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Hybrid Tips Optimizing mileage
Driving tips for getting the most mileage out of each tank of gas.
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As anyone can plainly see the Prius hybrid design is not optimized for hwy MPG. The Prius design is optimized for city slow, stop and go driving.
So the advantage of the design can be primarily shown by comparing city MPG figures with other cars of equivalent weight and loading capability.
The only real advantage the Prius design has is gained via recharging the batteries during braking or coastdown.
At a constant cruise speed on a level roadbed the batteries are not really used except to accelerate/(re-)gain speed and generally must be recharged using petro. Using petro to recharge the batteries results in an over-all net loss and therefore the cruise MPG advantage is non-existant.
If one were willing to disconnect the batteries and forego the "SuperCharging" supplied by the batteries in hwy use I have no doubt the Prius hwy MPG would improve substantially.
I think you are misreading what Wwest is saying. Wwest is saying that recharging the batteries while crusing is not really needed, because they are not being used normally during cruising. However in the current HSD design even during highway cruising the MG1 generator is contiually turing and contiunally charging batteries, that for the most part are probably alreay fully charge. What Wwest is saying and I very much agree that the continual charging is not needed and that the Prius would get even better highway mileage if it could be disabled. However because of the very nature of the CVT planetary differential transmission design, MG1 can not be disabled.
I never got the impression that Wwest was criticizing the mileage the Prius obtained or was he comparing it to other cars.
Let's say you could disable the MG1 and were able to then obtain an EPA rating of 60/55 wouldn't that 4 mpg gain on the highway be better ?
YMMV,
MidCow
Why does HSD need to recharge if it can route the electricity straight to MG2? The battery is recharged sometimes to power A/C, stereo, etc...
"If one were willing to disconnect the batteries and forego the "SuperCharging" supplied by the batteries in hwy use I have no doubt the Prius hwy MPG would improve substantially."
Incorrect premise comes to the wrong conclusion.
Dennis
The question is why would you want to? There is very little instances when MG1 should not be spinning. Most of the time MG1 needs to be spinning foward or backward to adjust optimal ICE output at a given speed. Stopping MG1 would mean ICE has to adjust RPM for a given speed, which would either reduce efficiency or power!
Dennis
The MG spinning is part of the CVT-Like function of the planetary gearset.
The way this is used to manage engine RPM/Load is one of the most mis-understood nuances of the HSD Design.
Let me try to give a generic example, with made up numbers.
The key is that the Atkinson Cycle engine is VERY efficient when it's in the right speed/load band, and less efficient when it's not.
One of the big reasons for normal ICE inefficiency is the need for the engine to work in a broad RPM band. Using a CVT you can keep the engine in it's sweet spot longer, which is a good thing.
So, the planetary gearset, using the MG, tries to keep the engine at it's prime speed/load point. That's cool, just like any CVT.
The real key to the added HSD efficiency is, when the MG is doing this, it can ALSO make use of the extra energy.
Made Up Example.
Let's say the ICE is at 27% efficiency at 3000 RPM and 37% efficiency at 4000RPM.
You could run it at 3000RPM, and get X mileage.
But, with the MG in the equation, it can let the ICE run at 4000 RPM, and take off the extra energy in the form of generated electricity.
The ICE can generate more energy than you need for immediate propulsion for the same fuel expenditure when it's running in the sweet spot, and the MG can recapture that extra efficiency for use later.
If you couldn't do that, you would be forced to run the engine at a less efficient load.
If need be, the MG can assist to 'spend' some of the energy it's accumulated then go back to generating.
It's truely ingenious, and makes the best use of the Atkinson engine characteristics (extreme efficiency, but only in a narrow power band).
That's one of the reasons it's also ideal for diesels, they have the same sort of power band tendencies that the Atkinson engines do.
If the HSD were designed so that the MG1 could be disabled when not needed then highway mpg would improve.
Think about how the solenoid on a convetional ICE start works. It would be a very easy modification to provide solenod engagement/diengagement of MG1 and get the highway mileage estimate up to 55 mpg A FOUR(4) MPG IMPROVEMENT ;
But then you would add another failure component to the HSD transmission .
YMMV,
MidCow
P.S. _ I find it very interesting that such statements as "especially for those that don't have engineering and/or automotive educations" come from those that obviously don't have engineering, mathematical or automotive educations.
P.S.S. - I appreciate your true "engineering" viewpoint.
Based on what? Smaller and lighter HCH(1.3L) manual tranny has the same 51 MPG EPA highway as Prius(1.5L).
Ever thought the other way around? Could it be that IMA is inefficient in the city? Could it be because Honda IMA(10kw) can only capture 1/5 regenerative energy of Prius(50KW)? Could it be that HCH does not take much advantage of electric superior efficiency at slow speed?
"If the HSD were designed so that the MG1 could be disabled when not needed then highway mpg would improve."
How can it be? What is your explanation? I'll give you a counter example. At 70mph, if you disable/stop MG1, the ICE has to spin 3,000 RPM instead of ICE 1,000 RPM with MG1 -6,500 RPM. You tell me if ICE 1,000 RPM is more efficient or at 3,000 RPM.
Dennis
I didn't mean to contradict Tempusvn's point. Another possible case at 70mph is ICE at 5,000 RPM with MG1 7500 RPM. The point is that, MG1 can adjust to whatever RPM that is the most suitable for the ICE at any given instance. MG1 at 0 RPM(disabled) is just one out of 20,000(-10,000 to +10,000) different possibilities.
Dennis
Let's say the ICE is at 27% efficiency at 3000 RPM and 37% efficiency at 4000RPM."
In reality, Atkinson ICE efficient band is very wide, about 80% is near peak efficiency.
"That's one of the reasons it's also ideal for diesels, they have the same sort of power band tendencies that the Atkinson engines do."
Diesel engines do have narrow RPM range but their torque curves are not very flat. For Atkinson flat torque, see below. Also, because diesel engines do not have spark plug, shut down/restart of heavier cylinder diesel ICE would be far more difficult. Another reason gasoline and electric synergize more than diesel with electric.
Dennis
Just needed to address that. It will never happen in Prius or other HSD cars. Overcharging the battery will damage it and shorten the life. As stated before, the electricity can also be routed to another motor and put it to work, instead of the battery.
Dennis
--Tip #1: Anticipate!
a) Redlights: I'll never understand people who race to the next stoplight only to sit there oblivious to the fact that the light has turned green. If you see a red light ahead, try coasting or timing it to keep up your momentum. The Prius coasts rather nicely.
b) Heavy traffic: If I'm stuck crawling in heavy traffic, I prefer slow & steady as opposed to stop & go. People see a little daylight in the traffic and they punch the gas only to have to hit the brake again seconds later. Studies have shown that this only worsens the bottleneck by creating a lag effect that ripples down the line.
c) Hills: If you see a hill coming up, accelerate before you get to the hill rather than when you're on the hill. I find this works for bicycles too
d) Other Drivers: Don't tailgate. Otherwise you're letting the guy ahead of you dictate your driving style (not to mention your blood pressure). A buffer zone lets you speed up when it's most efficient for you to do so, or remain coasting at a constant speed while he slows down, makes a turn, fumbles with his cell phone, etc..
Results...51 mpg on 5200 miles. Love that Prius!
I just got back from a trip to NYC, total round trip of 306 miles with 4 adults in the car. I set the cruise control at 65 and by the time I arrived at NY the display had 54.5 MPG.
On the return I set the cruise control at 70 and the display at the end of the trip shows 53.2
I have 8777 miles on the car and my mileage just gets better with every passing month.
My record is from Harrisburg PA to Philadelphia where I got 57.8 MPG. My speed was between 65 and 70 but I did have some tail wind.
It's my short trips that bring down my mileage. My average is 8777 miles and 180.9 gallons of gas for lifetime MPG of 48.518.
Using battery as little as possible will also prolong the life of the battery since you are saving the recharge cycles.
Dennis
Accelerate as gradually as practically possible.
--This would seem to make sense, but the efficiency of the engine varies with load (or so I'm told). With this said, it might actually be better to accelerate smoothly and briskly up to cruising speed --kind of a happy medium between a snail's pace and a jackrabbits.
--Also, I noticed you didn't reach 50 mph over the 1/2 mile course with your slow acceleration test. A car traveling at 50 mph vs. one traveling at 42 mph has more momentum. To be fair, your tests should all have reached the 1/2 mile mark at the same speed, say 40 mph.
--Furthermore, I'm not sure that what's good for the Civic in terms of acceleration is necessarily good for the Prius given their different propulsion systems. A Prius accelerating briskly to 40 mph and then holding that speed over a flat half mile may very well run on battery alone without engine assist to pull the vehicle forward. In that case, the consumption monitor would max out at 99.9 mpg for the better part of the test course.
--I suppose you'll have to let your gas tank do the voting as to which technique is better.
Even though in jest, every thing that can be done to lower the CD ( Coefficient of Drag) will imporve the mileage. The jest was someone recommneded removing the antenna ; actually this would help but only ever so slightly. Some hybrids such as the Prius already have a low CD ; the Prius is only 0.26
(1) Keep your car washed and waxed. This will help a lot more.
(2) Use rain-x on your windshield.
(3) Keep you speed a low as you can stand. Air resistance goes up squared compared to you speed. That means if you double( 2 times) your speed , your wind resistance will quadruple (4 times).
(4) buy a manual shift car if you have a choice: you will get better economy and better acceleration. For best economy up-shift to the next gear at the lowest RPM that does not tax or lug the engine, usually around 1,500-2,000 rpm.
(4) Is the most dramtic improvement. But only 10% of the people shift and some cars don't come with a manual transmission.
(3) Is probably the most Controllable, dramatic improvement. If you can keep you miles per hour at 55 you will save a lot of gas; remember when 55 mph was the national speed limit and all car speedometers had 55 mph highlighted in a different color ?
YMMV,
MidCow
--Big whoop: so you fill up once every 250+ miles rather than once every 500 miles. Where do you live that you have to go out of your way to find a gas station? If you have trouble getting to one of those elusive oases, then by all means fill 'er up. It's not a mandate --simply a suggestion for those eager to eke out every last drop of fuel efficiency.
How about unscrewing the antenna to save on drag?
--Go ahead, knock yourself out. It's a free country.
This economizing can be obsessive where does it end?
--It ends where you want it to end. That's called freedom of choice. If someone wants to save a gallon (or an eye-dropper) of gas/year by reducing vehicle weight, by removing the antenna, by washing off the wind resistive bird doo-doo, etc., what do I care? Doesn't hurt me. Doesn't upset me. In fact, if everyone saved just a little, the world would save hundreds of millions of gallons a year. And that's good for everybody ('cept maybe OPEC).
--Ahhh, so that's where the Honda Insight designers got the idea of removing the rear seats.
2) if you are driving a honda civic hybrid, pay attention as to how the auto stop works. you must first exceed 20 mph for it to be ready to work, and then go through a slew of requirements before it actually activates. when you are at a stop, the rev counter drops to 0, and auto stop flashes a green dot, don't push the brake down all the way to the floor or anywhere close to it, because sufficient brake vacuum pressure is one of the requirements for the auto stop feature to work. stay in gear and don't take your foot off the brake - once you do, the engine will start back up again.
3) when braking, start braking much much earlier than when you are in a normal gasoline car. just tap the brake down, barely holding it down, and the regenerative braking should kick in, giving the full charging status. this way, you maximize how much power you can recover from excess kinetic energy.
4) when accelerating on a non or low incline, don't floor it. try to keep the gas pedal reasonably down - you might even want to hold the car at the "between" point where the electric motor is neither assisting, nor the batteries are charging either - only the gas engine is working.
5) if you have time to spare, don't speed. what i usually do is leave earlier. if i have to travel on the highway, then i'll take my time, reaching 65 on the uphills, and coasting down them to around 55, then accelerating to 65 again - this way i cycle the battery's charge. some may argue that holding the car at a constant 65 with the cruise control will yield better mileage - but whatever works with you. i find that cruise control drains the battery more than it recharges(i.e. assists during uphills, but doesn't charge much during downhills), but whatever floats your boat.
6) this only applies to the civic hybrid. if its hot and you're sitting in traffic, or stop and go, don't use the a/c because..that just uses more gas. open the windows, or the fan or both and you'll save some gas.
7) unload your car. don't carry unnecessary things, because extra weight, although not much of a factor in gas mileage unless you carry reaLLY heavy things, can compromise handling, stopping time/distance, acceleration, etc as well.
8) if there are multiple routes to a place where you go to often (i.e. highway or local roads), use your trip computer to record the mpg of each route (3x each route if you want to be really sure). then, factor in the distance of each route - is the mpg difference make a difference if it is actually a longer distance? decide, and then stick to that route.
Leave the house at 4:30PM and begin my 45mile drive into the city of Atlanta. 90% of the traffic is headed out of the city.
I travel an extremely hilly 45 & 50MPH limit country road for 20 miles to the interstate.
Speed on this road is between 43 and about 60.
If there is someone behind me at a good distance nicely driving along then fine. If an aggressive driver gets behind then I find a place to let pass without wrecking my MPG such as hilltop or extended turning lane. I know where all these places are.
I could jump right onto the same freeway 2 miles from my house and gain 10 minutes but loose 10MPG.
If I MUST use this the limit is 70. I travel in the right lane going 62-75, about the same as large trucks.
So 20 miles from my house I jump on the 65 limit freeway for 7 miles.
MPG at this point is typically about 53MPG.
The rest of the trip is variable down hill.
On the freeway I'm always in the right lane except on occasion to pass a slow driver. Speed is 60-70MPH.
After about 7 miles the limit changes to 55.
At this point my average MPG is about 56.
I reduce speed to 53-60, still occasionally passing slow drivers. (They usually have cruise control set to speed limit)
43 miles from my home I exit into one of the worst Atlanta side traffic at 5:10PM.
I park in my space just after 5:30 and the trip typically averages 61 to 65MPG.
I leave work at 2AM and take the same route home.
MPG typically averages 59-63MPG upon arrival.
Since I've been maximizing my MPG I've only encountered 3 pushy drivers which I let by. But it also seemed that anybody who got in their way was victim as well.
Given these results, is my MPG typical? NO. Is it possible and duplicatable? Yes, by some.
The fantastic MPG I acheive is not due to one or two things but a series. Driving style is a major player but the combo of fuel saving designs in the car play the other part.
Remember I have a CVT, so the HX would also have to be an AT.
"The Civic HX Coupe is an excellent combination of performance and efficiency. Its 1.7-liter, 117-hp VTEC® lean-burn engine is one of the most fuel-efficient around. With its standard manual transmission, the HX Coupe gets an incredible 36 mpg city/44 mpg highway. You also get power mirrors and door locks, an AM/FM/CD audio system with 4 speakers, cruise control and a tachometer. There's an available continuously variable transmission (CVT) and, like all Civics, the HX is rated as an Ultra-Low-Emission Vehicle (ULEV).
Manual Transmission: $13,710.00
Manual Transmission with Front Side Airbags: $13,960.00
Continuously Variable Transmission (CVT): $14,710.00
Continuously Variable Transmission (CVT) with Front Side Airbags: $14,960.00"
I'm sure with careful driving you can get well past the 44MPG but not better than 60.
It still lacks an electric assist among other MPG devices and only seats 2. If my needs were a coup I'd go for an Insight.
I know how much more expensive the Insight is but I'm not talking a cheap ride here: mainly fuel consumption.
Many Insight owners drive carefully and get better than 90MPG.
BTW I made a funny HCH/Prius animation, Crank the volume! Don't miss it:
http://www.steve-dez.us/3d/content/hybrid/movie/pj2.wmv
(Windows Media 3.6MB)
http://www.steve-dez.us/3d/content/hybrid/movie/pj2.mpg
(MPEG 6mb)
Don't forget that HX weighs less than HCH.
Don't take me wrong, I embrace the technology. But, I think Hybrid technology is still the wrong way to go. If we insist on having internal combustion engines, I think running a diesel on used corn oil or biodiesel is a better alternative. Either of the fuels are renewable. Hybrids only relocate the pollution to other areas. To make the NiMH batteries you have to use some sort of energy, as well as they are a recycling nightmare. To charge the batteries you have to use up energy as well. It is not like the battiries charge them selves.
Yes, raising corn to make corn oil and ethanol requires energy as well, but these are renewable sources. This is in effect solar energy, CO2 in the air is converted into strach by the plants while releasing O2 with help of solar energy, and use water. Then we harvest the corn or soy or cotton or whatever Crisco is made of, use the product for consumtion or animal feed, and then take the by product, oil, and use it to run cars. Same with ethanol, starch source is processed by smiple bacteria and then refined into ethanol. Once again, it is renewable and uses free energy of the sun.
Can you imagine how well off farmers will be if we switched to renewable sources of energy. And how uncomfortable oil tycoons will be.
How is that any different from the lead-acid battery recycling that takes place everyday... except for the fact that the NiMH modules are smaller and easier to handle?
> To charge the batteries you have to use up energy as well.
NON-ISSUE! That energy is already accounted for in the gas.
> Can you imagine how well off farmers will be if we switched to renewable sources of energy
Ethanol programs are already in place in some of the Midwest and people are already using that ethanol in their vehicles. Imagination is not necessary.
JOHN
How is that any different from the lead-acid battery recycling that takes place everyday... except for the fact that the NiMH modules are smaller and easier to handle?
Lead can be melted and acid recovered, but the point is that we will be adding to the problem.
To charge the batteries you have to use up energy as well.
NON-ISSUE! That energy is already accounted for in the gas.
The energy is not free, yes, regenerative energy is "cheaper", but it is not the major portion of the recharging cycle. Here is the scenario, you get the new hybrid, and lets say it is not charged. The car will run in "gasoline only" mode to charge the batteries. So, you have the gas engine lugging the car and dead batteries around and you are telling me that this energy is free? No, it is not.
The benefit of Hybrid comes from higher efficiency of electric motor (about 80%), as oppposed to Internal combustion engine's efficiency (30-45%). So, theoretically, pure elctric cars would benefit the world more, but problem is that you still have to charge the batteries, which requires energy. Electricity has to be produced at the power plant. Hydroelectric is probably the most environmentally safe way. But, unfortunatley alot of electricity is still produced by burning coal or tar. By charging batteries at home, you are just relocating the pollution to where the power plant is.
Can you imagine how well off farmers will be if we switched to renewable sources of energy
Ethanol programs are already in place in some of the Midwest and people are already using that ethanol in their vehicles. Imagination is not necessary.
JOHN
I think you are referring to the 10% ethanol Gasahol used in some states. I am not aware of vehicles running on pure ethanol at this point.
Now I am often riding without the compressor on and the venting is still cool. Seems to be cooler air than other cars venting- my imagination or is this because, perhaps a smaller engine, less heat, vents are further away from engine compartment, etc?
Ron
Ah, that explains it. You are under a MISCONCEPTION.
The forced type of charging only applies to mild hybrids.
There is NO SUCH THING as "gasoline only" mode in a full hybrid. 100% of the time the engine is providing thrust to the wheels it is also creating electricity. So there is ALWAYS a benefit from the greater efficiency of electric, enough to provide an overall reduced loss. In other words, it is still more efficient than a gas engine alone.
JOHN
JOHN
If HSD is vastly more efficient than IMA then why are a large number of actual hybrid owners of all types reporting that Prius is about the same MPG given it's more complex than IMA, and pushing about the same size and weight vehicle?
http://www.greenhybrid.com/compare/mileage/index.php
And since the comparison I contributed to was between HSD and traditional, you're interjection with IMA requires some explanation...
Nonetheless, I find the combining Manual & CVT data (the link you provided) very very misleading for your discussion of IMA verses HSD, since IMA-Manual verses IMA-CVT is an extreme in itself.
Choose a topic.
JOHN
Sorry John, I miss-spoke there.
What I meant was that I don't think there is great differences in actual MPG efficiency between the two.....given that IMA and HSD uses the different cycles indicated.
And you are right, the database mentioned gives a diversified comparison.
Not according to my energy display. Sometimes I see the ICE just powering the wheels, no arrow to the battery.
Ron
Did I mention battery? No.
I said "creating electricity".
Notice that other arrow. It's the one I keep pointing out as the a key difference between mild & full hybrids. Shocking, eh?
JOHN