Why does the SAP whistle?
 

Why does the secondary air pump (SAP) whistle for apprx 60 seconds? And does the SAP kick in every time the car is started or only during cold weather/cold engine.

it runs for about 2 mins when the engine is cold.

its to help emissions on cold starts

SAP will start every time the cats are cold in order to aid the emissions.
Meaning has nothing to do with a temp outside.
if should whistle like a small vacuum cleaner. if it whistle more than that it maybe failing.

I thought the whistling sound is a sign there's something wrong with the SAP or there's a leak or blockage somewhere that's causing it(whistling). So you guys are saying a whistling SAP is normal even for a brand new SAP?

how loud are we talking about here?

you can most certainly here it when its on... even brand new ones...

but overly loud like some shrill/annoying sound...then something is wrong.

Its not something I typically notice unless I actually sit there and think about it.