I have a 06 coupe and I am looking to add HFC and exhaust. I know 2.5" piping would be ideal for all around performance and 3" could possibly cause low end loss in power/tq for NA setups.

Would the same hold true if I were to run a 3" single outlet from the Y pipe vs. a 2.5" true dual? Or could you give me opinions on pros and cons for both setups?

Thanks.

 

A single 3" won't cause a loss of TQ if its from the Y-pipe back.
If it were a true dual 3" from the cats back then yes it would lose TQ.


Most aftermarket Y-pipes use 2.5" tubing as primaries and transition to a single 3".
Dual systems commonly use 2.5" tubing all the way from front to back.
Some dual systems use 2.25" tubing all the way front to back.

The 2.25" systems will make a little more TQ and sacrifice some HP.

But to answer your question, a single 3" from the Y-pipe back won't lose anything as long as its not connected to restrictive or chambered mufflers.

 

one particular exhaust has been designed with progressively larger diameter - scientifically developed in specific length increments having diameter become larger... I forget the name of the company - some rocket scientist designed it

 

There are a lot of factors at play with exhaust, but assuming your car is pretty much stock (bolt-ons not internal mods) I would stick with the single 3" pipe from the Y back. No reason to look at a true dual setup as you will:

1) most likely wind up spending way more money for small HP gains (2-3HP, maybe?)
2) have this small gain be offset by the added weight of the setup

In short, what Hydrazine said.

 

Thanks for the replys.

On the flip side, do you think a 2.5" single exit from the y pipe back will be too restrictive?

 

Some, but it should be OK if its an all straight through design.