Can someone explain to me RPM at Idle and why it changes …
 

Hey guys,

So I’ve always wondered about this, and I’m not sure I’m asking google and searching the right question…

My question is - Why does RPM change at idle. Let me expand on that.

So I get why AC affects RPM - You’ll have a much lower RPM with no AC than with AC.

But for instance, I live in FL - it seems that weather affects the RPM range at idle as well?

Some days at idle, with AC on - I’m between 800-837 and other days I’m 865-880 (something like that)

Why is this?


Why I ask - is because it makes quite a different in idle volume in the cab :D


Thanks.

Our cars have an active engine management system, vs, for instance a '60s car with a carburetor that only has an idle screw on it. Between the Mass Air Flow (MAF) sensors in the intake, and the O2 sensors in the exhaust, the engine management system adjusts the air/fuel mixture to compensate for in-the-moment conditions.
There are also various special load-based conditions, like your A/C, requirements for onboard electronics, and even cold-start and warm-up automatic choke, all of which could affect idle.


Kirk B.

Awesome. Thanks 😊