jasonlee4180

Help my out here guys, please.

I finally put on my Kinetix high flow cats and gruppeS ypipe on today. Right away when I start the car, I get a strange buzzing/moaning noise. Hard to describe because I can't think of anything that sounds like it. Like the car is moaning!!

Ok, it's probably rattling on something right? Well, here's the strange part. I drive it around a while to warm up and this noise just disappears! Like it never existed. The buzzing/moaning going away after warm up can't be attributed to the cats/ypipe touching something right?

I know there was discussion about the engine torquing making the cats/ypipe possibly rub the frame but, since it goes away upon warm up, I can't imagine this to be a torquing problem?

Throughout the whole day, I noted when it made this horrible buzzing/moaning noise. It's fairly consistent. Usually at a cold start up and between 1500 - 2000rpm.

Anyone have this problem before or know how to fix this?

jasonlee4180

Hmmm....matter of fact, I did indeed use the factory layered gaskets. My car is also a G35, but I hope that's not one of the reasons its making this hideous noise.

What you say could make absolute sense. There are only 2 bolts that seal the gaskets from the cats->ypipe and also the ypipe->stock bpipe, so I question how solid the seal this makes.

I pray its not the gaskets from the headers->cats, it was such a pain holding everything up while trying to bolt things back together alone.

jasonlee4180

Update:

I swapped the layered gaskets from the cats->ypipe and the ypipe->bpipe and it fixed like 90% of the moaning noise. The layered gaskets and the difference in flange diameters are what seems to be causing this buzzing/moaning noise.

I just used the gaskets that came with the GruppeS ypipe and the Kinetix HF's. However, I did witness a leak from the ypipe->bpipe. Either the gasket is crap or the 3"->2.5" is forcing a leak to occur.

There is still a slight buzzing noise that exists at cold start up but I can live with this existing noise for now.

I'm putting my 3"->2.5" cone reducer on this week so hopefully this will cure the leak and clean up the exhaust note after 4k rpm.

vfr350

I have the same setup, The Gruppe S gaskets leaked no matter how much how tight they were. New stock gaskets sealed right up (cat side flanges). I had the reducer cone put on, but it doesn't clean up that note. I slowly noticed more rasp coming out, only to find one side on my mounts on the cats was cracked...Welded up, was good but now the otherside cracked and needs to be welded. Now the only thing missing to help with that cold start sound is that on the stock ypipe it had additional packing with a shell around it, think we will just have to live with it, as it must have something to do with the temp of the ypipe or sound that the stock shell quiets.....

taurran

iTrader: (18)

The difference in flange sizes between the hf cats and the y-pipe is a big problem. I kept blowing gaskets and getting exhaust leaks because of this.

DayBlueZ

iTrader: (13)

Crap! You guys gotta be kidding me. I just bought a Gruppe-s and Kinetix HFCs for my 350.
Can you get used to it or is it something that if not fixed soon will make you sell the items?
Anyone try beveling the lip in the 2.5" pipe to help reduce drag against the flat flange? Is the reducer the key? Know where we can get better gaskets or a custom set made?
VFR350, did they crack because fittment wasn't right and it caused undue stress?

vfr350

Everything seem to fit ok, I ran the high flow cats last year with the stock y pipe, but i never really looked for the little cracks. The Gruppe S pipe could have fit a little better, flex pipe made things fit. Maybe this put a little more pressure on the cats as the stock flex pipe in loosey goosey. Kinetix suggested not using the cat brace, but then my system vibrated like mad. The last bolts I put in was for the brace, and everything lined up just fine. Gonna try the welding thing one more time, and if the crack by the time I put my headers on, i'm going to gut the stock secondary cat, which would create a small resonates chamber, fixing the upper little goofy sound. Oh btw, the power is nice......here's some good reading......
http://superchevy.com/technical/engi...xh/index1.html

http://zhome.com/ZCMnL/tech/exhaust.html

jasonlee4180

nope, I was wrong, it didn't go away. There seems to be that annoying buzzing noise even after the car has warmed up. It's very consistent, between 1500 - 2000 rpm.

Does the dealer sell 3" gaskets?

vfr350

Check the top side of the Cats for clearance, had to bend the stock heat shields some, just a little tweak.......