Why exhaust sound deep during cold start?

[manu_b]

As question title says , why does it happen? I just put on NPP and first time when i started it, I was amazed by the deep sound but then it went little quite.

[KMPrenger]

Originally Posted by manu_b

As question title says , why does it happen? I just put on NPP and first time when i started it, I was amazed by the deep sound but then it went little quite.

On cold startup, the car runs the rpms a bit higher than normal idle and I also believe it purposely runs a bit rich. This is to help heat up the catalytic converters quicker....so basically it is strictly for emissions purposes. After 30 seconds or so, it idles normally.

[manu_b]

There should be a way to make car perform cold start every time. Or run it little rich under 1000 rpm

[ZL575 #26]

That sound at startup is invigorating.

[Angrybird 12]

Originally Posted by manu_b

As question title says , why does it happen? I just put on NPP and first time when i started it, I was amazed by the deep sound but then it went little quite.

It has always done that, but it was less noticeable with the stock exhaust. Both my 2010 and 2012 have always done it. It's just the cold start mode, sort of like what carbureted engines had with an automatic choke. It makes a cold engine easier to start.