[Flatland 306]

So it seems that if the cabin thermostat is calling for heat it will force the engine to run when it would normally be off. In some scenarios when the cabin is up to temp and it’s only -10c/14f outside I would be willing to trade some cabin comfort for increased mpg.

The last few days I have been shutting the heater off while I decelerate and only turning it back on once the engine has restarted due to acceleration demand. Then off again and so on.

I don’t suppose there is a hidden heater setting where the heat only runs when the hybrid calls for the engine to be started? That would save me wearing out my heater on/off switch.

 

[RennZ]

By trying to force the engine to stay off you will keep the engine cold and out of closed loop. The computer is trying to optimize efficiency by keeping the engine in a ready and warm state. It takes time to warm the coolant enough to provide cabin heat and when the engine is cold, it tends to run richer and less efficient while increasing emissions because the catalytic converter needs to be hot (search "catalytic converter light off").
Trust the engineers and don't try to micromanage the computer; it will continuously search for the most efficient mode.

 

[Sienna9816]

Do you have a 1500W outlet? If so, a properly installed small space heater might be of some help. Sienna has 1.8KW HV battery with about 30% reserve. A space heater can run for about an hour without forcing engine on. However, if it is very cold outside, engine will be coming on anyways to stay warm as stated in post above.

 

[wscan]

Once the engine is up to temperature, it no longer needs to stay on to provide heat. The heat is provided by circulation of the hot coolant while the engine is off. The coolant can cool down to the 120 F range before the engine comes on to provide more heat. If you are moving, the engine probably needs to come on anyway. The only time the engine seems to stay on for heat is during warmup which could take 10 minutes or so depending on the speeds you are driving and the outside temperature.

 

[Flatland 306]

Thanks for the responses guys. Always good to learn as much about these systems as we can. I likely should have given more back story on my driving but I was on my phone and typing is slow. So my van is always in a garage that is kept at 4c/39F when I press the start button it goes ready then 5 seconds later the engine starts even with my heat off and the van stationary and the battery 1/2 full or more. I assume it has decided to start the engine because it is not up to operating temperature. I have a 1/2 mile drive way that I drive 40kmh/25mph on, the engine will run even with heat off and battery 1/2 full. Also I assume it is warming up the engine. I then turn onto a gravel rural road that I drive 60kmh/37mph on for one more mile. Again the engine will not shut off as I slow down and stop at the stop sign even with the heat off and the battery 3/4 full. I then have 1 more mile on the gravel road going 60kmh/37mph and the engine will continue to run mainly due to accelerator position and load demand, its slightly into the second section of the green band. As I slow down to stop at the highway it will now finally go into EV and shut the engine off. So that took 2.5 miles of moderate driving.

Next I turn on the highway for 8 miles and travel 109kmh/68mph. This is where I turn on my cabin heat to 24c/75F. The engine will run the whole time due to the speed. After 8 miles the cabin is no where near 24c/75F. So as I come to stop when I get to the first traffic light the engine will only shut off if I shut the heat off. If I leave the heat on the engine will continue to run the whole time I'm at the red light. So what I have started doing is hitting the "cancel" button on the cruise control and then heater off button on the climate control and then the van goes into EV. After the light turns green I accelerate in EV until the engine starts then I turn my climate control back to 24c/75F and drive another 8 miles at 99kmh/62mph. I then need to slow down and turn at an intersection. Again the van is usually not up to 24c/75F by this time so since the cabin heat is still calling for heat it will keep the engine running. So I do the same as the last stop, shut off heat and slow down on EV then accelerate on EV until engine starts then turn the heat back on to 24c/75F. Another 4 miles at 99kmh/62mph and another traffic light then into city driving.

It takes a long time to get that big interior up to temp, I have kids in both rear rows, before the engine will shut off and go into EV while slowing down or stopped at a red light. Before the temp is at 24c/75F the cabin isn't uncomfortably cold and it is bearable so I would rather have the heater only run while the engine NEEDS to run. I don't want the heater calling for the engine to run.

RennZ, I can't force the engine to stay off if I wanted to, the computer controls that and will keep it warm like you say so that it is ready. I just don't want it running extra just to make heat, that is inefficient. I'm not concerned with emissions.

Sienna9816, Great idea, I saw that earlier in another thread and just tried it last night. It certainly helped. My heater was old and the fan is worn out and didn't have sufficient airflow over the coil to keep it from overheating at 1500w so I had to run it on 750w. I'll get a new heater and try it out.

Wscan, I agree with that too. The trouble I have is in our extreme climate -20c/-4F is that the cabin cools down very quick and the engine as well when its off. The little bit of heat in the coolant is quickly used up and the engine tends to run excessively just to make heat. Its not awful cold in there where you hate life but its not warm enough to want your coat off.

Anyway, long winded rant haha. But if anyone has any tricks or hacks to minimize engine run time I'm all ears...or eyes in this case haha.

 

[JohnHartshorn]

Just leave the HVAC in eco mode. (This is separate from the drive ECO mode).

 

[Flatland 306]

Just leave the HVAC in eco mode. (This is separate from the drive ECO mode).

Good point John. I forgot to mention I have only had the climate control in “eco mode” since we got it.

 

[JohnHartshorn]

Good point John. I forgot to mention I have only had the climate control in “eco mode” since we got it.

I think the only time I have changed it out of ECO was driving across Kansas in the summer, with temps above 100F. The ECO mode just couldn't keep up with the sun beating down on the top of the van, creating an oven.

 

[Chubbysumo]

as someone who drives in MN winters, the engine will do what it wants regardless of the HVAC, but, when you are calling for a large temp difference, it will run the motor with a slight load to heat the coolant up to heat the cabin. I find that when the outside temp is 2c or above, and I keep the cabin auto-temp to driver centered, at an auto setting of 70 to 72, it will still run the engine for heat, but not as much, especially once the cabin is warm. if the temp difference is more than 30C, it will turn the engine on no matter what. This means that if you are asking for 26c in the entire cabin, but its -5c out, it will basically run the engine constantly until the difference is less than 10c, and then it will gently try and maintain that. keep in mind, its also trying to keep the engine warm to keep it in closed loop mode for optimal fuel economy too, and the aluminum engine block loses heat really fast on its own, and then you are sucking more out by heating yourself.

 

[wscan]

The engine always will start when the car is first turned on when cold if the coolant temperature is below about 55 F. It then has to go through the engine warmup cycle that runs for a minimum of 3 minutes or until the coolant is up to about 100 F. If the heat is on, the coolant has to get up to 130-140F before the engine will shut off. However, this temperature is dependent on the difference between the desired cabin temp and the actual temp. Longer engine run times will occur if the cabin is not up to temperature. If cold is not too much of an issue, try setting the cabin temp lower - say 65-68F. Once the cabin is closer to the set temp, the engine will shut off. I think that forcing the engine to shut off by turning the heat off tends to keep the engine cooler and thus has to run longer to get up to temperature. If you leave the heat on at a lower temperature setting for the entire drive, the engine may shut off more.

To give an example, I was sitting in a line of traffic with the traffic not moving much. The engine would shut off when the coolant temp was 130F and stay off until the coolant was around 105F. The engine would then cycle on and warm up the coolant to 130F and then shut off. There seem to be many variables that the computer takes into account, so this may be different from time to time. This was also on a 2021, so the newer versions may have slightly different programming. I also have a 2022 RAV4 Prime and it seems to work a bit different with regard to the temps in that car. Might be a difference year to year also.

Another thing that keeps the engine running longer is the use of cruise control. The battery being half full is not very full. The engine will turn on when the battery has 3 bars left and sometimes will turn on when requesting power with 4 bars left. The engine also tends to stay on sometimes just anticipate a future need. Just coasting sometimes the engine will stay on until the brake pedal is used. Other times it seems to stay on for a period of time after stopping in anticipation of immediately starting up again. The engine computer seems to have a number of complicated decisions such that it is difficult to understand why the engine is still on. The best thing is to just set the heat conservatively and drive and let it do its thing.

 

[Flatland 306]

We scan, Thanks for the detailed post and specific numbers. That is very helpful to understand its logic. They also make sense.

 

[Sienna.Guy]

ECO mode for the climate control? Gotta check it out a la mañana.

 

[catfish93]

The Sienna is not a cold weather machine. The EV battery doesn't work as efficiently in cold weather, and the engine must build up coolant temp for cabin heat. All of this results in a van that gets the same MPG as an Odyssey and is a worse car objectively. Sienna works great in Florida, California, Texas.... warm places. When it's 60+ here in Tennessee the van gets a whopping 45MPG, but that falls off a cliff at 45ish, and it's so bad at 20F that when it's that cold or colder, I just drive my Volvo. It's more comfortable, has better heat, and they get the same fuel economy at that point.

 

[pamhar]

The Sienna is not a cold weather machine. The EV battery doesn't work as efficiently in cold weather, and the engine must build up coolant temp for cabin heat. All of this results in a van that gets the same MPG as an Odyssey and is a worse car objectively. Sienna works great in Florida, California, Texas.... warm places. When it's 60+ here in Tennessee the van gets a whopping 45MPG, but that falls off a cliff at 45ish, and it's so bad at 20F that when it's that cold or colder, I just drive my Volvo. It's more comfortable, has better heat, and they get the same fuel economy at that point.

Our Sienna in up north begs to differ.

While winter MPG is a bit lower then summer it is still higher the Odyssey in same weather [family member has].

When we drive in winter we wear winter coats and keep them on inside our vehicles so while we do heat it is never more then a 5-10 drive before the van is pumping out good warmth.

 

[catfish93]

Our Sienna in up north begs to differ.

While winter MPG is a bit lower then summer it is still higher the Odyssey in same weather [family member has].

When we drive in winter we wear winter coats and keep them on inside our vehicles so while we do heat it is never more then a 5-10 drive before the van is pumping out good warmth.

My heat sucks 🥶 I drove the van 4 miles to the car wash today and 4 miles home. Never reached operating temp, and heat was off for the first 4 miles. Temperature was in the low 40s and van had been sitting outside in the sun all day. When I'm out doing Uber, I will get up to temp, and it will stay there. But if 71 is comfortable for me to have the AC set to in summer, I need 77 to be comfortable with heat in the winter. Seems to blow out cold air when set to 71.

 

[pamhar]

My heat sucks 🥶 I drove the van 4 miles to the car wash today and 4 miles home. Never reached operating temp, and heat was off for the first 4 miles. Temperature was in the low 40s and van had been sitting outside in the sun all day. When I'm out doing Uber, I will get up to temp, and it will stay there. But if 71 is comfortable for me to have the AC set to in summer, I need 77 to be comfortable with heat in the winter. Seems to blow out cold air when set to 71.

So when we first got Sienna we noticed that did have to set temps bit higher for heat [like in 73-74F area] but this winter we've been managing with 71-72F and gets warm enough. We do prefer on cool side so that explains lower setting and perhaps we had HVAC in ECO setting when first got.

We do park mostly in garage so that helps.

Is it that heat not coming warm quick enough or that force of air coming from vents is low? That could be blocked or disconnected tubing?? Filters are clean?

Might be time to get checked at dealership especially combined with much lower winter MPG. We get low to mid 30s in winter.

 

[Vanfam12345]

Shutoff climate Eco setting

 

[catfish93]

So when we first got Sienna we noticed that did have to set temps bit higher for heat [like in 73-74F area] but this winter we've been managing with 71-72F and gets warm enough. We do prefer on cool side so that explains lower setting and perhaps we had HVAC in ECO setting when first got.

We do park mostly in garage so that helps.

Is it that heat not coming warm quick enough or that force of air coming from vents is low? That could be blocked or disconnected tubing?? Filters are clean?

Might be time to get checked at dealership especially combined with much lower winter MPG. We get low to mid 30s in winter.

It is that the engine coolant temp takes a long time to get warm. The volume of air out of the vents is fine. The specific situation I mentioned happens when the car is already warmed up, but after some time goes by, the temperature from the vents gets colder even if the coolant temp is still fully warm. Almost like the temp sensor isn't accurate and it thinks the car is hotter than it really is.

 

[ROJA]

I turn my HVAC completely off and just use the heated seats. Works pretty well unless it's really cold.

 

[pamhar]

I turn my HVAC completely off and just use the heated seats. Works pretty well unless it's really cold.

So literally driving by the seats of your pants!!