kenkaru

I posted a Q a few weeks ago asking whether 4" pipe is inherently louder than smaller diameter. No one answered so I figured I post this up in case anyone is wondering.

I drove around with 2.5" TD's dumped through bullets for over a year.
Yesterday, I uncapped my 3" Y to 4" setup just before the axle and holy **** was it louder than the dual 2.5's. The dumped 4" sounded just about the same as open headers where the 2.5 duals + X where about half as loud.

So the moral of the story is:
Smaller pipe has a muffeling effect.

I removed cats yesterday too. Now my 4" with spintech is sickly loud even exiting the rear. I don't know if the cops are going to be able to let this slide. I have an inspection in October too.

BTW, for about a day, I had the dual 2.5's exiting the rear of the car and it was pretty much silent in the car. I think I'm going to go back to that again if the cops get on me for being too loud.

Viper

iTrader: (6)

I've got a 2.5" y-pipe into a 3.5" cat back system and it's much louder than any 3" system I had ( FLP headers in the past, Random Tech catback ). It's much deeper too with the bigger pipes.

1999 SS

iTrader: (3)

i got the same set up going into my car as we speak(QTP's into a 4" straight pipe into a spintech with dual 3" outlets with two 4" tips and no cats). it was loud before with 3" straight pipe and flowmaster muffler no cats and dual 3.5" magnaflow tips so i cant even imagine how loud its gonna be now. i should probably pull the sound system out of it since i wont be able to hear it anyway.