass, not all the oil bypasses the filter element, only enough to keep the pressure drop across the element down to the bypass pressure limit.
When a full flow filter goes into bypass, it doesn't stop being a filter it becomes a high flow rate bypass filter.
I don't know why people worry about their oil filter needing to go into bypass operation when the engine requirements need it too. The only scenario I can think of that would be harmfull to the engine by going into bypass is if the oil filter wasn't cleaning the insolubles out of the oil while not bypassing the filter element under normal operation. But in that case, nothing's going well for the engine anyways.
The other thing that usually gets overlooked is that when a filter is in bypass, not all the oil bypasses the filter element, only enough to keep the pressure drop across the element down to the bypass pressure limit.
When a full flow filter goes into bypass, it doesn't stop being a filter it becomes a high flow rate bypass filter.
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I've tested filters that were 9k old ..in cold starting temps with heavy oil. The whole thing is way over blown ...REALLY. Now one engine or another can surely react differently. If you've got larger oil galleries that empty upon shutdown, then, until they're fully enveloped, you can see your elevated PSID ..and, as I mentioned, when the oil pump is in relief ..but these are transitional states and not long lasting.
I'll have to fill in the blanks for you ..the images are missing. I had thought that I had copied them ..but apparently I did not.
read this
The temp was sub-freezing - the oil was a 15w-40 (it was supposed to be 20w-50) and the max PSID was near 10 PSID. I used a differential pressure gauge in a remote dual mount where I used the second filter boss as a place to tap in the pressure tubing. I used the other ports for temp senders.
From loading, imo, it would take a very long time or a very dirty engine to wear out a filter. Otherwise, it's mainly how "much" you're in relief at startup (and beyond). The pressure differential is some relationship between the pump output and the flow realized to the engine. I can't mathematically model it ..except in reverse. That is, when the flow is 100% to the engine, the differential evaporates ..hence one would reason that the differential is an expression of flow divergence. One can also reason (but I cannot prove) that the lost flow can be some +/- of 100% vs. realized pressure.
For example: 80 PSI relief setting.
Upstream pressure/downstream pressure/PSID/ assumed diverted flow
80/70/10PSID/12.5%
50/40/10PSID/20%
Now these are always transitional states. The oil can't move from a standstill to pump speed on a dime, so you've got some tire spinning initially if the stuff is too heavy. As the fluid gets in motion, the differential retreats, even if the viscosity hasn't changed much.
I'll have to fill in the blanks for you ..the images are missing. I had thought that I had copied them ..but apparently I did not.
read this
The temp was sub-freezing - the oil was a 15w-40 (it was supposed to be 20w-50) and the max PSID was near 10 PSID. I used a differential pressure gauge in a remote dual mount where I used the second filter boss as a place to tap in the pressure tubing. I used the other ports for temp senders.
From loading, imo, it would take a very long time or a very dirty engine to wear out a filter. Otherwise, it's mainly how "much" you're in relief at startup (and beyond). The pressure differential is some relationship between the pump output and the flow realized to the engine. I can't mathematically model it ..except in reverse. That is, when the flow is 100% to the engine, the differential evaporates ..hence one would reason that the differential is an expression of flow divergence. One can also reason (but I cannot prove) that the lost flow can be some +/- of 100% vs. realized pressure.
For example: 80 PSI relief setting.
Upstream pressure/downstream pressure/PSID/ assumed diverted flow
80/70/10PSID/12.5%
50/40/10PSID/20%
Now these are always transitional states. The oil can't move from a standstill to pump speed on a dime, so you've got some tire spinning initially if the stuff is too heavy. As the fluid gets in motion, the differential retreats, even if the viscosity hasn't changed much.
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