how loud is the 3" cat back for a 240sx? is it illegal in CA?
 

im thinking buying a 3" cat but im worried that it might be a bit loud even at low rpms... not sure...does anybody know?

i used to have a 3inch on my 90 sohc (non turbo at that time) and i got 4 tickets for the exhaust...i was stubborn and kept putting it back on after taking it off :) this was SoCal...glendale area about 15 minutes from LA...most exhaust systems on a 240 that have over 2.5inch piping will be considered illegal and modified only because of the noise...if a silencer is used it may not be a big deal...depends on the cops in your area really. there are other exhausts that are less noisey with 3inch piping or a little less and might be preferable. RS-R Tanabe and Circuit Sports (random exhaust i found) have some quiet but good diameter systems

I run an SS Autochrome 3" cat back on my '89, and it's way too loud without the silencer. With it in, the car is around 85 dB inside (I actually have a dB meter) on the freeway, mostly from exhaust noise. I commute 5 days a week between San Diego and Santa Ana (75 mi each way) and have yet to get pulled over in the 2 years I've had the exhaust on the car.

Of course, a 1.5 inch silencer sort of defeats the purpose of a 3" exhaust, but even plugged up it did 135 hp on the motor to the wheels N/A and 210 on the bottle. I haven't dynoed it without the silencer yet, mostly because I never run it uncorked, even at the track, because it's so effing loud.

For a N/A car, a 3" with a silencer is probably more exhaust than you need anyway. Put that same pipe on a car with a whirly muffler and you could probably get away without using the silencer and not go deaf.