What sort of effect did you have in mind? While they might have changed something between gen 3 and gen 5, in gen 3 it just changes the math used in the power management control ECU to decide how much go you want from the go pedal position: ECO also, in gen 3, adds some limits on how hard the HVAC will work to heat or cool you. Again, that's what I know from gen 3, and things could be different in gen 5.
Like, implement a higher gear ratio, everything else being equal. Of course, while not lugging the engine. There must be a 'map' for that, although 'could I read it?' is another question.
It already implements the optimal gear ratio all the time. There'd be no ECO gain to be had by deoptimizing it.
Another gen 3'r, and I believe it has been somewhat improved: when we bought, for about the first 6 months I stuck with ECO, thinking it was good for mpg. I found it required a tedious amount of travel to get a reasonable throttle reaction, but stuck with it. Then, on a road trip, switch it off, basically opting for "Normal", and found no difference to mpg, and a more natural feel. In short, a not that useful gimmick.
I pretty much switch ECO on and off just based on what I want from the HVAC. I'll sometimes turn ECO off on a brutal summer day if I have a passenger asking "can't the AC do more than this?". I'll pretty much always turn it off on a chilly morning with the windshield fogged, because the electric supplemental heat only operates when not in ECO (in gen 3 anyway) and, though it doesn't make any difference I can feel, it noticeably speeds clearing the windshield. As for the slight difference in the go-pedal response curve between these two settings, my foot pretty much adjusts to that within a minute or so of me changing the setting, and after that it's not even something I notice. A fun thing about the pedal response curves, because of course they all meet at both ends, is the ECO curve is actually steeper than the normal or PWR curves, in the upper portion of the range. Sometimes when I've switched out of ECO (to defog the windshield, say) and forgotten to switch back, it's that difference I'll eventually notice and be reminded. Or I'll notice the car slowing more avidly than usual as I back off the pedal (because of the normal curve being steeper than ECO in the lower portion).
Perhaps, when I get the car, which incidentally is near Cuba on its way to a stop in Jacksonville, I’ll rig up a tachometer and compare. Again, CVT is new for me. I’ve driven a crosstrek with CVT and paddle shifters to simulate gears, that’s it.
prius has an eCVT, a bit unique. i think there have been improvements to eco mode, but not in a way that effects gear ratio.
The way CVT makes engineers smile is by turning a two-dimensional problem into a one-dimensional one. If you look at the engine efficiency plots (these are for the 1NZ engine used in gen 1 and 2 and c, and the 2ZR engine used in gen 3 and 4 and v; sorry I don't have one specific to gen 5): you see that these are 2D regions where there are a lot of different ways you could get the same amount of engine power. For example, if you wanted 30 kW out of the engine, you could do that at any RPM along that dashed "30 kW" curve, all the way from low RPMs where you'd be kind of lugging, up to high RPMs where you'd be making extra noise and burning extra gas. But there is only one point where that "30 kW" curve intersects the heavy path on that plot that passes through the middles of the highest-efficiency regions. In a transmission with fixed gear choices, you're pretty much always stuck with using the nearest gear that's either too high or too low for the amount of engine power you want. On the bright side, that kind of lets you express your driving personality by whether you more often like the gear that's too low or too high. But the efficiency win would be if your transmission always had the gear that's just right. In a Prius, when your foot on the go pedal is calling for so many kW of power, the ECU isn't going to search that whole 2D region for the possible RPMs to make that many kW. It will look just along that heavy path—a one-dimensional problem—to find the engine RPM that's best for that amount of power. It will run the engine at that RPM, and the CVT will match that to whatever speed the wheels are turning. Adding paddle shifters to that is kind of gimmicky; it panders if you're so fond of the too-high-or-too-low gear compromises that you used to have to make that you still want to make them even when you don't have to. But I don't think any Prius generation has supplied that particular gimmick. Because the CVT has already reduced the "what RPM should I use for so many kW of power" question from two dimensions to one, there just isn't much left for the "ECO mode" to do. It changes the mapping from go-pedal position to how many kW of power you want—because that's what's left for it to do.
