High Ambient (Desert) Temps Kills HVB Performance (MPGs)

[Hybrider]

Also another point I would like to make is that I see very little difference in cooling efficiencies with doing a semi-manual setting of the fan speed to low, versus setting the climate control to Auto with a high temp setting such as 80°. The fan is still blowing at the same fairly low setting in either case, but the A/C power draw for the manual low-speed fan setting is 1 kW less (1.5 kW vs 2.5 kW) than the Auto setting (temp = 80°), so the manual setting of low fan speed seems to me like a better setting for higher MPGs.

[acdii]

Understanding what the compressor is doing you need to understand how AC functions. There are 4 components to the AC system that has not changed since the first one was put in a car. Compressor, Condenser, Evaporator, and blower. The compressor sucks the gas from the low side, compresses it into a high pressure gas, the condenser cools the gas so it becomes a liquid, it then goes to an accumulator, or pressure regulator of some sort, this part varies by manufacturer, then to the evaporator. The hot air over the condenser gets absorbed by the low pressure liquid which turns it into a gas, in most cases the "Freon" is a gas as it enters the Evaporator by having its pressure reduced. When a car has reached its set temperature, fan speeds lower, reducing the air flow over the Evaporator, because the air is no longer putting heat into the evaporator, the coolant builds pressure. Its the changing of liquid to gas that occurs in the Evaporator, by heating up the coolant, the liquid under high pressure quickly turns to gas, lowering the pressure on the low side. When the air has cooled down enough that it isnt converting the liquid to gas fast enough to keep pressures low, the low side switch stops the compressor.

 

In a traditional car, this is how it functions, regardless of the type of "Freon" used. R12 or R134, the systems are the same. On the new Electric driven compressors, the flow of coolant is controlled by varying the speed of the compressor. For a hot car, the temperature rise between liquid and gas it very high, so it has to pump the "Freon" at a very high rate. As the air flow over the core decreases in temp, the amount of "Freon" required to cool down or maintain temps is reduced, so the compressor slows down to meet the lack of demand.

 

So the theory of starting with a high temperature of 80* when set to auto, and reducing the temp gradually is going to be the most efficient way to use the climate system because it doesn't have to work as hard to bring the temp down as quickly. This puts less demand on the compressor,

 

Hope this helps to clear this up.

[mwr]

So the theory of starting with a high temperature of 80* when set to auto, and reducing the temp gradually is going to be the most efficient way to use the climate system because it doesn't have to work as hard to bring the temp down as quickly. This puts less demand on the compressor,

Wouldn't that method also slow the cooling of the inside of the car?

[Waldo]

 

 

So the theory of starting with a high temperature of 80* when set to auto, and reducing the temp gradually is going to be the most efficient way to use the climate system because it doesn't have to work as hard to bring the temp down as quickly. This puts less demand on the compressor,

 

 

Sure it puts less demand on the compressor at any given point in time, but it's going to mean the compressor has to run at "medium" load for a longer period of time. I don't know anything about compressor efficiency curves. Is it more efficient to run a compressor on "setting 2" for 2 minutes vs running it on "setting 3" for 1 minute then "setting 1" for 1 minute?

 

Just like it's more efficient to accelerate the FFH at 2 bars instead of 1.5 bars, it could be more efficient to operate the compressor at higher loads for shorter times. We need a little more precision in Hybrider's data to determine that.

[Eddie Sessum]

Wouldn't that method also slow the cooling of the inside of the car?

It makes the consumption lower but in the long run it comes out to the same. Staying at 3kw for 20min or 5kw for 10min and working it's way down. I'd prefer to cool off as quick as possible.

 

Acdii, if you typed that out on your own great job. I'm 90% sure our cars have am expansion valve Btw.

[Waldo]

The electric compressors are different. The regular cars with belt driven compressors control that by mixing warm air. Any person with normal hearing can stand next to a new ford and hear the compressor cycling when it hits a certain pressure.

 

 

Go stand next to a non-hybrid 2014+ Fusion and wait until you hear the compressor cycle. You will soon be off to the doctor to have your hearing checked. Ford is migrating all the new products to variable displacement compressors, which act similarly to the electric one in that they can vary their output and thus control evap core temperatures without cycling or mixing with warm air.

[Eddie Sessum]

 

Go stand next to a non-hybrid 2014+ Fusion and wait until you hear the compressor cycle. You will soon be off to the doctor to have your hearing checked. Ford is migrating all the new products to variable displacement compressors, which act similarly to the electric one in that they can vary their output and thus control evap core temperatures without cycling or mixing with warm air.

I know someone with one, it still clicks on and off. On his you can hear the freon coming into the car when it first clicks back on if you have no other noise. Same as you can on our hybrids when you first turn the car in.

[acdii]

 

Sure it puts less demand on the compressor at any given point in time, but it's going to mean the compressor has to run at "medium" load for a longer period of time. I don't know anything about compressor efficiency curves. Is it more efficient to run a compressor on "setting 2" for 2 minutes vs running it on "setting 3" for 1 minute then "setting 1" for 1 minute?

 

Just like it's more efficient to accelerate the FFH at 2 bars instead of 1.5 bars, it could be more efficient to operate the compressor at higher loads for shorter times. We need a little more precision in Hybrider's data to determine that.

That would also depend on how long the actual trip is. There are too many varying factors to get a true answer to this as well. SOC of the pack when first starting, since the compressor uses energy from the HVB to run, if the SOC is low then the ICE has triple duty, charge HVB, propel the car and power the AC. If you are driving in the city this could mean lower FE when set to 72 instead of 80, but if you getting right on the highway, it can be just the opposite. Without a true reading of amps over time, its just theories.

 

From my own observations, when set to 80, the compressor draws max amps for a few minutes, then drops down, when lowering the temp a couple degrees at a time, the amp draw stays low until it reaches the final temp, but when set to 72 it will stay at max amp draw until it reaches the set temp which could take up to 10 minutes or more depending on how hot it is outside.