MPG "The Perfect Method"

BTW, the reason for the 62mph limit for EV mode is primarily a mechanical one: when you go over 62mph with the ICE off, the components in the power split device are spinning too fast relative to each other, so the ICE kicks to reduce the difference. But it is producing very little power (and burning very little gasoline) in this mode.

 

yes, i can and do it every day. there is no real comparison here. EVs are lightyears more efficient than the best gas engine period. the fact that you got home to a plug with EV range left means that EV range was wasted and gas was burned in its place and at a MUCH lower rate of efficiency for the distance traveled.

spin it anyway you want. uphill, downhill or thru the hill. the numbers do not change

 

But I think that 51% is an artifact of how the car computes EV vs HV miles, in that it includes EV mode using energy recovered from regeneration, which is really power from the ICE when going up the hills. Those HV miles climbing the hills are sucking in the gasoline to power the climb, but in the statistics, they are just HV miles, as if you were driving on the flats. I think what would be more meaningful would be to look at how much gasoline was consumed and how much electricity from the wall was consumed over the miles traveled.

One could perhaps argue that the Atkinson ICE is incredibly efficient when used to power the climb, as opposed to using it in HV on the flats. I don't know if this is true or not and I defer to others with more expertise in this area.

But amazing as the plug-in is, it is not a perpetual motion machine that can create energy from nowhere.

 

I just returned from a round trip to Reno, sea level to as high as 8,700 feet, Mt Rose Hwy to
lake Tahoe.

I noticed on the long downgrades during the trip the battery pack completely filled up
and I was wondering if I had the Plug in Prius how much energy I could have
recovered and how many more mpg's I could have received.

As it was the mpg for the round trip calculated was over 52 mpg with three people
and cargo, near max loaded.

 

These two posts are inconsistent. If you did not start trying it until you were 20 miles from home, then its not really related to your statement of 131 miles and 51% EV. Since you had some 4000 feet of elevation change, it will be nearly impossible for anyone to replicate it without that same elevation change. That is a bit more than 2 full charges worth of potential energy, so just from that added energy one would expect about 36-45 miles of EV (depending on speed), leaving 85-76 miles for HV mode. HV for 76 miles at 50mpg would 1.76 gallons for an overall trip of 86MPG. So your 91MPG is a bit better, but all of the above was approximate, and it's may easily be within the margin of error of the computation -- driving a bit slower yielding 55mpg in HV and if the initial charge plus elevation provided 45miles of EV, they overall trip would be 96MPG.

 

I am not missing anything. If you are able to discriminate when to use EV (which by the way no one was saying otherwise, nor were they saying you should use it in the beginning), you should be arriving home with no charge. If you are charging at every opportunity, you are using gas to make electricity, very expensively, instead of charging at home, which ought to be cheaper (otherwise a Pip wasn't your best bet). The only reason to arrive home with leftover juice, might be if you are at the bottom of a long decline, and you had no opportunity to use it.

 

I believe - and someone correct me if I'm wrong - that it prefers to use EV power until the ICE is warmed up. When I switch to HV when entering the freeway, it'll suck most of a mile of EV before it settles into real hybrid mode.

The trick is to switch to HV a minute or so before getting on the freeway.

Another thing I've noticed is that going up a hill in HV at freeway speeds, the MPG drops way down. So I'm wondering if it's a good use of the EV miles to go back into EV and get a boost uphill. I get a lot of it back going down on the other side.

 

Since the primary objective of Prius is still low emissions, the engine is held to a low RPM until warm-up is complete. That's 1500 unless you drop the pedal way down. When the coolant reaches 130°F, the boost from the battery-pack will subside. Then as you drive, some of the EV consumed will be restored. Under usual circumstances, you'll be back to where it started upon exiting the highway.

At slower speeds, you'll see something similar as well. Warmup will allow the engine to run at a modest rate. This is not only great for keeping emissions in check, it also helps with gas-consumption efficiency and promoting long-life for the engine.

 

Why is it a surprise that the mpg going up a hill is very low ? It takes energy to climb, and you are burning gasoline to get it. At least with the plug-in, you can recover much of the energy on the way down. It seems like it is just a accounting trick to switch to EV mode on the way down, so the EV-miles counter is run up. You are still burning the same amount of gasoline, regardless of the reported EV/HV ratio.

Forgive me if I am missing something fundamental here. I am not trying to be a smart-alec.