Engine Vibration at 4k+ RPMs - Zilvia.net Forums | Nissan 240SX (Silvia) and Z (Fairlady) Car Forum

DLo Eric · 03-16-2008, 11:38 AM

For the past few years I've been running some solid motor mounts that basically look like these

Same material for the tranny mount. So everything that goes on I can literally feel. I can feel a vibration difference in knock from 91 octane to 100 octane.

Now my problem is that ever since I went to these solid mounts I've been having a harsher than normal vibration from 4k+. There isnt any power loss and its directly from the engine and since I'm doing maintenance on my car I thought I'd try to tackle this problem since it's been bugging me for the past 2 years. My wideband isnt showing any dips/spikes at 4k and my SAFC isnt showing any knock either.

Its constant within all 5 gears which makes it unbearable to drive faster than 85 mph in 5th gear. I dont believe anything is loose, I've upgraded/replaced/removed/re-installed most of the exhaust/turbo components within the past 2 years and still the same vibration.

My assumption would be that RAS would help, what should I do?

s14unimog · 03-20-2008, 02:31 PM

I don't know why yours is doing that but my SR has a horribly loud rattle in the exhaust at 4k RPM. I don't think its a performance related issue but more so that something is loose or broken and the SR makes it apparent at 4k because that must be a resonant frequency of the motors sound.... Kinda like when everything in your interior vibrates a bunch at a certain RPM.

This may be totally wrong but it sounds good. Now if I can only figure out what the fu*k that noise is!

aNskY · 03-31-2008, 09:36 PM

Quote:

Originally Posted by s14unimog

I don't know why yours is doing that but my SR has a horribly loud rattle in the exhaust at 4k RPM. I don't think its a performance related issue but more so that something is loose or broken and the SR makes it apparent at 4k because that must be a resonant frequency of the motors sound.... Kinda like when everything in your interior vibrates a bunch at a certain RPM.

This may be totally wrong but it sounds good. Now if I can only figure out what the fu*k that noise is!

shit i thought i was the only one who had that problem

verge513 · 04-05-2008, 05:59 AM

yea could be the resonates...or that youre solid motor mounts are transfering all the engine vibrations. try either changing to a diffrent muffler to change the pitch on the engine, or go back to rubber or urthan engine mounts.. also look to see if youre transmission is touching anywhere. i had that problem in my sonoma and it pretty much rattled the whole cab at certain rpms

KiLLeR2001 · 04-05-2008, 03:36 PM

I had a strange rattle at 4k RPM on my KA24DE. It ended up being the heat shield on the exhaust manifold.

03-16-2008, 11:38 AM	#1
DLo Eric Zilvia Member Join Date: Apr 2004 Location: Las Vegas Age: 37 Posts: 245 Trader Rating: (2) Rides Gallery: DLo Eric Feedback Score: 2 reviews	Engine Vibration at 4k+ RPMs For the past few years I've been running some solid motor mounts that basically look like these Same material for the tranny mount. So everything that goes on I can literally feel. I can feel a vibration difference in knock from 91 octane to 100 octane. Now my problem is that ever since I went to these solid mounts I've been having a harsher than normal vibration from 4k+. There isnt any power loss and its directly from the engine and since I'm doing maintenance on my car I thought I'd try to tackle this problem since it's been bugging me for the past 2 years. My wideband isnt showing any dips/spikes at 4k and my SAFC isnt showing any knock either. Its constant within all 5 gears which makes it unbearable to drive faster than 85 mph in 5th gear. I dont believe anything is loose, I've upgraded/replaced/removed/re-installed most of the exhaust/turbo components within the past 2 years and still the same vibration. My assumption would be that RAS would help, what should I do?

03-20-2008, 02:31 PM	#2
s14unimog Nissanaholic! Join Date: Dec 2003 Location: In a place, near a river, over a lake Age: 37 Posts: 2,415 Trader Rating: (22) Rides Gallery: s14unimog Feedback Score: 22 reviews	I don't know why yours is doing that but my SR has a horribly loud rattle in the exhaust at 4k RPM. I don't think its a performance related issue but more so that something is loose or broken and the SR makes it apparent at 4k because that must be a resonant frequency of the motors sound.... Kinda like when everything in your interior vibrates a bunch at a certain RPM. This may be totally wrong but it sounds good. Now if I can only figure out what the fuk that noise is! __________________ Fuking ginger bread man stole my wallet... SHIFTlock_slide to side d3m3rs0n: if i have a baby im naming it Brandons Fault Emerson

04-05-2008, 03:36 PM	#5
KiLLeR2001 Post Whore! Join Date: Jun 2007 Location: オーランドフロリダ Posts: 7,955 Trader Rating: (46) Feedback Score: 46 reviews	I had a strange rattle at 4k RPM on my KA24DE. It ended up being the heat shield on the exhaust manifold. __________________

04-05-2008, 05:59 AM	#4
verge513 Leaky Injector Join Date: Mar 2008 Location: memphis tn Age: 36 Posts: 54 Trader Rating: (0) Feedback Score: 0 reviews	yea could be the resonates...or that youre solid motor mounts are transfering all the engine vibrations. try either changing to a diffrent muffler to change the pitch on the engine, or go back to rubber or urthan engine mounts.. also look to see if youre transmission is touching anywhere. i had that problem in my sonoma and it pretty much rattled the whole cab at certain rpms