Yeah I'm not sure on his confusion about 4 cats. He pointed to the piping in front of the cats (not the exhaust direction, the other side. Between the cat and the headers I guess?). So, almost as if he made it seem as if there was an additional cat in front of each one. If that makes sense.

Not sure what would compel him to think that.

Not gonna lie, i lol'd haha

:icon18:

Everything between the headers and midpipe on these cars is a huge restriction on your exhaust. So anything that opens that up (HFC, LTH, or Y pipe) will see a large increase. The rest of the exhaust, get what you like :)

Come on meow, that's a little far fetched...

In for the lols


A lot of mechanics identify cats by looking for the heat shielding, if a factory exhaust has bracing or just heat shielding for the heck of it, they usually yell cat!!

Which helps us all out when it is time for an inspection

Just picked up the car. He said everything went smooth, and it does sound really good.

Only thing is I can *definitely* hear air coming from where the cats are. At high RPMs on the road it's noticeable, and when I have the car stationary with the door open during revs. Should I be able to?

For example if I give it a nice rev up to 4k while in neutral, on the release I'll hear air from the front-middle of the under carriage.

I was a bit concerned at first, but I wasn't sure if it was because I'm not used to it, or something isn't right.

If its a hiss on deceleration, when you let go of the gas, then this is perfectly normal. Modifying any component of the 370Z exhaust has this effect, particularly the cats. If you hear it when revving up, when accelerating then you could have a leak.

You will hear a hissing sound at low RPM. TOTALLY NORMAL. My test pipes hiss like a mo-fo! Esp around 2k

Huh. I think I actually do hear it when accelerating.

How can I absolutely determine if there's a leak and how is it typically rectified?

Thanks for this info!

Do you hear the hiss when accelerating too?

No acceleration hiss

Some of the older VQ35 engines used in the maxima had four cats, two pre-cats ahead of the normal cat that you'd normally see in an exhaust. I'm not sure why he would say that after having the car up on a lift though, it would be immediately evident that the pre-casts were not present on the 370z.

In my experience, most mechanics will try to convince you that aftermarket parts are a waste if they are not an enthusiast themselves. They are so used to seeing cobbled up stuff that they usually push people away from aftermarket parts. I wouldn't give the guy to much credit because he obviously doesn;t know much about the 370. You've made a good choice and will be very happy with the money that you spent.

That's reassuring, thanks! My only concern right now is the possible hissing\leak during acceleration. I don't always hear it, only if I really step on it and it's between like 3k and 5k before it's no longer audible.

I wish I had other Z owners to hang out with or check it out to see if it's just me not used to the sound or an actual problem :eek:

Vid of the sound or it doesn't sound cool ;)

Also, it might help to hear the sound if possible.

What he said ^

One more thing. And I'm on mobile at the moment. But I revved the car just now and I can actually smell exhaust. Just throwing that out there ... Shouldn't be normal right...?


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