Thoughts on Engine Sound at High RPM's (kinda long)

jtsmith1

Graduated without using it and I dont use it at my current job (nor does anyone else), so I have never really played with it. Maybe I'll start tinkering around with it.

If the system does reach resonance and the engine is held at that state for an extended period of time, there will be failure. However, quickly reaching that frequency and quickly moving past it would not be as much of a worry.

I guess this is not as big of an issue for a lot of people on here, I thought everybody was turned off by the sound/feel at high RPM's.

Red__Zed

I guess we will have to wait for the SAE whitepapers before we can evaluate much further.

I do know for sure the that f/2 harmonic is increased significantly in the 3.7 over previous iterations, due to the changes in the intake manifold/collector.

phelan

...duh?

Are you an aerospace engineer?

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凛 ('Rin') - 2009 Nissan 370Z
With silence comes peace. With peace comes freedom. With freedom comes silence.

Armonster

I came from a 2001 maxima (3.0L version of the VQ) and it was MUCH smoother at higher rpms. Although it only revs to 6000-6500 (cant remember exactly). I have also driven a Cayman S, which is much smoother as well.

Glad I'm not the only one who thinks this engine vibrates like crazy. Kinda freaked me out the first time.

b1adesofcha0s

I came from a 2000 Maxima, but also had a 2010 for a few months.

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jtsmith1

No, I work in the aerospace industry and I am a mechanical engineer, haha. I work on a team that designs jet engines, I do mostly mechanical/air flow stuff. Newly graduated though, so Im still wet behing the ears. Worked on airplanes such as the F-16 and the KC-135 for the past 8+ years though.

Zed, I had an EM1 civic. Needed something for college, sold my 240's so I wouldnt keep dumping money into them and got something practical, but it still needed to be a little fun.

My wifes TL also has a v6, although smaller, is much more refined and no vibrations at higher RPM's. That is to be expected with a nicer/luxury style vehicle, but can we learn something from those platforms and apply it to ours?

phelan

So you're a compressible fluids engineer? Do you use ANSYS for CFD analysis?

And yes, there are multiple reports that a lighter flywheel increases vibration in the crankshaft. That much should be obvious. While it is tempting to consider the easy "oh just make the flywheel" heavier, however, don't forget that a dampener does exactly that - it DAMPENS the response. The full magnitude of the force still must be transmitted, but now it's over a greater time T. So basically...all of the responsiveness of the engine is now thrown out the window.

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凛 ('Rin') - 2009 Nissan 370Z
With silence comes peace. With peace comes freedom. With freedom comes silence.

jtsmith1

Hahaha, nope, still a mechanical (just as I was two post ago). I have not used ANSYS as of yet, but I do see it in my near future (just for my general understanding of the software). My job provides me with resources if I need any CFD done (i.e. a group of people who do nothing but CFD). I more or less use the results to make decisions regarding design. Keep in mind, I am not coming up with any brilliant, new concepts ( at least right now haha), I follow strict design procedure that has been proven with decades of experience and data.

I understand your point about losing engine response, as I think we all do, but some of use who are not tracking our cars may be willing to make a tradeoff, but first we would have to know what that tradeoff is. Minimal performance loss for decent decrease in vibrations, Ill take that all day, because I dont and wont ever track this car.

However, a heavier flywheel may be way out of the question, I dont know the answer, thats why I postulated the question and asked! Wanted to open it up to others who may have more experience and stimulate some outside of the box thinking. This may not even be an option, seeing as the flywheel seems to be fairly heavy to start with. However, if more weight (like less than 10%) could signigicantly decrease the vibrations and sound, I would be a buyer.