Warming up Prime in Cold weather.

I've read that iif you use the start button to start the prius, get it in the ready mode, and select the DEFrost button, the engine starts and continues to run (not sure if the FOB has to remain in the vehicle). Could this be helpful in warming up a Prius when its 14 F or lower temp outside ?

 

Does a 2024 PP XSE get any cab heating directly from engine coolant or heat exchangers gathering heat from the combustion engine as a heat source ?

 

This is what my Gen4 Prime does. I'm surprised this would not have been fixed in the Gen5.

 

for 2024 PP : Exhast heat recovery. Does that use a cat conderter heat exchangento coolant to cab heat ?

 

I don't see two pipes. Just an exhaust pipe hanger there !

 

I still just see exhaust pipe/componemt hangersm there. I see the rubber 'muffler bearings' (2) and two steel round stock hangers weldedd to the brackets on the exhaust system component there.

 

Pretty sure the gen5 doesn't use the exhaust heat recovery system like the gen3 and gen4 did. I'm looking at TIS, and the instructions for removing the exhaust don't involve disconnecting any coolant lines.

There are differences between the gen5 HEV and PHEV exhausts, but they appear to be only related to the exhaust hanger points. Likely because the undersides of the models are slightly altered because of the different batteries.

And RandyPete is correct; those are exhaust hangers in the photo, not coolant pipes.

 

The car will auto shut off after an hour, not 10 mins as fast as I can tell.

Also it only uses the battery when plugged in probably because most ppl would plug it in a garage overnight, so not using the engine for remote start is safe.

 

', that helps warm up the engine faster and thus you get heat from the engine sooner.'
_
Wondering how heat from the engine is delivered to the cab ? Are there engine/inverter coolant lines run to the cab thru a heater core and heat transfered with a fan and cab air ?

 

The Prime uses both a heat pump and a regular heater core for cabin heating. It doesn't have any kind of electric resistance heating.

The primary source of heat is the heat pump compressor(which also doubles as the A/C compressor). In heating mode, it sends high-temp, high-pressure, gaseous refrigerant into an internal condenser inside the A/C box behind the dash. Inside the condenser, the refrigerant changes phase from gaseous to liquid and gives up heat. The A/C blower motor pushes air across the internal condenser and sends the warm air into the cabin.

If the outside temp is too low for the heat pump to keep up with the heating demands, the climate system will switch over to the standard heating core. When that happens, hot engine coolant will be routed into the heater radiator unit sub-assembly that's also inside the A/C box. The A/C blower motor pushes air across the heater radiator unit(heater core) and send the warm air into the cabin.



Other stuff:

In previous generations of Priuses, there was a heat exchanger built into the main exhaust pipe that would run engine coolant around it. During cold starts, this would use waste heat from the exhaust to help warm up the coolant. In turn, this would allow the engine to get up to operating temp more quickly. The two benefits from this are better emissions(an engine at operating temp is more efficient than a cold engine) and quicker cabin heat on cold days. This system was phased out for the gen5(probably not needed with the new engine + extra costs to produce the more complicated exhaust pipe + the gen3 & gen4 exhaust heat exchangers were known to fail and leak coolant into the exhaust, mimicking a head gasket failure).

Full BEVs and some other PHEVs do use electric resistance heat as a backup when it's too cold for the heat pump to keep up with heating demands, but the gen5 Prius does not use this system.

Toyota is currently testing an infrared heating system that will be installed under the dash to radiate heat to the knee area. Toyota is finding that there are several areas on the body that make us feel cold. Of those areas, the knees are currently the last areas to warm up in a standard car. (feet, back, hands are some of the others) In early testing, Toyota is finding that they can shave multiple minutes off a driver feeling cold if they can get the knee area warm. If Toyota moves forward with this, I'd expect it to roll out to Lexus models first. I doubt the gen5 will ever get it, but maybe the gen6 will.

 

Interesting. Sounds like a cool system.

 

Thank you for the detailed reply,

 

To add, I'm not sure if the Gen5 does the same but the Gen4, while heating, it can also direct the refrigerant into the cabin evaporator to dehumidify the cabin air. That's what happens in a Gen4 when you press the A/C button in winter. It doesn't draw more power since the heat pump is already running anyway. I'm not sure about summer time though when it's basically all A/C that you use. Does it shut down the compressor when you turn off A/C? I would hope that's what it does, but I haven't tried it yet. Way too cold here to run just the A/C lol. Hybrid Assistant is very useful to figure these things out.

 

The gen5 can do that at 32F/0C and above when the defroster is off.

Here's a chart of the climate system behavior for the gen5 Prime (from TIS New Car Features)

 

Thanks, sounds similar to what the Gen4 is doing, minus the battery cooling since the Gen4 battery is air cooled from the cabin air, hence why it's important to run A/C with the windows closed when it's hot outside with the Gen4. A/C switch behaves like expected also.