Hot weather hybrid milage.

[Timothyd]

Went out to dinner with my XLT. About 94 degrees, decent traffic, AC on and got mid 40s mpg for the trip (20 miles). On the way home, about 88 degrees, no AC, lighter traffic, maybe 50mph tops, saw 62 mpg trip consumption.
Went down to 41 mpg average for winter then up to 48.5 mpg and now that it's hot it's going back down. Is it hybrid battery efficiency or running the AC in this weather? Maybe it doesn't matter that much, I'm not going without the AC, just curious.

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[The Real Maverick]

Some of each.

But under 120°F it's mostly A/C use dropping your MPG.

In any car; not just hybrids A/C is a 2-5 horsepower draw.

The batteries actually output more and more the hotter they get... right up until they catch fire. So at a point, the software starts to limit use to prevent said fire. But it's above 120°F internal temperature when that happens.

 

[Glen Baker LLC]

Went out to dinner with my XLT. About 94 degrees, decent traffic, AC on and got mid 40s mpg for the trip (20 miles). On the way home, about 88 degrees, no AC, lighter traffic, maybe 50mph tops, saw 62 mpg trip consumption.
Went down to 41 mpg average for winter then up to 48.5 mpg and now that it's hot it's going back down. Is it hybrid battery efficiency or running the AC in this weather? Maybe it doesn't matter that much, I'm not going without the AC, just curious.

The electric AC unit in a hybrid is powered by the high-voltage battery and does not directly draw power from the engine, like a traditional gasoline car. Where the compressor is directly connected to the engine via belt.
. In a hybrid car, the electric air conditioning (AC) unit uses a fraction of the power compared to a gas engine, typically drawing around 2-4 horsepower (around 1.5-3kW) at full blast, while a gas engine in a car might use 4 horsepower or more.
The hybrid AC operates in phases.
Where as the conventional gas engine belt connected compressor is 100% on when the clutch is engaged.
. The hybrid AC will require 3 kW during the initial cool-down phase and then drops significantly to maintain the temperature (around 1 kW or 1.34 HP).
. Of course newer gas vehicles do cycle the compressor on and off to maintain interior temperature. Versus the days. When you turned on the a/c. The compressor ran all the time and if you wanted interior a little warmer. You slid/turned the temperature handle and the blend door moved and added heat to the cold air.

 

[Master Blaster]

1. Winter fuel has a lot more volatiles in the mix than the heavier summer fuel, and consequently less energy/gallon. That changeover is worth 3-5% mileage.
2. It is normal in winter to add a lot more ethanol to the fuel in order to prevent water from dropping out of the mix and causing engine issues. A 10% mix will cost you another 3%, and some states go as high as 30% or 9% mileage hit.
3. The pressures on high-profile tires can vary by easily 10% between winter and summer. That's another 5-10%, depending upon how cold it gets in your area. Check and correct that, or you won;t have any tire life either.
4. In summer it takes about 5 miles of running on battery to heat up the converter from the exhaust heat exchanger. In winter that time is easily doubled. During that time the battery charging is limited, costing you recharging drag for longer afterwards.
5. In summer it takes about 5 minutes of engine operation to get the oil and more importantly, the catalytic converter up to temperature. In winter it is easily triple that time, especially if you heat the large interior space with coolant heat instead of using the seat and steering wheel heaters. During that time the fuel and cam management are open-loop and running at retarded and full-rich mappings to provide excess fuel and oxygen in the exhaust to heat the converter as fast as possible. During this period, fuel mileage can easily be halved, which is why short trips get terrible mileage. Figure on the average on long trips costing you maybe another 5% mileage. You can somewhat minimize that time by using a block heater.
6. 6. Pushing snow or water costs energy. Depending upon how much of it you push, the effect could be massive.
7. Cold tires don't deform the sidewalls as easily, costing mileage. Figure on maybe 3% for that.
8. Winter tires work a lot better, but wear out maybe twice as fast as they conform to the road surface much more tightly than summer tires. That rubber scrubbing costs energy.

 

[Escapologist]

My wife was on a longer trip in the same drivetrain Escape hybrid a couple of weeks back and it was the first heatwave we had. Air temps were mid to high 90s, plus humidity, but it is reckoned asphalt can go 20-30F over air temp in full sun, so it's possible the air 0-2ft off the ground on the highway is a lot hotter. Anyway, most sucktastic hwy miles yet seen, 34mpg, with 0.6 miles electric use showing in 120 miles on the trip report. She had Max AC on all the way. 45mpg is more typical when we run with the fan at 3 or 4, AC temp to 20-21 in 80F temps.

 

[AutobahnSHO]

Running the AC all the time might run the ICE more.
PLUS other factors already mentioned.

 

[Timothyd]

My wife was on a longer trip in the same drivetrain Escape hybrid a couple of weeks back and it was the first heatwave we had. Air temps were mid to high 90s, plus humidity, but it is reckoned asphalt can go 20-30F over air temp in full sun, so it's possible the air 0-2ft off the ground on the highway is a lot hotter. Anyway, most sucktastic hwy miles yet seen, 34mpg, with 0.6 miles electric use showing in 120 miles on the trip report. She had Max AC on all the way. 45mpg is more typical when we run with the fan at 3 or 4, AC temp to 20-21 in 80F temps.

Yeah, same for me. With the cold and my snow tires I expected worse winter mpg. I was getting better locally till the heat wave hit in mid May and the AC was on always. I suppose it was on for the HV battery too. I've turned into a wimp, it's too hot and humid to ride my motorcycle in the 90 degree muck.
I suppose when I was getting 12 mpg in the bigger truck the AC hit wasn't as noticeable.

 

[dochawk]

Of course newer gas vehicles do cycle the compressor on and off to maintain interior temperature.

Not just newer--Cadillac has had thermostatic control (set a temperature) since at least the sixties.

Also, clutches on the compressor have been the norm for decades.

 

[Escapologist]

My 95 Escort had the smarts to turn it off going up hill, you'd start to notice it getting warmer if it was a long one. Had to make sure all 88 of those ponies were going to the wheels. Though after I ported the head, back cut the valves and added a header, it didn't cut out so much... though after a while it was blowing fuses a lot, so wondering if it was exceeding it's duty cycle which was normally capped by lack of engine power.

 

[dochawk]

My 95 Escort had the smarts to turn it off going up hill, you'd start to notice it getting warmer if it was a long one.

My '83 Cougar had so many clutches under the hood for this and that that going up the grade to the Texas St offramp in San Diego sounded like the rods had gone bad! (which they eventually did, I think but that' another story).

There were so many, that the clutches may well have had clutches . . .

 

[Timothyd]

My '83 Cougar had so many clutches under the hood for this and that that going up the grade to the Texas St offramp in San Diego sounded like the rods had gone bad! (which they eventually did, I think but that' another story).

There were so many, that the clutches may well have had clutches . . .

And now we have sensors on top of sensors.

 

[Master Blaster]

My 95 Escort had the smarts to turn it off going up hill, you'd start to notice it getting warmer if it was a long one. Had to make sure all 88 of those ponies were going to the wheels. Though after I ported the head, back cut the valves and added a header, it didn't cut out so much... though after a while it was blowing fuses a lot, so wondering if it was exceeding it's duty cycle which was normally capped by lack of engine power.

The ac cutout is based on engine vacuum, not duty cycle. Going uphill with your foot right into it, you have little or no engine vacuum. Since the ac is using 8 of your 88hp, its load shedding to get you up there.

 

[Escapologist]

The ac cutout is based on engine vacuum, not duty cycle. Going uphill with your foot right into it, you have little or no engine vacuum. Since the ac is using 8 of your 88hp, its load shedding to get you up there.

I didn't say it was based on duty cycle, I said that more power apparently changed it's duty cycle.... and I think we're into one of those things where I used the general sense of a term which you are only aware of being used in a specific sense, i.e. PWM type duty cycles. In the general sense, if you use your car for 10 minute trips twice a day, then move to using it 4 times a day the duty cycle changed, but doesn't mean you drive the car for 4 fractions of a second vs 2 while you're driving it.

If you were familiar with the EEC-IV set up in the 90s Escorts you would know it has a MAF and has no direct way of measuring vacuum and that no mechanical vacuum transducers are used in the control of AC clutch. Therefore it is derived values that the EEC-IV determines engine load from and cuts the AC in and out accordingly, it kicks the throttle body to high idling when AC is on for example.

 

[dochawk]

And now we have sensors on top of sensors.

Om my 1990s Cadillacs, the "coolant low" light actually means, "replace coolant level sensor".


there's a float in a tube off the the surge tank, and after several years it sticks.

I hit another similar problem recently, but my mind is blanking on it.

 

[Escapologist]

I had an oil pressure sender keep blowing out on a Chrysler 2 decades back... and it was gushing out of it... like that's the opposite of what you're for, but yeah, "bong bong, low oil pressure" the sender blew out again grrrr (happened several times it's like gates couldn't make senders right any more, then finally got one that lasted.)

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