i just changed the rubber hangers with different, stiffer ones. i lowered my car and have 35's on, so it's a real bumpy ride. this has taken care of the pipes banging against the sway bar.

 

Ok you can here it in this video.

You can here it after the pops around 6-7 seconds into the video.

this is with the h-pipe joint already sealed.

https://my350z.com/albums/albun48/abi.mpg

 

yup, that's it. the light hiss at the 6-7 second mark. any additional thoughts on how to fix this (if at all)?

 

Well, it has been several weeks since the last post on this thread. I am interested in knowing if anyone figured out the "downrev flutter" sound.

How about you Vic? Did you solve the problem or are you just living with it?

I think I have it now. No exhaust hiss while on the throttle, but a flutter sound on downrev (after releasing the throttle).

 

I believe the flutter is caused by the H pipe. Pushing the H pipe together as much as possible and Tightening the clamp seems to at least temporilary fix the problem. I think welding the H pipe together could be a permanent fix.

 

I've come to the conclusion that we just have to live with it. Welding the H pipe isn't the solution, as there's really no leak, and moreso because of air/back pressure. But Wedge, i'm surprised you get it with high flow cats, I thought it was just with people with test pipes.

 

I leave it be, my guess is that the only solution is high flow cats.

I feel dumb for jumping on this mod, shoulda waited for reviews...

high flow cats flow just as well and gain just as much

*sigh

 

Thanks for the quick response guys.........I appreciate the information. I didn't want to fight a never ending battle trying to get rid of the downrev noise if there was no hope of doing so.

cinergi 1, I will try readjusting the "H" pipe again as you suggest. It was perfect before the cats but who knows, maybe the joint was moved on installation.

brgerflipr......Yep, started happening after the cats were installed......weird huh? Then again the flow is about the same with the cats so the result may be the same as well, some sort of Cat/Borla combination thing.

Victor, I don't think you were dumb for jumping on the mod. I think the noise is something that only occurs with the Borla combination. Just some weird airflow thing that happens in downrev. Since Borla is the only exhaust system with the "H" pipe set up. Some sort of cross over air turbulance from right to left that does battle in the middle of the "H" pipe? Who knows?

Anyhow, unless I gun the engine while sitting still, I don't hear it. While driving it is not noticable when shifting. As I said, I will check the "H" pipe joint one more time, then I will just learn to live with it.

Thanks again for the info!


Note to brgerflpr: I love that moron joke you have in your sig. My wife and I have been telling it to our friends.......always gets a laugh. Thanks!

 

The noise definitely is the Borla, and not the combination of the Borla with test pipes. It is obviously more noticeable with test pipes as the exhaust overall is much louder. I think it is inherently part of the design. I have test pipes + borla and have yet to hear RT cats + borla. A friend has RT cats + borla, I will ask him if he still hears this down rev.

 

Wedge, glad to bring a smile to fellow forum member.

 

I have the borla + RT cats. The downrev flutter, at least in my case, has nothing to do with the RT cats. It was present right after the initial install of the borla only. We pushed the H pipe together as much as possible and really tightened the clamp. Flutter was gone. Two weeks later I installed the RT cats. No flutter until about 500 miles later and its very slight. I suspect I need to re-tighten all the clamps. I'm considering welding the H-pipe for hopefully a more permanent fix.

 

cinergi1.....that is very interesting. Did you tighten the clamps to spec? (32-35 ft.lbs.) That is what I did on the initial installation of the Borla and had no leaks at all. As soon as the RT's were put on, I had the flutter. They say you have to be careful about over tightening the clamps because you will deform the pipes and get a heck of a leak if you tighten them too much.

Another question for you. When you put on the RT cats, did the Borla mate to the new cats exactly, or did you notice that there was a gap and you had to pull the exhaust forward to mate up?

The RT's seemed to be a little lower than the stock cats to me. In fact, the rear portion of the Borla (passenger side) had to be adjusted because after the new cats were in, the pipe was rattling on the sway bar (which never happened with the stock cats).

Will you take off the H pipe to have it welded, or have it welded while still on the car. I wish the H pipe had been welded in the center right from the factory.

 

Part of the difference may be that I have a G35 cpe 6MT. I don't remember there being any gap. I remember the guy helping me do the install tightening the clamp by hand so I don't know how much pressure was applied. I would assume we would take the H pipe off to do the weld but I think I'm going take your recommedation and tighten to 32-35 psi and leave it for a while to see what happens. I had plenty of sway bar clearence. I think the clearence problem only applies to the Z.

 

OH! You have a G35.......nice car! Yep, not much sway bar clearance on the 350's.

Let me know how the tightening to spec comes out. I am so busy getting the house ready for all the Christmas guests (like Clark Griswold.......seems all the relatives in the east like to head to California for a Christmas visit) that I have no idea when I will be able to put the car on stands and get under there again.

 

G35 coupe borla exhaust is not made out of a bunch of different pieces like the Z's..

 

Really Jason? Hmmm........wonder why they made the Z's exhaust into an erector set then? The more joints and clamps.........the more chances for leaks.

 

yeah,

my guess is the piping is different, not as many bends needed on the G... the piping would have i dont know how many mandrel bends in the Z to be 1 pipe for each side...

 

Does it amplify when you drive next to a wallor barrier?

 

all exhausts doo.. even stock.. you just notice it alot more with louder systems..

borla isnt very loud. but deep and smooth..