Subject: What happened when we rev-up the engine?

I have seen so many people reving-up their engines when idle, from mechanics in 
the repair shops, race cars in the track, to ordinary people with their ordinary 
cars.  These ordinary people, I observe, rev-up their engines while warming up 
in the morning.  So, I am really curious whether there are any advantages in 
reving-up the engine of an automobile, or a motorcycle other than my perception 
of high-wear and tear in a short amount of time.

Re: What happened when we rev-up the engine?