When is an EV not EV?

Sounds like you were in a "glide" which is power neutral; the holy grail of hypermilers!

 

It's not an EV - it's a hybrid. The computer looks at many settings - your climate control, inside and outside temps, speed, battery charge, whether the ICE is warmed up, throttle position, probably even recent driving style etc etc and decides whether it will use ICE or Battery, a mix of the 2, regeneration etc.

I've noticed that the Energy Monitor sometimes is in front of the instantaneous MPG (l/100km here) by a couple of seconds - I get the feeling that the Energy Monitor is right (can hear the ICE shut off when slower) - maybe the instantaneous MPG is taking sampling over short periods of time, or slightly "historical"?

Playing with trying to force it to "EV" when it doesn't particularly want to doesn't seem to help my mileage usually, except in very limited situations. That is unless you are trying seriously to hypermile - which most of us don't, and we can't in many driving situations unless away from traffic.

 

the monitor is only semi reliable. if you really want to know what's going on instantaneously, get a scan gauge or some such.

 

Yeah, there's times where we're just gliding... must be in fuel cutofff (or pretty close to it).

There are times when my instantaneous reads about 75-80mpg, but I can't seem to stay in glide mode for that long.

If only there was lean burn mode....

 

NOT like a TESLA, I hope?

 

Lean burn mode would massively increase NOx emissions, which is unacceptable, especially nowadays.

So, the reason why lean burn improves efficiency is because it allows the throttle to be open more, reducing pumping losses - a significant amount of power is lost in sucking air past the throttle plate. However, the Prius has several strategies to reduce pumping losses without having excess air in the cylinder (lean burn).

Atkinson cycle operation is one of those strategies - essentially, all Prius engines push some excess air back out of the cylinder, reducing their effective displacement, while maintaining their full expansion. A Gen 3 or 4 Prius engine only takes about 1.1 liters of air per 2 revolutions, not the 1.8 that the stated displacement implies.

Variable valve timing allows the computer to tweak how long the intake valves are held open, allowing it to change how much air gets pushed out.

Cooled exhaust gas recirculation allows the engine to replace excess air with inert gas - the throttle can be held open further that way. That only works to a point, though.

Finally, there's the hybrid system. Its primary goal is to keep the engine at its most efficient operating range, which is relatively high load, moderate RPM. If there's too low of a power demand to satisfy that, a normal car will just have to close the throttle plate and run inefficiently. The Prius, however, can do one of two things - it can instead use excess power to charge the battery, or it can shut down the engine and use stored battery power to propel the vehicle (and, in fact, at lower speeds, it will cycle between the strategies).

Note that the Gen 4 Prius is up to 40% peak thermal efficiency without lean burn. There's only three other gasoline engines that have reached that target, as far as I'm aware (I'm not including the Mazda SkyActiv-G family, because there's nothing concrete saying that it's actually hit 40%, just that it's in the ballpark) - the hybrid variant of the Hyundai Kappa 1.6 liter as used in the Ioniq and Kia Niro (which uses some of the same strategies, as well as direct injection, which allows higher compression, and therefore more expansion ratio), the Toyota Dynamic Force 2.5 liter most likely destined for the next-gen Camry (which uses a more extreme variable valve timing approach to drastically vary the amount of Atkinsonization, and direct injection), and the hybrid variant of the Dynamic Force 2.5 liter (which is at 41% thermal efficiency). None of those are lean burn, and two of those are intended for hybrid applications (which can, again, keep it on the peak much more closely, further reducing the need for lean burn).

Now, I'm going to go against my entire point here, and mention that diesels are always lean burn, and there are more efficient diesels out there - Toyota has a 2.8 liter diesel for pickups and vans at 44% thermal efficiency. (The increased expansion ratio enabled by the high compression ratio helps, too.) So, it can help, but you've got an emissions penalty to pay (both because of lean burn, and because of how it injects its fuel and starts ignition), that needs complex, expensive aftertreatment systems, pricing it into the work vehicle or the luxury space. And, the weight of the diesel engine, plus the weight, cost, and packaging penalty of its aftertreatment systems makes hybridization much harder.

 

EV indicator (EV mode icon) is on only if EV mode is forced on by pressing a designated EV mode selection button. In my Prius 'forced' EV mode is available on low speed up to 30-32 km/h. At a higher speed battery propelling (or EV condition if you will) is controlled by on-board computer without EV mode indication.

 

There's an "EV" indicator in the Hybrid System Indicator, as well, though, independent of the "EV Mode" indicator in the speedometer.

 

"EV Mode" and the icon for it refers to a mode enabled by hitting a button labeled "EV Mode", and that only works up to about 20 MPH, and only with moderate throttle at most.

However, the EV indicator in the HSI can be illuminated due to the engine shutting off at higher speeds, and the engine is off there. I've seen that happen as high as 73 MPH.

 

That's perfectly true, but bhtooefr is talking about the EV Mode. That is, when selected by pressing the EV button. Only pressing that button technically selects the EV Mode.

 

But your electric was all made from gasoline.

 

most electricity is from fossil fuel...

BTW, Happy New Year!!!

 

In power plants with average thermal efficiencies greater than seen in a car ICE.

 

burning is burning = CO2 + H2O

 

With apologies to Frozen, let it go....