engine harshness at high revs

m4a1mustang

I think maybe the M6 guys feel it more than the 7ATs. I get a lot of that coarse feedback not only from the seat but from the gearbox and the clutch as well.

I am willing to deal with it but it does irk me every now and then considering the test drives I did with the Cayman S... so every now and then I think about how silky smooth that engine feels compared to the Z. But thinking about the price differential usually kills any "should have bought the Cayman" thoughts.

Though it is funny, I think, that my '03 Mustang GT's 4.6L V8 was a lot smoother and a little more refined feeling than this V6. I'm not really a fan of the gearbox in the Z either so it kind of annoys me every now and then.

Maybe I'm just picky, though. I've pretty much accepted the fact that no matter what car I have I will never be totally happy with it.

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RCZ

maybe 6mt is a lot worse. I can feel it in the floor, shifter, steering wheel. I've noticed the transmission mounts need some serious work too. The mounts are too soft.

wstar

Hmmm, I tried to pay better attention this morning, but no I don't think I'm getting vibration like you describe. It could be that your vibration is largely coming into the body though the clutch/transmission, and my torque converter is eating it up instead on the 7AT.

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zZSportZz

I have a 6MT and the whole car vibrates and almost feels like its going to rip apart at any moment lol (slight exageration) at high rpms. You really do feel it in the floor, steerng wheel, shifter...even the seat to some extent.

mrmixitup

If the mounts were firmer, wouldn't you be getting alot MORE vibration? Engine movement would be directly transfered to the entire chassis.

RCZ

Yes sir, but thats not the reason why I want harder mounts. I just feel the transmission mounts flexing and the shifts could be a lot more "positive" with some bushings. The car will feel a little crisper response if you remove the flex in the tranny.

VTalumni

Yeah thats true. And usually with stiffer mounts you feel it more at idle. Since it seems like this problem isnt noticed at idle, the harshness must be more than just the mounts.

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m4a1mustang

Yeah, I definitely think the we 6MT guys feel it the most. You really feel the vibrations in the clutch pedal when you shift at high RPMs. We get feedback from the clutch pedal and the shifter that the 7AT guys aren't getting.

Usually for them it's two hands on the steering wheel and the feedback you get from the wheel seems mostly to be from the road.

I know at times pushing the clutch pedal in just feels downright nasty.

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Scribe

Likely this has to more to do with the natural imbalance of the V6, which has been exacerbated as they stroked the original VQ engine design more and more. Another engine recently revised with a longer stroke and VVEL is the VK50DE. How harsh is the VK50 in the FX50 at high rpms?

Edit: After finding Edmunds review, they stated that the VK50, 'much like VQ35/37 this V8 isn't quiet or smooth @ high RPM.' So we can rule that it's either the longer stroke, the VVEL or both.

VTalumni

So, the problem must be related to the engine since it is noticeable in both the 6MT and 7AM (I know more in the 6MT but that doesnt matter).

Was this problem noticed in the 350z? Someone mentioned the VQ35DE was smooth. I am not familiar with engine names, but is that the 350z engine?

To me, the problem seems like its related to the VVEL. Do the vibrations increase gradually as you rev higher or is it an instant thing? Has anyone driven a Honda with VTEC? VTEC kicks in full force at a certain rpm. Its like a whole nother engine. The intake seems 17 times louder than before VTEC kicks in and the whole car becomes harsher. Does it seem something like that? If so and the vibrations really kick in all at once at a certain rpm, then we can confirm that it is something related to the VVEL. If not, maybe it is an imbalance in the crankshaft or camshaft, something rotating.

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m4a1mustang

It's really a gradual thing. It gets worse as you go up in revs. It's nothing like the VTEC transition where at a given RPM *bam* you have a new engine.

VVEL may or may not have something to do with it, but I'd venture to guess that it probably isn't the root cause. It's probably just how the engine naturally behaves and we just have to deal with it. It's definitely wierd, though, because it doesn't feel right when you drive the car hard... but it probably is right. Just have to get used to it I guess.

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6SPD_FTW

The electronically controlled motor mounts are usually 'soft' at <950rpm and
'hard' at >950rpm. The VQ35DE in the Altima/Maxima/Murano has a vacuum/solenoid controlled system that softens the mounts at idle and hardens them at speed. The 370Z doesn't have this system. There's vacuum tubes that lead to the motor mounts that would be there and they aren't on the Z.

Dunno bout fluid-filled mounts, though. Nissan used fluid-filled mounts on the transmission and front (side) motor mount on the Altima VQ. Judging by the harshness of the Z, I'd doubt there are any fluid-filled mounts on this car.

Late,
Trav

RCZ

Our glorified vtec might be responsible for the vibration...

DIGItonium

I've not revved my car much to notice harshness (1800 mi. so far), but I notice a hint of it compared to my VQ35DE. Engine sound of the VHR seem to be more relaxed at 4k, which is like 3k in the DE (it gets angry quicker). From watching the Genesis 3.8 videos, the VQ definitely lost some smoothness.

What I really like about the VQ37 is the lower engine note that compliments the higher note of the exhaust sound. With the VQ35, that lower engine note is not present.

Overall... love it!

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imag

I agree that it's the valvetrain. That VVEL system is slick, but it somehow is causing more vibration than a well-refined camshaft, is my guess. I think it's worth it overall, but that's just me.

My counterpoint to the car mags is that Porsche flat sixes - every single one of them - sound like complete rubbish below 2000 RPM. They may sing a decent song above that, but the fact that 100K+ cars sound so much like VW Beetles at idle is inexcusable in my book.