Longnose

Someone recently told me that the IMS bearing issue did not exist in the 996 Turbo and that surprised me. I thought that the 996 Turbo had the same 3.6L engine as the normally aspirated 996. Can anyone confirm if the IMS bearing failure is a non-issue in the Turbo?

808Bill

No IMSB (issue) in the Turbo, completely different engine.

jhbrennan

NA 996 has the M96 engine with the problematic IMS bearing. Turbo 996 has the Mezger engine which does have an IMS bearing but completely different design and configuration than M96 and not prone to failure.

RngTrtl

confirmed no IMS issues. different engine.

dporto

^This^... and, from Total 911... "While the engine still uses an intermediate shaft to drive the camshafts, the oil pumps are driven directly by the crank. What’s more, the GT1-derived block has a different oil gallery design that ensures the IMS bearing remains lubricated at all times."

kromdom

THAT someone gave you good gouge

TonyTwoBags

perception IS reality

RngTrtl

I edited my post previous your post. It should have read no IMS issues. Im pretty sure that all H4/6 type motors have to have some kind of IMS to spin the over head cam shafts.

TonyTwoBags

Understood - it's one of those things where people have this built in heuristic of Mezger or air-cooled = no IMS, bulletproof when it's not exactly the case. An m96 can be updated to the reliable IMS design as we know. Beyond that, I'm not at all convinced a turbo is a cheaper car to run in any reasonable timeline. More money going in, more complexity & different bugs to be dealt with aren't exactly the panacea that some make ownership out to be.

FRUNKenstein

808Bill

Yes "bearing issue" would be correct.
Now the "Solution" would make it a non issue in a qualified m96 engine.

TonyTwoBags

If only that was all that's needed to keep an m96 happy into old age!

garrett376

Well of course, a turbo costs more to buy initially, is more powerful which means it eats more gas, gets going a lot faster so you get tickets easier or crash easier, so yes, it's more expensive in some controllable ways. But the big difference: the turbo doesn't have the 20 or so (how many are there?) catastrophic modes of failure that on a whim, can and very likely completely destroy the engine rendering the car a roller. That, as we all should know around here, is the big difference.

Mike Murphy

Porsche has long used intermediate shafts in many engines, even air-cooled variants.

One of the big reasons why the IMSB fails in some 996/997s is because Porsche wanted to use a lower-cost cylinder head design and have just 1 cylinder head casting for the engine instead of two (unique) heads.

Porsche did the same type of mistake when they went to a single head gasket design in later M96 engines and had to standardize coolant holes. This cost savings measure is thought to contribute to bore scoring issues.

So there you go - the balance between cost/performance/reliability on the two items became...unbalanced.

426H

Anything is possibe on the web forums!