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

phelan

I think a design parameter for any automotive engineer in building a new engine is to make sure the resonance frequencies are far, far away from any operating condition. The last thing you need is someone taking their car out, high-revving through the gears on the street, then watch the engine hit resonance and displace itself into the road.

Keep in mind that engines (and most mechanical components on mass produced products for that matter) are built with a high margin of safety. For something mass produced like a car, the margin of safety is typically beyond 1.0, to cover remote and extremely remote probabilities. So even at high RPMs, I doubt we are anywhere near the resonance frequency, or achieving any damaging modal shape on the VHR platform.

RCZ nailed it when he said the engine is just rough. Granted some of the mounts could have dampeners on it to soften the vibrational effects, but then you add weight in a car that really doesn't aim itself to be a smooth driver. That's half the fun of the Z; a simple sports car (or as simple as you can get these days....except for the newfangled SRM thingy).

Considering your theory about the flywheel - yes, a heavier one will act as a dampener and reduce the vibration in the transmission. But consider the mass of the flywheel against the amount of force acting on it. To get an appreciable level of reduction will require the flywheel to much more mass than it is worth performance-wise. Do the simulation in MATLAB using a maximum level force input based on the power output of the engine at high-RPM, and you'll see it.

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凛 ('Rin') - 2009 Nissan 370Z
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