Poor AC Cooling at Low Engine Speed...Why?

[JamesDean]

Hello everyone,

I was thinking about this recently. A few of my cars have pretty poor AC cooling performance when the engine is at idle. It does not appear to be due to lack of air flow as I tripped my aux fan(s) and the temp was only marginally lowered. However when I increase the engine speed to 1500-2000 rpms the system cools much much nicer.

I was wondering if anyone knew why this was occuring?

I've always charged my refrigerants/ac at high idle, and attempted to match the numbers found on ACKits' website.

I was curious if this is something I'm doing wrong or just part of the design.

I've seen other people post about not being able to achieve low vent temps at idle too.

If low compressor rpm is the problem..why not just make the pulley smaller?

Anyways I'd like your thoughts on this!