How often is it above 100F? Would it be worth it if you could? Your talking about 4 or 5mpg hit for what 20 days out of the year? It would only cost you another 1/2 gallon of gas per hot day @ about 50miles per day.

30mpg/50miles = 1.67 gallons

24mpg/50miles = 2.08 gallons

Difference is about 0.417gallons/50 miles.

I guess you could do it if you spend enough $$$ for the conversion.

 

It wouldn't help unless you also could reprogram the car's CPU. Otherwise the car will still add 500 RPM when the A/C button is pressed. Unless you had a different switch for the A/C, some kind of aftermarket thing.

But then you would also need to reprogram the CPU so that the vehicle knew the A/C was running, and for the extra load on the battery.

Ummm, maybe it is not such a good idea after all. Besides the up front costs, the Ford engineers designed both software and hardware (not to mention battery air conditioning) around a mechanical A/C compressor...

 

Not so quick...

The HVAC controller has a compressor clutch output signal that goes to/through the engine control ECU and from there the A/C clutch is controlled. Just remove the signal wire to the engine control ECU and route it directly to the electric compressor controls.

 

But you still would not have adjusted the extra 500 RPM directed by the ENGINE CPU, nor would you have adjusted the electrical system to efficiently account for the additional drag on the battery. So I don't see what the electric compressor will accomplish.

A hybrid, especially a full hybrid, is a complex interactive machine. Apparently some people think you can just go down to the local auto store and pile on modifications, without any impact.

 

You seem to be grasping at straws to discourage the idea of an electrically driven A/C compressor....WHY...??

Personally I'm of the opinion that if the ICE is to run anyway then that should be the source, DIRECT source, of the A/C compressor power, and the electric drive only used to avoid an ICE startup ONLY for that reason.

 

Drove wife FEh Thursday and today, what diff temps makes here in Phoenix. Thursday rpm was around 2K mark at 45 mph and this morning with temp at 90 deg rpm was 1500 @ 45mph with a/c on.

These hot days here are a killer for fuel mileage. Just have to live with it for app 3 more months. Overall we luv this SUV.

 

It might be worth keeping in mind that yet another reason for the RPMs to be somewhat elevated is if the hybrid battery needs to be charged.

 

If I read your suggestion correctly, you are suggesting TWO compressors, one for when the ICE is running and one for electric only? Interesting, though it would be expensive to have two compressors.

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It is the people who wish to change Ford's careful design who are "grasping at straws", as you put it. I am telling them that it is not that simple.

I am simply pointing out that a hybrid system is far more complex, and the parts interact more closely, than a conventional drivetrain.

Ford certainly knew they could go to an electric compressor, yet they did not, even with the 2009 (so far as we know). So the car we bought is designed to use a mechanical compressor. That means that the computers (especially) are designed to compensate for the engine driving the compressor, NOT for an electrical compressor. This particular thread is listing an interesting part of the programming, namely that at temperatures above around 98F, the CPU directs the engine to add around 500 RPM when the A/C is engaged.

As a software engineer, it irks me that people think they can simply swap stuff out and have the vehicle simply work the same as before. These vehicles are very precisely computerized, and any such change would require adjustments to the CPU programming - for the engine, and possibly for other components, to compensate for the ELECTRIC compressor - which draws FAR more AMPS than the factory sound system.

 

I don't have a SG, but it appears that the battery is pretty well charged; it happens on the freeway as well as on surface streets.

Also, if I de-select the A/C, the engine returns to normal. If the battery needed charge, I would expect the engine to continue to run fast.

 

I'm not saying, nor proposing, that there will not be times that the A/C is the EXCLUSIVE reason for seemingly inordinantly high ICE RPMs, just that sometimes you might see a high rate for other reasons or combined reasons.