Thanks. Yeah, I've seen that thread, and even posted in it

I just think I'd rather spend the extra money and get a full midpipe replacement rather than cut and weld the stock pipe. YMMV

 

lol, gotta love that bird, seems determined to outdo your exhaust...

I like the way it sounds, and you said you felt the gains from the install, right? Have you taken it to the dyno to see how much of a gain it the hfc gave you? just wondering

 

Sorry, no before or after dyno numbers yet.

I got back under the car and checked and retightened all the bolts. Checked for leaks and found none, but the car still makes a strange raspy noise that sounds just like a leak (a rapid pfft type of sound). It only happens at WOT. I'm not sure if thats just how the cats sound, or if the 3" -> 2.5" connection at the y pipe to midpipe area is the cause. I should just spend the money and get the Fujitsubo Legalis-R I've been wanting for awhile now

 

sounds bad as *****!

 

Any droning at all?

 

I also ended up cutting a hole in the driver side exhaust tunnel where it was rubbing, but I later found that I got more clearance by messing with my Injen exhaust and probably didn't need to cut the hole.

 

UPDATE: Helix Cats + Motordyne Spacer = Horrible Rasp!

I'm not a happy camper right now. I installed a 3/8" Motordyne Spacer last week, and now I have a REALLY annoying buzzy rasp between 2500 and 3000 RPM's. It's not an exhaust or spacer leak, as I've checked both thoroughly and 3 times already. I've also noticed that the cats are hitting the frame more often now for some reason.

Guess I'll have to hop back under there and get busy with the hammer again ... or just put the damn stock cats back on again

 

UPDATE #2:

Removed the spacer and the sound is still present, so I know it's the cats. Gonna check them out again this weekend and probably put the stock cats back on.

 

Am surprised to hear this about the Helix Cats. Let us know if you determine this to be just a fitment issue or if the Cats themselves are bad.

Really appreciate your updates...

 

deviant1, noticed you have a g35... didnt someone mention something needs to be cut or shaved down for a good fitment for g35?

i heard it fits the 350z better.... let me find the thread on this...

 

https://my350z.com/forum/intake-exhaust/116664-ts-headers-and-helix-hf-cats-pics.html

look at Zquicksilver's post #11

 

jkoc: Yeah, I had to modify (bend) the underside of the frame with a hammer to get the cats to even fit on the car. I guess I didn't do enough since the cats still hit the frame under hard acceleration.

However, this buzzing sound I have now does not sound like the cats hitting the frame. It happens at exactly 2600 RPM and lasts to 3000 RPM or so, and happens no matter how much throttle is applied. It sounds like a buzzing civic exhaust and it vibrates throughout the whole car. I can only imagine how bad it sounds outside the car

 

Was this sound present when you filmed the video?

It didn't sound like that in your video.

 

deviant1,

If the Video is an accurate representation of just the Cats installed, I will be a happy camper Even if the Spacer is not present during the Video, I think I can live with rasp for 500k between 2500-3000k. A range I usually pass thru while driving. A small bit of rasp for a small amount of time, IMO, will make the car sound a little exotic.

Just as long as it's not between 1500-6000k, like a true CIVIC with a sewer pipe sticking out the back :P

Then I would be pissed...

 

Done. I did this just for you:

https://my350z.com/forum/intake-exhaust/121993-video-injen-ses-helix-high-flow-cats-nismo-cai.html

 

King tut you are > than me!

 

yeah that bird noise is funny as hell... at 1st i thought it was coming from my window....

car sounds mean though

 

UPDATE #3: Finally got back under the car today, and thankfully it was just a fitment issue. And not just the fitment of the headers, but my Gruppe-S y-pipe as well.

Issue #1: The drivers side cat was really close to the frame, so I just had to pull the cat off, and bang the frame in a little more.

Issue #2: The drivers side Y-pipe flange was like 1mm away from the frame. The flanges on the Gruppe-S Y-pipe are gigantic, much bigger than the stock cats, or Helix cats flanges. Solution, break out the grinder and get to work. I ground down the flange to match the gasket, and freed up enough room for it to fit properly.

With both issues taken care of, the cats no longer hit the frame, and the annoying buzz is 90% gone. There is still a very small resonance around 2600 RPM, but it seems like the noise was amplified before by the contact with the frame making it resonate throughout the whole car.

 

Glad to hear the terrible noise was just fitment problems. Hopefully you'll get rid of the noise 100% when you get that exhaust or cone reducer.

I'll be sure to put work into grinding my GruppeS pipe before I put everything on.

When you said the "frame", did you mean the heatshield???? Bending the frame on purpose sounds unappealing.

 

Nice clip. Really like the sound. Those birds are louder than your exhaust LOL JK.