I just recently put on the Megan Racing resonated test pipes (ebay special $95 + ship) and I was actually happy with the sound when combined with the UT y-pipe and stock exhaust. I had the pipes on for a few days and then became aware of how serious an issue running catless in CA can be, so I had second thoughts (i.e. wimped out =) and decided I might as well spend the extra and have some peace of mind knowing my cats would pass smog (not concerned about visual inspections).

So I head over to Gruppe's (they have a post on here about the pipes, just search for Helix) and pick up a set and did the install a few hours later. The sound is pretty similar to the resonated test pipes, but slightly more tame and quiet when cruising. There is absolutely no rasp or drone, and they sound great under throttle. There is also that little burble when you let off the gas and the RPMs drop to idle. So far I'm very happy with this combo, and think it's just about the perfect balance of power and sound for something with Infiniti badges.

The quality is excellent, with machine welds and high quality metal internals. The install went very smooth and the flanges fit perfect with very little adjusting to the ypipe required.

There is one problem that I know of, which is due to the large size of these cats. Even on my coupe they sit close to the underbody and sometimes rub due to engine torque (I only noticed it in reverse). I actuallly saw this as a potential problem before I installed and hammered the underbody up a bit, but it wasn't enough. I may just try some exhaust wrap and hope that solves it. I've already done cats twice this week with rhino ramps and it's not exactly a fun job.

BTW - the Megan Racing pipes are for sale if anyone is interested. I'm selling these at my cost which was $115 shipped. They are in like-new condition and include all hardware and gaskets.

 

I recently installed a set of Helix High Flow Cats on my sedan and had the same problem on the passenger side. I had to remove the cat and beat the underside with a hammer to create about a 1/4 inch gap. Car sounds great and runs even better.

 

I do admire the spirt that lets one do what ever it takes to make "it" happen, but,....to beat on the car with a hammer, whoa. (I know I know it's on the underside).

 

Notice any performance gains, I am seriously thinking about getting these cats.

 

i was thinking about these too.....but iono about beating up my car for them to fit. If engine torque is causing the cat to rub would an engine dampener help solve this problem? or is it just that bad?

 

That is something I am looking into right now. I think also if you had the stock cat bracket custom fit to the new cats it may eliminate the problem as well...

 

get the crawford hi-flo cats instead... they have no fitment problems.

 

Please let me know what you find out, i'm really interested in the results.

but the helix cats look so sexy.....

 

I can give some definitive results in about one week. I had my sedan on the dyno last Saturday 02/26/05 and it dynoed at 246 rwhp with a kinetix intake plenum, z tube, nismo air cleaner, and Stillen cat-back exhaust. Now with the Helix cats, I plan to go back in about a week to dyno it again.

 

Update on the Helix Cat clearance issue. The right cat was up against the underside of the car when bolted in place. Per Neil at Intense Motorsports who sold me the cats; he spoke with a rep at Helix and while they are aware of the problem, the two recommended fixes were to either dent the outer shell of the cat, which I did not want to do or dent the underside of the car. There is room for this because the area where the cat goes is double-walled sheet metal with space between so you end up having to dent it in a little to create a 1/4 inch gap. Hopefully Helix will fix this problem moving forward so that it is no longer a problem.

 

Helix is supposed to update the cats with a new smaller version which should fix the clearance issues. I'm not sure exactly when though.

 

I've decided that I'm going with the Stillen engine damper. It's currently in production and will be shipping again in a couple weeks. I'm expecting that to eliminate the problem, and it's a wise mod anyway because all the engine movement is just wasted energy, why burn it off bending metal when it could be going to the wheels

 

lemme know if it works.....i've got the dampener already...if it solves the problem then helix here i come

 

The damper would not have fixed my problem cause the right-side cat was hitting the floor board just sitting there. I had to dent the floor board about a 1/2 inch to make clearance and leave a 1/4 inch gap.

 

Good news, I just got confirmation that Helix is coming out with a smaller cat in about 4-6 weeks, and you should be able to request an exchange through your vendor if you are unable/unwilling to fix the fitment issues with the initial version.