m444

The catalytic converters need to be very hot to be efficient & need to heat up very quickly for cold start emissions, being close the the turbo is the best place for reduced emissions. Some newer engines are placing the cats even closer to the turbos. APR is not as concerned about this.

"The compact size and neater packaging of the cylinder head enables engineers to position the catalytic converter next to the turbo. This reduces the length of the flow path for hot exhaust gases, allowing the catalytic converter to heat up quickly and start the emissions control process sooner."

https://www.greencarcongress.com/201...60930-vct.html

m444

Also check this poll

spdemon91

Thanks for explanation and I guess that makes sense. While it may be more efficient for cold start emissions, I would think it is a negative for engine longevity. I guess the turbos and exhaust are already screaming hot so maybe the heat from the cats is a non-issue. Why couldn't they just do some fancy programming in their software to handle emissions?

m444

The fancy programming was already tried on diesels, big fine.

The cat needs to be hot, needs a heat source quickly, not practical to use electric heat.

spdemon91

I know dude. That was a joke.

MP4.2+6.0

FWIW, cats (or at least pre cats) were moved close in board all the way back to 2004, so that is not really a "new" thing. Instead, what is probably being referenced is the "hot V" design where the exhaust is on the inside of the V and the intake is on the outside. In fact, trim cover off pic showing that has literally been my avatar picture since I got the D4 S8. That in turn is exactly how Audi got a bunch more power out of the V8. Also how they caught BMW and Mercedes with their pants down for several years. All have been scrambling to catch up on hot V layouts and to get related power and responsiveness gains. And yes, it does move cats higher up right behind motor. But that part I'm not so concerned about given the after run fans, oil and coolant circulation systems. The issues instead are apparently in the internal oil circulation in general and simple flow with a blocked screen going back to a part in there for decades pre turbo's. It's not the old coking to be clear--where without after run systems the oil could cook in the turbo bearing area after hot shutdown and then prevent flow. Even by later 80's Audi was dealing with that with the internal fluid after run approaches.

m444

Innovative GM, Hot V engine introduced 2018??

https://media.cadillac.com/media/us/...-turbo-v8.html

MP4.2+6.0

Yep, them too. They are all "innovating" by looking at the other guy. On hot V's, that basically means our 4.0T for production volumes. Even Porsche folded it in, and then quietly grabbed the tooling as of recently. It will now be the supplier for all V8's going forward, Audi included. Part of why the long D5 V8 delay, plus TDI mess distraction (let alone guys with handcuffs...), plus corporate stupidity dealing with new Euro emissions and fuel economy testing, plus Porsche now probably first in line for Pannys and others they are rolling it into, plus... Thus, continue to enjoy the D4 implementation the 99%+ time it works as intended.

TinyElviss

Yes, seemed they introduced the engine then cancelled the car. .... or did they??

spdemon91

*** CONCLUSION *** Preventative maintenance is complete. Thank you to all who contributed their knowledge and input. I appreciate it. Since I have benefited from everyone’s knowledge on this forum and other forums, I wanted to provide a detailed write-up on my experience from start to finish as it may help others in determining how to proceed.

CAR HISTORY – My car is a 2013 S8 which was owned by a corporation in Maryland from May 2013 to June 2017. They put 69,000 miles on it (17,250 annually) so probably lots of highway miles. They changed oil initially at 5,000 miles and at every 10,000 miles thereafter. In June 2017, the car was auctioned to a dealer in Easton, PA. He added another 5,000 miles to the car. I purchased from him in Sept 2018 when the car had just under 75,000 miles. Around 76,500, I did the Liqui Moly 2037 Pro-line Engine Flush prior to changing the oil. The oil came out black as tar so the flush definitely cleaned something.

CONCERNS – Around this time, I became very concerned due to the large number of 2013 4.0Ts blowing with far fewer miles than mine. The engine flush also became a concern as I thought it may have loosened material which could have become lodged in the fine mesh oil screen. Considering Audi redesigned the oil screen, check valve and oil separator to address certain design problems, I decided to have these parts replaced as preventative maintenance but wanted assistance from Audi.

AOA & DEALER RESPONSE – I took the car to my local Audi dealer where I expressed my concerns and requested assistance. Initially I was met with resistance since the car was beyond warranty and purchased used from a non-Audi dealer. I persisted and premised my request on Audi’s acknowledgement of faulty designs in the car’s oil system as noted under TSB # 2044640 which documents the issue of blown turbos and Audi’s redesign of the oil screen and check valve. In addition, I noted TSB # 2044644 which documents the issue of the oil separator failing and Audi’s subsequent redesign. After my initial discussion with the Service Manager, I followed up with an email clarifying my position. Here’s an excerpt… “When I purchased my S8, I was prepared for above-average maintenance costs based on the assumption I would be owning a superior well-engineered machine. Since owning my Audi however and reviewing the forums, I have come to learn of several very costly issues due to poor design, namely, the restrictive oil screen leading to potential turbo failure (TSB 2044640), oil air separator failure (TSB 2044644), 1k/3k vibration due to downpipe design (TSB 2036392), and coolant leaks (TSB 2036167), to name a few. Regarding the biggest problem which is the restrictive oil screen, Audi is well aware of the problem and has redesigned the screen to address the defect. In my opinion, Audi should stand behind their product and assist their customers in making this right especially considering the premiums paid for their "S" model cars. I am willing to pay for the parts to have the job done and I don't think asking Audi to cover the labor cost to replace the oil screen with the revised part as goodwill to a first-time Audi owner is unreasonable.” AOA’s response was agreement to cover 50% of the labor & parts to replace the noted parts. The Service Manager noted this is rare for AOA to cover preventative maintenance. It then took many back-and-forth communications with the dealer regarding the parts and the dealership mark-ups which I took issue with. Ultimately the Service Manager agreed to provide all parts at cost which allowed for the replacement of all associated gaskets, o-rings, etc. as outlined in both TSBs in addition to the revised oil screen, check valve and costly oil separator. They also changed the oil and filter as part of the service. All-in negotiated cost to me was $1,000 plus tax which all things considered, I believe was fair.

CONDITION – Parts were replaced at 78,000 miles. Left side turbo had maybe a millimeter of play, if that, and there appeared to be a faint single score mark on the housing. In speaking with the mechanic, he indicated turbos appear fine and he had seen much worse. Right side turbo was solid but does have oil residue which I understand is normal due to the PCV system. The suspect oil screen had teeny bits of grit in it. Upon initial inspection, the screen appeared fine but upon very close inspection, you can see there are particles of what appear to be dried oil clogged in the filter. I can definitely see how this mesh could accumulate more bits and pieces and become completely clogged over time. I cleaned it with some degreaser and attached pictures so you can see the progression from what the screen looked like 1.) when it came out; 2.) after an initial wipe-down; 3.) after my first cleaning effort with dawn dish detergent; and 4.) after being degreased and wiped down. Regarding gaskets, all appeared to be in good condition with no unusual wear or warping so I would think that the initial bare-bone list of core gaskets would have been sufficient to do the job.

FINAL ANALYSIS – The oil screen looked much better than I anticipated considering what others have posted. Based on this, I suspect that the engine flush I performed 1,500 miles prior may have helped to clean the oil screen. I would consider doing the flush again maybe after another 50,000 miles. This coupled with a more rigorous oil change regimen every 3,500-5,000 miles should help keep the engine nice and clean. Regarding the preventative maintenance, I am glad I had it done for peace of mind. For those of you who are capable of doing on your own, I would recommend it. For others, dealer cost without any goodwill for an A8/S8 to replace the oil screen, check valve, oil separator all associated gaskets and fittings per TSBs, and change oil and filter was approx. $2,250. Had I taken to my general mechanic, assuming purchase of parts at wholesale cost, I would have probably spent around $1,100 including labor. Feel better having it done by Audi-specific mechanic and finally I am back to enjoying my car without fear of it blowing up.

Hope this write-up helps others. Best of luck to everyone. Relevant pictures are attached.



parts list 1

parts list 2

1.) oil screen upon extraction

2.) oil screen after wipedown

3.) oil screen after cleaning with dawn

4.) oil screen after cleaning with degreaser

left turbo

right turbo