OK, it's been very cold for 6 weeks so the ICE won't shut down until the coolant reaches about 65C. Normal. Well, the cold snap finally broke. Pearl was parked at a restaurant for a few hours, and cooled off to a coolant temp of 30C or so. Started up, and as it was nice and warm inside, I thought I'd shut off the A/C (I use "auto" most of the time). Came to a stop at a light, and the coolant was only up to 50C, but the ICE shut down! I switched on A/C "auto" and the ICE started right up. Turned the A/C off, and the ICE shut off! With the A/C on "auto" the ICE won't shut off until I see 65C coolant temp. So, did Toyota change the firmware? I presume I was in stage 4 otherwise the ICE wouldn't have shut down. Anyone else notice stage 4 operation with the coolant at only 50C?
As I read the stages, the ICE will shut off at 40C (stage 2 entry) when the vehicle is stopped. It is gliding below 42mph that requires stage 4 (73C plus the obigatory Stage 3 transition stop) in order for the ICE to shut down while in motion. It won't shut off if the demand of the AC, etc. is deemed too great.
I agree that it sounds like S2 behavior, assuming you weren't moving. It will shut off in S2 while at idle. I don't know the lowest S2 temperature I've seen, but it could have been as low as 30C. I know it's been lower than 40C.
I'll toggle the "air conditioner" (climate control) off to encourage the ICE to stop at lights. When underway again, I'll toggle it back on. Or I'll just leave climate control off entirely on short trips when the Prius is cold. Harry
This is similar to my approach also. On days when I have the EBH plugged in and the car in the garage, it will usually enter Stage 2 right after the normal Stage 1 warmup period. I usually leave A/C Auto off until I can get some engine heat buildup. The only exception is when I need the defrost. In that case, I turn on the main defroster, then go into the Climate screen and turn the fan down to the minimum I need to clear the windows. This way I don't freeze from the fans running on max with heating air only slightly warmer than the cabin. If I do need the heat right away, I will tend to run it only while driving when the ICE would be on anyway, and click off the Auto switch. I do one other thing to save gas after a long enough trip to warm the car and the ICE. I will turn off the climate control and try as much as possible to run on electric only for the last 1/2 mile or so to my garage. Usually, the battery is 7 bars (or 8 if I've come off the freeway). If I park when it is that full, the battery won't take any more charge in the morning, even though it will be running more frequently to warm up. I figure that if I use up the residual heat and some of the battery power, the heat will be gone anyway, and when I start out in the morning, some that extra ICE running time will charge the battery back up to 6 or 7 bars instead of being wasted. Even with the low efficiency of the charge/discharge/recharge cycle, getting 20% from that gas already burned is better than 0%. And yes, I did pull that number out of my a**, but I think my point still stands.
ICE - Internal Combustion Engine This refer to the 1.5L Gasoline Engine in our Prius' Hybrid drive system.
