nVH Concerns

[shendrick]

So my 2008 is 3 years old, completely stock, and has 22K miles. All wheels/tires are perfect so no contribution to potential NVH concerns. I do plan to keep the car for a very long time and will probably not extend the warranty when the time comes. I don't flog the car much which has gotten me thinking. After reading about the occasional bearing issues with 08s I keep wondering if this could become an issue in the midle of my car's lifecycle? The reason I am thinking about this is that my benchmark for low NVH is our 2005 330i zhp. Despite its I6 architecture, that car/engine transmits only very low levels of NVH into the cabin. It's amazingly different from an engine smoothness standpoint than the M3. I'll also take noise off the table (despite use of the term NVH - so I'll modify to nVH) since it's vibration that I'm most concerned about. The M3 has much higher levels of nVH by comparison despite its inherently better balanced v8 architecture. Maybe some of this is engine mounts, drive train wind up, stiffer suspension - all of which can transfer more nVH into the cabin. However, what is the likelihood that none of this is really the case and much of the vibration is linked to increasing wear inside the engine that will bite me after warranty? The good news is that I still have 12 months to figure this out. But the question is: do i really have an engine related nVH issue and how would I figure this out?

[El_Duderino]

It would help to post the definition of an acronym when using it extensively in a post...and in a thread title. After a quick wiki search, NVH: noise, vibration, harshness.

In answer to your thread, I would think the overall stiffer chassis in the M3 plays a significant role in the increased NVH compared to your 330i. Perhaps, others can weigh in?

[JB_Vert]

I've got an '08 also and drive like you--no flogging, just healthy runs up the tach here and there. I would characterize my situation the opposite way--instead of nVH, I have Nvh. The added noise vis-a-vis a less sporty car comes from the road (wider sticky tires); the taut, robust drivetrain with relatively less sound isolation; and the exhaust.

I don't perceive any undue vibration. In fact, one of the things that I really like about this car is how smoothly the engine revs--all the way to redline. The only thing that might be classified as harshness would be certain road imperfections making it through the taut suspension, but even there I find the suspension very comfortable. I've never perceived anything from the engine or transmission that I would call harshness. Just some good ol' mechanical noises that let me know she's alive.

JB

[rourkem]

After test driving an E92 M3, I'm amazed at how quiet and civilized it can be. The bluetooth kit in my E46 M3 is utterly useless because the engine can always be heard loudly in the cabin. Anyone on the phone with me complains that they can't hear me over the noise. I'm hoping that in my on-order E92 M3 that won't be an issue and I can use the built-in bluetooth kit rather than a headset.

[sarddenso]

Originally Posted by shendrick

S Despite its I6 architecture, that car/engine transmits only very low levels of NVH into the cabin. It's amazingly different from an engine smoothness standpoint than the M3. I'll also take noise off the table (despite use of the term NVH - so I'll modify to nVH) since it's vibration that I'm most concerned about. The M3 has much higher levels of nVH by comparison despite its inherently better balanced v8 architecture. ?

From everything I have read, I6 is a perfectly balanced configuration and is better balanced than a cross plane v8.

http://www.autozine.org/technical_sc...ne/smooth3.htm

[JB_Vert]

Originally Posted by sarddenso

From everything I have read, I6 is a perfectly balanced configuration and is better balanced than a cross plane v8.

http://www.autozine.org/technical_sc...ne/smooth3.htm

I agree with the observation that the OP's charaterization of the architectures of the two engines may be flawed. However, I'm not sure that there is any real difference between an I-6 and cross-plane V-8 in their abilities to cancel 1st and 2nd order vibrations. The article you referenced seems to agree:

"The resultant vibration is nearly zero, thus inline-6 is virtually a perfect configuration."

"Therefore 90° cross-plane V8 employ[ing] full-weight counter weights can achieve near perfect smoothness."

The author is careful to not claim perfect smoothness for any architecture.

IMHO, if the OP is perceiving any "harshness" from the S65, then he/she should have it checked out. I've never experienced a smoother engine, particulary at high revs--including my previous E90 335i, which was undoubtedly affected by all the turbo hardware.

JB

[M3PO]

Originally Posted by JB_Vert

I agree with the observation that the OP's charaterization of the architectures of the two engines may be flawed. However, I'm not sure that there is any real difference between an I-6 and cross-plane V-8 in their abilities to cancel 1st and 2nd order vibrations. The article you referenced seems to agree:

"The resultant vibration is nearly zero, thus inline-6 is virtually a perfect configuration."

"Therefore 90° cross-plane V8 employ[ing] full-weight counter weights can achieve near perfect smoothness."

The author is careful to not claim perfect smoothness for any architecture.

IMHO, if the OP is perceiving any "harshness" from the S65, then he/she should have it checked out. I've never experienced a smoother engine, particulary at high revs--including my previous E90 335i, which was undoubtedly affected by all the turbo hardware.

JB

I have to agree. I6's are usually known for their smoothness due to perfect balance. That said, the S65 is a very balanced, smooth engine. That's not the case with a lot of "V" engines. My previous car was a 350z, and despite being a pretty decent engine, the VQ35 creates a lot of vibration and harsh sounds. Before I added breathing mods (to disguise the harsh sounds), I always felt like I was breaking it.

[sarddenso]

Originally Posted by JB_Vert

I agree with the observation that the OP's charaterization of the architectures of the two engines may be flawed. However, I'm not sure that there is any real difference between an I-6 and cross-plane V-8 in their abilities to cancel 1st and 2nd order vibrations. The article you referenced seems to agree:

"The resultant vibration is nearly zero, thus inline-6 is virtually a perfect configuration."

"Therefore 90° cross-plane V8 employ[ing] full-weight counter weights can achieve near perfect smoothness."

The author is careful to not claim perfect smoothness for any architecture.

IMHO, if the OP is perceiving any "harshness" from the S65, then he/she should have it checked out. I've never experienced a smoother engine, particulary at high revs--including my previous E90 335i, which was undoubtedly affected by all the turbo hardware.

JB

Ignoring all the theoretical discussions, the S65 is very smooth all the way to redline. It is so smooth and willing to rev, that I have hit the rev limiter a few times because the engine just sounds like it wants more and more!!!

The car practically has a race engine in it, and considering that I have never thought it harsh at all, so you are right, OP should have his car checked out.

[shendrick]

Thanks for all the feedback. I agree that having the car checked out makes sense.