Only really get it on the more expensive, more powerful cars but when you start the engine it sounds like it revs up to 3-4000 then drops back to normal
it could be a couple different things.
first is the fact that its a cold start.
right upon starting, the engine control unit will use a more rich fuel mixture.
this lets the engine run with a bit more stability considering it isnt up to operating temperatures and the engine oil hasnt been moved around to lubricate the unit.
these cold starts tend to produce a bit better sound than when the engine is already warmed up.
another thing that you might be talking about the different starter types that you will typically find on high performance engines.
in a regular engine, you will typically see medium levels of compression. this makes less power from the engine but it means that you can run regular fuel and wont run into reliability issues.
high performance engines run higher levels of compression and typically higher cylinder counts and higher displacement. they will also have tighter tolerances meaning parts fit tighter together.
all of these factors make these engines harder to start.
to make up for this, these engines will have starter motors that will pick up speed beforehand and then move the engine. right after, since the engine is still hard to move, the engine control unit will rev the engine quickly before it stabilizes.
this is where you get very different startup sounds from high performance engines. like this.
you will hear there is an initial high pitched whine. this is the starter motor. you then hear the click of the starter engaging to the actual engine and then very quickly after that, the actual engine revving up to get stabilized just after starting.
Your motor should't rev more than 1,200 to 1,500 rpm's on start up. It does that because of the extra gas being injected into the cylinders for cold starting. Oil pressure isn't up to full operating pressure on cold starts and if you rev your motor to 3 or 4,000 rpm you take the chance on scoring the crankshaft and rod bearings which certainly is not a risk you want to take just to hear a varoom!
Its called revving the engine.
It is caused be stepping on the accelerator.
It means the 'driver' is more interested in THINKING they are impressive than they are in the proper operation of the vehicle.
Thats from pushing the gas pedal, No engine does it on its own, NONE
You don't need an expensive car to have a high idle.
not really adviseable,as on initial starting,the oil has not had time to circulate,and is cold!