OK...here's a weird one...is this normal? My Hybrid Synergy Drive on my 2005 frequently races the gas engine for no reason. And on the display, it doesn't show the engine running! But I can hear it, clear as day...the 4 cyl. buzzing. This odd behavior happens in the same place frequently and always has: After a 10 mile drive on the freeway, I enter a log stretch of downhill road. The battery is fully charged by the time I get to the bottom. At the bottom is a stop light. Inevitably, 100% of the time, the 4 cyl. engine is running at very high rpm's while I sit at the light, and as I slow down. The display doesn't show that it's running, but the mileage calculation, which declines as I slow down, clearly shows the Hybrid Synergy Drive knows the gas engine is running. I tried turning off the heater, thinking the engine was running to keep the car warm. It still happens....very high rpm's! Is this normal? Am I missing something?
Yes. Yes. The battery-pack is totally full and the system is spinning up the engine as a method to discharge. So, the engine isn't actually running. It's just the smaller electric motor cranking it up to the startup RPM, allowing it to slow down on its own, then repeat. This is how the system ensures longevity. Allowing the battery-pack to stay at that high of a level for too long shortens it life. "B" mode is available to help prevent this situation. .
It intentionally wastes energy by turning the gas engine (with electricity, no gas) as an air pump. B gear would basically do it on your downhill so the car won't have to do it at the light.
Using "B" manually you would most likely waste a little more energy (and thus fuel) than the car would by itself.
