I've had my new Z for about 2 weeks, and I must say that I love
the exhaust tone when I turn on the ignition.
However, lately I noticed whenever I turn on the car, the noise is even
more louder/stronger. Seems like my Z roars.
Does this mean that engine's broken in? Or is it just my exhaust?
Although I feel happy, but at the same time it bothers me that something
might be wrong.

Yesterday I took my car to the dealer for the service, and there were
two other Zs (SB and PPW)
As I was standing outside watching the service techs take the 3 Zs one by one,
I noticed that mine made noticably louder tone when turning on the ignition.
Any ideas? Maybe I'm cranking the engine too long or something...

 

What time do you hear this louder idle? If it's in the morning it's normal on all cars. It's the way the ecu responds to warm your engine up.

 

It's normal.

 

How do you know that? Where do you find this information?

 

I have test-pipes, y-pipe, and Blitz exhaust w/ removed resonator, when i start my car in the morning it is loud enough to set off alarms in my neighborhood!

 

It's pretty much standard on all engines.

Specifically, you can find in the technical manual for the Z that the fuel injection will have the injectors run in batch fire mode when the engine is cold (ie ALL 6 injectors fire at the same time, twice every cycle (one cycle = two crankshaft rotations), flooding the plenum and running pretty rich.

Once normal operating temperature is reached, the injection goes to sequential fire (ie each injector fires just before the intake valves opens on it's cylinder).

This explains why, when cold, the engines response is a bit sloppy.

 

I learn something new every day here.

 

very thorough, I couldn't of put it better myself.

 

damn! Can you post a video of that, please!

 

btw, when i turn on my z in the morning, the idle sound is SICK. However, once the engine warms up, the sound goes away