Filter Bypass valve opening pressure. H in MM. Outer W in MM. FRAM HP1. 1.5 Bar / 22psi. 145. 92. Mann W791/5. 2.5 Bar / 36.25psi. 123. 76. Mann W 940/1. 1.2 Bar / 17.4 psi. 142. 93. (GSF) 120LR0070. 1.2 Bar / 17.4psi. 142. 93. (K&N) HP-3001. 0.55-0.75 Bar / 8-11 psi. 145. 93. (Anyone know how to post a table correctly?) Hope this info is of use to anyone with external oil filters on Type one engines I've always used the Mann W791/5 as a cheaper alternative to the Fram HP1. My engine builder recommend it and I know others on here use the same filter (@mikedjames) Last night a few people told me that the Mann W719/5 filter's bypass pressure valve is too high rendering it pointless and that i should use the GSF filter above I don't really understand, so I thought id post this info as it may be helpful to others and so I may learn more about the matter. Am I right in thinking that the w719/5 oil filter is bypassed (not filtering the oil) if the oil pressure is below 2.5 Bar? Isn't the idea to filter the oil as much as possible, including at lower pressures? Links: http://www.fram.com/media/7069/fram_hp_product_specs.pdf https://catalog.mann-filter.com/EU/eng/catalog/MANN-FILTER Katalog Europa/Oil Filter/W 719~5 https://catalog.mann-filter.com/EU/...aulic Transmission Filter, Oil Filter/W 940~1 https://www.gsfcarparts.com/120lr0070 https://www.knfilters.co.uk/search/product.aspx?prod=hp-3001
I have always been under the impression that the bypass is to give flow even if the filter is completely blocked
The bypass is for if the filter gets blocked and reduces oil flow, if the pressure is to high the valve one operate when the filter is blocked and you will get zero oil flow , in theory
I'm easily confused Here is something i found whilst googling (thanks Bob) ....but i still don't know if my filter is bypassed whenever the oil pressure is below 2.5 Bar https://www.bobistheoilguy.com/forums/ubbthreads.php?ubb=showflat&Number=309756 The oil enters the oil filter under pressure through the holes on the perimeter of the base plate. The "dirty" oil then passes through the filter media where it is "cleaned". It then flows to the central tube and back into the engine through the usually threaded hollow center mounting stud. Oil Filter Flow Diagram The only thing that holds the "spin-on" oil filter to the engine and keeps the oil from leaking is the base gasket (shown in above picture in red). The Bypass Valve Under ideal conditions, the bypass valve will never open. When it opens, the oil by passes the filter and goes on through to the motor, obviously unfiltered. It is a safety valve. However, in real operation, it opens often. One example is when you start the motor when cold. The oil is thick and does not pass easily through the filtration medium, thus building up to a high pressure drop. So, the bypass valve opens to prevent oil-starvation of the motor. How long it stays open is dependent on how cold the oil is and how long it takes to get near operating temperature. When the pressure drop across the filtration medium drops below the bypass valve setting. Another example can occur when the motor is fully warmed. At idle, the oil pressure is about 15 to 20 psi, and the pressure drop across the filter is about 1 or 2 psi. You take off towards the redline, and quickly build oil pressure. During that full-throttle acceleration the pressure drop across the filter will exceed the bypass setting, and send unfiltered oil to the motor, until the pressure across the filter has time to equalize. During a drag race, shifting through the gears, the bypass will open several times. A third example, which you should never experience with frequent oil and filter changes, is when a filter becomes clogged. A spin-on filter can commonly hold 10 to 20 grams of trash before it becomes fully clogged. The bypass valve opening is the only way to keep the motor from becoming oil-starved if the filter becomes clogged. According to Purolator, the Honda OEM filter bypass setting is 12 to 14 psi. WIX (NAPA Gold) builds their oil filters with a bypass setting of 8 to 11 psi, while AC Delco builds theirs to a setting of 11 to 17 psi. How much do these differences matter? I don't think anyone knows, even the engineers, and each has its own set of advantages and disadvantages. If you do lots of racing, you're probably better off with a higher bypass setting. If you do lots of *cold* starting, especially in the winter, or seldom change your filter, I think you're better off with a lower bypass setting. However, with few exceptions, bypass pressures for spin-on filters run in the 8 to 17 psi range, and any of them should work acceptably. Here is a picture of the breakdown on some oil filters anatomy As you can see, some bypass valves are built directly in the middle of the filter while a few do not have one. Here is a cutaway of Bosch's and how each component is located in a filter. 1) Rubber seal 2) Steel baseplate 3) Anti-drainback valve 4) The bypass valve 5) Filter media 6) Filter can Hopefully this gives you a better idea about filters and how they flow.
Bypass pressure is for high pressure drop across the filter. Not for absolute pressure.. I have not seen the bypass pressure as particular issue as my filter is connected in a loop off the oil pump cover plate, so it is before the pressure gauge sender in the usual sender hole. As the engine cranks the oil pressure cold climbs to 15 psi after the filter on the starter at 350 rpm. I started with the HP-1 but its overpriced. The Mann filter is off a Golf so is likely to see more abuse there , they seem quite heavily constructed. The pressure sender always reads normal pressures for a 1600 TP (10psi per 1000 rpm) with a 26 mm oil pump... the filter has not burst at well over 105 psi at -3 degrees C with 20W/50 oil. But an oil pipe loosened and fell off once...
Nice one @mikedjames . Thank you I think I now understand it If my engine pressure is at 2.4bar, then the filter is probably still filtering the oil The filter only stops filtering if the high pressure drop across the filter is below 2.5 bar (which I have no way of knowing) (I think) My set up is full flow, top and bottom gallery method? out of the crankcase (rather than the oil pump cover), then oil filter, then thermostat, then external oil cooler. My twin terminal oil pressure gauge sender, has replaced the oil pressure switch I'll keep using the same oil filter, as it has never burst on me Perhaps at the next techenders, you would be so kind as to look at my set up and help me understand it a bit better!
I also use mann filters.........I use w719/30 and it has bypass at 2.5 bar and anti drain back valve. my set up is drilled oil galleries top and bottom and routed to a mocal thermostatic valve and oil filter and a mocal cooler and the filters have been fine and you will find them on most vw golf Passat t4/t5 even some audi tt's so must be up to the job of an old bus........ what it means to me in real life is it fits and does what it is supposed to, filters the oil
If the pressure drop across the filter is above 2.5 bar. So, if the filter is blocked and/or cannot flow sufficient oil (when the oil is cold and thick for instance) the valve lifts to allow oil to by-pass the filter.
Thanks, I had it the wrong way round then. I've used these filters for 12k miles, changed regularly, but was told by a couple of people that I should use one with a lower pressure relief figure. So I'm glad I asked on here now. The k&n filter has a really low bypass valve figure and that is the one John Maher recommends after apparent quality issues with Fram Thanks everyone for your input
