Has anyone noticed how fast the FEH/MMH warms up? How much sooner you can heat the cabin than many of the vehicle you've owned in the past? Well, your about to find out why and how to even speed up the warm-up process.
All this time I thought the strategy to use the electric motors during warm-up was to allow the oil to circulate before putting the ICE under a load. That may help the ICE last longer, but it's not the real reason Ford developed this strategy.
One of the reasons I get good gas mileage is I work hard at understanding how things work. Sometimes, or most of the time I have a hard time communicating things to everyone like saving energy by not running the heater pump. So bear with me while I try to explain what I've learned about warm-up.
It is very important to slowly accelerate from a cold start or any starts after the engine has been shutdown for over 5-10 minutes. There are a number of reasons for this which include torque demand from the ICE and conserving the battery SoC. The strategy of using the battery and electric motors for torque is to allow the PCM to retard the timing and keep the ICE running at a predetermined speed. This is to advance heating of the engine and CAT converter to go "lights-OFF" ASAP. Lights-Off is a state of the converter where the temperature is hot enough (~550 F) for the chemical breakdown of bad pollutants. Ford developed this strategy for emission reasons, not to prolong the life of the ICE as some of us first thought. The strategy also includes special battery limits to maintain the warm-up procedure. Who would have ever thought keeping the RPM's down would heat up the engine faster!