Stanley-

While I do not have hard data from particular tests, I can tell you with the utmost certainty, that I can repeatedly achieve, and sustain 54 MPG or more in various conditions, over various roads, in various weather ( all "mild" ) doing "pulse & glide" with EV boosts over "humps" in the road, and brief bits of battery recharge during the pulses.

Arriving at the exact SOC at the end of my trip, that I started with, becomes unimportant after 50, 60, or 100 P&G cycles.

So I can get 54 to 60 MPG ( regularly ) using P&G with EV on the glide in the 25 to 42 miles per hour speed range. I have found no other way to get 54 MPG without lots of P&G and lots of EV use.

Not using any P&G, or any EV driving, the best I can get is 48 MPG.
This occurs around 48 MPH steady speed. "48 at 48" is something I see often on my scangauge, and is what I tell others. I get 42 MPG at 55 MPH steady speed.

Now, I don't often drive at 25 or 30 MPH steady speed without the car shutting down, so I don't have much data on that. I could set A/C to max. cooling and force the engine to stay on, but that would add a new variable.

My gut feeling, after 2.5 years of driving is, EV is a benefit to MPG in most scenarios. There can be some cases were it is worse, but the long-term average with regular use is a net positive. But driving style plays a huge role.

This car ( FEH ) and maybe hybrids in general are often counter-intuitive.
I always get better MPG driving in steep mountains. Always...weather I try hard to hypermile or not. It is hard to explain, but it's as if the car uses 30% more gas ( than flat ) on the uphill drive, but saves 80% more gas ( than flat ) on the downhill, ending with a net positive result.

I understand there are losses ( costs ) with conversions from mechanical to electrical and vice-versa... however, it very strongly appears the benefits out-weigh the costs. Think about how much energy is lost to heat with internal combustion. Think about how little is lost with an electrical motor.
It's not easy to measure all the variables.
It is easy for me to show I can only get 60 MPG with lots of EV use.
-John

 

Interesting. I seem to recall a trip I did from sea level to up to about 3500 feet elevation. The total trip was about 80 miles. I was bummed to only get 31 mpg on the way up, but happy to get something like 51 mpg on the way back, for a net of 41 mpg. This is better than I usually got at that time in my TCH. I typically got about 37 mpg. All of these numbers are from memory, and it was several months ago, so they are iffy. But I do remember that the overall trip average was above what I had been getting.

 

Actually, getting 31mpg one way and 51 the other doesn't average to 41mpg, but more like 38.6 mpg, which isn't far off from your typical.

 

As I discussed at length earlier in this thread, in order to get meaningful results, it's essential to control as many contributory variables as possible, and to change only the ones whose influence on FE we're trying to assess. In our case, the claim that I have challenged people to try to refute is that, all else being equal, one will generally get worse FE by trying to force the TCH into pure-EV mode as much as possible, and that better results will be achieved by letting the TCH's ECU computer make the decisions when to use the NiMH battery and when not to use it. For those who have just recently started looking at this thread, I suggest that you should go to the beginning and read both my reasoning and the comments of others on this matter. I conducted a very carefully controlled series of tests one day last year, and achieved very consistent results between repeated return trips made either (a) with maximum forced EV mode, or (b) with essentially no EV mode at all (using cruise control). I can't see anyone producing equally reliable data (to support or refute mine) without being willing to spend at least half a day doing the tests. Nobody so far seems willing to do so. It's easier to type than to actually do experiments! Come on guys, a half a day and half a tank of gas and care in conducting the test is all it takes! Yes, that's work; but that's what it will take to produce good data to support the claim that I'm wrong.

ag4ever — Yes, you must return to the same SoC to get meaningful results! Otherwise you could be given say a fully-charged flashlight, run the batteries down using it, and then claim that it had used no electricity. I'm say that, if you want to know how much energy was used, you must recharge it first! The tests you suggest conducting in Kentucky would be ideal, but it's perfectly feasible to conduct a good test by driving a there-and-back route multiple times on the same day, thus largely controlling the effect of temperature, wind, altitude, etc. This is what I did, and it largely achieves what your proposed test would achieve. Look at my data (Post #48) to see the consistency that I achieved.

gpsman1 — Sorry, but no Pulse & Glide is allowed in this thread! That's not the question we're trying to answer here. Yes, P&G can certainly do better, for the ICE is then totally "off" while gliding, but we're talking about "normal" driving.

chestr and chris_h — We need hard data here! Sorry! I encourage you to see if you can produce such data to support your beliefs. But do try to change only the amount of forced-EV-mode driving used. That's what this thread is about.

Stan

 

Stanley, I don't have the same car, so maybe it is pointless for me to even respond, and if that is the case, let me know, and I will not put another minute into this.

HOWEVER... If I do 50 charge/discharge cycles in a single, half day drive as you put it, and each charge / discharge cycle is ~400Wh, then the total amount charged / discharged is going to be 50 * 400Wh used, +/- 400 Wh.

20,000 Wh +/- 400Wh is a maximum error of 2%.

In real life, the error is probably less than 1%.
Is this amount of error acceptable?
You only need to carefully monitor SOC for very short trips.
If you cannot carefully monitor SOC, then a long trip will get the results you are looking for.

Some P&G is required.
How else are you going to charge/discharge the HV battery!?

Are you suggesting driving at 25 MPH EV, then 25 MPH gas, then 25 MPH EV followed by 25 MPH EV?

I do not know a single person who does that, or one who CAN do that, or one who WANTS to do that in their daily route. What's the point of all this again? I'm loosing track!
-John

 

Well I guess I just really don't care enough then... I'm perfectly content getting my current tank's 48+ mpg driving the way I do. Sorry. *shrug*

 

How do you figure that? The distances covered were the same.

Doh! I just did the math, and you are right. I guess I was thinking of constant gas not constant milage.

 

Stan,

I am just not interested in investing half a tank of gas to do this test. Even my daily commute does not lend itself well to do the kind of testing you are talking about. And I think you need to have the SOC be identical, as you have stated, at start and finish to have meaningful results. I do not have a scanguage, and as has been stated, the bars on the nav display for SOC cover a very large range of SOC.

Sorry I can't help to provide hard data. I suspect that your assertion is correct anyways. In any case, I am a "just drive the thing" kinda guy.

 

It's not my intention to insult anybody! I'm just hoping to goad someone to do a careful experiment along the lines of what I did and see if they get corroborating data. The whole point of this thread is to address the frequent claim that, the more you can run your TCH (or any similar design hybrid for that matter; e.g. a Ford FEH/MMH) in pure-EV mode, the better your fuel economy (FE) will be. I dispute this, for the simple reason that all the electrical energy stored in the NiMH battery ultimately can be traced back to energy provided by the ICE, but with the added penalty that the multiple conversions between mechanical, electrical, and chemical (in the battery) introduce significant additional losses. I'm not suggesting that shutting down the ICE when stopped, or recovery of kinetic energy by regeneration are bad — they are good! What I'm saying is that I doubt that you can in general beat Toyota's ECUs in knowing when is the most efficient time to use and to recharge the NiMH battery. Many posters had suggested that they were sure that they could indeed do better. They were pretty sure that I was wrong. I challenged them to provide good evidence for their claims. The test I suggested, and eventually conducted myself when no-one else stepped forward, was as follows. Choose a relatively flat route of 30 km or so. Drive it back and forth (i.e., round trips) multiple times. Alternate round trips should be driven at:
(a) A speed that allows for pure-EV operation; i.e., it must be below ~64 km/h (~40 miles per hour) — say, trying to maintain a speed of ~60 km/h (~38 miles per hour) as a target. Then try as much as possible to maximize the amount of pure-EV operation achieved. Of course, the ICE will come on every so often to recharge the NiMH battery, after which you force pure-EV mode operation again.
(b) A speed of ~65km/h (~41 miles per hour) with cruise-control on. This means that the car will almost never run in pure-EV mode. It's a bit faster than the speed in (a), which has a FE penalty due to wind resistance, but it's as close as I could get without EV mode operation occurring.

I achieved a huge difference in the amount of pure-EV mode operation that occurred between cases (a) and (b). I ran the round trip twice in each of modes (a) and (b) and reported my methods and results in detail in my Post #48. I believe that I proved what I had claimed, but the doubters still claim that they can do better by forcing EV mode. I'm asking again for them to prove it by going to a bit of trouble to gather meaningful data. That's all.

Achieving meaningful results means that the SOC must be returned to as close to the starting SoC as possible at the end of each round trip. This is not an issue when using cruise-control at 65 km/h, since the battery is continually being discharged and recharged by small amounts only. In forced pure-EV mode driving, however, the SoC drops and rises substantially during the trip. At the end of the round trip, one must keep on driving small closed loops back to the starting point until the SoC has been returned to its starting value in order to make the results meaningful. The very coarse spacing of bars 6 and 7 of the MFD's SoC meter (which is all I have — the NAV version is similar, I believe), as mentioned in my Post #98, makes achieving this more difficult. I do not have the ability to read the battery's SoC directly. ScanGaugeII (SG) does not monitor it, and the Prius codes for SoC that have been reported did not work for the TCH when I tried them out in SG's Custom menu.

gpsman1 — No, you're most welcome here, and you could probably do a similar experiment in your FEH. But this isn't P&G. You never glide on the sort of flattish route I'm talking about using. The car is being driven "normally" all the time. All that is being done is that, when trying to force pure-EV mode, one manipulates the accelerator to encourage the ICE to shut off and the car to run on electric power only. In my experience, it's difficult to maintain my suggested 60 km/h while in pure-EV mode without having the ICE re-start. For long EV-mode runs, the car's speed gradually creeps lower and lower (to maybe 55 km/h) before it's necessary to allow the ICE to restart and recharge the battery. But this was the best I could do while maintaining basically just the amount of pure-EV mode as the difference between driving modalities (a) and (b). Unfortunately, this means that the average speed in modality (a) was not 60 km/h, but more like 58 km/h as you'll see from my Post #48. The ideal would be to have the same average speed in both modalities. I achieved average speeds of ~58 and ~64 in modalities (a) and (b) respectively. This 6 km/h difference is to the advantage of the modality (a) tests. I didn't know how to avoid this and be able to vary the amount of pure-EV mode driving, which is what I wished to compare. Can you do a better series of tests with your FEH? I would be most interested in what you can achieve if you try to duplicate my test, while observing my test conditions as far as possible, for the reasons noted above and in all my earlier posts (please read them).

I'm not suggesting that this test relates directly to what an average user would achieve. But there are too many variables in play in uncontrolled casual tests as to make it impossible to draw meaningful conclusions from them. Hence the need for the stringent controls that I imposed. I'm trying to expose how forcing the car to run as much as possible in pure-EV mode does not help one's FE. Nobody else in this thread has yet done an experiment to refute (or for that matter, support) this!

I hope this helps clarify my earlier comments.

Stan

 

Well Stan, I did try a similar test, although the conditions were not as controlled as yours. I did 3 runs on the same 30 mile loop of suburban roads (not flat, light traffic, and quite a few stop lights), attempting to measure the effect of driving style on mileage. This was with an Altima, but the Camry ought to be very similar.

The first run, I attempted to sustain EV as long as possible, e.g. letting the car slow down on slight rises, but keeping the speed in the 35-40mph range. I accelerated cautiously, but not slowly enough to stay in EV mode. The battery state ranged from about 80% down to 20% (and back) for several cycles over the run. Result: 47.6mpg.

The second run, I attempted to sustain a fixed target speed (40mph) instead, and let the computer decide when to use EV mode. The actual average speed was slightly higher than the first run, since I didn't slow as often, but the two were pretty close. The battery state ranged from 80% down to about 50%, so the charge/discharge cycles were not as prolonged as the 1st run. Result: 46.8mpg.

For the third run, I drove "normally" for these road conditions (about 45mph, with faster starts, and no special attention to mileage). Result: 45.3mpg.

Now, while the 'sustained EV' run did in fact give the best mileage, it was still within the margin for error for these instruments (which I'd estimate at +/- 1mpg), so I don't think it contradicts your results.

The thing that struck me was how little effect driving style had, compared to other factors I've seen (trip length, speed, AC usage). I expect that the effect would have been more pronounced if I really pushed the car (jack-rabbit starts, sudden stops, higher speed on straight stretches), but almost any reasonably careful driving style did well.

Sorry, this isn't a rigorously controlled test either, but I don't think the data is entirely useless.