what is that vibration rattle sound on decel when reving on the second video...is that the cats?

 

....not sure about G35 fitment. I hate to be the the first and find out the hard way that they rub or don't fit. It's not a 5 minute job to install. I've changed engines, rebuilt auto and manual transmissions and do know a little about working on cars and a cat install is not my definition of fun. If you could get your hands on a G35 OEM cat already removed and match to a Z OEM cat this could shed some light on fitment. I would think these are readily available....have two Z cats in my garage.

Key factors in my Ultimate Racing HFC decision were:
1) No reports anywhere of issues (cracking, fitment, blow-outs etc.)
2) 100% stainless vs. some brands are partial or aluminized
3) Warranted for 50,000 miles
4) Don't look aftermarket (stealth if you will)
5) OEM style mounting brackets
6) O2 sensor bung
7) Like the idea of better sound/HP without polluting
8) Expect that they will pass sniffer emission test
9) No CEL issues
10) "Reasonable" price

 

your cheap speakers

 

IMO they will unleash the potential of your exhaust/header mod's by allowing it to flow much better as the cat's tend to be the bottleneck, if you will, in the exhaust system. Will likely add some dbs to the sound level too.

If you do it, please let us know the results.

 

Thanks for the excellent link on cat technology. I almost forgot about the earlier bead technology. Also worth noting is that the story talked about the by products created and how stainless casings are used to avoid corrosion. Evidently some manufacturers are not aware of the corrosion potential? Beware if you are considering cat's that are not stainless steel.

 

Glad you enjoyed the info. I too forgot about the bead technology, I can remember an uncle of mine emptying one out, a long time ago, from his 196? mustang in his garage and me asking what he was doing, he said "this will make my car faster."

Gary

 

Good research...Looks Good

 

I just installed these and was dissappointed to find out that there is a metallic buzzing sound when under WOT between3-5k rpm's especially when the car is cold.

 

sounds like your bracket is loose or your exhaust is loose and you are hearing the resonance.

 

I don't know whether its "rasp" or the left cat vibrating against the heat shield. I've heard that there is only a small amount of clearance on the drivers side.

 

I don' tthink its the exhaust cuz i didn't hear anything like it when the exhaust was installed. It started immediately after i got the cats installed.

 

could you show me a picture of the "bracket" so i can check it?

 

http://www.z1auto.com/prodmore.asp?m...ust&prodid=580

or could be the heatshield too...it is a close fit and bending it up slightly is a good idea.

 

also.... why would it get better after the car warms up?

 

is the bracket the thing connected to the cat with a bolt?

 

How does the UR compare w/ the Crawford Cats. I havent heard of cracking problems on UR that the Crawfords have w/ the Nismo exhaust.

 

It is a close fit on the driver side. When I installed mine, I made it a point to hold the cat with pressure away from the floor board while I tightened it. There is just a bit of play caused by the diff in the stud diameter vs. the hole. You may be able to loosen then re-torque the way I just described.

I'm not sure if you installed yourself or had a shop do it. This is one of many reasons I don't take my car to a shop. In many cases the focus is on speed, not fitment or quality. If it's the only Z they've done they would have no knowledge of the potential problems.

Personally, I don't like the idea of hammering on the floor board of the car. If that's the only option I guess you have to but I don't like it myself.

 

wouldn't what you're decribing cause it not to seal correctly?

 

what if i just removed the heat shield?

 

Not if you torque it properly. There isn't much "slop" in the holes but it may be enough. I saw a number of posts on the subject of the cat contacting the floor boards (various brands) so I took this precaution. If I didn't do it would I have had a problem? .....don't know.