Ericson38

Reading through the discussions on the LN full flow adapter, and reasons for having it, I'm wondering how that system responds if the pressure drop across the filter media inside the conventional metal canister gets too high ? In other words, without a bypass (filter bypass), the oil pump relief valve in the engine (upstream of the filter) will open and dump the oil back in the crankcase, unless I am missing something.

The whole purpose of the filter bypass is to allow flow in the event of a filter media blockage, into the oil galleries. Full flow descriptions mean little by themselves, but if it means all the oil the engine will ever get needs to 100% get through the media first, would that always be the right condition for an engine ?

The nominal purpose of the oil pump relief valve (not the bypass valve) is to limit the amount of pressure the pump can develop at its output port to a safe (5 bar or 79 lbs/sq in) value, with excess oil (if the valve comes off its seat) diverted right back into the sump, never seeing a filter.

Does the OEM system incorporates a bypass valve in the filter canister ? If so, where is it ? In the bottom of the canister ? If so, I need to look closely at my next oil change. Does it need to be rinsed out or flushed, or checked for operation ?

Here's a scenario----10 K miles, time for oil change (for me, every 3K for 3 in a row for our new to us 997), factory filter configuration, and the media is partially loaded with carbon and what not, meaning there is a real pressure drop across it, and accordingly, depending on engine RPM and oil temp-viscosity and position of the oil pump relief valve, less pressure for the oiling circuit than if the media were 'new'. In the OEM configuration, the bypass is going to partially open and bypass the media, meaning full pressure, but not full flow filter anymore, since part of the flow is not going through it.

With the LN system, in the above case, no filter bypassing, pressure drop across the partially loaded media present, but reduced flow of oil (and oil pressure senses by the sender).

This seems logical, but if I'm missing something, please advise, as I am considering the LN route.

Thanks

2006 C4Cab MT (seal grey-black)

Ericson38

Hoping to get some opinions on the utility of filter bypass (OEM design) versus LN full flow adapter, where 100% of oil goes through filter before the oiling circuits.

NAM VET

If something really bad happens in your motor it won't matter what kind of oil filtration you have. But for the minor problem of cold unfiltered oil carrying particles thru your engine the LN system will avoid that issue. I put one on my 997S with NAPA corvette oil filters "be sure and use the correct one" before I sold it for a GT3.

All the best.....

Bruce In Philly

I gotta wonder about the value of modding such a critical Porsche system.......

What strikes me as odd, is a belief that a short amount of unfiltered oil is so bad. Why would it be if the oil was always being filtered anyway. In short, you are flowing filtered oil... it is just that it bypassed the filter just this time. It was always filtered; the "unfiltered" oil is as as clean as the filter system can get it. I am usually a pretty paranoid person but this appears to be a problem where one does not exist.

Peace
Bruce in Philly

semicycler

The metal cased oil filters used with the LN engineering filter adapter have a fail safe bypass filter built in. Napa Gold filters are commonly used and highly recommended. Here's a link showing the internals of a Napa Gold on youtube. At about 1 minute in there is an exploded diagram showing an upfront safety by-pass valve. A clogged filter causes raised oil pressure allowing the safety valve to open (see the spring at the top). But under normal oil pressures all oil is filtered - there are no bypass openings.


The OEM filter does not have a spring loaded bypass. The bypass is always there allowing some percentage of oil to shoot past the filter entirely.

Bruce In Philly

Really? On my 2009 C2S, the oil filter is just a simple filter, but the whole mechanism has a spring in there and some other pieces parts. Hmmmmm

Peace
Bruce in Philly

gpjli2

All I can say to OP's query is that until you have a clear sense of whether this is an improvement or just an unnecessary marketing ploy leave it as it was intended to be. I suspect that under certain unique circumstances each system may have it's advantages. Spin on filter technology is not exactly a new breakthrough after all and was available at the time these engines were designed.

Unlike things like IMS bearings and RMS gaskets I am not aware of anyone's claim that their engine suffered a needed repair or premature failure due to it's oil filtration setup. My take on this is to keep up frequent timely oil changes (2x yr for me) inspect my filter's contents, use a modern oil and add Militec every 2 years.

If it ain't broke.....well you know. Happy driving.

Ericson38

Fixing (Texas in my past) to do another oil change this weekend (T+1000 miles since purchase).

I'm not understanding the stock "always in partial bypass" design, or where some got that information, unless it is real obvious when you look at the filter and canister parts. Some, like Bruce with his 2009, say that the bottom of the OEM canister has a spring and valve, not sure about my 2006.

I was pretty sure the OEM oil filter element slid up the oil pipe and covered any holes that would let unfiltered oil get around it, but plan to study this issue a bit more with the next change.

The oil from the pump goes through (after the relief valve in the block) the outer oil passages that surround the oil pipe (360 deg). Then it can go either of two ways to the engine oil galleries. One way is laterally through the media and then back up the oil pipe (filtered). The other, if the pressure is too high (through the media) is to the bottom of the canister, through the oil pressure bypass (spring loaded poppet valve that is lifted off its seat by pressure), and then up the oil pipe (unfiltered).

I have heard it said that some M96/97engines did not have this bypass at the bottom of the OEM plastic canister, and there are concerns that the spring tension would get weak over time, allowing too much oil to just bypass the medial as a matter of normal rpm, warmed up oil engine operation.

Then there was an observation that the bottom of the OEM canister, where the bypass mechanism is located, becomes a sort of settling area for heavier debris that the oil pump brought up from the crankcase, and that-

1) the debris can block the bypass open (believable)
2) the debris can make it up the oil pipe when the filter is in partially clogged bypass (believable)

If this is correct, then I can see a failure mode in the OEM design in that the bypass is located in an area that can get compromised by debris, which would be less likely if the bypass was encountered initially, at the top of the filter. Then there is the concern that the bypass assy at the bottom of the OEM canister can loose either sealing properties by spring tension reduction or simple debris borne wear of the sealing surfaces (when it is in the closed or by bypass state).

The problem I have with this is that a lot of innovative thought, R&D, mockup testing, production engineering, and reliability field testing went into making the variocam plus system a reliable part of the engine, and that this section of the engine is so easy to find fault with. That plus the fact that there is an instant backyard mechanic remedy for it !

Luxter

I've seen sludge buildup (in some cases 1/2" or so) at the bottom of oil filter canister. But that's only for very poorly maintained or using incorrect lubricant cars. When bypass eventually opens, that sludge goes straight to your engine.

Amen.
Use best oil you can afford.
Eventually I would also replace the oil filter canister to ensure that the bypass spring ain't fatigued and bypass opens as designed.

Cheers,
=L=

Ericson38

Inspected the OEM filter canister last night while chaining out the oil pressure switch. The OEM media end disk sits right down on the bypass circular valve and underlying bypass spring. No debris or sludge down there.

This appears to be a full time 100% filtered arrangement (not full time bypass), with the only partial filtering mode being due to clogging filter forcing a bypass operation. At that time (bypass), some oil is going to flow through the poppet and then up the oil pipe.

Possibly earlier cars didn't have the bypass at the bottom of the OEM canister, but if they didn't, that would be the reason for posts stating the system (OEM) is not a 100% full flow type.

If there is a good layer of sludge down there (say a 1/2" buildup), it will inhibit the operation of the bypass and force 100% through the media, no matter what the pressure drop across it. At some point, the sludge would be rinsed away from the bypass area, and into the engine.

gpjli2

Nice rational and informative post. I'll bet Ericson warms up his motor before draining the oil Sounds like oem system is up to the job. Thanks for the followup.

mikeborden

I believe the argument by some is the the factory filter spring will loose some of it's resiliancy after it's gotten older and it will filter less than before and the bypass spring "pops" a lot sooner than the other filters.

I always read a post that the discribes the LN as a complete filter and that's not really the case. All filters have a bypass. Just some, might be, better than others. The bypass that is.


Mike

FWIW, I still use the factory housing.

Mike

NAM VET

Some oiling systems have a bypass in the filter others in the engine filter mount.

All the best.....

Macster

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.

Thus - if this info is right -- there is never any unfiltered oil routed to the engine. The Porsche oil flow diagram shows a bypass at the pump and none at the filter.

'course, there is counter info that this is wrong and the filter has a bypass and this of course justifies using an aftermarket filter with no filter bypass.

I don't know who is right since I've never been up close to the engine.

When in doubt I prefer to leave the engine as it came from the factory so I have not gone to an aftermarket oil filter and adapter for either of my cars.

I can tell you that the filter housing oil can collect a nasty bunch of trash -- I have a pic from the 750 factory fill oil and filter from my 2008 Cayman S - that if there was a filter bypass I would think twice about any chance of that oil being routed to the engine and its clean oil system.

The stock filter is a real good filter and has plenty of filtering capacity. The filter doesn't get that dirty and has plenty of reserve flow even when used for the whatever miles the factory guidelines call for leaving it in service. For instance, for my 2002 Boxster the oil filter change interval was 30K miles. The oil change interval was 15K miles. I didn't adhere to those numbers, changing both at 5K miles, but some owners have I'm sure and I have not come upon anyone reporting the filter getting blocked and causing any problems.

gpjli2

[QUOTE=Macster;12386385]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.