Mountain trip mileage

I do not mean to be critical, but there is a flaw in your math....

On the way up, you got 38.5 MPG, so you burned 2.4 gals, on the way back, you burned 1.2 gals, so you burned 3.6 gals total whil traveling 188 miles. 188/3.6=52.2 MPG

 

Good catch although the original poster may have used Trip A for total mileage and Trip B for each leg. The local driving at Lake Tahoe and back home might not have been included and reported, a reasonable thing to do if the climb and descents were the reported segments. But this does raise a question I'd not considered before, the linearity of Trip A and B.

I've done a number of 'hill climb tests' that involve measuring the active climb ascent. So typically I don't measure the 'turn-around' and subsequent descent nor the acceleration at each end.

I typically use Trip A to track the tank. However, I've pretty well mapped the ZVW30 tank characteristics (~2.1 gal. remaining after flash begins.) so I can use it as part of a differential, hill climb test.

 

Thank you,

I needed another hill climb to compare with my data:

I'm going to use:

• 94 miles - user reported distance (Rocklin to Kings Beach is closer in distance)
• 38.5 MPG - user reported mileage
• 55 mph average speed - using Rocklin to Kings Beach, Google reports 93.4 mi, 1 hr 42 mins
• 56 mph - 75.6 mi, 1 hr, 21 min to Donner Summit Pass, Google report

So now to use my hill climb data at 55 mph climbing a 525 ft. hill:


Then we also need to calculate the linear fuel burn at 55 mph:


I would expect at 55 mph, to burn ~0.0680 gallons per 525 ft.. Next comes the fuel cost to travel 94 miles @ 55 mph and I would expect 64 MPG or ~0.0156 gallons per mile.

• 0.907 gals altitude change - 0.0680 * (7000/525)
• 1.466 gals distance @55 mph - 0.0156 * 94
• ~2.373 gals total from performance charts
• 2.44 gals - 94 miles / 38.5 MPG - user reported upgrade segment
• ~2.74% error - (2.44-2.373) / 2.44

Methodology:

1. Measure highest change in altitude (works for a single hill)
2. Measure distance traveled
3. Measure speed
4. Lookup fuel burn in climb chart and calculate altitude change fuel burn (note: multiple hills may require summing of climbs)
5. Lookup MPG at given linear speed and calculate trip distance change

Now I'll be insufferably smug for the rest of the day. <GRINS>

This ZVW30 is an excellent engineering system. The vehicle performance appears to be readily, reproducible. Of course there are minor variables that need to be included in a final performance model but the major ones determine the vehicle performance (my Thanks to Ken@Japan who several years ago emphasized the importance of altitude change in measuring vehicle performance.)

There is more work to be done to incorporate secondary effects such as fuel quality, tire pressure, road surface, wind, temperature, multiple hills and load. Also, I need to map the low-speed performance and factor in an 'age factor' for the traction battery. But like you, I'm very impressed with the ZVW30 and the engineering team that brought us this marvelous machine.

Bob Wilson

 

i also did a climbing trip as well, but mine was different. it was just over 175 miles going, just under 178 miles coming back. (thru the mountains there is frequently only room for one direction so the other direction was not always parallel.

now, mine was not all going up and down coming. crossed thru two mountain passes each over 4000 feet. but total trip average was still 57 mpg on MFD so "real" mileage was probably around 54 -55.

posted pic of screen when i crossed the pass, kinda of a bummer, basically coasted down a 6% grade on the other side for a good 20 minutes and only did regen for the first 3...after that, only thing i could hear was that quiet little whine of the battery pack rejecting the charge from the motor (probably not the battery pack whining, but ya know what i mean. was probably me whining about the lost power)

 

Yeah, you can't just average the two legs because...

Well, let's suppose you got only 20 MPG on the way there, but somehow managed to use absolutely NO fuel on the way back (infinite MPG). Then your overall efficiency would STILL be only 40 MPG because you doubled the distance without increasing fuel usage, so quite literally, you doubled your miles per gallon.

Oooh, another way to think of it: if we did GPM instead (gallons per mile), then you COULD just average the two. You'd have 0.05 GPM on the way, and 0 GPM on the way back = 0.025 GPM, or 40 MPG!

Perhaps this is why the Europeans prefer to use Liters/100km instead. Writing it as volume/distance allows intuitive averaging to be used.

(As long as the distances are the same. But even if they aren't, one can just do a weighted average, which is still pretty intuitive.)

 

My Prius experience is still too brief to have a solid answer. But another thread computed an elevation change potential energy equivalent to about 10,000 feet per gallon of gasoline burned at the Prius ICE efficiency. So I have been figuring fuel consumption as needing an additional 0.1 gallon per thousand feet of net climb, and a similar savings on the descent, provided no friction or compression braking is needed. So far, with very little data to explore, this is roughly matching my own experience.

Let me apply this Rule of Thumb to the OP's trip. Never mind Donner Pass. Lake Tahoe is 6000 feet higher than Roseville, so the climb should take 0.6 gallon more than a similar flat trip. The return trip should take 0.6 gallon less than a flat trip, for a difference of 1.2 gallons between the two legs. OP needed 2.44 gallons on the climbing leg, 1.17 gallons on the descending leg, a 1.27 gallon difference -- well within the accuracy of this rule of thumb.

 

Sounds about right at 52mpg. I did the same trip a couple weeks ago except I went to Carson Pass which was another battery draining uphill event and I ended the tip at 47mpg. I was also driving pretty fast.