EV mode above 42 mph

42 mph sounds like the Gen2 threshold speed that forces the ICE to spin. The threshold speed is a bit higher in the regular Gen3, and I understand to be significantly higher in the Gen4.

 

Actually enough fuel to maintain catalytic converter temperature . . . even while descending a steep grade in "B". Some have claimed the engine spins without fuel but that only occurs in the first cold-start of the day in the Gen-1 and Gen-3. Injector timing shows there is fuel consumed.

Bob Wilson

 

13:00 to 17:15 Talks to why M/G1 is slower in the Gen3 & Gen4 than it was in Gen1 & Gen2
Near 20:20 to 21:10 he discusses the differences between the Liftback and v, and the PHV, and the C

 

Final drive in the P610 transaxle is 3.476:1, ratio between ring gear (to final drive) and sun gear (MG1) of the power split device is -2.6:1 with the engine stopped. (Somewhere in there is a negative sign, I believe that's in the right place.) This means that MG1 spins at -9.0376 times the speed of the wheels, which are doing (on Dunlop Enasave 01 A/S 195/65R15 tires) 836 revolutions per mile - so MG1 does 7555 revolutions, in reverse, per mile.

We don't know MG1 maximum RPM, but on Gen 3, it was 13000 RPM. Gen 4 uses a smaller and lighter motor, so maximum RPM is likely higher. At 13000 RPM, however, this means that MG1 can support speeds up to 103 mph while maintaining the engine at 0 RPM. (However, IIRC, the limit is lower.)

 

On the Gen 4 the ScanGauge shows 0.04GPH fuel flow when EV light is on at higher speeds.

What puzzles me is that the same 0.04GPH shows even at much lower speeds (say 25MPH) when the ICE is turned off - I thought???

 

What is your source for that final drive number? Another thread here devoted to the P610 transaxle found using EPA published data (presumably supplied by Toyota) that the final gear ratio was 2.834, not 3.476:

P610 transaxle | Page 2 | PriusChat

What is your source for MG1 on gen 3? The references that I have seen say either 10,000 rpm or that it was later reduced by Toyota to 9,500 rpm. Perhaps you are thinking of the MG2 rpm limit which is about 13,000 rpm in gen 3.

Using a final gear ratio of 2.834, -2.6 for MG1 vs. ring, 836 revs per mile for the tires leads to a maximum speed of 92.5 mph (which they limit to 84 mph on the Prime in EV mode).

 

Is the information you have specific to Gen4?

If that information is older than Gen4, or generic to the Prius line, then I claim that it is the wrong number for your new Gen4.

For my Gen3, the threshold speed is 46 mph, and every thing I've seen says that the Gen4 threshold is significantly higher, e.g. above 60.

 

Development of New Hybrid Transaxle for Compact-Class Vehicles on the first page (so in the free preview).

There's a few posts on here claiming it (versus 13,500 RPM for MG2), but I can't actually find anything conclusive. I went with it anyway, but it may be wrong. Gen 4's MG1 RPM would be more important anyway, given that we're talking about the Gen 4. (I would like the actual MG1 RPM limits for every Toyota hybrid driveline (and MG2, and all the tooth counts for every stage - I've got all of the P410's tooth counts, but my spreadsheet is missing a lot of info on other models), though, as I'm considering making a simulator of every version of the transmission, including the L110/L110F (as found in the Lexus RWD hybrids).)

 

Interesting! So, assuming the gas engine is at zero rpm at the Prius Prime's 84 mph maximum all-electric speed that means MG1 is spinning around 10,500 rpm.

That P610 thread also said the MG2 gear ratio was 3.118 in gen 4 so 3.118 X 3.476 X 836 is 7,555 rpm on mg2 at 60 mph. At the new maximum mg2 rpm of 17,000 that implies a max vehicle speed of 112.5 mph. Car & Driver lists the max speed of the 2016 Prius 2 Eco as 115 mph.

The 3.476 final gear ratio also explains faster vehicle launch times that Toyota has hinted at since MG2 to the wheels would be a relatively high ratio of 10.8 which helps to make up for the slightly downsized mg2 vs gen 3.

 

There is a bug in the scangauge that causes the GPH display to be wrong when the vehicle is in EV. It also exists in Gen 3 (it's 0.02 GPH for me in my 2012). No one seems to be sure what value it is getting from the car that leads to this (maybe last known value or something) but the worst part is that the scangauge uses it in its MPG calculations. So your MPG will slowly drop even if you are stopped with the engine off. The good news is most of the time this has a pretty negligible effect on the scangauges mpg calculations over a trip (0.04 or 0.02 GPH isn't much fuel).

Hopefully linear logic will figure this out at some point. Sometimes the GPH does show 0, but this for me is usually when the engine is on, but throttle is off (this is the engine spinning without fuel we were talking about earlier). I don't use GPH as one of my gauges normally so this is all to the best of my memory.

 

Yes in my 2011 I saw GPH=0.02 when RPM=0. I have never noticed GPH=0 in either car while the car is moving. I think I see 0.02 or 0.04 even when the car is in autostop at a traffic light.

In the Gen 4 when the EV light is on while I am at higher speeds (say 50-65mph), I still get RPM=0 and GPH=0.04. Then sometimes the gas engine will switch on (presumably to keep the catalytic converter warm or to satisfy cabin temperature settings?), EV light turns off, and RPM>0 and GPH>0.04.

In the Gen 3 going downhill at speeds >46mph the gas engine would not switch off, and the GPH never reported 0.02. The GPH was higher, and when I shifted into "neutral" (yes I realize it isn't a real neutral) the GPH dropped about 50%. Extrapolating from the Gen 3 to Gen 4 can be dangerous because they do behave differently in some ways.

I use the Prius' MFD for trip mileages and never bother with trip mpg on the ScanGauge so I don't care too much about whether the 0.02 or 0.04 are accurate.

 

When the EV light is on (I'm assuming you're talking about the EV light on the Power Bar), that means the ICE is not on and you're being propelled by electricity. The light can be on above 42mph (like when I'm on the freeway going 72mph). If I press on the accelerator lightly, I can propel myself with EV only. This will not keep you at a constant speed, however. There is only so much the electric motors can do at 72 mph.

To stay at EV, you need to stay in the first section of the bar between charge and eco.

 

Twice I have seen 73mph with the green EV icon illuminated. It is rare at 65 and above.

Furthermore, the EV light is far less prone to illuminating with cruise control on. I can hold a steady speed without cruise and the light is on. Engage a that same speed setting with the cruise control, and the light goes off. I don't get it.

 

Yeah our third gen too, rolling down a steep hill by momentum alone, engine kicks in around 74 kmh, or 46 mph.

 

If the load bar is below halfway and the engine is running, you can frequently induce the Gen 4 go go into EV by letting off the accelerator momentarily and then reapplying pressure, being careful to keep the load below the halfway point. This procedure works often but not always, both on the highway and at lower speeds.

Cruise control cannot use this tactic.

Basically the problem with cruise control is that it tries to maintain a constant speed. Constant speed does not equate to most efficient use of gas to get a hybrid from A to B.

 

Well clearly the ICE stops rotating at speed (I am not sure that the EV icon lights up 100% of the time this is true).
So here is a question. Does the scan gauge show the .02 to .04GPH while it also indicates 0 rpm? If so that would point to some discrepancy in the electronics. It is impossible for an ICE to burn gas at 0rpm.

 

Whenever the EV light is lit the Scangauge shows RPM=0. It might take a second or two to get to 0 and briefly show something intermediate like RPM=32

Yes always. It might be something in the Scangauge to avoid reporting MPG=infinity if the engine is off - perhaps an infinite number would fluster its little brain. Or it could be something in the OBD system that the Scangauge is reporting faithfully.