Nissan 370Z Forum - Does FI CBE have any drone or rasp?

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- - Does FI CBE have any drone or rasp? (http://www.the370z.com/intake-exhaust/22771-does-fi-cbe-have-any-drone-rasp.html)

Quote:

Originally Posted by '10Anamoly (Post 652228)

Zsteve, you are partially correct that straight through exhausts have the strong tendency to drone because the mufflers dont break up the sound waves. However, as mentioned above you can fix this drone with tuned side branch resonators. This lets you keep the straight through exhaust and get rid of the drone too, best of both worlds with performance, sound and comfort. Side branch resonators reflect the wavelength of drone back at itself at a quarter the wavelength and effectively cancel out that frequency. Since the drone is actually the pipe resonance frequency echoing in the cabin, you eliminate drone by targeting the frequency at which the resonance occurs.

:tiphat:

Yea I have read up on this some and actually opened a thread on it way back, before that one company came out with the results of thier side tubes. I have thought about doing that to my FI but I know that you need to get the right length to match the freq that the exhaust is making. So I never pursude it. Pics of yours would be great.

If your drone is like mine, from 2200rpms to around 2700rpms, 28-30" pipes, one per site, should do the trick. Your drone frequency should be close to mine.

I used a mic to record the drone and then analyzed it with Audacity. Drone occurred at 125hz-ish. My pipes are 28" and its dead silent from 2300rpms to 2700rpms and no drone above or below.

Pics are in the intake/exhaust thread I posted about recently near the last posts.

LINK

Quote:

Originally Posted by '10Anamoly (Post 653060)

do yo have any other resonators on your exhaust? I have the 12 inch ones with my FI. So would that change the freq? So you have your tubes not going the same direction as the mufflers?

I have OEM resonators and 4" Magnaflow race mufflers. The side branches go at 90 degree angles to the exhaust flow so the sound will travel down them effectively. As they are capped, there is no real exhaust flow through them.