Factors affecting MPG

Sorry about helping to hijack the thread.

 

I've only read the general conclusion presented by the studies - that DRL lower collision rates. I trust they did the obviously correct thing and controlled for your dawn/dusk concern.

 

Wasn't DRL a show on MTV sometime ago?

Why are we still talking about it and what was it about that show that would increase or decrease my safety?
Did they even receive the show in Norway and Canada? Or did they get a different version of DRL with local substitutes for Carson Dailey?

Would my mileage be better if I watched DVD's of the DRL show while driving?:noidea::noidea:

 

Aces Rules for Improving FE:
1) Get the Prius in best FE Shape by:
a) 5W-30 oil @ 1/4" below the Full mark (Check after dealer oil changes!)
b) Tire pressure - I use 42psi Front/40psi Rear
c) Install an EBH, & plug it in 3 hrs before driving (use a timer)
d) Don't carry unneeded extra weight. Avoid Roof Racks.
2) Get yourself in best shape for driving by:
a) Leave with plenty of time to get to your destination - no stress.
b) Wear clothing that will reduce the need to run AC or Heat.
c) Wear shoes that let you feel subtle differences in gas pedal pressure.
3) Drive the best route by:
a) Avoiding hills (as long as you aren't increasing your distance too much)
b) Pick roads where it's okay to drive slower - Multi-lane & residential roads.
c) Avoid the freeway.
4) Avoid using accessories UNLESS NEEDED like:
a) AC is a big one to avoid. You can use the climate controls on the MFD to run defrost w/o AC. But if you use the button on the steering wheel, it will automatically put AC on.
b) heater will also force more running of the ICE. (But be sure you aren't driving w/fogged up windows either.)
c) Anything electrical will have some effect on FE. But you still need it to be fun to drive. Find your own balance on this.
d) Cruise control tends to cause worse FE then pulse & Glide. But it will help you to keep your speed down. If you find you tend to drive 5+ mph over the limit, then use it; (set to at the limit).
5) Driving techniques:
a) Time the lights. If you commute the same way, you'll get pretty good at knowing which lights you can make and which ones you won't.
b) If you know you'll need to stop, slow down as drawn out as you can. Remember - the brakes don't regenerate. But coasting does.
c) Keep your speed below 42 mph if possible.
d) Pulse & Glide. If traffic won't allow it, just keep your high & lows close together.
e) Keep an eye on the consumption screen. You will soon learn when the ICE is running and when it's not. I like this screen because just a glance out of the corner of my eye will tell me if I'm 99.9 mpg or not. But remember, Safety First! If checking the display seems distracting... it probably is for you. If you learn to feel the ICE kick on through your foot on the gas pedal, you won't need to look at the MFD. So this is best done in calm driving conditions.
6) Keep reading these forums for new ideas And for support.
Have fun, & be safe out there.
-Kevin

 

Great list Kevin. I learn something about how to save fuel with my Prius almost every day it seems. For example, until I read your post I was under the impression that the Prius brakes generated electricity to the battery. Even though I do try to drive like I have no brakes, I now know that I will be able to save more fuel becasue I will concentrate even harder to stay off my brakes and anticipate stops.

I do have one other area that is confusing me quite a bit. Acceleration rates. I don't have any confidence about how hard to accelerate in any given situation. I used to accelerate very very slowly all the time trying to use the electric only. That strategy does not work and so now I am accelerating briskly. But I would like a better strategy than "accelerate briskly". Also the related area of hill climbing is an issue for me. I live in a hilly area and I'm always climbing hills wondering whether I could change my technique to get the best FE possible.

 

I have a 2007 Prius and love it. I will say that there is a large miss-understanding with new Prius owners between City and HWY expectations as it relates to MPG. I will try to give you some of my experiences with that may help you better understand what you may be encountering or an idea of how to look at it differently as you continue to work towards better MPG.

1. Winter/Temp does effect MPH. I Have noted that once the temperature rises above about 50deg F. My MPH will increase significantly. I drive mostly HWY miles. Out of each 160mile trip only 16 are non-highway. The highway miles are that of the the NY LIE on Long Island. My average from mid spring to mid fall is between 52 and 56 MPG over 450-500 miles. In the Winter my MPG drops to about 48 -50 on the same trips. I might need to play with tire pressure a bit more to help.

2. As noted above my driving is mostly highway. If I even make one trip of say 5-10 miles to the stores locally, I will drop my mpg by 2-4mpg.

3. City driving. Most think of this as other than highway. It is not. My personal opinion. City driving is the perfect environment. Flat roads. Traffic lights all synchronized. If you can keep the car running on flat ground with no stops and maintain a speed less than 30 MPH... you can stay in elec mode.

3. Terrain. Well, you live in upstate NY. I have been there a few times. There are hills and hills kill your MPG no way around it unless you are willing to be the guy everyone wants to pass going up the hills. While you hope to make it back on the other side of the hill it will never be equal.

That is my take on PRIUS theory for us operating here in the NE. To speak to your test with the dealer. It is difficult. The gas pedal in the prius is EXTREMELY sensitive. The slightest touch different causes some of the conditions you note. Add in there is some sort of brain (computer) running the car and, well... you get what you get. Your MPG that you quote sounds in line with what I have encountered.

I will leave you with one other operating trick I have been playing with as I stare at the info screen doing 65 in the HOV on the LIE. Don't be too afraid to use the gas to get up to speed (Works on HWY... not so well on the around town side). Once you are at your speed.... come completely off the gas and then just touch the gas pedal with your toe. Elec. will kick back in and depending on the terrain you should be able to see 54 and up on level ground.

Hope this helps some.

 

Some people on PC have tried to describe and quantify "accelerating briskly" based on a ratio between instantaneous fuel consumption and velocity or something like that. I never understood it, because the are talking in American units and my MFD is in metric 'cause I'm in Canada, eh. I'm to lazy and dumb to convert.

Others have a Canview and/or scangauge and they can see the engine RPMs and use that based on experience. I forget the rpm band that they say is best, sorry.

I don't think you have to worry too much about it. Accelerating briskly but not flooring it is probably close enough. But don't do that if you will probably have to stop ahead. The trick to getting good mileage is to avoid decelerating.

Lastly, how fast you accelerate is not so important according to the world record holding Prius hypermilers in Japan. They rationalize it like this: the faster you accelerate the less time you accelerate so it's mostly a wash. You'll find that quote on PC somewhere I'm sure.

 

Fibb222,

The prefered band for accelerating is ~1800 - 2400 RPMs. From watching
my ScanGuage, I am in this band If I keep up with "typical" folks leaving a
stop. Let the lead foots scream ahead, if you're on a familiar route and
have a sense for light timing, you'll see them stopped at the next light.

Generally, I lag just a bit so I can allow the car in front to move out, and
gradually leave 100 ft. or so as a tactical buffer zone to use for Driving
Without Brakes, DWB.

Hope this helps.

 

I am beginning to understand that the highest FE is achieved by striving to keep away from driving techniques that cause the ICE to charge the battery AND that cause the Battery Pack to propel the vehicle - with notable exceptions of course when both actions are necessary - and some where it does make sense to vary from this. My understanding - and I will defer to the many others far more knowledgable than I - is that when you use battery to drive the vehicle you are ultimately going to have to charge that battery and often (not always) that means running the ICE to do the charging. If you have a long downhill run to recharge then yes - this makes sense - but if not you end up hurting your FE on average - not helping it - by overusing the battery to propel the vehicle. This took me a long time to get into my little pea brain - and i could still have some misconceptions about it - but I am convinced that I was operating with a major misconception when I believed that using the battery for propulsion was the goal. My FE has improved greatly since I started trying to keep the battery pack just a little above 50% all the time with a narrow range of variance. I try to accelerate as much as possible with no arrows going to or from the battery. I try to glide as much as possible and anticipate stops so I can stay off the brakes. It is hard in the cold and in the mountains - but I have not had a tank below 50mph in a while and I had one at 56 recently. I am optomistic that I can achieve 60mpg if I keep reading and learning and practicing. Its not as simple as it first appears.

Thanks for the input in acceleration rate. Very helpful. I often have long hill climbs around here and I have a lot of time to experiment - I don't have a gauge but lately I have been using the consumption screen and watching how the instantaneous mpg readout varies with speed. But I think I could benefit quite a bit if I had an rpm read out. Seems like that ought to be a standard feature on a Prius, no?

 

OK, heres my two cents on the DRL thing. If it is daytime, and you have sunglasses on, plus you have window tinting, it might just be as dark as dusk or dawn. Here in Kelly-fornia, when it rains, you MUST turn on your headlights. My 2005 prius does NOT have DRL's. It does have HID's and I wish it did have some kind of DRL (especially for the OTHER driver with tint and sunglasses on). So we HAVE to turn on the headlights when it is raining. Now picture how dark some of the window tinting jobs are then add sunglasses and you can pretty much create dusk or dawn driving conditions just by looking through different windows of the tinted car.

My car averages 48 to 50 MPG all the time. My commute is mostly freeway at 58 to 62 MPH with cruise control on. I always use the AC on automatic climate control when I need to. We just passed the 100,000 mile mark and the car is getting the same mileage it always has. I learned that the best way to increase fuel efficiency is to slow down, check air pressure in the tires, and use the brakes sparingly when needed. I have used Mobil One since the first oil change. I fill the engine with oil up to the line on the dipstick...good luck to you in your mileage quest.

I think that DRL's help cars stand out during the daytime. Especially when the other drivers are wearing really dark sunglasses and looking through their tinted windows. We do not have tinted windows. Having tinted windows is like wearing sunglasses at night when you cannot take them off. I have considered adding tint but have never done it. A friend was pulled over by a CHP and ticketed for too dark tint. The officer asked him, why would you wear sunglasses at night. He removed the tint, cleared the fix-it ticket, and promptly had it added agian...DOH!

anyway...back to work...

 

If you're interested in commenting on the Daytime Running Light issue, please
do so on this thread:

http://priuschat.com/forums/prius-m...ning-lights-drl-effective-not.html#post732370

By your so doing, both these topics can be discussed separately on their own
merits.

I have done this because for reasons I do not know, the Mods are unable or
unwilling to split this thread into two.

Thank you very much.

 

HI there I am a new Prius owner. I don't think I am getting the mileage that I should be and I tried the to get the pdf article that tells you how to get better mileage and I couldn't get it. I am running Windows 95 still so that might have something to do with it. I am disappointed with the mileage as two of the Prius' that I test drove had over 1100 km on they and still had 2 tenths of a tank left. I am trying to improve the mileage by changing the way I drive but still not great mileage. Can anyone forward me the article so I can look at it and try some of the suggestions.
Thanks

 

Using electric decreases your overall mileage. If you use too much, you force the car to WASTE GAS charging the battery up. Charging the battery from the engine is EXTREMELY inefficient.

Also, other factors that factor into your parkinglot cruise is what stage the car is in. If its not in stage 4, any low-speed drive will destroy your mpg.

 

Thank you for the information you posted. I think it will help my driving as I have been doing a slow acceleration and trying to use the battery pack to drive the car. What is an FE?
ecogrw

 

Good to see you've seen the light.

FE is just an acronym for Fuel Economy.

 

So is it correct to infer from this that 1800 - 2400 is a good rpm band to to stay in on a long moderate or steep climb? As distinguished from a typical acceleration from a stop light on fairly level terrain? We have many climbs around here that go on for miles.

 

rpg51,

Good question...

The two short answers: Not exactly, and Maybe. And the rest of the story...
(I'm discounting the use of a ScanGauge, CanView, etc.)

It is meaningful that you have separated accelerating from a stop in traffic
from accelerating while moving on the open road. This means to me that
you recognize the nearly infinite number of driving situations, for which any
specific recommendation cannot universally apply. My thoughts on this one
specific case; going up a long hill:

The big questions are:
* What do I want my energy inventory to look like at the top of the incline?
* What should/can I do to try to get it?
* Can this be done safely?

Three reminders:
* Ultimately, all the energy that the car has at any time is the result of
burning gas.
* The most efficient way to use gas is to turn the wheels directly, without
going through one or more conversion process, from gas to
motor/generator(s) and either to the wheels or HV battery.
* At any given time the car has four different kinds of energy in its energy
inventory: chemical (gas in the tank), electrical (in the HV battery), kenetic
(a function of its velocity), and potential (a function of it elevation relative
to some arbitrary point, usually the place from which you started). The HSD
manages the first two, with some leeway in its algorythms for responding to
driver initiated requests. Awareness and use of the latter two in conjunction
with the HSD are the sole province of the Driver-Energy Manager.

OK, what's the desired state at the top of the incline?
Simply put, safely maintain as much fuel in the tank as possible.

How do I do achieve that state?
Burn fuel as efficiently as possible. Use the other three forms of energy as
needed or as the HSD will let me to maintain a safe speed.

Can it be done safely?
On a public road with others, I feel that I need to maintain a safe speed
which does not unnecessarily impede or disrupt the flow of traffic. Not more
than the speed limit, rarely less than 10 MPH below the speed limit. This is a
judgement call wholly dependent on the conditions at the time and place--
that's all I can say on that, YMMV.

Ideally, you should proceed up the incline burning only just enough gas to
maintain your safe speed, with no orange arrows coming out of
the Engine on the Energy Monitor screen and going to the Elec.
Motor/generator. But this is very difficult, if not impossible to do as this
trade off is the heart and soul of the HSD system. The computer is fiddling
energy flow in nanosecond intervals, and well, it's virtually out of your control.

Realistically, you should proceed up the incline using just enough gas to
maintain your safe speed with no yellow arrows going into or out of the HV
battery. This you do have some control over. How much depends on the
State of Charge, SOC, in the HV battery, and how finely you can modulate
pressure on the go-pedal to get the desired micro-adjustment needed.

There is a way to fiddle the go-pedal to minimize electrical flow, yellow
arrows, into and out of the HV battery when accelerating. I call it the Snake
Game, and you'll find it in post #4 in this thread:

http://priuschat.com/forums/fuel-ec...st599391.html?highlight=snake+game#post599391

And what about the right RPMs to use: Well, it may be in the 1800-2400 RPM
range, it may not. Since you have to be mindful of maintaining a safe speed,
this whole best case scenario may go flying out the window as you use HV
battery power, and finally 3000 up to 5000 RPMs to "keep up." I think it was
Gen. George Patton who said something like, "No battle plan survives first
contact with the enemy unchanged." (Or was it Pres. A. Lincoln?)

So you have to be attentive and flexible. Have a plan, follow it as long as
you're able, identify and accept inevitabilities, minimize losses, live to fight
another day or on the next hill.

Going up a long hill I monitor my speed, and play the Snake Game for as
long as I can. I don't look at my ScanGauge or the iMPG readout on the
Energy monitor. What good would looking at them or anything else do? If I
can't maintain my safe speed or higher with the Snake Game, FE/MPGs goes
by the wayside; you have to step on the gas. Safety first, last, and in the middle.

As to how to gain the most energy going down the other side of the hill,
well, that's another story, best saved for another day/thread.

One Driver-Energy Manager's point of view... Hope this helps.

 

Managing hills - Avoid using the accelerator while climbing a hill: If you see a smallish hill ahead, speed up while you are still on the flat or the less steep part (when it's less work for the engine). While going up the hill reduce your acceleration down so that you are mostly coasting up the hill. Your speed will drop a lot as you go up. If you are expecting to go down a hill on the other side, try managing it so that you are cresting the hill with a speed somewhat under the speed limit. Glide down the other side, letting gravity bring you back up to speed. Adjust as required.

Be careful when doing this - don't take stupid risks or speed too much before the hill.

 

Great stuff guys. I guess I'm making progress if I'm asking good questions, eh? I live in a very hilly area by comparison to the average member here and it colors everything. I have to take the concepts I learn and adapt them to my situation. Also, I have to lower my expectations a bit.

Most of the hills are big and long. Of course, we also have big and long downhills. But we go up and down a lot of big long hills around here. In fact, its rare we drive on flat terrain. It is usually next to impossible to get up the average hill we face at a safe speed without using the accelerator. I think the single most important thing I can do for my FE is to learn how to go up and down big hills in the most efficient way consistent with safe driving.

I also have cold weather - that is a whole 'nuther issue. I have a blocked grill and a EBH which is making a world of differene.