Front pipe variations and exhaust volume
 

I've had a catless front pipe and Q300 catback for a while. This setup gave me a nice sound, but rather quiet.

Last weekend I installed my OFH and an Invidia overpipe. With the full setup I had great volume, and it sounded pretty good. However, I didn't like the catless smell.

So last night I put the stock front pipe back on. Now the car is very quiet. I was rather enjoying actually hearing the exhaust note in the cabin with the catless pipe. The OEM front pipe took the level down to what it was before the header and overpipe. But it doesn't stink anymore.

So my last resort would be to get an aftermarket catted front pipe. Can anyone comment on how the sound (particularly volume) will be effected?

A catted front pipe will definitely increase volume a bit. Not a ton, but there's definitely an increase. I had my 2.5" catted FP on for about two months with the stock cat back and you could hear the difference for sure.

Thanks for the reply. I had my catless front pipe on my stock exhaust for a bit too. It also increased the volume as well as more growl.

I guess I need to know how the sound of catless FP compares to a high-flow FP.

The overpipes and cat/test pipes (front pipes) only change the sound minimally. The actual cat-back piping (design and diameter) and muffler setup affect the sound the most.

Over and front pipes will cause more in-car drone (unless they're resonated like the ARK or similar) rather than change the final exhaust note. A straight front pipe no cat will add a bit of volume.

A catless FP will be more raspy than a catted FP, but how raspy will depend on the whole exhaust (including header). It'll also be a bit louder, but not much.

It might seem obvious, but the physical location of the pipe you change will also dictate where the perceived sound occurs. The most distinct volume change outside of the car will occur from the axleback section while the rest of the pipes will alter tonal qualities, especially inside of the car in addition to outside of the car. Changing the OP/FP will alter the sound from outside of the car for sure, but remember that these two pipes are nearest to you and to the cabin as well.

Not even going to discuss headers as that's a whole story in itself.

With my setup, the sound changed a LOT going from the catless front pipe to the stock front pipe with the same catback (Q300). Now the stock front pipe does have that wierd lunch box on the back, not sure what that is. Perhaps you are comparing between aftermarket pipes only?

Both setups I ran had no drone. Maybe this due to the Q300, which is considered quiet for an aftermarket system.

From wparsons response, I would expect an aftermarket catted front pipe to increase the volume over the stock front pipe, but would it increase the volume as much as a catless front pipe?

That's a great point. The stock front pipe seems too quiet to me now, inside the car. Guess I better setup the camera and do a drive by. :party0030:

Comparing two pipes (let's make it easy - same manufacturer, same pipe ID, etc.) with and without cat will largely change the tone not the volume though volume may change slightly. Perhaps a better way to say it is that a cat changes the tone more than it changes the volume.

Yes of course. I'm only comparing between aftermarket setups. Stock is always going to be significantly more quiet, especially in an OEM cat setup versus straight pipe (front pipe). Basically on a full aftermarket setup, the catback determines most of the sound (volume and tone) -- switching between an aftermarket catted or non-catted front pipe won't greatly affect the sound (tone maybe a bit more raspy with no cat -- slight volume change for no cat).

The only thing you get is a non-catted version can cause in-cabin resonance if there's no resonator (external or in line).