Is there a way to turn off EV mode?

As far as I know, there's no way to turn off EV entirely. I wouldn't worry about the switching in and out of EV vs ICE; the car will do its best to get the best mileage according to what you are asking of the car. Recharge cycles must reach into the millions over the life of the HV battery, what with regen every time you lift off the accelerator even if only for a few seconds.

 

If you don't have EV mode then your engine is spinning. It might not be burning gas if you're coasting, but it would have to be spinning. EV, regardless of how much energy is moving in/out of the battery, is what lets the engine stop completely while the car is moving.

Now, even if no gas is consumed, there are efficiency losses due to friction and drag whenever the engine is spinning. So which inefficiency is greater? Mechanical or electrical?

I'm going to trust the computer on this one. And remember that its goal is to reduce overall *emissions*, not maximize instantaneous MPGs. To that end, the hybrid battery is a consumable resource; it will wear out (be consumed) but the rate of consumption is so carefully controlled by the computer and slow enough that you shouldn't worry about it and just drive the car.

It's funny, most people who want to micromanage the battery use often want it to be in EV more, not less. Too much isn't good for the battery, of course, but then it's there to be used. You don't get bonus points for a less used battery if it means you're burning more gas overall.

 

Wouldn't the engineers who've been working on and improving the HSD for the last 20 years have consider this?

 

It may be more efficient at high speed if the system was able to fix the gear ratio, engine to driven wheels, but then it would be less efficient at other speeds. The 2017 Honda Accord Hybrid does something like that.
See: Explaining how Honda Accord Hybrid system works: video

 

In third gen the cut-off for EV use is around 73 kmh (translates to 45 mph), so at highway speeds EV doesn't happen. It's significantly higher cutt-off in fourth gen I think.

Still, I wouldn't second guess it, just let it do it's thing, for the most part. At lower speeds, if I see our (third gen) using up the EV fast, and I want to preserve it, I'll resort to more pulse-and-glide, ie: give a pulse of gas, enough to activate the engine and give good momentum, coast a bit, repeat.

 

I had a European Ford 2ltr Granada 4x gear auto that could lock the revs to the drive wheels in top gear. Don't remember what year, but I had it 2nd hand in the 90s so probably late 80s model.

 

Short answer - NO.

A "charging cycle" is a bit different from what PRIUS does - imagine your Ni-Ca vacuum cleaner, you charge it, vacuum till it drops, then charge it again - same with your battery drill, dog clippers etc. It goes from FULL (very in many cases without a smart charger) to FLAT.

PRIUS doesn't do that, it is a HYBRID, using both power units in conjunction, controlled by a computer. It won't overcharge, or go FLAT, but will work within a range - with a NiMH Battery, mine rarely goes past 7 bars, and hasn't ever gone below 2. And TOYOTA has programmed it to use a narrower band than what is indicated on the 8 bar display.

With your PRIUS - try putting up the ENERGY MONITOR:

and you'll see that there are about ½ dozen power operations. At highway cruising speed (not HIGH speed), going UP a gentle incline, you might see ICE plus BATTERY sending power to the wheels. As such, the BATTERY is improving the ICE's fuel use by supplementing it. Then go DOWN a gentle incline, you'll see it just using BATTERY driving. If the incline becomes steeper, it will send power from wheels to BATTERY to recharge it. Then up the next steeper incline, it might use ICE to both charge the battery and to drive the wheels.

Just let the computer play it's games - it seems to know what it's doing.

 

I've seen my Gen4 light up the EV indicator (making it specifically different from max MPG but engine spinning without fuel) while *coasting* above 70mph. Under power, I find it's rare above 65.

 

There are times I know more than the computer or the engineers in Japan. I know I am on the top of a long downhill and shift to B, or I know I need to sneak in late at night and engage EV, etc. But for normal driving, trying to out drive the computers will just lose MPG for no reason (My examples also lose MPG, but I have a reason) When you have a need to 'out-think' the computer, do so, but I doubt it will be more efficient.

(there are times you can out-think cruise control, if it is hilly. It is never hilly here, so I don't know them)

Mississippi Delta - Wikipedia

 

I had a 1988 one that did. So did the 2008 Mondeo diesel Auto I had.

 

There's no such thing as a highway that's completely void of any hills or wind or traffic. So, any idea that a very specific engine operation speed or adjustments to RPM is lost opportunity. The continuous & rapid interplay of electricity flow from motor, generator, and battery is how the higher efficiency is squeezed out.

 

still, i'd love to see what a prius could do with just an efficient engine, equivalent in hp to the combo ice/motors.

 

Basically, COROLLA has the "same" engine but with OTTO cycle rather than ATKINSON. I can't remember where, but I read that ATKINSON cycle isn't as driveable in non-hybrid form. And, COROLLA is approx more-or-less roughly the weight of PRIUS minus EV components. And COROLLA won't get anything like the l/100km that PRIUS will.

Yes, lots of differences like aerodynamics & Corolla looks hideous compared with PRIUS, but you get the idea.

Most late model AUTOs have lock-up Torque Converters or Clutch packs - my VOLVO and MITSUBISHI did in the '90s (both had same Aisan Warner 'box).

 

I notice that on prolonged highway driving of 60mph sustained(15mins or more) or prolonged aggressive driving([PWR] range + power mode), the ICE keeps charging up the battery which results in the battery get full and heating up which results in the fan kicking in at high speed to cool off the battery. There's also increase in cabin temperature and noise as a result of the battery heating up.

Wish toyota allowed for a ICE mode/button where I can tell the system to just stop charging or using the battery so frequently and just use the ICE as much as possible(e.g. reverse function of EV Mode).

 

Besides being near impossible - there would be no point in doing what you're suggesting - it would just waste fuel, and you'd add considerable complexity, probably requiring a dual transaxle.

The Atkinson Cycle engine (ICE), the Starter/Generator Motor and the main Traction Motor, are all assembled to work together. They are totally integrated into the planetary gearset transaxle which TOYOTA call HYBRID SYNERGY DRIVE. Splitting them off would probably need some sort of transfer case - the complexity would add LOTS of extra weight.

Just buy a non-hybrid Corolla instead.

 

Have you read the WIKIPEDIA article which is very informative?

Hybrid Synergy Drive - Wikipedia

 

I hardly ever notice my battery fan, even sustained 4-hour drives averaging nearly 70mph. Actually, I can't honestly recall ever hearing my Gen4 battery fan to date. I also have never, in any of three different Prius generations, experienced noticeable cabin temperature swings due to the battery in normal operation.

I will say that I notice my wife's Gen3 battery fan more than I ever did in my old Gen2 or my previously leased Gen3. She keeps the audio system off more often and so maybe that's enough to hear the fan over the road noise.

 

Or buy a Camry if you need more space than a Corolla. Part of the reason I bought the Prius instead of a Corolla was due to extra capacity for transporting dogs.