Plug-In Prius: real winter driving

It feels like I'm confusing matters by interjecting seemingly random values. We may uncover a pattern as some point, ultimately identifying all the parameters used to determine when the engine is used. But the criteria is so much more complicated than in the past. Toyota really did their homework... delivering a system able to respond in such a dynamic way, we cannot beat respond in a way to achieve better.

That makes sense. A computer should be able to take more into account more than a human, especially when it comes to delivering longevity in addition to great emissions & efficiency all at the same time.

It's redeeming to see the flexibility in action. There are so many fine adjustments continuously at play. Yet even in the extreme temperatures we're experiencing now, the results are still great.

I do yearn for warmer weather though. Having already witnessed the increase in capacity from higher temperatures, it certainly is something to look forward to again. Engine warm-up is so much faster too.

 

Introducing AUTO as yet another variable would be end. That's already too many...

Last night, the Prius had been sitting outside for about 2.5 hours, it was only 9°F. Even if the battery hadn't been totally depleted, I would have started the engine immediately anyway. That's simply too cold to endure... which is why I don't actually start the heater until the coolant reaches about 100°F degrees. Fortunately, warm-up began with it at 40°F. It's nice still having a tiny bit of warmth left from the previous drive.

2 minutes into this drive, the benefit of having a heated seat became evident. It was then that I looked over to see how the coolant was doing. What the heck? RPM stated zero! The coolant was only 101°F, yet the engine was off. I was in Stealth mode (low power & speed EV) already.

How come the usual engine warm-up to 130°F didn't happen?

Needless to say, there are so many variables at play, it would be too much of a chore conveying our findings to those without aftermarket gauges and keen observations skills. Because even with, it's a challenge.

It's not worth it anyway. The other day I finally encountered what another owner had complained out, saying window fogging could be dangerous... but never elaborated about the circumstances. I wondered why anyone would push it... but then again, was well aware of how some owners disregard the refill warning. So, I kept experimenting. I refrained from turning on any ventilation, allowing the steam to build up really heavy on the windows. Then I hit them hard with outside air from the blowers. The condensation flash-froze to ice. That was indeed a dangerous situation. But with the temperature only in the teens, I can't imagine someone not just turning on the heater long before that would ever happen anyway. Then again, it's a common sight to see people driving around with only minimum snow & ice removed from the outside of the vehicle. Some take chances more than others.

 

To add to the complex array of parameters we already have, I made yet another discovery.

It was 12°F degrees on the commute to work yesterday. I set the heater at 65, then watched what happened when I turned it on (pressed the fan button) and off (pressed the off button) while driving.

The hypothesis was the engine would remain off while the coolant temperature was still above the usual 114°F threshold. After all, it doesn't start when the heater is running. Why would the engine start up upon starting the heater?

Turns out, it does. Huh?

I performed the test three times was in motion, at 118°F, at 123°F, and at 128°F. Each time, the engine fired up and ran until reaching the usual warm-up shutoff temperature of 130°F. I also tried it once while stopped, at 127°F. Same response.

Needless to say, we are dealing with a very dynamic system, one that takes a wide variety of conditions into account. The "set it, then forget it" advice is proving to be an excellent recommendation. The Prius will figure out how to achieve the best results for you. It is no longer the early days of hybrid driving, when the suggestions to improve efficiency were so simple you could easily to the same yourself.

 

On the simple side, I stopped at the coffeeshop this evening with a toasty warm Prius. It sat there outside in the 23°F parking lot for 1.5 hours while I relaxed. The estimated EV distance remaining was 7.7 miles. My drive home would be with only the heated seat on high. The heater itself would stay off. Since the interior was still warm, there wasn't any need for window clearing. The glass had retained enough energy to resist condensation. Maximum speed would be 50 mph.

It was a remarkably efficient trip, despite the cold. The entire drive home was with electricity only. I arrived home 7.5 miles later. I even had 0.9 of EV left.

 

I changed it to this for clarification: turned it on (pressed the fan button) and off (pressed the off button)

 

If stuck, just drop the pedal and let the special alternating-wheel-power feature dig you out. If that doesn't work, just revert to the usual strategies.

I actually did get stuck, screwing around (experimenting, yah that's it) in the first too-dangerous-to-drive snowfall we got here. It was roughly 8 inches deep, not plowed, and very slippery. In fact, I feel trying to take photos. I ended up having to back out of the rut and ram my way through the pile in front. No big deal.

 

Minnesota Morning.

Looking at my scribbles from the commute yesterday morning, I like what I see. It was 10°F outside. I drove the usual fast route, starting the engine a block shy of the highway by turning the heater on. My garage is insulated but not heated. It's plenty comfortable to drive those first few blocks in EV. That way, I don't get stuck at a light with the engine running. The heater was seat at 74. I didn't use the heated seat today. I wasn't wearing gloves either.

At the conclusion of the 70 mph section, at the 9.5 mile mark, the coolant temperature climbed to 159°F. Upon slowly down to 55 mph, which shut off the engine, I turned the heater down to 65 to keep it off as long as possible. At 10.8 miles, the engine started back up again. The coolant was at 136°F, clearly higher than the usual 114°F threshold. My theory is the outside temperature influences when too.

After 2 miles, the engine shut off again. The coolant had reached 146°F. With the heater still at 65, the newly generated heat only latest 0.9 mile. That was no surprise, being that cold outside. It was getting pretty warm inside though. So when the shut off 0.8 mile later, I shut the heater off too. Why let it start again. I was already 14.5 miles into the trip and only had 2.2 remaining. So, the rest of the drive was without any blower running and using only electricity.

I arrived at my parking spot in the ramp with 0.5 mile of EV left. The overall average was 114 MPG. That's amazing considering how cold it was outside and how little was done to achieve that outcome.