I am basically done modding my car. The last thing I need to do is get it tuned via a reflash, utec, etc. Before I tune it I need to decide if adding hi flow cats is worth it. I like the way my car sounds now. I could stand it being a bit louder but not much. As it is now I feel the pop charger is louder than the exhaust at WOT. I've actually thought about reinstalling the stock airbox because the popcharger can be too loud when accelerating at WOT. I haven't removed it because it has been proven to add about 6 hp and the sound doesn't normally bother me. I know adding hi flow cats won't add a lot of horsepower but from what I've read 4-6 hp is the average gain. I would like to try some but if they are going to make the exhaust too loud I won't bother.

Basically, has anyone here installed hi flow cats then removed them because they were too loud? If so what exhaust and cats did you have?

 

Hahahaha, no.

Unless I lived above a library in a small town of old people, and it always rained so I could never put my window down.... ya know what I'd still like how loud it is.

 

For performance go test pipes.
If you have to pass a visual emissions test, go high-flow catalytic converters.

 

You HAVE to get either hfc or tp...you have done everything else to the exhaust side! Just finish her up

 

since you're planning on the tune, might as well free up some more hp/tq with the Cats/TP's.

 

I was figuring it wouldn't be too loud since the Borla is fairly quiet.

I don't want to go with test pipes for several reasons: the smell, rasp, too loud, check engine light problems on 04.5 and newer models, etc...

If I do anything it will be high flow cats.

Now I need to decide what brand....

 

i run R/T cats with my Borla set up and love it. I also have intake and headers, but the cats livend the exhaust up dramatically. Definatly the biggest performance and sound gain from the intake back. (-minus a spacer)

 

Make sure they do not say "legal only for off road use" or some other crap, or you may as well get test pipes.

 

My HFC's are too loud for me. It drives me nuts actually & have considered taking them off. Sure the hp is nice when your are on the pedal but for most of the time, it is simply too noisy. I suggest you do not get them if a pop charger is already bothering you. The HFC will be much louder.

 

Buy the Kinetix Resonated Test Pipes and i will trade you for my Kinetix High Flow Cats.

 

What brand exhaust do you have?

 

Nismo exhaust & RT HFC.

 

I haven't removed the cats 'cause my exhaust got too loud for them, but I did switch exhausts because of 'em. I had the Nismo and swapped to HKS for this reason. It's still a loud setup, just a ton less droney now.

 

does the HKS come with silencers? Is there anyways to make the exhaust and HFC combo quiter with out loosing performance?

 

try this, ditch the cats 4 test pipes, amd get a single exit exhaust. then explain loud lol

 

i just installed test pipes with my Borla TD, its not really loud at all, its almost the same! you have headers which i dont so your car may be louder, but i doubt high flow cats will make the exhaust much louder. i would say go for it....if you dont mind smells and being illegal, go for the test pipes....i got the kinetix resonated pipes and i'm happy with them.

 

I've read that the Nismo tends to drone around 3000 rpms. I imagine it would be much worse with hi flows or test pipes.

The Borla doesn't drone at all. Except when below 2000 rpms and accelerating in 6th gear. That can happen when driving in 30-60-30mph traffic on the highway and I don't feel like down shifting. If I start accelerating at like 1200 rpms in 6th gear it can get boomy until 2000 rpms. I rarely drive it like that but that is one reason I love the Z so much. I can leave it in too high of a gear and it has enough low end torque to still accelerate.

I've read a ton of posts from Borla owners that love the way it sounds with high flows. I haven't found a post from a Borla owner who didn't like them.

I guess my question now is have any Borla TD owners removed hi flow cats because they were too loud?

 

I have a roadster, and I love my crawford cats with my Borla. Nice sound, but not too loud.

 

I have nismo headers, Crawford cats and Nismo exhaust. It is quiet when driving normal. But if you put your foot down it will let the world know your coming. It was even louder when I had RT cats(they collapsed).

 

Unresonated test pipes are too loud. HFC's should be a nice addition.