Corolla Hybrid RPM when idling

[Steve Trice]

Hi all.

I've noticed that when the car is idling, such as in a traffic queue, if the petrol engine kicks in over the hybrid electric, it revs at nearly 1500 rpm. I've had diesel engines for years prior to getting the Corolla, and they ticked over at half that rpm. Is this normal for a plug-in hybrid engine?

Thanks,

          Steve

[TonyHSD]

Hi,

yes it’s absolutely normal. The Rpm can go even higher in certain situations like when going long downhill and the Battery gets fully charged the engine will kick in and scream at close to 2000rpm for 10 seconds or so. When in traffic and Battery gets low the car will start the engine and it will be loud and unrefined but that’s for short time. How much loud and for how long will depend from the temperature, hvac settings and hybrid Battery state of charge. Nothing unusual here.
 Enjoy your hybrid 👍

[Steve Trice]

Thanks, Tony.

[TonyHSD]

19 minutes ago, Steve Trice said:

Thanks, Tony.

You are welcome 

[AndrueC]

There isn't really such a thing as 'idling' with a hybrid. The ICE is either doing useful work or it's off. The ECU will ensure that should the ICE have a reason to run it will do so at the most appropriate RPM for the task being performed.

If the vehicle is stationary and the ICE is running it is charging the Battery and it will do so at the optimum RPM for that task depending on how much of a charge is required.

[quote] Is this normal for a plug-in hybrid engine?[/quote]

Corollas are not plug-in hybrids. They are 'self charging' hybrids. Although it makes no difference in this respect.

[Gray86]

3 minutes ago, AndrueC said:

There isn't really such a thing as 'idling' with a hybrid. The ICE is either doing useful work or it's off. The ECU will ensure that should the ICE have a reason to run it will do so at the most appropriate RPM for the task being performed.

If the vehicle is stationary and the ICE is running it is charging the battery and it will do so at the optimum RPM for that task depending on how much of a charge is required.

[quote] Is this normal for a plug-in hybrid engine?[/quote]Corollas are not plug-in hybrids. They are 'self charging' hybrids. Although in this aspect it makes no difference.

Generally that’s all true, with the exception of very brief moments of idling I’ve noticed, once it stops doing the MG1-based charging / cat heating / GPF clearing it needs to do, you can have a lovely smooth sub-1000rpm idle. . . . Then it switches off & becomes a normal hybrid again. 

[AndrueC]

40 minutes ago, Gray86 said:

Generally that’s all true, with the exception of very brief moments of idling I’ve noticed, once it stops doing the MG1-based charging / cat heating / GPF clearing it needs to do, you can have a lovely smooth sub-1000rpm idle. . . . Then it switches off & becomes a normal hybrid again. 

That's a good point but I'm not sure if that qualifies as idling. In those situations the ICE is being turned either by the road wheels or one of the electric motors so no petrol is being consumed.

Exactly why it does that is unclear. I have noticed though that it's more likely to do that when it's cold so I've wondered if perhaps the water pump is driven off the ICE and in some conditions it turns the ICE in order to disperse heat into the cabin.

[TonyHSD]

Ok, not idling but engine working. 👍

Water pumps on Toyota hybrids are electric and can work without engine running ( idling) and provide heat to the cabin as long as the engine has been warmed up enough. 
This is what I just did exactly in my car while typing here. 10 min of  heat without burning a drop of fuel , like in an electric car 😉👌

[Gray86]

23 minutes ago, AndrueC said:

That's a good point but I'm not sure if that qualifies as idling. In those situations the ICE is being turned either by the road wheels or one of the electric motors so no petrol is being consumed.

Exactly why it does that is unclear. I have noticed though that it's more likely to do that when it's cold so I've wondered if perhaps the water pump is driven off the ICE and in some conditions it turns the ICE in order to disperse heat into the cabin.

Mine does it parked in the garage, in ‘P’ occasionally. Weird to have the engine running, but not doing anything. Will only do it for 30 seconds or so, then cuts out 

[AndrueC]

52 minutes ago, Gray86 said:

Mine does it parked in the garage, in ‘P’ occasionally. Weird to have the engine running, but not doing anything. Will only do it for 30 seconds or so, then cuts out 

Interesting. I've never known that happen. Only time I've seen it is when the car has switched to electric power but the ICE continues to turn over at 1,000 rpm for a while.

I did find an article online that suggested the car will sometimes use the electric motor to turn the ICE over in order to discharge excess Battery power.

The other odd thing I've seen is (according to the dashboard/infotainment) the ICE charging the Battery and powering the wheels at the same time as the electric motor is powering the wheels.

[AndrueC]

Ooh. I've rediscovered the in-depth info site I lost years ago:

http://prius.ecrostech.com/original/PriusFrames.htm

[tfc]

When the vehicle is in park when does the ice kick in to charge the batteries or should l say what level of charge does kick in

[TonyHSD]

55 minutes ago, tfc said:

When the vehicle is in park when does the ice kick in to charge the batteries or should l say what level of charge does kick in

That is different all the time, however the car is trying to maintain charge levels between 40-80%. Anything outside these numbers the engine will kick in either to charge below 40% or discharge 78% + the Battery. If you are interested of what is going on under the hood you can buy an obd 2 adapter and with suitable app you can see Battery processes , voltage, engine speed etc 👍

[Cyker]

Mine will kick in when it drops to 3 blocks (Out of 8 )

 

[Phil T]

In the Prius PHV after a long downhill stretch 70% Battery the motor would kick in. I was told burning off spare electricity, No one could explain why, when the Battery was 30% below capacity, it was doing it. Logic of the Toyota way of doing things is hard to fathom.

[TonyHSD]

1 hour ago, Phil T said:

In the Prius PHV after a long downhill stretch 70% battery the motor would kick in. I was told burning off spare electricity, No one could explain why, when the battery was 30% below capacity, it was doing it. Logic of the Toyota way of doing things is hard to fathom.

It’s all about preserving the Battery health and extending its life. I had monitored previously the Battery with app and hybrid system performance and I noted that at around 36% lowest the engine starts and max charges up to around 76%, then if soc goes over those numbers (long downhill) the engine is working at very high rpm to discharge the Battery.
Another interesting thing about Toyota hybrids and battery charge discharge cycles is that those depends of outside air temperature and battery temperature. In summer times the battery gets topped up quicker and engine kicks in sooner. Toyota have done a good job with their batteries and thermo management, although only air cooled in non phev models. 
Here my hybrid battery parameters from January 2021 at 162000 miles.

 

and here from January 2023 at 234000 miles. There are some differences but the car still drives fine., I would say even at that age and mileage almost unchanged from when was new. 

 

[fred88]

How come running the engine discharges the Battery? Sorry if I'm being thick!

[TonyHSD]

24 minutes ago, fred88 said:

How come running the engine discharges the battery? Sorry if I'm being thick!

Yes it sounds counter intuitive but it is indeed the case with Toyota hybrids. The engine spins the MG1 which waste the extra energy to set the Battery at more appropriate levels. You will notice that after a long down hill and fully charged Battery, when you had driven longer on the motorway and you come to a stop at the roundabout before entering the services for example.

Off topic more interest facts about the hybrids: 
The warmer the weather the more often and more pronounced is that event.
Another example If you are staying in the car in ready mode with heating set at 22C for long time the engine will kick in every 6-10 minutes and will run for  around 1-2 minutes to produce heat for the cabin but meanwhile will charge the Battery too until at some point while engine is working and battery gets fully charged you can notice how engine gets unloaded and changes it’s rpm and sound ,, not charging anymore and if you keep waiting it will soon even change again it’s sound and load because now it is discharging the battery.
It is a continuous game of battery charge maintenance.
This is also happening when cruising on the motorway at a steady speeds, battery helps engine then engine tops up battery then repeat again. 
If you push the car to the max at high speeds pedal to the metal you can drain your battery to lowest % and then it will take longer  time than usual to be recharged back to more normal levels. 👍

[fred88]

Fascinating, thanks for the explanation Tony.

[Glynn H]

11 hours ago, TonyHSD said:

Yes it sounds counter intuitive but it is indeed the case with Toyota hybrids. The engine spins the MG1 which waste the extra energy to set the battery at more appropriate levels. You will notice that after a long down hill and fully charged battery, when you had driven longer on the motorway and you come to a stop at the roundabout before entering the services for example.

Off topic more interest facts about the hybrids: 
The warmer the weather the more often and more pronounced is that event.
Another example If you are staying in the car in ready mode with heating set at 22C for long time the engine will kick in every 6-10 minutes and will run for  around 1-2 minutes to produce heat for the cabin but meanwhile will charge the battery too until at some point while engine is working and battery gets fully charged you can notice how engine gets unloaded and changes it’s rpm and sound ,, not charging anymore and if you keep waiting it will soon even change again it’s sound and load because now it is discharging the battery.
It is a continuous game of battery charge maintenance.
This is also happening when cruising on the motorway at a steady speeds, battery helps engine then engine tops up battery then repeat again. 
If you push the car to the max at high speeds pedal to the metal you can drain your battery to lowest % and then it will take longer  time than usual to be recharged back to more normal levels. 👍

I find it amusing turning the ICE on and off with the temperature control.