Engine revs up before shutting off?

My C is always in EV mode when I shut down so I don't even hear the ICE. Are you shutting down with a cold engine or a HV battery in a low state of charge? That might explain what you are hearing.

 

well.. yes.. but most times when i hear the ICE really rev up when i come to a stop is when the ICE is still cold.

 

Normal for mine. Pull up to red light, engine revs, then shuts off.

 

I just noticed the same thing after more than six months of use. I'm assuming its normal? Is there any follow up with this?

The RPMs rev up right before the car transitions into EV mode when still moving. Any new insight out there?

 

I've also noticed this, so it seems to be normal. I'll pay more attention to see if it happens more when the engine is cold. Not sure about the reason why.

 

I wonder if this is a cut off of the fuel supply. Just a theory, but if the fuel supply is cut to an engine, it will run leaner and leaner until it can't run any more. A lean engine runs hotter and faster...so, that could be what its doing. Cutting the fuel supply as a method of shutting down the ICE and therefore causing a lean condition right before it dies. I experienced this with many a small engine. Lawn mowers, weed whackers and RC cars. Thoughts?

 

This reving of the engine before shut-off its the fuel injection computer calibrating itself against atmospheric pressure changes ( air
pressure changes).

The genIII does this also but not as offen as the prius-C.

Possible conditions for fuel injection recalibration;;
Prius driven long distance to a city with higher elevation?
Prius driven in mountainous environments?
Drastic weather condition changes?

All the above could be reasons if precise air fuel mixture is desired.. resulting is less fuel build-up in oil.

I think this is a wonderfull way to precisely measure air fuel mix (14 to 1) before fuel trim is added or subtracted..(highest engime rpm at idle = precise 14 to 1 air fuel mixture).

I wish my genII did this more often.. It only does it after disconnecting 12 volt aux battery..

 

I'm glad someone clarified this, I knew it was normal but never understood why

 

Thanks so much! It makes sense then why it is sporadic.

 

I think it's a change from sending ICE power to the wheels to sending ICE power to the battery during the second between stopping and shutting off the ICE.

 

I agree. Further, it seems plausible that the revving results from the change from MG1 placing a load on the ICE (battery charging) to no load on the ICE just before the car enters EV mode. If you watch the hybrid system info screen right before entering EV mode, you can see that battery charging is stopped as a precursor to the ICE shutting down. Removing a load (in this case, the load MG1 acting as a generator places upon the ICE) from an engine under load will cause it to rev up. This seemed normal to me from day one.