Questions
Does anyone have a set-up of any of the ff;
1. test pipes on stock exhaust
2. cats on stock exhaust
3. test pipes and cats on stock exhaust?

Or would the test pipes or cats be best used with aftermarket exhausts?

What's the diff. of using test pipes from cats and vice versa?
which is louder, any problems between the two?

 

Test pipes are generally louder than high-flows and can lead to a more 'raspy' sound from your exhaust. Also, they will not pass emissions if your state tests for them.

You could consider resonated test pipes, which should help to cut back on the raspiness. However, I've seen a few threads where people had TP's and took them off because they were too annoying and in some cases, lost power.

 

I did a post on this a while back using instrumented sound level measurements. Basically, high-flow cats and resonated test pipes will be louder than the stock cats with any exhaust. How much louder will be up to the exhaust.

Unresonated test pipes, though, will be the loudest of all your options. Think of it like this: there are 2 stock cats on each side, and each of those cats acts like a little resonator (muffler). Aftermarket cats and resonated test pipes only have 1 resonator per side, so they are a bit louder. Straight test pipes, though, have no resonators per side, so they are even louder still.

On my stock exhaust, I noticed little difference between stock cats and high flow cats when cruising on the freeway. No droning. When getting on the gas there was a bit of a meaner growl, but not too much. Still perfectly reasonable.

With my Nismo exhaust, though, the aftermarket cats made it *much* louder. On the freeway the droning was almost unbearable. I ended up putting the stock cats back on with the Nismo exhaust, and that made a huge difference. Droning is virtually nill on the freeway now, but you still get that nice deep growl from the Nismo when getting on the throttle.

 

this is a great question on which to practise and develop your search function skills.
ps: what i liked least about and was the main reason for selling my test pipes, but is not mentioned a lot, was the strong gas smell that is characteristic of tpipes, resonated or not.

 

Are there any HFC's that can be used in california that are safer than others? I'm not trying to get caught with them.

I dont drive like an idiot around town, but I'm worried it will be super loud. Further I want to keep an exotic tone, so I dont want anything raspy. Are there any cats that can pass any tests in CA..visually and audibally?

I'd greatly appreciate the info. From my knowledge Kinetix can pass the visual. I have the Injen Straight Tip Exhaust.

ravi

 

Nothing but the stock cats should pass the visual, but all HFC should pass the sniffer.

 

i will be installing HF cats on an OEM exhaust soon...along with headers...
the exhaust is going to have to wait till next year, currently $ tapped $ out


didn't realize the gas smell was that bad with TPs.

FYI...do your research for your specific setup and you will be a happy man...
ps may help: https://my350z.com/forum/intake-exhaust/114798-tp-w-resonators-or-carb-legal-hf-cats_.html

 

Like Zivman said, *no* aftermarket cats are legal in California. You must use the stock cats, and you aren't allowed to touch them. However, they will indeed pass the sniffer test just fine, and I believe a number of folks have actually done this already. The only trick is the visual part of the test. If the cats you have look relatively stock (meaning not polished and fancy looking), then the inspector might simply overlook them. It's a risk, though. I guess most people are just planning to put the stock cats back on temporarily when they go to get smogged, then slap their HFCs back on later.

 

Yeah, cars with no cats smell pretty darn bad. It's pretty obvious when you don't have them. Anyone driving behind you should instantly be able to tell when you don't have cats on your car. This is especially bad in turbo cars where they run rich. It's so strong it can make your eyes water.