ICE warmup right before shutdown

"The engine during warm-up doesn't contribute toward propulsion". How did you prove that?

 

I don't think anyone has. And, IMO, is faulty logic. If you are driving the car (without stopping), at say 45-65 mph, you are getting full use of the gas for propulsion and you are generating plenty of waste heat to warm up the engine, oil and the catalytic converter. I'm not sure why people think there is extra fuel used to warm up the car. Yes, it happens all the time when you start up first thing in the morning when you have no EV miles or in a regular Prius. Typically, my commute starts with going a few hundred feet, stopping at a stop sign, driving 1/4 mile, stopping at a red light, driving another 1/2 mile, stopping at a light, etc.

This is one of the primary advantages of the PIP. You can do all this on EV and engage the ICE once you are going to be driving (mostly) without stopping during the warm up time, such as getting on the freeway. But you are using the "waste" heat of propelling the car to do the warmup...rather than wasting gas sitting at a stop sign or red light.

Mike

 

I agree, I have been deliberately going into HV at some point in suburban trafffic, at 35-40 speed limits knowing that I will be entering the freeway shortly. Generally, my destination has a outlet so I can revert to EV at will after freeway exit, and use it all up. ( that is: try to).

 

Any time the gas engine is running, it contribute propulsion to the wheels. During the warmup, it is making very little power so you may not notice but it is propelling. That's how the power split device works.

 

The water build up is minimal. I shut her down. The only way I can see this being a problem is if you repeatedly do this day after day. But even this is unlikely as the PiP is designed to run the ICE if you've driven more than 124 EV miles continuously.

 

I just shut it down before the warm up is done. It does two things:

1) Saves gas
2) Reduces emission

The engine stops (warmup completes) when the catalyst bed temp reaches 380 deg C. It takes 200 kJ (56 Watt bulb for an hour) of energy to reach that temp.

PiP is rated SULEV (AT-PZEV in CARB states), so even during the warm up, it only emits about 0.1 gram of HC (hydrocarbon). Optimization was done to control emission below the SULEV level and provide maximum energy (waste heat) out the exhaust to deliver the required 200 kJ. It was done by adjusting engine RPM, Spark Timing and Load %.

I see no reason to let it continue as the goal was to send 200 kJ of energy out the exhaust.

 

my only concern is the cold soak problems some genIIIers have had.

 

Could you provide a brief description of this problem?

 

there are a couple threads. it appeared with the gen III 2010 model and seems to occur if you start the hatchback and shut it down quickly, as when moving it from the garage to the driveway, etc. then you let it cold soak for a day or more and the next time you start it, it misfires so badly it sounds like the engine is coming apart. there is a tsb for an updated manifold i believe, but i'm not sure the problem has been totally solved. i have never experienced it.

coincidentally, i just went for a joyride and didn't notice until i turned down my street that i was down to .1 mile. i crept it into the garage and just as i hit the park button, bam! ice came on. took it back out and 30 seconds later, it shut down. 92 degrees outside.

 

That loud bang is definitely still an issue with the PiP. If it's cold out, let it warm up. If it's warm out, just shut it off IMHO. I'm sure Toyota designed the PiP with these scenarios in mind, and I don't recall reading any warnings in the manual which tell you to allow it to warm up.

 

No loud bang with my PiP so far. I got it last Oct.

 

me either, but i haven't given it the cold soak opportunity.

 

As a sidenote that may be somewhat related, I had to run to the post office to mail a letter before the 5PM pickup. I had NO EV charge, so it was HV all the way. I left the ignition on at the PO. When I got home I had 61 mpg for 4.2 miles with numerous Stop Signs!

 

you won't do that in the hatchback.

 

I agree firing of ICE then shutdown on COLD days is not great for the motor, especially if done many times. A few times here and there is not gonna hurt anything, but over and over can cause sludge in the oil.

In summer on HOT days this is much less of a worry. When its cold and ICE fires there is much more condensation buildup due to extreme temp swings, and that should be allowed to burn off. Hot temps will create much much less condensation.

Also if you turn it off very quickly after it fires, there will be very little heat created so much less condensation. So either turn it off quickly after it fires, or just let it warm up, especially in winter.

Dan