Winter driving too cold weather MPG down

I don't think it's that simple because of the way the three rotational power sources are couple in the planetary gear assembly. Toyota explains:

The Prius Prime is powered by Toyota’s Hybrid Synergy Drive powertrain, which seamlessly combines the output of the gasoline engine and electric motor through a planetary-type continuously variable transmission. ... To help make extended EV mode driving range possible using Hybrid Synergy Drive, Toyota modified the system. For the first time in a Toyota hybrid, the system uses a “dual motor drive” with a new one-way clutch which engages both the generator (MG1) and electric drive motor (MG2) for drive force, the first time MG1 has been used for that purpose.​

I believe that if the ICE is turning, it's contributing to the the traction power of the vehicle.

If you want to see a lot more detail about how the Prime's transaxle assembly is constructed, take a look at John Kelly's excellent (and lengthy) YouTube video "The Evolution of the Toyota Prius P610 Transaxle." John Kelly heads the Department of Automotive Technology at Weber State University in Utah.

I am neither an automotive technician or a mechanical engineer, so please let me know if I am misunderstanding how this assembly works.

 

I just saw a robin...so winter is about over.

 

I'm trapped in the Minneapolis airport right now, stuck waiting the foot-plus of snow to finish falling.

 

It's simple: in EV the two motors join their forces to spin the wheels by means of the spring clutch.In general, a motor can either drive or generate electricity, but not concurrently. Hence, either the "fake" EV mode is not EV mode at all but simply HV mode, or is an EV mode with ICE burning fuel just to produce heat.

 

HV mode includes electric-only driving, so the "fake" label really doesn't serve abby purpose.

Remember, plug-supplied electricity is used even when the engine runs.

 

I'll give you that, therefore let's assume that EV mode with ICE running for cabin heating purposes only is "real" EV mode, I will label it EV(Ice) and come back to my original question: considering that ICE is as much efficient as it is loaded, is EV(I) an efficient mode? I doubt it, because ICE is idling at low RPM. Viceversa, in HV mode ICE drive the wheels and MG1 through the PSD, and warm up the cabin. It seems a more efficient process, however only a comparison test of both modes in similar conditions would answer the question.

 

ICE may be more efficient when under load, but when the system is cold it is also more polluting and wears the ICE more. So Toyota has it idle while the engine coolant, catalytic converter, and more warms up. I see the cylinder fireing timing and RPMs change (on ScanGauge II) as the coolant warms up and the ICE starts to contribute to propulsion, usually within 60 seconds.

 

Yep.

I'd be most interested in seeing the exhaust profile during an ideal warm-up.

 

Me too. My understanding is that there are significantly more pollutants in exhaust when ICE is cold and under load.

 

Here is what I found on my google search. I consider the Prius to have a near ideal warmup, so look on page 11 of the link below to see exhaust profiles of 3 generations of Prius.
http://www.sae.org/events/training/symposia/esvp/presentations/2011/michael_duoba.pdf

I wish they profiled normal ICE vehicles too in the paper.

 

I think I can estimate the emissions ICE warm-up for my Prius Prime on a 50F day:

The EPA has a drive cycle called HWFET. The Prius Prime in ICE mode (similar to any late generation Prius) generates 6 mg/mile Nox+NMOG averaged over the test, but we know that essentially all the emissions are during the warm-up phase. The test is ~ 10.6 miles long, so the warm up emits 10.6*6 = 63.6 mg



Since the Prime is able to use the battery during warm-up to keep the load low, I presume the warm-up during a city cycle could be similar. When I owned a Prius, I would drive gently out of my neighborhood to let the ICE warm-up under low load. For some people with a regular hybrid who cannot or will not drive gently at first, it may make sense to idle some 30-60 seconds before driving if they want to minimize tailpipe emissions, albeit at the expense of some increased CO2 emissions.

A sticky in the Prime forum that I wrote talks about a strategy to reduce tailpipe urban emissions to zero in a Prime. At the time I estimated 100 mg warm-up emissions penalty, but the EPA data suggests less. One thing is for sure: the less warm-ups, the better. Particularly in a plug-in, some thought should be given to heating up the ICE once (if at all) and then keeping it warm for the drive.

As for warm-up from colder temperatures, I'm not sure. There may be bag data in the more involved EPA report that would be informative.

 

Ahh .. here we go, from the CSI report for the Prius Prime:



This is the FTP cycle starting from a 20F cold soak, 11 miles long.
So the NOx warm-up penalty is 11*7.65 = 84 mg
And the NMOG emissions are 11*12.2 = 142 mg

I warm up my Prime out of town on the highway at ~ idle, so hopefully even less emissions.

 

I bought gas today. Yet, I still had 81 miles left for gas, according to the car. Last time I filled up was Aug. 23rd. in West Des Moines as I was returning from the eclipse out west. I literally had to re-read the manual to remember how to reset the trip odometer, as it has been such a long time.

The next 10 days we might have low single digit temps at night, so I expect the car to start in ICE mode every day, so I thought it best to get some of that petrol stuff, just in case. I feel just awful about needing to do this.

 

just wear your winter jacket hat and gloves and leave the climate off

 

I usually do dress a little warmer when I drive in EV in the cold. Like when I filled up at Costco, which was a 15 mile round trip at 16 degrees. I was in EV the entire time, but the temps were falling from something much warmer, so the car didn't see the 14 degree threshold. Never turned on any heat or seats, or steering wheel warmers.

But when it is 4 degrees F, like it is right now, the batteries will remain temperature lagged even if the outside air temp is warming to 18 or 20. The car will start, and remain running with ICE, to and from work. That's just the way it is when the car cold soaks outside all night near zero, all alone, lonely, silent, and in the dark, without a friend.

 

how about some nice warm cofefve? to warm up your Prime?

 

A little warmth goes a long way. I've had to be happy with up to 90 mpg on my 89 mile work commute for the past month or two but yesterday it was mid 50s F on my way to work and high 30s F back home. The Prius soaked up the sunshine and heat and managed 104 mpg for the trip.

My car, my PV, my tan ... I'm too concentrated in the sun sector. Maybe wind ?

 

Do you mean "covfefe?" Whatever that is, or whatever Trump thinks it is, I'd bet my Prime would like some of that at night, as it is politically agnostic.

 

Here's more real-world data to ponder...