I've been traveling on the highway a lot lately for work and it seems like whenever I put my 2006 Prius on cruise speed at around 72-76 MPH, engine noise is through the roof. Now I understand that Prius has a small engine compared to my stronger Camry, but I was wondering if anyone knows about about highway speed and RPM's for 2nd Gen Prius? Thanks!
Firstly the answer is, whatever the computers feel like, but here are some examples. When I was doing well and showed more than 50 MPG at 61 MPH my RPMS were under 1800. When I was getting under 45 MPG at 61 MPH, it was over 2200. There is no fixed relation between RPMs and MPH
My experience (and I've had my Prius since new in '07) is that 55mph puts it around 50 mpg or so and 65 in the upper 40's. Add a big hill and forget about it! Speed limits by me don't go above 65, so I don't speed as the engine races and clearly doesn't want to go that fast. I don't have a tach, so I can't report engine rpm. This is normal.
Firstly, the Prius has Hybrid Synergy Drive, meaning it is powered by a combination of electric power and gasoline engine. To further complicate things, it has a CVT, meaning Continuously Variable Transmission. There are no pre-defined "gears" or "gear ratios" to be more specific. The transmission ratio is variable over a continuous range. The goal is to keep the gasoline engine RPM in the peak power band (torque band) throughout a large range of vehicle speeds. Thus there is not the relationship between RPM and speed you see in conventional drivetrains. Are you monitoring your State Of Charge (SOC) while driving? This should dictate how "hard" your gasoline engine needs to work to maintain speed. A low state of charge, means there is little or no electric assist, thus all power/speed is coming from the gasoline engine. In this state, you are likely to hear the gasoline engine at high RPM to maintain your desired speed. If you are hearing high RPM with a good (Blue) state of charge, maybe there is a real problem with your car's "computer".
