uttevrec

I brought the oil filter bypass up because, when the oil filter is being bypassed at high RPM/load, and the screen has been removed, completely unfiltered oil/debris will be sent to the turbo bearings. This is obviously not good for the turbo.

The worst situation is (1) the screen becoming plugged and there is no oil flow to the turbo. The second worse situation is (2) that the screen is removed and unfiltered oil/debris is sent through the turbo during filter bypass conditions.

What’s not really known is if the newer coarse mesh screen is the best solution (prevents bypass debris in turbo), or if no screen at all is the best solution (prevents possibility of clogged screen oil starvation).

In my opinion, more frequent oil changes definitely do not hurt, but it’s not clear that they help either. The turbo failures are caused by oil starvation due to debris buildup in the screen. The debris buildup happens because the oil filter is occasionally bypassed. None of this is due to oil/additive breakdown. It’s also not due to the oil filter becoming plugged and not working. But rather it’s because the engine was designed to completely by pass the oil filter under high RPM/load and allow unfiltered oil, which occasionally contains debris, to be sent to the turbo.

I think the best way to prevent this situation is to completely avoid high RPM/load filter bypass conditions. But what’s the fun in that? Buying an A6/A7 with the V6 engine is a better option at that point.

schalliol

Very interesting. I didn’t know that the engine can avoid the regular filter under high load.

It certainly begs the question of what engineer would design a filter and not have a way to remove inevitable filter cake. Maybe one thinks it’s not common for there to be debris to filer, but the whole point of the thing is to stick that debris on the filter.

Striker2237

Is has been a thing since the 60s, it was found to be preferable to have a engine use unfiltered oil vs no oil at all if a filter was full.

skiracer

Actually the Jaguar XK engine developed right after WWII and first used in the 1948 XK120 had a pressure relief valve in the oil filter housing that bypasses the oil filter if the pressure in the filter becomes too high. This is the engine that won Le Mans 5 times in the '50s so something was done correctly. I'm sure there are more engines from this era that have the same system.

Mike911A8

I believe another factor should be looked at by those D4 owners who are on the fence about installing the revised oil screen. To wit, are they going to have to keep their cars quite a bit longer than they originally anticipated? I say this because we could be in for a deep and prolonged shortage of replacement vehicles, both new and used. Anyone who doubts this should drive past dealer lots; I just did so about an hour ago. Audi, BMW, Mercedes, Porsche, Lexus, and Honda. Virtually no new cars, just a few used cars where the new cars were previously parked.

if it were me, based upon the lack of reports about the new screen failing, I would make the switch. I should add, my D4 purportedly received the new oil screen when it was manufactured over four years ago, and to say that has been a comfort , would be an understatement.

One other thing; I believe there is an ongoing NTSB investigation into this issue, and there is always the chance the government will order a fix. Typically, such an order would require reimbursement to owners who had already done the fix, so if you do the job right away, there is a chance you may be reimbursed. That’s some comfort, anyway.

another reason to take care of the fix soon is the possibility of parts shortages. I say this because I have recently encountered significant delays in obtaining normal replacement parts; specifically, a set of Cayenne brake rotors, and a coil pack for a 997. The paradox would be, if the TSB ordered a fix, and then the supply chain couldn’t deliver the required parts.

lost in the attention given to the turbos is the lack of any other major issues with the 4.0 TSFI engine, or the D4 in general.

mike

A8L_New_England

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I was agreeing with Mr. Striker's previous comment..
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Agreed... Nonsense!
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"The 4.0L V8 TFSI engine uses a flow-rate controlled oil pump. The pump operates in two pressure stages. In addition, the oil supply to the engine is constantly adjusted through volumetric fl ow control of the pump in both pressure stages. By using this pump, it was possible to reduce fuel consumption. In lower rpm range, the pump is operated in a low pressure stage (reduced output capacity). The low pressure level is at a relative pressure of approximately 29.0 psi (2 bar). The high pressure level is controlled to a value of approximately 65.3 psi (4.5 bar). The pressure relief valve in the pump opens at approximately 159.5 psi (11 bar)." (Engine self study program 920223)
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But again, I'm just trying to bury this ancient topic, which has been discussed Ad Nauseam... hundreds of posts ago in this very thread, IIRC. I myself suggested screen removal months ago.
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A8L_New_England

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Maybe take a quick look through the other 5200+ threads on this forum...
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Mike911A8

I’ll take your silence as to the main thrust of my post as agreement. Thank you.

as to my general statement you apparently challenge, I note that your 4.0 has a stage one tune, and I can’t imagine that you would have gone that route if you didn’t have faith in the engine.

A8L_New_England

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Don't know where you sense a challenge... I found no reason to argue with your points of speculation. My crystal ball is broken.
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Re/ my decision to tune, it's probably more of "I just don't care", than having a lot of faith in any machine. If it breaks, I'll fix it. Additionally, I bought it 20K miles after new turbos (and screen) were installed. I do 5K drain and fills, and 10K filter changes. Next time the turbos quit, I'll pull the screen out, and run it like the other 99.9% of cars that don't have one.
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Striker2237

Amen to that mentality