DIY Guide: 'Full-Flow' (non-bypass) oil filter housing mod for $1. No spin-on.

Might post this on another forum in another life.

can the stock filter handle the starting pressure? I seem to have read that the bypass is on when engine first start. Would like to see how long it holds up for you. I am too chicken to test this myself...

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Your DIY solution will work just fine, but disclaimer, the Napa 1042 filter I chose to use on the spin on filter adapter is from a 97-04 Chevrolet Corvette and sized plenty big for the M96 engine. The stock Porsche filter was sized for 24,000 mi drain intervals originally. The 1042 we recommend 5k intervals, which is still less then GM's recommended interval on that filter.

Good info, thanks. Not entirely sure why my Napa 1042 partially collapsed then. Still, in extremely cold weather it's better to have a better-flowing filter to avoid oil starvation.

fwiw, the Napa/wix 51522 has another inch or so of filter material and fits the LN adapter.

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Burst pressure is 290 psi versus 320 psi, but that shouldn't be a deal breaker. I don't see any problem with the Napa 1522 / Wix 51522, other than it being an inch longer. Just be mindful of ground clearance. You want to make sure the filter isn't the lowest point on the car. Another option is the Napa Platinum that has wire backed media, if there is a concern about the pleats folding over.

Another advantage of using spin-on oil filters is that you can easily add a Filter Mag to them. One more layer of protection.

I have been disabling the factory by-pass for years on my (3) m96 engines, using two different methods. One by flipping the valve/spring to the opposite side, and the other by just filling the plastic cup/valve with Loctite E-120HP Epoxy. Have had no issues with filter crushing with either method using the Porsche/Mann/K&N filters with the plastic center cage.I also Epoxy neodymium magnets to the outside of the plastic canister for the extra filtering. I prefer the canister filter simply due to larger filter area and the ease of inspection. That said the L&N adaptor is a nice piece and well engineered.

Epoxy would've been a nice one too, might be looking into that next time when I have the time to let it set. I tried flipping the valve first, but found the seal on the sharp lip inside wasn't as good as the rounded recess (air could go past if I simply blew into it), so I opted against it. Thanks for your info on long-term running experiences!

I know there is lots of good engineering around the "no bypass" filter mods. Having worked on jet engines in an earlier career, I have always felt (and been trained) that contaminated oil bypassing the filter is better than no oil. It causes damage, but not catastrophic failure like Oil starvation can cause. I know many here disagree, but I thought I will share a different perspective. I will keep my factory setup.

When is the bypass triggered, when the filter is clogged to the point of restricting flow?,

That, and I believe it also triggers when there is high oil pressure.

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The way the bypass works is if there is an 8# spring in the bypass, you have to have a greater than 8# delta between both sides of the filter to open the bypass. Start-up is often the only time it opens unless the filter is completely plugged.

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It only opens on a large delta P between the inside and outside of the filter; that only happens if the oil is too viscous to pass through the element easily, the filter is very clogged or a combination of the two. For most of us who change oil at 5-7k intervals and don't start the car in very cold ambient temperatures its a non issue. I left mine alone and instead added external magnets which really work, last filter change they collected some fine ferrous spooge and my element was spotless at 5k miles

While I do agree contaminated oil is better than no oil, my particular engine had an IMSB failure which let some contaminants in there. I won't feel safe running the stock setup at this point.

I'm not I understanding the problem with keeping the bypass. Why wouldn't I want bypass? If my IMS bearing fails, the bits from it will only get into the engine if the pressure differential is greater than 8 pounds when it happens the filter goes into bypass. If the filter isn't in bypass, the bits won't pass through. Is it a given that when the IMS bearing fails, the filter will go to bypass? And wouldn't the bits from the IMS already have gone through some of the engine on their way to the filter?

Normally you want a bypass to counter oil-starvation; this is only an issue with cold start at extremely low ambient temps or a severely clogged oil-filter. If your engine had an IMSB failure, like mine, there will be leftover metallic debris in the sump and oil pump. Until those are fully washed out with several oil changes, you might want to opt disabling the bypass to be absolutely sure no debris passes by. A small percentage of valves apparently have a faulty spring, which allows the valve to open prematurely (thus at higher ambient temperatures). If this is the case, you also may want to disable the valve with this mod. If your engine had a properly working valve you should be safe however, even if you had IMSB failure.

Bypass mechanisms also exist to prevent the oil pump from destroying itself. Liquid are practically not compressible, so if there is a blockage in the delivery side of the pump, without a bypass, something will blow up or come apart, including any pressure lines, pump housings, shafts, etc. I believe most oil pumps have a bypass (pressure relief valve) to solve this problem. In the 996�s case, I�m not sure where the oil pump bypass exists. Does it divert oil back into the sump? Oil filter bypass exists for a similar reason. If the filter becomes blocked, something has to give, including the filter media, filter housing, lines, whatever is in the way. The 996 oil filter bypass is routed to the engine, not the sump. �It�s better to deliver some oil to the engine, even if contaminated, rather than run it dry�, the Porsche engineers decided. The better approach would be to have sensors on both bypass mechanisms to have the ECU turn on the oil light on the dash. That would have driven up the price/complexity.

Oil pump bypass sits at the front of the engine, basically a piston with a spring. It limits maximum oil pressure at the filter to 5 bar. Anything over that gets rerouted to the sump.

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The main oil pump has a bypass valve to limit max pressure to 5 bar as Boxman suggests, but the return is not to the sump, but rather back to inlet side of the pump. As Murphyslaw correctly suggests, Porsche (as well as most manufactures) assume "dirty oil is better than no oil" and more problems would arise from customers not properly maintaining there engines and running oil and filters too long causing filters to become "low flow" and a by-pass would be beneficial. IMOP our engines are more likely to be endangered by debris by-passing the filter under cold start conditions, than it would be by "low or no flow" due to filter blockage/dirt from long term useage.. I suggest not using a by-pass on the filter, change oil and filter at low intervals, and install lots of high strength/temp magnets in the sump pan to collect any ferrous debris, and check/clean sump with each oil change, it is easy to do..

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Why would multi-weight oil be a problem when it's cold? If you're running 0W-40 weight, isn't the cold weight 0 and hot weight 40? Once the engine warms up, the oil is 40W weight but at start up on a cold day it's 0W. Anyway, did my first oil change on the C4S yesterday. Seems pretty straight forward. I like the canister too. No need to cut open a filter case. Is there any advantage to the spin on adapter? Dave

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Because 0w oil is still thick when cold. Not as thick as 5w or 10w, etc., but still very slow moving in terms of hot vs cold.

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Murph, I thought the 0W-40 would stay at about a 0 weight down to well be 0C. Here's a chart I found of 10W-30. It shows that it stays at 10 weight down to -20C. If it can flow to every part of your engine that it needs to get to, why would it blow off the bypass at the filter? Dave

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If you apply the mod described above? No, except the spin-on costs about 199$ more. The spin-on also has a smaller filter medium and thus a reduced flow capacity, which under normal circumstances is not a problem at all; in extreme cold, however, the spin-on will starve your engine for oil sooner than the bypass-less canister. So if you're worried about the bypass letting unfiltered oil by AND you want to start your engine in arctic conditions such as a true Nordic winter, you're even better off with the modified canister than the spin-on, in terms of oil starvation. It does, however a 0W oil doesn't have the same viscosity throughout it's temperature range either. Just like any other oil, colder = thicker. A 30W at 0 deg C is thicker than 0W at 0 deg C, but a 0W at 0 deg C is a hell of a lot thicker than 30W at 100c

The filter we use is a 1042 and is from a 97-04 Corvette and flows 9-11 gallons per minute: https://www.napaonline.com/en/p/FIL1042

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The napa 1348 (not 1042) filter also has a bypass mechanism. Two aspects different than the stock filter though: 1) It has a much stronger spring (also you get a new spring for every filter change so no chance for the spring to go weak) 2) During bypass, the debria will tend to stay at the bottom of the canister so a little bit safer Check out its construction here.

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1042 has no bypass.

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I had made the exact error in the past, however their construction vid is a 'general' filter - individual differences apply. I've dissected a 1042 and it doesn't have the bypass as depicted in that picture. I specifically said it flows fine under normal conditions. Would you argue it flows more than the original cartridge? The filter medium inside is significantly smaller in terms of surface area, a factor two almost. I'm talking about differences in an extreme case; extreme cold. If one flows more than the other, the one that flows most is the safest when starting up in extreme cold ambient conditions.

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Hi Charles, the ones I took apart are constructed exactly like the in the diagram, including the "up-front safety by-pass valve". I believe the spring allows the filter element to drop down in case of extreme pressure so oil could escape from the silicon anti-drain valve and by-pass valve in the diagram. Edit: sorry I was referring to NAPA 1348, not 1042. The 1348 does have a by-pass valve inside.

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Perhaps the design has changed since you took one apart? I just took one apart a few days ago and it has the by-pass valve as shown in the diagram.

It had the spring in the bottom, but that's to make sure the cartridge is pressed firmly against the gasket at the top. Now that I think about it, that probably operates the silicone anti-drainback valve when the engine is turned off. Since the oil is free to surround the cartridge inside the filter, there's no pressure differential between the cartridge's top and bottom in case of blockage. I did not find the perforated spring-loaded assembly at the front, but just a collar without holes/springs whatever. This pic shows it, part in red was not found on my filter: https://imgur.com/a/T7xvpP7 . Was it on yours?

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No changes. Perhaps you are seeing the anti-drainback valve. http://www.nfhconnect.com/Lookup/Par...and=NAP&hb=688

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My bad. I have the NAPA 1348 (for the IMS Solution) so my comments referred to that and not the NAPA 1042 (for non-IMS solution spin-on adapter).

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Charles, would you be able to comment on the extreme cold considerations in terms of protection against oil starvation during startup in such conditions? From your earlier comment you seem to agree that - while the Napa definitely flows plenty under normal conditions - the OEM Porsche filter has a much high flow capacity due to its size: Any thoughts on how you think that affects tolerance to extreme cold?

This whole idea that spin on oil filter is something beneficial really stumps me. I was thinking it might be a good idea but I'm just not seeing any advantage so what am I missing. Oil changes might be a minute or two faster but checking the filter element is going to be quite a bit longer so no real benefit to a spin on can versus a cartridge filter. Does a spin on oil filter adapter and a filter without bypass but a higher flow rate that Porsche originally intended help? Wouldn't Porsche specify a filter that meets the engine's needs? Have any of our engines been starved for oil using a Porsche recommended filter? Does anyone have any evidence of the bypass opening with 0W-40 at cold temperatures? Does it even matter if the bypass does open? Keep in mind that if it did, it's still passing oil that was filtered when you were last running your engine so is there any real risk?

The main problem with the stock filter setup is that the bypass-valve is located in the bottom of the canister. When debris collects in the oil filter (= the only place where debris collects), it may sink to the bottom when the engine is turned off and collect right in front of the bypass-valve. If the valve then opens, the debris may be sucked into the engine. This is something I'd like to see as well, as it's being hammered on time and again as a major selling point for the spin-on, as "the bypass opens frequently on cold starts" (IMO only with a faulty valve). I have no doubt that the by-pass opens at cold temperatures, but only in extreme abnormal cold. But the key point I want to drive home is that if the bypass would open due to cold oil, you'd always be better off with a bigger filter if you delete the bypass. So modding the stock would be better than spending 200$ for an adapter and smaller filter.

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You have to take the "multi-viscosity" thing out of the equation, but it's not as important as temperature. Think of it this way: an engine that's fully warmed up and operating at the most ideal temperature, 100C, would be used to oil viscosity, let's say between as low as 10 and maybe as high as 25. So at full RPM, 7300 for our 996s, that's where we are. However, at 40C, cold start, viscosity for some 0w, 5w, and 15w might range from 70 to 125. That's a HUGE difference. Now, let's look at pour point in extreme cold. Differences between 0w, 5w, and 15w might be -54C to -39C. That's the temp the oil won't even pour out of the bottle. I don't have number for 0C, but you can see in your graph, we are in the several hundreds to thousand for viscosity number. What this means is that oil simply will not flow enough at certain temperatures and at certain RPMs. So think about starting your 996 at 0C and going to redline. It's very possible the oil will simply not flow anywhere near the volume that is does at 100C. Because an oil pump is a positive displacement pump, the volume flow has to be the same, but it won't move that fast. The excess oil has to go somewhere before something breaks.

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Thanks Murph. Makes more sense now!! DAve