engine harshness at high revs

m4a1mustang · 06-30-2009, 10:16 AM

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.

Scribe · 06-30-2009, 11:48 AM

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 · 06-30-2009, 02:11 PM

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.

mrmixitup · 06-30-2009, 02:27 PM

Quote:

Originally Posted by 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.

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

RCZ · 06-30-2009, 02:32 PM

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

RCZ · 06-30-2009, 02:34 PM

Quote:

Originally Posted by mrmixitup

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

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 · 06-30-2009, 02:37 PM

Quote:

Originally Posted by mrmixitup

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

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.

m4a1mustang · 06-30-2009, 03:09 PM

Quote:

Originally Posted by 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.

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.

6SPD_FTW · 07-04-2009, 08:44 AM

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

turbo8765 · 07-06-2009, 10:04 AM

It's largely an inherent property of the engine. A V6 is not inherently balanced. Neither is an inline 4 cyl, a boxer 4 cyl is.

Straight 6 cyl and 90 degree v8s are inherently balanced also. That's partly why BMW uses straight sixes and refers to a V6 as a bent six.

When u take a motor that's not inherently balanced and give it large pistons and a long stroke (high velocity), it's going to vibrate a lot. You must then add counter weights to smooth things out, but that robs power and increases complexity. They can be made smooth ie NSX, but it's not easy.

I have an M3 and a 335, and they're smoth as silk. Coming from that, the VQ37 feels VERY harsh.

You can't compare the vq37 to the v8 because the v8 is an inherently balanced configuration.

I could explain in much more detail, but I'm typing on my iPhone

turbo8765 · 07-06-2009, 10:07 AM

It has nothing to do with VVEL.

Scribe · 07-06-2009, 11:03 AM

Quote:

Originally Posted by turbo8765

It's largely an inherent property of the engine. A V6 is not inherently balanced. Neither is an inline 4 cyl, a boxer 4 cyl is.

Straight 6 cyl and 90 degree v8s are inherently balanced also. That's partly why BMW uses straight sixes and refers to a V6 as a bent six.

When u take a motor that's not inherently balanced and give it large pistons and a long stroke (high velocity), it's going to vibrate a lot. You must then add counter weights to smooth things out, but that robs power and increases complexity. They can be made smooth ie NSX, but it's not easy.

I have an M3 and a 335, and they're smoth as silk. Coming from that, the VQ37 feels VERY harsh.

You can't compare the vq37 to the v8 because the v8 is an inherently balanced configuration.

I could explain in much more detail, but I'm typing on my iPhone

That was my theory, but the V8 "version" of our engine is also rough in the high revs. That's what my post pointed to, but it's got to be something else or the VK50 would be smooth and apparently it's not.

FricFrac · 07-06-2009, 11:19 AM

Quote:

Originally Posted by wstar

Well, it certainly sounds quite loud and raw up around 6-7.5K, and I could see how some would call it unrefined, but I wouldn't say the car is vibrating in a really noticeable way, and doesn't seem as bad as some people seem to be making it here. Are you feeling that through the steering wheel, pedals, shifter, etc? Tomorrow if the rain is gone I'll go for a drive in the morning and specifically pay attention for it so I can compare.

I'm confused about the vibration issue. To me the car seems very smooth even at 7K - is it possible that there is a difference between cars? Or have I just been driving older vehicles for too long? Is it possible I just don't have enough miles (around 2000 miles) on the vehicle? I'm not detecting any significant vibration yet I can feel every nook and cranny on the road...

Modshack · 07-06-2009, 01:30 PM

Quote:

Originally Posted by FricFrac

I'm confused about the vibration issue. To me the car seems very smooth even at 7K - is it possible that there is a difference between cars? Or have I just been driving older vehicles for too long? Is it possible I just don't have enough miles (around 2000 miles) on the vehicle? I'm not detecting any significant vibration yet I can feel every nook and cranny on the road...

Mine's been smoothing out more as it gets miles on it...Plus my intake/exhaust is fully adapted now. 2100 miles and it keeps getting better. I found it very annoying when the car was newer..

There is an inherent Harshness factor with this motor, but it does seem to vary a bit between cars...

DIGItonium · 07-06-2009, 01:42 PM

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!

06-30-2009, 10:16 AM	#31 (permalink)
m4a1mustang A True Z Fanatic Join Date: Feb 2009 Location: Northern VA Posts: 55,385 Drives: on two wheels Rep Power: 6962	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. __________________ - Steve Zs & Coffee - Saturdays at 10AM in Fairfax, VA and Columbia, MD (Click the banner!) LIKE us on Facebook!

06-30-2009, 11:48 AM	#32 (permalink)
Scribe Base Member Join Date: Jan 2009 Location: Houston, TX. Posts: 182 Drives: Touring-Sport-Manual Rep Power: 220	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. Last edited by Scribe; 06-30-2009 at 11:58 AM.

06-30-2009, 02:11 PM	#33 (permalink)
VTalumni Base Member Join Date: Feb 2009 Location: Germany Posts: 31 Drives: 370z soon to come Rep Power: 16	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. __________________ '98 Ford zx2 '04 SRT-4 '07 Scion tc

07-06-2009, 01:42 PM	#45 (permalink)
DIGItonium A True Z Fanatic Join Date: Jan 2009 Location: Kansas Posts: 3,800 Drives: 09 Z34-TT 6MT Rep Power: 42	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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06-30-2009, 02:32 PM	#35 (permalink)
RCZ A True Z Fanatic Join Date: Nov 2008 Location: Miami Posts: 6,403 Drives: '09 370Z Rep Power: 1118	Our glorified vtec might be responsible for the vibration...

07-04-2009, 08:44 AM	#39 (permalink)
6SPD_FTW Base Member Join Date: May 2009 Location: Bristol, VA Posts: 59 Drives: 09 370Z Bl 6MT Rep Power: 15	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

07-06-2009, 10:04 AM	#40 (permalink)
turbo8765 Base Member Join Date: Jun 2009 Location: Southeast Posts: 11 Drives: M3, considering 370z Rep Power: 15	It's largely an inherent property of the engine. A V6 is not inherently balanced. Neither is an inline 4 cyl, a boxer 4 cyl is. Straight 6 cyl and 90 degree v8s are inherently balanced also. That's partly why BMW uses straight sixes and refers to a V6 as a bent six. When u take a motor that's not inherently balanced and give it large pistons and a long stroke (high velocity), it's going to vibrate a lot. You must then add counter weights to smooth things out, but that robs power and increases complexity. They can be made smooth ie NSX, but it's not easy. I have an M3 and a 335, and they're smoth as silk. Coming from that, the VQ37 feels VERY harsh. You can't compare the vq37 to the v8 because the v8 is an inherently balanced configuration. I could explain in much more detail, but I'm typing on my iPhone

07-06-2009, 10:07 AM	#41 (permalink)
turbo8765 Base Member Join Date: Jun 2009 Location: Southeast Posts: 11 Drives: M3, considering 370z Rep Power: 15	It has nothing to do with VVEL.