What would be the positives and negatives of using the EV button to delay a stage 1a warmup, such as first thing in the morning when leaving the house?
If you're actually underway from the start (not sitting still immediately at a traffic light or something) you might as well have the engine warming up and contributing to the vehicle motion. Doing EV mode unnecessarily means that what you use of the battery charge will just have to be made up later with the efficiency losses of discharging a recharging the battery. In my case I have about 3/4 of a mile at 20 - 25 mph followed by 45 mph on the larger street. I figure I'm better off having warmed up the engine before I need to accelerate onto the 45 mph street.
The HSD draws heavily on the HV battery for torque/speed during the warmup cycle. Drawing down the HV battery through EV mode use before the warmup cycle typically leads to the ICE then diverting a lot of power to recharge the HV battery rather than moving the car. This of course results in lowered MPGs due the multiple energy state changes going to, and later from, the HV battery. I agree, get the car moving using the ICE as soon as possible (Possible exception being going downhill immediately after getting underway.) Also, get the car up over 20 MPG as soon as possible. Even thought the ICE is not running efficiently during warmup, the FE peak -theorhetically ~100 MPG butnot applicable here -- is around 20 MPG, you might as well get as good MPG as you can during this period. Getting up to higher speeds quickly during warmup doesn't hurt either in my experience. During warmup extra fuel is run though the cylinders into the cat converters where it ignites to get the CC up to operating temps. The only way to establish anything near a respectable MPG is to cover as much ground as possible during warmup.
One route away from my house usually means waiting for a stop light, with the engine still in the 70s or 80s F, much too cold for autostop. If the green light is more than a few second away, I usually power down, then power back up into EV mode. This pauses the warmup cycle, but leaves the car in a state ready for immediate takeoff. The EV mode promptly cancels itself when the car starts moving.
Mark, I think the question you are asking is not really what you want to know. This post, I believe, is a result of watching Wayne's ride-along video from Yakima Toyota. In the video Wayne used various EV driving techniques like delayed ICE firing and cruising through parking lots in EV mode. The premise behind all of this the engine works very inefficiently at very low speeds and using EV driving is more efficient despite conversion losses IF you can recapture that used energy through regen braking (mostly). In such case you should not try and use EV for initial acceleration if SOC is dropping into the low 50s and you do not anticipate being able to recover lost energy through your next braking session. If I am traveling down long urban or rural roads I may choose to delay engine firing until after 15mph. I watch my SOC and try to ensure that as I approach my next stop I apply just enough brake pressure to recapture energy without engaging friction brakes or lessening my glide distance potential. You just have to figure out when to start applying the brakes. FWIW, I have miscalculated my braking energy recapture and ran SOC too low and the engine worked harder to maintain my speed and recharged the HV battery such that my iMPG was lower than it normally would have been for that stretch of road. I think this results in an overall net loss because I screwed up. LOL
