Featured Mileage calculator chart

How or where do you find a 'v' engine efficiency that high? It is still a Gen3, which was still (barely) sub-40%. Toyota didn't break 40% until well after Gen3 was introduced.

Toyota’s World’s Most Thermal Efficient Engine; 38.5 percent, Turbo Joining! | PriusChat

For something closer to reality, set engine efficiency to 0.385, and parasitic overhead to 400 watts. The later item will produce a low-speed mpg peak, with reduced mpgs at lower speeds, 'sorta' consistent with what the low-ago Japanese commuter-hypermilers were recording.

For a real-world check point, look at this chart:
Updated MPG vs MPH chart | PriusChat

 

2016 was the first year of the gen 4 Prius.

 

40 percent is for the Gen4 Liftback, 2016 and later. Your 'v' falls under this line from that article:

"The 1.8-liter engine in the current third generation Prius is at 38.5 percent."

That is an empirical estimate from other PC members, posted long ago. It represents the computers and ECUs and inverters and displays and brake system and whatever other electrical items must be running whenever the car is driving.

 

I probably should have said 'guestimate' instead of 'empirical estimate', as I don't recall much real measurement behind it. So the fact that it produced a chart coming so close to your actual mileage is more good luck than actual accuracy.

I'm remembering two different paths to that guesstimate. One was from the Japanese hypermiling community, using engineering and empirical curve fitting to produce a reasonably accurate maximum mpg vs speed equation. That equation contained a fixed overhead term that can be translated to watts. But that was long ago, it may be difficult to dig it up out of the PC archives to get its actual number.

The other path was from folks using the Prius as a stationary electric generator, adding inverters from either the 12V bus or the hybrid battery, to produce 120VAC. In this mode, the ICE will cycle on and off, charging the battery a bit then shutting down for a while. I'm remembering the 400 watt guesstimate as derived from their observations of the engine on-off time ratios, and of the hourly fuel consumption when powering known loads. So it is a coarse figure, not fine tuned.

 

Nice indeed! But also do take in account that the ICE does not work 38.5% thermal efficiency at all loads...

 

many get lower than 38% efficiency by simply driving much of the time in cold weather ... or short distance ... rain ... hilly areas .... poor maintenance ... poor driving habits ... heavy loads etc. Some are variables we have control over - some we don't.
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So I guess the moral to the story is that, if you want more than 100 mpg, drive like the tortoise not the hare.

 

I think the mechanical losses belong under the 'drivetrain efficiency' line, which is defaulted to 95%. The 400 watts should represent the electrical baseload needed to operate the car, independent of speed.

That baseload term is needed to show that mpg doesn't keep increasing as vehicle speed drops all the way down to walking speed or a crawl. It shows that maximum MPG happens at some higher speed, then the fixed baseload starts to overwhelm the propulsion power as speed goes lower. In past threads, this maximum mpg speed has been determined as very roughly 15 mph from one source, and somewhere in the 10-20 mph range from another.

The baseload is not just on 12V. It should include the basic minimum power needed to operate the high voltage inverters and motor controllers too.

All these are Toyota-HSD-specific things whose details are not properly rolled in to a generic calculator. E.g. real-world results will show some bobbles at speeds where the ICE can shut down and the car can run on just electric, with occasional ICE operation to partially recharge the battery. This calculator is too simple to cover such sorts of things.