Prius Prime Plus in my hands

To keep vehicle overhead as constant as possible.

Bob Wilson

 

Upon further reflection, I do not see a reason for 'rolling test' and would suggest the proponents 'get their hands dirty'.

I have a metric for car in "D" and 'charge mode.' If in motion, there will be a vechicle drag loss that I have already plotted on mph vs MPG. But my interest is in the gasoline cost to raise the SOC as an energy reserve, a safety factor. At worst, using the vehicle overhead to calculate the SOC burn means the calculate distance on the remaining gas will be slightly higher.

Any error is in my favor for safety and range. This is a hard concept to understand so I'll work on a graphic. Because I 'see numbers', sometimes I write in 'Bob' which can seem obtuse.

Bob Wilson

 

So I converted my benchmark fuel burn to gallons per hour. I then added it to my earlier Prime mph vs MPG and plotted both curves:

	mph	MPG	MPG+charge
1	5	59.7	8.6
2	7	75.7	11.8
3	9	88.2	14.9
4	11	97.7	18.0
5	13	104.7	20.8
6	15	109.4	23.5
7	17	112.4	26.1
8	19	113.9	28.5
9	21	114.1	30.7
10	23	113.4	32.7
11	25	112.0	34.6
12	27	109.9	36.2
13	29	107.4	37.7
14	31	104.6	38.9
15	33	101.6	40.0
16	35	98.4	40.9
17	35	98.4	40.9
18	37	95.2	41.6
19	39	91.9	42.2
20	41	88.7	42.6
21	43	85.4	42.8
22	45	82.3	43.0
23	47	79.2	43.0
24	49	76.2	42.9
25	51	73.3	42.7
26	53	70.6	42.4
27	55	67.9	42.0
28	57	65.3	41.5
29	59	62.9	41.0
30	61	60.5	40.4
31	63	58.3	39.9
32	65	56.1	39.2
33	67	54.0	38.5
34	69	52.1	37.8
35	71	50.2	37.1
36	73	48.4	36.3
37	75	46.7	35.6
38	77	45.1	34.9
39	79	43.5	34.1
40	81	42.1	33.4
41	83	40.6	32.6
42	85	39.3	31.9
43	87	38.0	31.2
44	89	36.8	30.5
45	91	35.6	29.8
46	93	34.5	29.1
47	95	33.4	28.4
48	97	32.4	27.8
49	99	31.4	27.1
50	101	30.4	26.4
51	103	29.5	25.8
52	105	28.7	25.2
53	107	27.8	24.6
54	109	27.0	24.0
55	111	26.3	23.5
56	113	25.5	22.9
57	115	24.8	22.4

Unfortunately the outside temperature, 34F, is outside the standard temperature range so I'll have to wait a day or so before running the test. I will have to use my flatter benchmark routes to minimize hill-pumping the charge.

Bob Wilson

 

It is a dialog, a conversation we might have sitting around a bar or office white board to work up ideas. Hopefully we all learn something and optimize any experiments and refine the data. I do it because I appreciate the feedback from those who understand my posts.

We need to separate the 1,000 mile tank challenge from 'how to run the tank dry.' The 1,000 mile tank challenge is from a Japanese club of people who see how far they can go on a single tank. I did mine on our Gen-3 Prius in 2013: Efficient driving for a 1,000 mile tank | PriusChat This driving stunt showed it could be done over a three week period by a single driver just by application of what we know about the car.

Running the tank dry is a safety problem that over the Prius generations has gotten worse. The Gen-1 would display a lot of error messages which meant you had about 1/2 mile to find a safe place to park. Add one gallon of gas and drive off to a gas station. I did that test about 30-40 times.

The Gen-3 would silently use the traction battery reserve with only one subtle clue . . . the power flow arrows would go away. I did this 7-8 times but again, there was enough remaining traction energy to reach a safe place to park. Add one gallon and the car starts and you drive to a gas station. I did this at the end of my 1,000 mile tank.

The Prius Prime (Gen-5) gives NO indication the gas is gone unless there is some EV charge. Worse, when the car coasts to a stop, adding one gallon was not enough to start the car. I had to do a 12V, power-on, reset. But knowing its use when running out of gas fully justifies having a 'charge mode.' Put an EV charge on the car when the 'low gas' icon shows up and when it starts to count down, find a safe place to park and add one gallon of gas.

Yes, some folks follow my musings and occasionally share a chuckle at my occasional bon mot. Hopefully they've come to realize there is neither malice nor morbid voyeurism (although some anonymous moderator(s) may have a different point of view.) I study accidents as 'but for the grace of God.'

There is an open question of the effect of 'charge mode' on our Prius Prime. I've done one static test and am planning on a moving test. For that test, I'll need a safe way to operate the iPhone camera without having to touch it and risk changing the orientation. As the driver, I want the data, not the risks.

Bob Wilson

 

I did my Gen-3 changes at 5k, 15k, and 25k and the first changes did show machining particles. However, the Prime (Gen-5) did not have the silicon bead particles. There was evidence of silicon leaching in the Gen-5 but this does not 'set my hair on fire.' Particles are a different matter.

IMHO both the 2k engine and transaxle oil change appears to make sense. Neither the engine nor the transmission appear to be a 'break-in' oil. I'm of the opinion that getting the early, larger particles out will lead to fewer smaller particles and their friction and heat effects in the future.

Bob Wilson

 

There is about a 2x factor between the typical EPA range and what can be gotten at the minimum, cruise control speeds: 24 mph Gen-3 and 28 mph Gen-5 (prime). So the EPA range of 595 mile for the Gen-3 means achieving 1,000 miles on one tank is achievable. The 2013 driving stunt was to emphasize the efficient driving is all it takes.

I would expect a similar range difference in a single-charge, 300 mile, Tesla. But a 3x range in the Tesla would be a challenge. Once an electric car gets into the 500 mile range, achieving 1,000 miles on a single charge becomes practical.

As for the 640 mi range Prius Prime, it becomes trivial. I'm just waiting for Standard day temperatures, 60-80F, before doing my second one.

Bob Wilson

 

I did but upon getting more 'seat time,' I'm leaning towards Gen-5. The flywheel, one-way clutch is the primary reason but around town, I'm seeing what should be impossible mileage even in cool weather. Like the BMW i3-REx, it is teaching me bad habits for example:

Both the BMW i3-REx and the Prius Prime have led me to using the 'Gas Echo' route with the time savings while achieving better than Gen-1 mileage. This is truly remarkable . . . not that I'm learning bad gasser habits . . . but I can do it with better than Gen-1 and Gen-3 mileage.

I've always driven on cruise control but this past week, I'm starting to move towards using "Normal" mode from "ECO." This makes it much easier in traffic with fewer gaps in traffic. I'm not sure about "Power" mode as it seems a little fidgety. I prefer a smooth ride and certainly "ECO" smooths things out although sometimes the gap can get so large the speed difference requires gentle use of my foot brake.

Engine warm-up had been the bane of the Gen-1 and Gen-3 Prius. But someone took a shinai to the warm-up control laws and beat them into submission.

A lot of these things I didn't see during my initial benchmarks but this car is really well polished. Understand I skipped the 2016 Gen-4 Prius because someone forgot TSS-P for the Level 2 ECO.

I once read an article about computer products that claimed generations:

1. Got the big things right but a lot of nagging, bugs, 2001-03 Prius, Gen-1
   
2. Fixes many of the nagging bugs but introduces others, 2010-15 Prius, Gen-3
   
3. Finally gets everything right, the Prime, 2017-current, Gen-5

This is not a slight against the Gen-4 Prius as much as the first model year was badly mixed. Make the one-way clutch standard and a little more capacity in the traction battery and it will be a star.

Bob Wilson