Ericson38

Mercedes has a very well designed 3.0 liter V-6 diesel (OM642) with a 72 deg V angle and counterweights (Sprinters use them and a host of other MBZ wagons and sedans). Mercedes OM642 3.0 CDI Engine Specs, Problems, Reliability, oil - In-Depth Review (motorreviewer.com)

Continental Engines even uses it as the basis for their CD300 aircraft engine, at 300 hp. Continental_specsheet_JetA_CD300_Engine_Series_v3_WEB.pdf

Based on test driving quite a few sprinters, I can say that offset crank pins and balance shafts result in a balanced engine (would Continental tolerate designed in vibrations in an aircraft application?).

Our two V6 90 deg Audi engines are very smooth (Cayenne and Panamera). I don't think the 2.9 or 3.0 liter engines are part of the problem.

Ericson38

On the Magna Tru Track hang on Transfer 'Box' (not called a case in their world), is it really a clutch pack or a viscous AWD affair, like my 2006 997.1 C4 Carrera ?
Or, like the link below shows, in the 997.2, not viscous, but clutch with more control over torque split. I don't know how all that fits into the hang on Magna Box, but it fits in the 997.


Porsche documents explain how the Porche Traction Management (PTM) control the coupling (front to rear torque split). For anyone who has spent time around the 'Box', is there a wiring harness connected to it? If its disconnected, it should throw an error on the dash. Wonder if there is a communication issue between the PTMS and the 'Box' which then turns messages (or voltages) into degrees of slip.

Magna Tru Track production for 9Y0 applications runs into the thousands. Let's say there are 20,000 Cayennes of the 9Y0 type. Is every one defect free when built? How would a defect manifest itself (excepting obvious things like gear noise or a leaking shaft seal)?

chassis

Funny you mention the OM642. There is no other engine that has had a more tragic market experience and large number of notorious failures than the OM642 "Bluetec". The use case is mainly North American markets (poor U.S. diesel fuel quality and different fuel spec vs the European home market) when the engine was used with DPF and DEF systems. This is MB's analogy to VW's Dieselgate. There is consumer compensation from MB available for eligible OM642 owners. W166 ML350 Bluetec and W212 E350 Bluetec owners seem to be highly represented among the affected population.

The prior CDI engine seems to be well-loved. Sprinter use cases seem to have fewer problems, likely because the light commercial vehicle falls under different emissions rules and the emissions hardware and software are different. ROW markets seem to be less affected, again likely because of different emissions regulations and fuel quality.

Regarding "balance". Any engine which uses a balance shaft is not balanced. Period. EA839 and OM642 engines use balance shafts. They are inherently unbalanced. It's physics, not opinion.

Ericson38

I'm aware of the blue tech issues, which aren't related to how the engine was balanced. I have good exposure to blue tech and def issues, but the engine balance is very good.

Even its highly regarded replacement, the OM654 (inline 4 twin turbo 2 liter) uses balance shafts. I have driven it also and its almost as smooth as the OM642 in a 2024 model 2500 sprinter.

Mercedes-Benz introducing new diesel family in E 220 d this spring; new OM 654 with 13% lower fuel consumption; diesel “indispensable” - Green Car Congress

kayjh

The mount is supposed to absorb vibration. maybe it isn't doing it's job properly.

achashatan

Nobody said Porsche produces junk. I purchased the Macan when it was first released. What an awesome crossover. No issues with that. But the Cayenne is a different story. I also have a Panamera in the family.

Cayenne is the one with the issues.

achashatan

Porsche did update the transmission mount for the newer years. If there was nothing wrong with it, why update/change it?

So the old transmission mount definitely has issue(s) related to either the 6th gear shudder, the jerking or the harsh idle. Or maybe something else, I don't know.

I do plan on replacing the transmission mount, transfer case & driveshaft next month. (Unless I just decide to give up and sell it - which could happen as well)

chassis

Let's review - the OM642 engine is not balanced. It requires a band aid, to wit: a balance shaft. Please give us your view on why the OM642 and EA839 V6 engines have balance shafts, and why the M276 3.0/3.5 engines do not have balance shafts.

Engines which do not require balance shafts: I6, 60-degree V6, V8, V12, are balanced.

Ericson38

The inline 4 (OM654) and V6 (OM642) have balance shafts, as does the EA839. My R129 (M113) didn't. This is basics. The counterblancing shafts work well in industry. I drove the Sprinter OM642 and OM654 2023/2024 2500 series back to back. Counterbalancing works well on both, but of course the OM642 was smoother than the 4 banger OM654 (which has the improved emissions treatment system--better than blue tech).

Crankshaft Counterweights on an 90 degree V8 (5 main bearings) with common crank pins between adjacent cylinders are larger than in the same displacement 6 cylinder engine in a boxer configuration, with each rod having its own pin (7 main bearings). But I don't consider crankshaft counterweights to be band aids.

The Porsche M97/M97 boxer engines have an IMS (intermediate shaft) that runs at half speed to enable chaining over to the 4 overhead camshafts with small sprockets. They could have done this 1/2 speed reduction with much larger cam sprockets, and deleted the IMS, but calling the IMS a band aid ? No. It made the overall package more compact.

The EA839 has an IMS also, for the same function, and a single counterweight in the rear of the engine. Not a band aid. A solution to a problem of giving space for a hot V turbo configuration for obvious reasons.

I'm coming to the conclusion that most modern inline 4 cylinder engines are running dual balance shafts.

chassis

I hold the view that this is the guilty culprit causing vibrations in the V6 powertrain. V8 powertrains do not have the vibration because of higher mass and different vibration dynamics vs the V6 powertrain. V8s have no rubber flubberdobber isolator. V6 powertrains have a large rubber donut flubberdobber - the smoking gun.

PorscheACC

Not all 9Y0 Cayenne S with the Audi 2.9L TT engines have shudder or vibration issues..

Luckily, I never have had shudder or vibrations, at almost 100K miles now..

chassis

This video shows the "inside out" hollow shaft arrangement which transfers torque to the front axle, from the shudder-producing multiplate coupling. The coupling example in the video uses a Torsen worm-gear device. The wet clutch plate device is also used in the same position interchangeably.

chassis

Which model year do/did you have?

lucian95

I just wanted to chime in on the topic of shudder/vibration. On my base Cayenne 2022 I did notice some vibration during acceleration while going through the gears, from app. 40 mph onwards, in fully auto mode. Same during downshifting. I'm not talking vibrations attributed to engine noise during acceleration, the sensation was quite different and I always felt it under my driver's seat. I just did my 2nd oil change (I'm currently at app. 20k on the ODO). After the 2nd oil change, the vibrations are literally gone and the engine runs like a charm. I don't get it. Oil change was done at Porsche dealer and that was the only service I asked them to do, they reset the service interval and nothing else. Go figure.

jtsmith18

Similar with my 2022 base now with 21,000 miles. The vibration didn’t show up until about the 10K mark but since then I know right away when it’s in 6th gear as I can feel the mild vibration in the steering wheel and base of the seat. The car has had 4 oil changes and that never makes a difference. Only occasionally can I notice it in 7th but never any other gear and it’s not really RPM dependent. Like others, I’m convinced it’s in the hang on transfer box or whatever they call it. So far I can live with it until perhaps eventually a fix. I’ve not reported it to the dealer as they can’t fix “they all do that” anyway and it’s got the extended warranty.