Acceleration question?
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 |
Re: Acceleration question?
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. |
Re: Acceleration question?
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. |
Re: Acceleration question?
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 |
Re: Acceleration question?
Originally Posted by SteveHansen
(Post 166068)
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 miles per hour. 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. 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. |
Re: Acceleration question?
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. |
Re: Acceleration question?
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:
Let me attempt to illustrate these facts.
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 |
Re: Acceleration question?
Originally Posted by SPL
(Post 166460)
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:
Let me attempt to illustrate these facts.
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 |
Re: Acceleration question?
...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!) |
Re: Acceleration question?
Originally Posted by haroldo
(Post 166476)
...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!) |
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