ZinMiami

iTrader: (2)

I just got back from an exhaust shop and what they found and did has lead me to reevaluate my original opinions of the Helix Cats I had put in about a month ago.

I went to the shop because Friday the car suddenly got very loud. Only momments before I heard what I thought had been a rock bounce around underneath the car. It wasn't! It was a bolt from the exhaust, the mid-pipe/y-pipe joint to be exact. It lost one of the bolts and spit out the gasket. The remaining bolt bolt was ready to go too. They also found the welds around the flange to the Fujitsubo mid-pipe had hairline cracks. They welded the cracks, replaced the gasket and bolts so that is all fixed now.

Next I asked them to fabricate a solution to allow the Helix cats to use the OEM cat support bracket. They welded a couple of steel tabs onto the Helix cats and bolted everything up so thats all good now too. Not bad for $45.

So what did this have to do with my earlier not so great impressions of the Helix cats you say?

Well all these items were contributing to vibrations all along the exhaust causing what seemed was awful rasp and a crapy boomy hollow sound. Now that everything is ship shape under there, the exhaust is back to sounding great. It's still the subdued rumble that is typical of the Fuji exhaust, but with just a little more growl. As for the percieved rasp there is an ever so slight momentary rasp just as you hit 4K rpm but lasts only a second as it gets replaced by a sweet roar on the way to redline.

So I can now say that the Helix cats are ok in my book. As for power, the butt dyno always sensed a change once they were in its just more pleasant and now it feels even better.

King Tut

iTrader: (1)

Sounds like the issues are more with the Fujitsubo mid-pipe not allowing enough flex since all of the exhaust systems flex is left to the mid-pipe section whereas on most cars the flex is done prior to the cats. As for the exhaust bolts. They should be re-tightened, like most bolts that see vibration, after about 100 miles. I have been meaning to get back under the car and check mine out, I might get to it this weekend.

ZinMiami

iTrader: (2)

I agree. That is exactly what is happenning. All the flex is clearly at the y-pipe/mid-pipe joint.

Jason@Performance

iTrader: (11)

The question is... Would that have happend to your Fujitsubo Exhaust if you were using stock cats...

I would bet... No...

We have seen alot of problems with Headers Cracking at the flange where they bolt up to the Cat or Y-Pipes cracking either at the Flange next to the CAT or Mid-Pipe.

But, this happens 95% of the time to car with Test Pipes.

I have seen this happen to cars with Stock Cats but their resonator canister on Fujitsubo or NISMO exhaust is scrapped pretty bad and the exhaust cracks at the mid-pipe / y-pipe flange...

Alot of test pipes / high flow cats are just a little bit too long so it pushes the exhaust piping down. This would put extra stress on the exhaust flanges and even more under torque movement...

Usually if you have to space the rear cross brace down to let the exhaust clear you may have this problem in the future...

I had it to with my test pipes... Ive put even more miles on my car with Stock Cats and havent had any exhaust cracking problems...

ZinMiami

iTrader: (2)

Good questions and observations, Jason. It doesn't seem the Helix cats are too long. The y-pipe/mid-pipe joint is not too tight. They butt against each other in what I would say is a correct manner.

I think it may owe more to the fact that most aftermarket cats have no support system like the OEM's. Hopefully I have now remedied that with the custom work that the shop did to utilize the OEM bracket. It sure has stopped all the excess vibrations I was having. Everything is quiet and smooth now.

Jason@Performance

iTrader: (11)

Yeah, that is probably one of the first things that turned me away from the Helix when I first saw them up on the rack.... I forgot to mention that before...

That was one good thing about the RT Cats, they had a very strong support... The Stillen are, well, like a thin flimsy piece of metal sticking out he side...

I originally ordered a set of Mines test pipes back in like August of 2003. But the vender I ordered them from didnt get them to me for 6 months after that! By then, I had already had something else on my car and sold them to someone else so never got to see them...