Engine braking. Very normal, computer controlled. It is "loudish", but saves some on your brake pads. I think regen braking is more effective but when the batteries are full there is no place else to send those electrons, so it switches to the friction/compression of the engine to slow you down......kind of like those annoying loud 18 wheelers using their engines for braking.
This is true for ICE vehicles too, which is why automatic transmissions have almost always had an "overdrive" gear that could be disengaged or a 2/L position on the shifter, and more recently, sequential gear selection via "manual mode"
Pretty sure there’s no fuel injection going on when engine braking and the engine is just acting like a big air pump being driven by the wheels.
Actually, in Toyota hybrids, it's actually the engine acting an a big air pump driven electrically by MG1. The wheels drive MG2 to generate electricity, and when the batteries get full, the electrical power is dumped to spin MG1.
Right, I've verified via odb there is no fuel burn. I was talking about the fuel burned getting me UP the mountain and gaining me gravitational potential energy. That energy fills up the tiny HV battery in a few miles and then all the rest of that potential energy I gained from fuel burn just goes to heat.
A bigger battery would certainly be nicer, but that adds cost. With a bigger battery, you could add a plug, and then potentially have 30-50 miles of EV only range. Of course, more cost. This is why EV vehicles are expensive.
