I knew there was something wrong. That's not really a true FI exhaust. You still have stock cats?

I never said it was the FI exhaust, just the same style. I however have OEM resonators and the Magnaflow race mufflers instead of the FI setup, and yep they are stock cats. The x-pipe is actual FI back from the cats though to the x-crossover. The rest is custom.

KEVTEX is right, the extra bends and longer exhaust path move the frequency at which the exhaust resonates to eliminate drone. It is similar to a Helmholtz resonator but technically it is called a side brand resonator, running at a quarter the wavelength of the pipe resonance frequency. Similar though, much like the resonators on stock intake tubes!

Sounds good. 15 points=how much bandwidth?

Nice job on the Helmholtz solution!

Sorry points was not very tech savvy, I meant 15hz. The frequencies from 115hz to 130hz seem pretty tame now, per Audacity on my PC when I did re-recording spectrum analysis reviews.

I love my FI 18" Resonator catback but I can't agree with you more, I feel this is not the drone but vibration which literally shakes my car long with my head for a certain rpms which you mentioned, apart from that this thing is amazing.

I have to drive a distance of 90miles on motorway and 70mph cruise this drone/vibration/sounds is annoying.

I was told by someone if I can fix two flex pipes on the far most end near stock cats it can kill this thing, as our FI exhausts doesn't comes with flexpipes. Check with Tony as well and he was very cooperative as usual, but my problem comes I live quiet far so to get flex pipes shipped and get those TIG welded was an issue.

Man thanks for the pics, I am a bit nobb in these frequency and size things. Would it kill this sound if I just attached something between these two tips or the size of the pipe has really a big importance and what kind of welding did you use?

It really should not be the lack of flex pipes causing the drone, it has to do with standing wavelengths through long pipes. The length does matter a lot, what you need to know is the frequency of the drone. It should be close to what mine was.

Is the drone on your car heaviest between 2200rpms and 2800rpms? If so, you need around a 28" side branch resonator on each side, coming at a 90* angle off the area between the tips and the rear mufflers. That will kill off most of the drone. I had a local shop with a good welder make them for me for $100 and then I coated them in 2000* high temp flat black paint. They are tucked up behind the muffler so you cannot see them. Make sure to cover your rear bumper and the car undersides before you paint anything so you dont get spray paint on your paint job!

Here is the video of my setup with the side branch resonators and custom exhaust:

'10Anamoly's 2010 370Z - OEM Intakes, FI X-Pipe, OEM Resonators, Magnaflow 4" Race Mufflers, Side Branch Resonators, OEM Tips (1080P Available)

I have seen usually majority of aftermarket CBs are with flex pipes and someone said that this vibration might die with flex pipes

Anyways thanks for the reply, so 28" is the length of each pipe right and im not wrong then I should just weld these to the pipe behind the top without any hole or anything and then weld both of these pipe one behind the other right?

What should be the pipe diameter 2.5"???

For vibration I exactly havent noticed at what rpm it comes on, when you push the car hard it comes a bit early otherwise a bit late but within your mentioned range

This is exactly what Tony from Motordyne Engineering has done with the 350z. His are called Advanced Resonance Tuning pipes and they're integrated into the test pipe and DO create an HP gain.

If its a pipe vibration (not due to sound vibration) you have a different issue. If its that head thudding noise vibration in the cabin (resonance), then you want a 28 pipe coming off the pipe between your rear mufflers and tips.

1. First, use a hole saw to cut out a 2" to 2.25" opening on the pipe between your muffler and tips on each side (one hole per side of the car, hole should face towards the other pipe so the resonator you are welding on will extend into the area where the OEM muffler sat).

2. Next, have the exhaust shop weld a permanent cap (to seal one end of the pipe) on two pieces of 28" long, 2.25" pipes. Basically you want two 28" pipes, each has one open side and one capped side which reflect sound inside the pipe back at the open side.

3. Next, weld each straight piece of 28" to the area of the pipe that you cut the hole out of. You are basically t'ing off the stock exhaust with a 28" piece of pipe at a 90 degree angle, per side. This lets the sound go down that pipe and back and cancels out that annoying droning frequency.

4. End results should be that you have tee'd off of both side with a 28" capped extension pipe, each extension going up into the area where the OEM muffler sat.

Check my pics and this should all make better sense.

has anyone pinged Tony from FI on this, be interesting to see what his take is?
what kind of power loss would you get if doing this, and im sure it also impacts your warranty

The resonator pipes are back by the tips and meet the exhaust at 90 degrees. As they are capped and are perpendicular to exhaust flow, there is no power loss.

I know this because I had the same exhaust before and after the pipes and have noticed absolutely zero loss with them off, just much more comfort due to the reduced drone.

Just to clear I dont have to make any hole in the FI exhaust or have to make hole where these new pipes will connect

WOT burns? black on ur bumper?????? :shakes head:

Yes, you have to use a hole saw to open up a 2" to 2.25" hole on the FI exhaust. That is where the sound waves travel through, down the resonator pipe, and back to cancel out the droning frequencies.

It's a trade off, keep the drone and dont touch the pretty exhaust or mod the exhaust and enjoy the silence (lack of drone, depeche mode style).