[obermd]

This morning temperatures were hovering between -5F and +1F. My car reported a combined 39 MPG between ERDTT and electric. The problem is ERDTT never gets the engine to full operating temperature, so I would have been more efficient running entirely on Hold mode in these conditions. I'll remember this for future mornings like this (I think tomorrow will be the same.)

 

[arbus]

When it gets cold enough for ERDTTs, I flip to HOLD and use Fan Only so the ICE heats the cabin. That gets between 43 and 47 mpg. Not the best, but better. And I'm nice and toasty - that's always a bonus.

 

[Steverino]

To get the most efficiency out of my car in these conditions, it's best to set the Hold mode for the entire drive tomorrow. That way, it'll be sure the engine is at full operating temperature and can get the best out of the car. It is also possible to improve the car's efficiency in cold temperatures, such as by adding an engine block heater or using a fuel additive.

In contravention to the owners manual ... Seems like another Philippines botsponse, especially given how often the country experiences -5°F to1°F temps for "his car", lol.

bye, bye bot

 

[wordptom]

Volt chief engineer Pamela Fletcher, in her video presentation on the 2011 Volt, said the concept of the Volt is to minimize the use of gas. That’s why they engineered Mountain Mode to recharge a fully depleted battery only to the SOC level that enables the car to maintain performance in high power demand driving conditions, rather than burning enough gas to fully recharge the battery.

In like manner, ERDTT and EMM functions don’t really require the Volt to shift fully into Charge Sustaining Mode, so the use of gas would be minimized if you continued to use grid power for propulsion. The function of ERDTT is to meet federal requirements for heating air to keep the window clear, and the engine doesn’t need to reach full operating temperature to accomplish that. The function of EMM is to lubricate the engine, not to maintain the generator. If the engine is not performing any "vehicle propulsion" tasks during ERDTT or EMM such as creating output torque for propulsion or generator cranking, then you don’t need to burn additional gas to heat the engine to full operating temperature.

So, during ERDTT, is your Volt being propelled by grid power or is the charge being sustained? Has anyone checked the energy usage display on the center console after driving several miles during an ERDTT episode to see whether or not the kWh Used increases as you drive, which would indicate the system is still using grid power for propulsion, even when the engine is providing hot air to keep the window clear, and even if distances are recorded as Gas Miles because the engine is burning gas for the heat? An EMM is over so quickly it might involve too short a driving distance to increase the kWh Used.

Of course, it would be difficult to determine the impact driving on grid power during ERDTT would have on overall statistics (Gas Miles driven using grid power but also while gas is being burned for non-propulsion purposes?), or if using Hold Mode instead would be more efficient overall. The immediate use of Hold Mode at the start of the commute would avoid using grid power for electric heat used before ERDTT kicks in (unless you preheat before departing?), but once ERDTT kicks in, grid power no longer needs to be used for cabin heat so the ev mileage would improve if you were driving on grid power...

 

[arbus]

My experience has been that, in my 2015, when it’s -5 f, between the age of the battery and the draw of the electric heater, I end up with less than 15 miles of electric range, even with preheating from the grid. EDDT does provide minor charging, but not nearly enough to keep up with demand. Since on almost any drive I take when it’s that cold, the ICE will run to power the car, it’s far warmer to put it in Hold right off the bat and let it heat the car.

 

[obermd]

References to a Volt are to my 2017 LT.

In like manner, ERDTT and EMM functions don’t really require the Volt to shift fully into Charge Sustaining Mode, so the use of gas would be minimized if you continued to use grid power for propulsion. The function of ERDTT is to meet federal requirements for heating air to keep the window clear, and the engine doesn’t need to reach full operating temperature to accomplish that. The function of EMM is to lubricate the engine, not to maintain the generator. If the engine is not performing any "vehicle propulsion" tasks during ERDTT or EMM such as creating output torque for propulsion or generator cranking, then you don’t need to burn additional gas to heat the engine to full operating temperature.

The battery alone can easily clear my windshield - I know this because it clears the windshield during preconditioning, which I have set to never use the gas engine when plugged in. The real issue is it takes a lot of power to do this using the resistive heater in the Volt, so it drains the battery faster. Further proof for this claim can also be found in the 2019 Volt where the deferred temperature was changed from +15F to -15F, so those folks who don't go very far can avoid using gas until it get really cold.

So, during ERDTT, is your Volt being propelled by grid power or is the charge being sustained? Has anyone checked the energy usage display on the center console after driving several miles during an ERDTT episode to see whether or not the kWh Used increases as you drive, which would indicate the system is still using grid power for propulsion, even when the engine is providing hot air to keep the window clear, and even if distances are recorded as Gas Miles because the engine is burning gas for the heat? An EMM is over so quickly it might involve too short a driving distance to increase the kWh Used.

During EMM and ERDTT I see both battery and gas consumption numbers incrementing. EMM uses about 0.03 gallon (~1 cup). ERDTT uses about a third more gas than Hold mode for the same distance travelled. I used Hold mode this morning and my gas MPG was 36.8. Yesterday my gas MPG was 28, which is why I created this thread.

Of course, it would be difficult to determine the impact driving on grid power during ERDTT would have on overall statistics (Gas Miles driven using grid power but also while gas is being burned for non-propulsion purposes?), or if using Hold Mode instead would be more efficient overall. The immediate use of Hold Mode at the start of the commute would avoid using grid power for electric heat used before ERDTT kicks in (unless you preheat before departing?), but once ERDTT kicks in, grid power no longer needs to be used for cabin heat so the ev mileage would improve if you were driving on grid power...

Not really difficult - my Volt does this for me in fact. Once you convert the electric miles to MPGe it's a simple ratio computation to get the overall MPGe for the trip. While the EV miles do improve during ERDTT the bulk of the propulsion is coming from gas so the EV miles actually go up very slowly relative to the gas miles. This forces the trip MPGe down towards the piss poor fuel efficiency of running the gas engine below its optimal operating temperature.

 

[hellsop]

Sure, it clears the windshield on preconditioning. While I'm not in the car supplying warm humid air to cold glass, and over a period of 10 minutes. That's not the same conditions as "while driving", which has the additional load of my exhalations refogging the windscreen and the imperative of "Get this glass clear ASAP so we can goooooo!"

 

[hellsop]

So, during ERDTT, is your Volt being propelled by grid power or is the charge being sustained?

Yup, I have. And the electric consumption during the cycle changed about 0.2 kwh downward over the course of a mile and the six minutes it took to drive it with the heater blasting. But I have an OLD Volt that predates the changes to the operation that Chevy did to implement sophistications like Hold Mode and adjustable ERDTT temperatures. It's probably primitive enough that ERDTT may well have just turned on CS mode without the charged-up "turn off engine" command because 0.2kwh is ALSO the amount that charge wanders (between 4% usable and 6-7% usable) while on CS as read out by MGV.

 

[ken.deken]

This morning temperatures were hovering between -5F and +1F. My car reported a combined 39 MPG between ERDTT and electric. The problem is ERDTT never gets the engine to full operating temperature, so I would have been more efficient running entirely on Hold mode in these conditions. I'll remember this for future mornings like this (I think tomorrow will be the same.)

I live in Cleveland with plenty of cold temperatures. I think engines burn cleanest if I can keep the engine temperature at a normal operating level, i.e., about 190F or so coolant temperature. I don't like the cycling from about 160F down to 120F that occurs during ERDTT operation. For that reason, if the temp is around freezing, I just turn on the HOLD mode to allow the engine to run continuously. I know that generates more CO2, but I have a sneaking suspicion that given the choice, the engineers at GM would rather have their engine operate at the higher temperature rather than cycling. However, they use cycling as a nod to more battery operation. Have a 2018 Gen II with 71K miles, so far so good.