I read on one of the Prius sites, they recommend a faster acceleration and then roll along and the suggested speed for the best fuel economy. I was wondering if this would hold true for the TCH? I would think a longer slower acceleration would be better. (If permitted by traffic)

I would be interested in your thoughts and experiences.

Thanks in advance!


Bill

 

I've been wondering about that.

I have been using my MPG meter as an acceleration meter. That is when I am accelerating to speed on flat road in little or no traffic, I look at the MPG meter to judge how quickly I am accelerating. (Obviously, on hills it doesn't work. And in traffic the eyes need to be looking out the window.)

For a few tanks, I tried to keep it on 5, and got pretty decent mileage. For a couple tanks, I tried to keep in on 10, and got about the same. For a couple tanks, I tried to keep it on 20, and got shitty mileage. Using slow (20-mpg) acceleration, I have to accelerate almost all the way until the next time I have to stop for a red light, and I don't get hardly any coasting or steady-speed distance.

I think the best acceleration-rate probably depends on terrain, average distance-between-stoplights, traffic, and other variables. So there is probably not one best rate. But, keeping the MPG needle near 20 during accelerate-to-speed sure isn't it.

It would be nice if some engineers at Toyota could do some lab work and some modeling and figure this out. Then program the computer in the cruise control to use the best acceleration-rate. And, provide an easy-to-find throttle position (maybe some feedback, like a detent in the gas-pedal force) that also uses the good acceleration-rate. It might require some onboard computation... but it's not as if these cars don't have computers in them already.

While they're at it -- they could program the cruise control to slow down a little while going up hill, and speed up when going down hill. Limit the deviation from the assigned speed, of course, to maybe 3 mph. But notching down the speed while going up a small hill can use momentum to avoid starting the ICE, or avoid running it hard. And notching up the speed while going down a small hill can recover the average speed, and take advantage of the gravity.

 

Cruise control was designed (and perfected) over the last 15-20 years to maintain a constant speed, not to maximize fuel efficiency.
I imagine if you wanted to have engineers design it to operate at maximize fuel efficiency (aside from the increased expense to design it) many would complain when they notice their car speeding up and slowing down when they preferred (and expected) constant speed..
Not everyone is focused on fuel efficiency.
You can't please everyone.

As to the best acceleration technique, no one can replicate the driving conditions or variables experienced by another. The guy in San Diego driving 60 miles per trip would have different results from the gal in frigid upstate New York with 10 mile trips.
The best thing to do is personal experimentation.
Try two tanks with quick acceleration and two tanks without. See if there is a difference and post it.

 

I agree it would be interesting to hear from some of the Toyota engineers. I think this would be hard to measure over a tank of gas. I have two drivers with completely different driving styles, temperature changes and driving conditions. We live in Colorado with very few places where the roads are flat.

I know some of the Prius users have laptop connected to the cars computers gathering all types of information.

It would be interesting to hear from the pros!!

Bill

 

Good point Steve on the variable cruise control for the Hybrid. Perhaps where you could turn that added feature off or on. That was my first move to increasing my gas mileage back in the 80's. Usually slow the cruise 3 to 4 mph to the peak of the hill, then 3 to 4 mpg increase using the cruise on the way down the other side. I found over the years I do that almost without realizing i'm doing it.

In the 40's my dad said he owned a Chevrolet that had a throttle lock. If you locked it at 55 mph. Then the car would slow down to about 50 going up a hill. It would speed up to 60 going down the other side and level off back to 55.

The accelerator would be nice if they included a detent. Even one that would move some depending on start ups from a standing stop or when at highway speed but not using the cruise maybe due to traffic.

My wish is that Toyota or other will put some medium brightness led's in the speedometer area that would show green/yellow/red for how far the accelerator is being pressed. Stay out of the red and increase the gas mileage. I do this with the scan gauge on throttle position but you have to look at the digital number and not a easy to see color led.

 

Steve, I think the best acceleration-rate probably depends on terrain, average distance-between-stoplights, traffic, and other variables. So there is probably not one best rate. But, keeping the MPG needle near 20 during accelerate-to-speed sure isn't it.

You may be right about your particular need. Traffic, distance between lights so you can coast.

I use 20 but sometimes 15 and 10 on the mpg gauge depending of any traffic behind me when leaving a red light.

My wife and I drive up a long rather straight climb into the mountains near Ruidoso almost weekly to a restaurant. I found on the steeper grades the needle drops to 20 mpg as the rpm goes up to 3000 while climbing at a 50 mph.

I thought the mountain driving would kill my gas mileage. But no, what goes up comes down. The engine idles at about 995 rpm all the way back down. The car is coasting along at 60 to 70 miles per hour using very little fuel.

 

HyCAMBill — I have addressed this issue before (I don't recall offhand in which thread). The essence of the misconception about trip-average fuel consumption (FC) in L/100 km, or trip-average fuel economy (FE) in mpg, is to understand that time doesn't enter into these expressions at all — only distance travelled (in kilometers or miles) and volume of fuel used (in liters or gallons). So, speed of travel or time taken does not directly affect the FC or FE results.

If one looks at the mathematical expressions for trip-average FC and FE:

1. Trip-average FC in L/100 km = (liters of fuel used) / (hundreds of kilometers travelled)
2. Trip-average FE in mpg = (miles travelled) / (gallons of fuel used)

and asks whether they can be meaningfully related to instantaneous FC and FE respectively, one finds that only in cars with metric (L/100 km) instantaneous-FC readouts does a somewhat useful relationship exist for trip-average FC. [The reciprocal relationship of the FE measure to the actual fuel consumption is the reason for this.] One finds that:

1. Trip-average FC in L/100 km = distance-weighted average of the instantaneous FC in L/100 km. It is very important to note that this is the average calculated with respect to distance and not with respect to time. Thus, when estimating overall FC for a trip, it's not the time spent at a poor instantaneous FC that degrades the trip's FC the most, but rather the distance travelled at the poor instantaneous FC. For trip-average FE, the best that can be said is that:
2. Trip-average FE in mpg = volume-weighted average of the instantaneous FE in mpg. This latter is not a practically useful result, however (see below).

Let me attempt to illustrate these facts.

1. Metric example: Travelling 10 km at an instantaneous FC of 5 L/100 km (however long it takes; i.e., whatever your speed may be) uses 0.5 L of fuel. Travelling a further 10 km at 10 L/100 km (however long it takes) uses a further 1.0 L of fuel. This 10 + 10 = 20-km trip has used 0.5 + 1.0 = 1.5 L of fuel. The trip-average FC is thus 1.5/0.2 = 7.5 L/100 km, equal to the distance-weighted average of the individual FCs of 5 and 10 L/100 km of the two legs. [Since each leg in this example is of the same length (10 km), the trip-average FC in this case (50 + 100)/20 equals the simple average of the two instantaneous FC numbers: (5 + 10)/2 = 7.5 L/100 km.] The first section could have been undertaken at say 60 km/h, and the second section at say 120 km/h. The first leg would then have taken 10 minutes, and the second leg only 5 minutes. But these times are irrelevant to the overall-FC calculation, and the time average of the instantaneous FCs would have given (50 + 50)/15 = 6.67 L/100 km, the wrong result! The instantaneous-FC averaging must be with respect to distance and not time.
2. US example: Travelling 10 miles at 40 mpg (however long it takes; i.e., whatever your speed may be) is equivalent in fuel usage (namely, 0.25 gallon) to travelling 5 miles at 20 mpg (however long it takes). This 10 + 5 = 15-mile trip would have used 0.5 gallon of fuel, thus giving a trip FE of 15/0.5 = 30 mpg. This is equal to the volume-weighted average of the individual FEs (40 and 20 mpg) of the two legs. [Since each leg in this example used the same amount of fuel (0.25 gallon), the trip-average FE in this case (10 + 5)/0.5 equals the simple average of the two instantaneous FE numbers: (40 + 20)/2 = 30 mpg.] The first section could have been undertaken at say 40 miles per hour, and the second section at say 80 miles per hour. The first leg would then have taken 15 minutes, and the second leg only 3.75 minutes. But these times are irrelevant to the overall-FE calculation, and the time average of the instantaneous FEs would have given (600 + 75)/18.75 = 36 mpg, the wrong result! The instantaneous-FE averaging must be with respect to volume and not time.

It is difficult to deduce a strategy for optimizing the trip FE by using the instantaneous FE readout in mpg that is present in the US model TCH, since averaging with respect to time is fallacious, and averaging with respect to volume is not feasible in practice. Distance averaging is, however, feasible to apply in practice, at least approximately, and so the metric instantaneous FC readout in L/100 km that is present in the Canadian model TCH can be useful. Roughly speaking, a poor instantaneous FC is tolerable for a short distance, and hence it’s likely that brisk acceleration for relatively short distances is better for overall trip FC (and of course also for overall trip FE) than more moderate acceleration over long distances.

Those with a US TCH who also have a ScanGauge (SG) can access an instantaneous FC readout in L/100 km (LHK), for exploring what I’ve said above, by setting the units used by SG to liters and kilometers (instead of miles and gallons).

Stan

 

I have said that many times myself.......................

 

...but if one drives 15,000 miles very carefully per year and gets 37 MPG, he will end up using 405 gallons of gas. If another drives carelessly and gets only 35 MPG, he uses 428 gallons of gas.
The 23 gallon difference comes out to (@$3.25/gal) ~$75/year difference in fuel cost.
That's about $1.45 per week!
I say, live it up!
Accelerate in a fashion you feel comfortable.
If you feel lazy, go ahead, turn on cruise control.
If your freezing your butt off, go for it, turn on the heat!
If $2 a week is the difference between driving yourself crazy altering your driving habits and enjoying a comfortable ride, I say, skip a 'soy venti mocha latte with two pumps' every week and use the savings to cover your wreckless driving habits.
Life is very, very short...enjoy it!

(if you find that you are $1.45 short, reach under the seat and you'll probably find loose coins there!)

 

I tend to agree; my big savings are my overall 1/3 in gas costs going dow by moving to a more efficient car. Plus or minus a few bucks is not the plan.