Today was brutally hot—nearly 100% relative humidity at over 96° F with local heat island effect. We spent much of the day in stop-and-go driving, the AC failing to keep up even on its highest settings, visiting bargain shopping centers in a marginally-suburban, high density, planned community not far from home. My wife was very much looking forward to the opportunity, and I even found sorely-needed new shoes at a reasonable price that I could just as reasonably afford.
However, and as much as I love spending time with her, a most memorable part for me was the odd behavior of our vehicle; I always do the driving. It seemed as if, past a point, the 2024 Prius gave up on its usual control algorithms that I’m used to feeling.
Normally, it prefers to run the engine for acceleration and at high speeds. The electric motor is preferred when coasting. I’m also told that energy is blended from both sources under various conditions, but perhaps not today. Amusingly, it ran the motor continuously leading to a weird control experience. It almost seemed as if it was huffing and puffing, awkwardly revving up even when gently creeping through parking lots.
I’m not sure if it was the cooling demand (less likely as this doesn’t normally happen on most hot days) or some kind of protective mode when the hybrid system gets very hot. Even the acceleration felt wrong, lethargic, sleepy but functional. I wonder if the heat was too much to safely operate the electric part of the hybrid system or maybe the battery, allowing the normally hidden weak-torque characteristic of the Atkinson engine to leak through to the user.
Regardless of the algorithm specifics, it’s a wonderful example of graceful degradation.
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