What powers Prime HVAC in winter?

Maybe the muffler has a sweet tooth.

The 4 speed transmissions Toyota was selling in new cars were also obsolete. Got to squeeze every penny out of that production line

Assuming the supply is place, they'll likely use a unit designed for a bZ. The point I should have made was that the new Prime's system in unlikely to be of worse spec; it isn't going to be worse at heating with under freezing temps.

 

i haven't seen any heat exchanger talk in the reviews so far, but it will be great if they have made improvements. isn't constant improvement their motto?

 

I remember being told that it added (at least in the Prime) a recovery of heat from the catalytic converter. I was surprised since coolant leaks into the exhaust from a head gasket is one of the common killers of the catalytic converter's catalyst.

 

Prii have been recovering heat from (not the catalytic converters exactly, but the exhaust downstream of both of them) ever since Gen 3 came out.

So the Gen 3 Prius Plug-In does it too, and all Gen 4s do it, including the Prime.

Somehow, they got the Gen 3 system fairly trouble-free, and then their constant-improvement motto produced the Gen 4 heat exchanger known for leaking coolant into the exhaust. Maybe Gen 5 will re-improve it back to the way it was in not-leaky Gen 3.

Anyway, coolant leaking from the exchanger does not kill the catalyst, because the exchanger is in the exhaust pipe downstream of both catalytic converters.

 

gen 4 leaks don't seem to be a major problem. yet. but maybe if they aren't leaking now, they won't, idk

 

Not all gen 4 have the same algorithm for heat at very low temps. A change was made in 2020 or 2021 if I recall correctly based on early model owners complaining about poor heat. My 2022 prime has a very heavy bias to run the ICE when temps are below -10C, the lower limit of the heat pump. And never runs in EV mode below -20C.

At very low temps(below -20C), I do not charge the traction battery since it never goes into EV mode. But I can engage the charging while driving with the ICE and the ICE warms up quicker. As someone else pointed out, the heat is from the exhaust coolant loop when operating in very low temps.

BTW: the 200w block heater is of no value when below -20C.

iPhone ?

 

The TSB for it seems to apply to 2016–19 Prius and 2017–19 Prime.

T-SB-0135-19

Hard for me to tell from here how "major" a problem it is, other than seeing a bunch of posts from people with the issue, and seeing that Toyota issued a TSB and updated the front exhaust pipe / heat exchanger.

 

this seems odd if you look at lee jays post on his 2017 vs prius16's 2022

 

not nearly as many as blown gen 3 head gaskets, and no tsb there

 

... where also I have little to go by besides reports on PriusChat. I won't pretend to know how either translates to real-world prevalence.

 

me neither

 

My 2017 has never leaked. Makes sense to put the heat recovery downstream from the catalytic converter. I never looked into the details. Recovering heat there makes sense, the converter(s) run HOT to do their job.

 

From my experience, there are huge disparities in the PP's heat pump performances depending on who you ask. I attribute this primarily to the subjective sensation of warmth rather than to objective hard data. To me, the PP's heat pump was a total failure in terms of providing the heating needed when I wanted it most. Very similar to the story of @prius16, from early on in my first 2017 PP, it never worked to my expectation in the lower temperature environment. Here, my "subjective" category of lower temperature is below 25F. Above this line, I usually don't feel I need heating. The heat pumps alone in 17, 20, and 21 PP all failed to warm up the cabin quick enough and adequately at temp range below 25F. I only used the HVAC switch after the engine has started.

My winter morning routine was as follows.

• A day before when the car is parked, make sure the HVAC is turned OFF
• Charge traction battery overnight
• Never use useless climate pre-conditioning feature
• As soon as I start the car in the morning, if the temp is low (below 32F but above 14F) and I feel I need heat (wet, windy, before daybreak departure) then switch the car to HV mode (i.e. gas engine starts at this point to preserve EV range for later use)
• If the temp is low (below 32F but above 14F) but I don't feel needing heat (calm dry sunny day), then I keep on EV mode
• If the temp is very low (below 14F), then the car almost always started the engine by itself, so I would switch to HV mode at the start to preserve the EV range
• If the temp is warm (above 32F), just drive in EV mode without any HVAC
• Always use a heated seat and heated steering wheel before turning on the engine to use the HVAC
• Never use the AUTO setting on HVAC
• use only a low fan 1 bar or 2 bar with the direction of heat aiming at either to window or cabin depending on my need (if defrost is needed, then aim at the window)
• Never use FULL window defrost unless the engine already started.
• Overall, my impression of the heat pump on 3 PP year models and trims heat pump was mostly negative. Yes, it helps to conserve the battery SOC, but the heating performance was subpar on all occasions I really felt the need for heating.

Just FYI, contrary to my experience with the PP's heat pump, my initial experience with the heating system in the 2022 Escape PHEV is that it is a much better performer, as far as heating is concerned with one huge drawback. Apparently, the Escape PHEV uses two heating systems 1) a high-voltage electric heater located in the coolant stream that is sent to the cabin heat exchanger and 2) a 12v PTC heater located in the heater housing. I have not figured out which one works in what situation, but heating when operating is so quick and absurdly hot, it is amazing. The drawback is that I think both heating systems use huge watts to heat the element. I don't know the exact draw, but it is substantial. To circumvent this large electric draw by two heaters and minimize the battery usage for heating purposes, Ford implemented a very strict algorithm for when to turn on the engine, I believe. The car will automatically turn on the engine whenever the ambient temperature is 32F or below. And so far, I am finding out this happens even when there is no HVAC operating. This was a very big disappointment for me, and I am currently trying to figure out if there is a way to suppress this engine turning on when no HVAC heating is called for, something I did not have to worry about on PPs at this temperature.

 

Are their experiences at extreme low temps?


iPhone ?

 

do not know, you'd have to ask them. their posts are on the first page of this thread

 

With all the debate here...any idea when we get actual tech documents from Toyota? I remember seeing those for the 4th gen shortly after announce...and they did a great job at detailing the improvements they had made over Gen3. I'm assuming we will get a similar set of documents for Gen5? Kind of puzzling though...I would have thought that we would have seen them already.

 

The major bunch of that information will be in the New Car Features manual, and anybody whose TIS subscription is paid up can tell us whether that has appeared yet.

Toyota Service Information and Where To Find It | PriusChat

 

electro engineer always seems to refer to that

 

What the heck are you guys talking about?? I never had an issue with the gas injected heat pump on my 2017 Prius Prime. I had heat in about 30 seconds in EV mode down to 15ºF (-26ºC). It doesn't work the same way as the ICE climate control as it doesn't try and heat the cabin to your set temperature. Usually I never changed it from my normal setting of 65ºF (18.3ºC). The heat pump then pushed out heated air at 65ºF. Not very effective when it is 20ºF out but keeps the windows clear. When you have a heated seat and heated steering wheel you don't really need a lot of heated air. If you turned it up to 74 or so, which was required when Mrs. drash was with me, it sucked battery juice pretty good. In the winter I preconditioned while it was in the garage by turning it to max heat while still plugged in, which also helped to heat the battery compartment, with the remote heat on the app. If it was in the single digits or minus temperatures I'd be able to go a couple of miles before the ICE kicked on.

This was much better than Big Blue, which is what I called my Plug-in Prius, which had no heat at all in EV mode.

 

I think you pointed out the main reason why you hear the discrepancy on the PP heat pump effectiveness for the comfort level of the operator. As you said it, 65F air coming out of the vent when it is 20F does not warm up the cabin like the traditional ICE waste heat-based HVAC. And try to pump 75F air coming out, it drains the traction battery very quick. I used to drive my PP with the HVAC set at 68F with the heat pump on EV mode in the morning commute in winter. If the ambient temp is below 20F, the cabin temp never reached 32F during my 18 miles commute if the engine does not come on. If I wanted the cabin heated, then I just turned to HV mode, otherwise, I kept on EV mode and HVAC off. I reported this on one of the very early PP threads somewhere.