gulzarh

Why the car engine idle at 1200rmp when we start it and when we put in D gear it idle at 700rmp ?

ezone

Cold engine startup faster idle is expected.

Idles slower/normal RPM after warmup? Good.

gulzarh

why faster idle is expected.?

ezone

Without a lengthy technical explanation.......it's designed that way.

Almost all gas engines are designed and programmed to idle faster while cold because a cold engine is very inefficient and difficult to run (requires a lot of extra fuel and air) and it runs unstable at a low rpm cold.....and fast idle speeds up warmup a little bit.

gulzarh

but why we need to warm up the engine? the motor vehicle in quebec, say it is not important to run the engine more than 30sec and i think it make sense also because if we start engine and leave it in park or drive, both way pistons are working, engine is runing,

ezone

Yes you can drive away as soon as it's running, no wait time.

gulzarh

so what is the reason for what they design to idle high startup? if it is warup, why we need to warmup? it warm up at normal speed also.

CraigW

iTrader: (1)

All the answers needed are here. ^^^

If there was NOT a reason for high idle when cold... then why do ALL manufactures autos do the same exact same thing ?

ezone

".....and God invented fast idle, and, behold, it was very good. And the evening and the morning were the sixth day."

gulzarh

i know there mut be very very good reason behind this, and i want to understaned that hidden reason behind this.
i am not saying they are crazy or they just add it for pleasure, they spend million of dollars before making any model i am sure so there must be goods reasons, and this is what i want to know.

thanks

ezone

An unloaded slow running cold engine doesn't run with much stability and gasoline doesn't vaporize quickly in a cold engine.

Very easy to stall it with sudden load changes if the RPM is too low.

thetut

For your reading pleasure: https://www.reddit.com/r/explainlike...gher_rpm_when/