2008 m35 muffler noise / low frequency humming noise

[humblepie]

I just got a used 2008 infiniti m35 w/ 11k miles on it. I love how the car handles and accelerates, but I can't stand the level of (I believe) muffler noise this car makes when I'm just cruising. Note: I don't mind the engine rev noise and the cabin noise from the 'performance tires'.

I recently took this car for a drive along the PCH / Santa Monica mountains. So the driving terrain has lots of inclines. The constant low pitch humming noise of what appears to be the muffler was giving me a headache after 20 minutes. Perhaps I was under-revving the car somewhat... but this engine can't be that powerful to merit all this noise.

But even on regular driving sessions, there's a noticeable, persistent low pitch hum noise that wont go away until I completely let go of the gas.

Perhaps, I just need to adapt my driving habit to accelerate faster to the desired speed, then barely keep my foot on the gas there after.

I'm on the fence right now debating whether I should look into getting 'quieter' mufflers installed, but not sure if the issue I'm describing is indeed the muffler related or just engine 'growl' noise.

In any case, I was just wondering if anyone else has had a similar experience w/ this car.

Any suggestions / advice would be much appreciated.

[humblepie]

The more I drive this car, I'm beginning to feel the issue I'm experiencing is a direct result of a combination of my driving style and the muffler. The issue is most noticeable in the 4th and 5th gears.

When driving and I barely have the foot on the gas (just enough to keep the RPM steady), then the noise is at a minimum and I'm at constant speed. However, the problem is that on most terrain, you have slight inclines as well. So I need to give a little bit more gas than is required to keep the RPM steady (or else my speed will start to drop). So this is when I apply a bit more gas, then I start to hear a very low pitch growling noise partly from the engine, but I think most of the noise that annoys me is magnified by the muffler.

So can anyone suggest some mufflers that might minimize this effect I'm hearing? Or if I don't know what I'm talking about, then please enlighten me as well.

-------- UPDATE 1/1/09 ----------------

I took my m35 to the dealer to have it checked and they found that the exhaust pipe leading to the muffler was offset - probably due to some object on the road hitting the pipe. I just got the m35 back and found that the noise at ALL levels are much quieter and smoother.

No longer does my cabin floor resonate and no longer do I hear an excessive low freq drone at lower RPM range. And the quality of sound from the engine revving up to higher RPMs is much smoother tone than the raspy noise I heard before. I'm so happy now

The only issue now is I'm noticing a slight drone when @ idle from the exhaust. I think it's more pronounced if I have the fan/AC on, but will have to test it more.
Modified by humblepie at 2:03 AM 1/1/2009

[striz923]

I can't imagine that a "normal" sound would cause you a headache in about 20 minutes. Most of the noises at any speed are the tires and wind for my 06.

[DashingMax]

Thank you for the update...keep us posted.Did the dealer fix that under warranty?

[humblepie]

No, this was not repaired under warranty. I had to pay about $100 to fix the muffler.

Recently, I tried Redline's fuel injection cleaner and this significantly improved the tone of the engine revving. The sound characteristic of the exhaust and the engine is much smoother and the car feels and sounds much more like a quality performance vehicle. I highly recommend it.