A/C and idle speed increase

[mclasser]

This is about my Elantra. First really hot day out, with temps crossing 100. I was idling for about 10 min in a parking lot waiting for my wife. I had the auto CC set to 70 and after a few minutes, I noticed the idle increase to around 900 RPM. Normal idle w/the A/C on is about 750. I increased the CC to 72 and the idle dropped back down. Went back to 70 and again the idle increased.

I've never noticed such behavior in my other cars. Maybe it's just a characteristic of this small engine in hot temps.

Anybody else with Hyundais notice such a thing?

 

[Trav]

Seems to be common on many cars and appears to be normal operation.

 

[The_Jeff]

I remember in the 80s when cars had regular AC and "econo", whatever that was. Seems like Hyundai has your back, with regular AC and "turbo", which I would be running today, too.

 

[mx5miata]

Sounds like normal operation for a vehicle being abused with the a.c. blasting while idling in extreme heat.

 

[PimTac]

Normal operations. Our cars back in the nineties did the same thing.

 

[Chris142]

Your car is all computer controlled. It reads ac pressures and engine temps. It may speed up the idle to spin the water pump faster to help cool down the engine or spin the compressor faster to facilitate cooling. A faster spinning compressor is more efficient.

 

[oilpsi2high]

110% normal as your car has a variable-rate compressor.

The owners manual for my car states the car will adjust idle speed based on engine load demand.

 

[oilpsi2high]

Originally Posted By: mx5miata
Sounds like normal operation for a vehicle being abused with the a.c. blasting while idling in extreme heat.


It's not abuse at all, unless the fan isn't working or the engine is operating outside of it's temperature range.

 

[mclasser]

Originally Posted By: oilpsi2high
110% normal as your car has a variable-rate compressor.

The owners manual for my car states the car will adjust idle speed based on engine load demand.

Originally Posted By: Chris142
Your car is all computer controlled. It reads ac pressures and engine temps. It may speed up the idle to spin the water pump faster to help cool down the engine or spin the compressor faster to facilitate cooling. A faster spinning compressor is more efficient.


Oh yeah, I didn't think about the VDC. The PCM info makes sense. It must be tuned to really ramp up the idle when the A/C is encountering a high heat load.

This is the first 4-cyl car I've had with a VDC. My old Infiniti V6 had a VDC and it operated so smoothly that I barely noticed when it was on. FDC's seem so crude in comparison, with their muggy lapses and vibrations when cycling on/off. The A/C in this car overall performs great. It blows cold air fast and the blower fan isn't annoyingly loud. I'm surprised this car only has one cooling fan. It's barely audible, even when running full blast.