Engine only MPG

So in effect the fuel economy you get when driving with an empty battery?

The theoretical “load level” economy that happens with cycling is sort of meaningless

 

Yep so everything I mentioned is 100% accurate

With a “dead” hv battery I can definitely decelerate in a way that makes the motor shut off and “glide “ with minimal regeneration .
Likewise I can accelerate in a way that doesn’t appear to dig into the battery buffer while not being a total wet blanket and charging during acceleration

Even in the Volt I can do the above and in the Gen IV I tested ditto

I see no reason that old school economy couldn’t be calculated driving without plugging in at different average speed tankfuls. Just time consuming

Also likely on “gas only” you will find as stated a hump above and below which economy is worse.
Every other PRII I tested had that Goldilocks speed

 

So we both agree with @jerrymildred. The PiP has a trip meter-ish menu for EV miles and kWh used. I never reset mine so it's a lifetime usage for my PiP sans whatever the dealer did for the first 50 or so miles.

I'm curious why your EV ratio isn't zero if you trip has no stops and average speed is above 43 mph. I haven't driven a Prime so I'm not versed in it. But in the PiP, if the EV portion of the battery is depleted and one never stops or goes below 43 mph, then on your two example trips EV ratio would be zero as the ICE never turns off. Does the Prime engine turn off at higher speeds?

 

It's probably a warmup effect. You're seeing poor mpg because of a cold engine in short trips with a lower average speed.

 

Right, @Salamander_King, we're both overlooking the obvious.

 

First, let me say that I'm flattered that some of you like my theory. But it is just a theory. I'm not 100% sure it's right.

But regarding the quotes I have here, having driven both the PiP (2 years) and Prime (3 years), I really miss that feature on the PiP that told you exactly how many miles you drove in HV mode and how many in EV mode plus the kWh used. It's not relevant to @Salamander_King's question, but it's nice to have. Instead, the Prime says, in percentage, how much of your driving is with the ICE on and how much with it off regardless of the mode chosen by the driver. Also interesting info. I wish I could have both.

As for the difference in when the two cars have the ICE on or off in HV mode, it's pretty amazing. The Prime is seemingly eager to shut off the ICE. We have lots of very flat roads here. At 50 mph, my ICE is off nearly 50% of the time. That percentage increases at lower speeds. It still shuts off a lot at 60 mph, but above that it needs a tail wind or downslope.

Because of the one way clutch between the engine and transaxle in the Prime, MG1 can help MG2 in powering the car in EV mode. That allows EV speeds up to 84 mph. That's not possible in a PiP or even a regular Gen 4 Prius.

 

The Prius Prime engine is one of the most efficient engines, along with the latest Camry Hybrid GDI engine. Here are the efficiency contours:



5. Efficiency contours of Toyota 2.5-L Atkinson-cycle engine when... | download scientific diagram



Complete BTE map generated from Toyota's publicly released map images... | download scientific diagram

 

My thoughts exactly! There is no such thing as ICE only.

 

Interesting. I used to keep ~0.5 mile of EV in reserve in my PiP on trips where I know there are declines. This allows me to coast with the ICE off up to 62 mph instead of 43 mph. The trips have always been too irregular to accurately measure whether there was any benefit at all. Learn something new everyday, thanks.

 

As I make several 200 mile round trip commutes a week and gasoline here (as of yesterday’s fill-up) is 7.83$/gal (2.07$/litre), I’m ecstatic about the fuel efficiency, whatever mode I’m in. This breakdown noted above is quite interesting and also reassuring regarding my decision to buy my 2021 Prime. In one year and 3 weeks of driving, I have about 47,000km/29,000 miles, so my happiness with the car is genuine.

 

Sal is ignoring me so wouldn't see this post and Quote it again, but he forgot to mention if he noticed any SOC changes during the trip (which he started at 100% SOC (thus no room for recharge)) as stated in post # 34 and 34 . On longer trips that I start at 100% I typically notice SOC changes, not that I'm actually looking for that stat. So I agree with Jerry that it's at least Very hard to calculate ICE only mpg in a Prius Prime if not near impossible. I for sure haven't figured out a way to do it.
edit I'll do my best to honor Sals request to ignore his posts as well in the future. And I hope this doesn't offend anyone else.

 

That is remarkable. I recall the worst fuel economy I ever got for my PiP was on a drive between San Francisco and San Diego on mostly flat Hwy 5: 43 mpg. This was with a speed limit of 70 mph and frequent jaunts to 85 mph when I could find a shiny BMW to follow in the fast lane. This is with a full car with luggage for a week vacation. I unfortunately didn't log what average speed was.

As flat as Hwy 5 is, I think the traction battery did play a role on fuel economy on small elevation changes. Charging on the way down and providing a little oomph on the way up.

 

Concur, CC often brings my PiP into the power region and out of ECO mode at the slightest inclined. Whatever "lean burn" mode the engine goes into, it is barely enough power to maintain speed. Therefore, I toggle CC speed down to prevent this from occuring. Occasionally, I have to disable CC on steeper inclines. Isn't this what the eco drivers call Driving with Load (DWL)? If only CC had a DWL option.

On a side note, I also stay under 85 mph because beyond this speed, the engine goes out of ECO mode at least according to the HSI. Not a big deal for most but vital for an eco driver on an empty stretch of Hwy 5 right along a pungent cow farm.