Hypermiling: A new hobby for gas savers & environmentali

Our "pub" where you can post about things completely Off Topic or about non-silent PC issues.

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Post by AZBrandon » Tue May 27, 2008 7:13 am

Cistron wrote:Oh sorry, I just typed in gallon on google. I'm not used to any non-metric units at all.

I think Neil has mixed it up as well ;)
No problem. To be perfectly honest, I wish America would just bite the bullet and make the changeover to metric. Of course, the aviation and marine world use Knots / Nautical Miles still, but they are a far smaller faction than the general public which is used to miles / pounds / gallons, etc. instead of meters, grams, and liters.

Metric is so much more elegant, I love how things line up, like the stunning revalation I had when I realized that a liter of water is a both a thousand cubic centimeters as well as a thousand grams of water. It's brilliant, we need to be using metric for everything!

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Post by NeilBlanchard » Sun Jun 15, 2008 11:33 am

Hey folks,

There are two major things you can do to improve your fuel mileage:

1) Inflate your tires to an optimum pressure-- this is probably somewhere between the recommended pressure (usually found on a sticker on one of the door jambs, or in the manual) and the maximum recommend on the sidewall of your tires. Doing this can lower the rolling resistance, and help you coast farther (see below) and uses less fuel to maintain a given speed.

An example of this is on my Scion xA, the recommended pressure is just 29psi, and the sidewall max is 44psi. I have found that 38-39psi is best: it coasts very well, and I don't lose any traction.

2) Drive as if you do not have any brakes. This means accelerate gently, anticipate your stops, and use one of two methods of coasting as often as possible. The first type of coasting is meant to let you coast as far as possible on as many hills and slopes as you can -- eat the "road candy"! On standard shifts, you should put the car in neutral and take your foot off the accelerator. On automatic shifts, you can also put the car into neutral and/or take your foot off the accelerator. Use your experience with familiar roads and traffic conditions to optimize your approach to stops; using your brakes only at the end of your coasting.

The second type is for when you need to stop anyway: downshift to a lower gear and use the engine to brake the vehicle. This shuts off the fuel (on most cars), so instead of wasting the energy as heat (from the brakes), you can stop using any fuel (while idling the engine and using the brakes).

For more driving tips and for other methods of conserving fuel, you can visit:

http://ecomodder.com/

Here's a direct link to their 105 driving tips:

http://ecomodder.com/forum/EM-hypermili ... riving.php

As an example of how these sorts of things help your efficiency: driving my Scion xA, I have 3+ year average of just over 37mpg (EPA rates it at 30mpg Combined), and my past 90 day average is 40.1mpg, while my 3 most recent tankfuls I have averaged almost 45mpg!

Here's a thread where I show the aerodynamic mods I have used to help achieve this:

http://ecomodder.com/forum/showthread.p ... -2969.html

If you are interested, you can buy a gage for $150 that plugs into the diagnostic plug (on all vehicles after 1996), that can display all sorts of information like instant fuel mileage, coolant temperature, etc.

http://ecomodder.com/forum/showthread.p ... -2469.html

Low rolling resistance (LRR) helps mostly at lower speeds; say below 40mph. Above this, aerodynamic drag become much more significant. (Drag goes up by the SQUARE of the speed!) So, limit your highway speeds to 55mph -- this speed has almost half the drag as driving at 75mph. Go slow and steady -- and gently. Learn how to coast, and to anticipate stops -- especially in stop and go traffic: let space open up ahead of you, and gage your speed so you can avoid stopping. This will actually help the overall flow of traffic as well!

Keep track of your mileage. Pump up your tires, and practice your driving techniques to gain as much as you can from the fuel you use.
Last edited by NeilBlanchard on Sun Jun 15, 2008 5:50 pm, edited 1 time in total.

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Post by zoob » Sun Jun 15, 2008 12:50 pm

Catching up on my newspapers, I saw an article in yesterday's Toronto Star.

Hypermiling: the extreme way to save gas

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Post by wim » Mon Jun 16, 2008 5:38 pm

NeilBlanchard wrote:The first type of coasting is meant to let you coast as far as possible on as many hills and slopes as you can -- eat the "road candy"! On standard shifts, you should put the car in neutral and take your foot off the accelerator. ... The second type is for when you need to stop anyway: downshift to a lower gear and use the engine to brake the vehicle. This shuts off the fuel (on most cars), so instead of wasting the energy as heat (from the brakes), you can stop using any fuel (while idling the engine and using the brakes).
now i'm confused, these two statements seem to contradict .. if you are able at anytime to coast downhill in gear, isn't that better than putting into neutral (which uses fuel as the engine is idling)

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Post by NeilBlanchard » Mon Jun 16, 2008 7:30 pm

Hello,

If you can coast farther (if the road allows you to) then getting the distance is better. If you have to stop, then coast in gear, and get the fuel savings.

IOW, if you can coast a mile in neutral (which I do all the time), then that is a much better average than the 100 yards or so that a down shifted coast can muster. A little fuel to go a long way is better than no fuel for a short way -- because you then have to use the engine to move the car to make up the difference. Geddit?

The crazy hypermilers do what they have dubbed EOC aka engine off coasting, so they get the best of both methods -- but at a pretty high cost, of loss of steering and brakes! Have you ever tried to stop a car w/o vacuum assist for the steering and the brakes? It ain't fun -- the handbrake is far more effective... :shock:

I value my car -- and my life, more than that!

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Post by aristide1 » Mon Jun 16, 2008 7:41 pm

New cars are out with electronic power steering. I wonder if they steer with the ignition on and the engine off?

I downshift to decelerate only when I want to turn the a/c compressor. Even with very limited use (mostly downhills and coming to a stop) my last trip burned 1 gallon of gas more with the a/c running. Trip was 170 miles.

Other thought. I have 4 side marker lamps in front, and four rear lights, which obviously get brighter when I brake. I'm guess all 8 lights use at least 1 amp (12-13.6 watts) each, so the question is would anyone see a mileage improvement when driving with the light on if one were to replace these lights with LEDs?

(That's ignoring how most dashboard indicators would throw a fit if the current in these circuits dropped to next to zero and would warn the driver of a burned out bulb, assuming the LEDs don't have resistors in place to waste the electricity they could be saving in order to keep the indicator lights off.)

I won't mention which mountain but there is a mountain I coast down on the west side that lasts just over 7 miles. If I had my Vega I could shut the engine off as well, but it's in rust heaven now in the good company of Fiats and Datsun 510's.

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Post by kaange » Mon Jun 16, 2008 8:26 pm

NeilBlanchard wrote:The crazy hypermilers do what they have dubbed EOC aka engine off coasting, so they get the best of both methods -- but at a pretty high cost, of loss of steering and brakes! Have you ever tried to stop a car w/o vacuum assist for the steering and the brakes? It ain't fun -- the handbrake is far more effective... :shock:
It depends on the car. A smallish car (eg Ford Focus) can still be steered and stopped with the engine off. You do need to have pretty good shoulders and quadraceps but for most men and some women, it is not unreasonable. The biggest danger is the point where the brake vacuum assist runs out as the brake pedal will suddenly firm up.

It's quite hard on the steering wheel as you need to turn it with a lot more force and you need to pull back on it to get enough braking force if stopping fast.

It's also quite a challenge to hypermile in peak hour traffic - almost more difficult than driving fast (like I used to).
aristide1 wrote:New cars are out with electronic power steering. I wonder if they steer with the ignition on and the engine off?
Yep. It does for the Mitsubishi Colt, anyway.
aristide1 wrote:Other thought. I have 4 side marker lamps in front, and four rear lights, which obviously get brighter when I brake. I'm guess all 8 lights use at least 1 amp (12-13.6 watts) each, so the question is would anyone see a mileage improvement when driving with the light on if one were to replace these lights with LEDs?
I saw an article which analysed the extra fuel used by cars running with headlights on during the day (eg recent Volvos). The extra amount was not insignificant but considering that they are on continuously and are far higher wattage, I doubt that the intermittent use of brake light and indicators would add much to fuel usage.

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Post by NeilBlanchard » Tue Jun 17, 2008 8:50 am

Hello,

I am 6'-4" and 245 pounds, and in decent shape; and I drive a small car: a Scion xA (see the pictures I linked to above).

I tried a little EOC (engine off coasting) at about 3mph (in line at a toll booth) and it was all I could do to keep from hitting the car ahead of me! :shock: The handbrake was far more effective -- which is damning with faint praise, so to speak...

The steering was also very difficult.

If I was to try to EOC at highway speeds, and something happened -- I would need to change my underwear, I think. Not a safe thing to do!

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Post by aristide1 » Tue Jun 17, 2008 3:44 pm

kaange wrote:... I doubt that the intermittent use of brake light and indicators would add much to fuel usage.
I meant the lights that are on all the time along with the headlights, but your point remains.
:idea:
How many white LEDs to equal a headlight :?:
:idea:

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Post by aristide1 » Tue Jun 17, 2008 4:07 pm

mr. poopyhead wrote:..smart driving usually gets you there as fast as agressive driving... slowing down for red lights means that it might actually be green when you get there, :P

anyone have any tips for being more efficient on a manual transmission?
I found out by accident actually, but smart driving is very low stress driving. You feel like you got there quicker because you're less tired and wound up. This is why drivers that mature (no longer drive like teenagers) all gravitate towards smart driving, only the young, the stubborn, and the ones who always have a need to break a rule continue with the foot-to-the-floor mentality. I didn't care they did that when it didn't cost me money as well, but now?

Yes, sorry for being late but I've tried to do better with in town stick driving as well. I used to believe that the lower the rpms the better the mileage, but that is not always true. Mileage is best when you are running the engine in its peak torque range, which is a much broader range than just 10 years ago, and an order of magnitude better than the peaky cammed up engines typical of the 1960's.

Anyway, I use to approach stop at an intersection. When the light turned I would go straight about 2 blocks, passed a school, and then turn left. I'd go another 2 blocks and then turn right. Initially I would get my 5 speed up to 3rd gear as quickly as possible. I did not lug my small 4 cylinder, but it was below 2000 rpm. At the turns I would have to downshift, and then upshift as soon as I could. I often had to slow in front of the school at 8:00 a.m., causing more shifts. While I have fuel injection I recalled that each stab of the throttle would have to compensate for the added air with more fuel. Ever see the center squirters on a 4 barrel carb? Well one day I did it different. The first light turned green and I went from first to second and I stayed there. Occasionally the engine would go over 3000 rpm, but with very little throttle. I eliminated the downshifts and subsequent upshifts and my right foot barely moved. The engine clearly did more revolutions in this portion of my drive, but my mileage went up.

Peak torque range = peak efficiency. Peak does not mean one engine speed, it's a range, and with variable valve timing you have a good range where more than 80% of the maximum torque achievable is at your disposal. Below that things just don't work as well, and you will use more gas. Lug the engine and you risk severe damage as well.

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Post by aristide1 » Tue Jun 17, 2008 4:46 pm

NeilBlanchard wrote:....The second type is for when you need to stop anyway: downshift to a lower gear and use the engine to brake the vehicle. This shuts off the fuel (on most cars), so instead of wasting the energy as heat (from the brakes), you can stop using any fuel (while idling the engine and using the brakes).
Except for sending some of that energy to my AC compressor I would have to vote no on that one. I have no intention of causing more wear and tear to my clutch, which is a very expensive replacement, compared to my brakes, which can be replaced without dropping the engine. I have no intention of robbing Peter to pay Paul. Conserving fuel properly saves me money as well, it doesn't just send the money on another expenditure or worse, cost me even more money.
NeilBlanchard wrote:....
Low rolling resistance (LRR) helps mostly at lower speeds; say below 40mph.
That leaves out way too many variables. My top gear doesn't even engage until 50mph. There's no way to obtain optimum mileage in a lower gear. Your best mileage should occur in top gear in the peak torque range, which varies between a 50cc moped and a tractor trailer. Given how Corvettes are geared these days it would not surprise if they have almost no penalty from 55 to 75mph, the massive V8 is bored to tears the entire time. A Lexus with an 8 speed transmission can probably do the same or better. Let the designers deal with drag, where and when its a significant problem varies from one car to the next, from Corvette to box van.

You touched on rolling resistance, which I will tell you from experience is a knife that cuts both ways. New cars today routinely come out of the factory with tires that have prioritized reduced rolling resistance. They pose hazards. They simply do not grip the road as well. They are still ok when new and on dry roads, but when half worn out and rain slick they can be treacherous. Again, one variable is given too much priority without finding the optimum overall performance.

People who research and buy higher performance tires routinely see far better wet weather traction and braking, along with the same on dry roads. Yes, they notice something else, they may lose 1 mpg, and exotic tires may lose more. Something else also happens. Reading user reviews of such tires there's a common observation - it seems that ABS stops working. Well it doesn't, it's just that such tires are not losing their grip on the road, so the ABS pulses a lot less, especially in the rain. Better adhesion can make the car stop quicker, if the driver keeps his wits about him, but safety features these days are geared for the average and panic stricken driver. But I'm trying to make the same point here as before. I'm not going to sacrifice tire adhesion, and the safety it buys me, for tires with lower rolling resistance, which if I get into even a minor fender bender, will not pay for themselves even over the lifetime of the car.

Neil - power steering does not work from engine vacuum, rather (typically) an engine driven pump and power steering fluid. Drivers who routinely turn off the engines of these cars to coast are not playing with an optimum cranial capacity. Your power brakes should work fine for about 3 stops after the engine stops, thanks to the reservoir.

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Post by mr. poopyhead » Tue Jun 17, 2008 7:31 pm

aristide1 wrote:I found out by accident actually, but smart driving is very low stress driving. You feel like you got there quicker because you're less tired and wound up. This is why drivers that mature (no longer drive like teenagers) all gravitate towards smart driving, only the young, the stubborn, and the ones who always have a need to break a rule continue with the foot-to-the-floor mentality. I didn't care they did that when it didn't cost me money as well, but now?
i love it when i'm coasting into a red light and some impatient moron feels the need to gun the engine, swing his car around mine and fly into the intersection at 80km/h before slamming on the brakes at the last second.... i just keep coasting, and when the light turns green, put the car back into gear and go right past the guy without ever braking... i wonder if they ever notice that they just got passed by the "slow" guy on the road.

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Post by kaange » Wed Jun 18, 2008 9:26 pm

NeilBlanchard wrote:I am 6'-4" and 245 pounds, and in decent shape; and I drive a small car: a Scion xA (see the pictures I linked to above).

I tried a little EOC (engine off coasting) at about 3mph (in line at a toll booth) and it was all I could do to keep from hitting the car ahead of me! :shock: The handbrake was far more effective -- which is damning with faint praise, so to speak...

The steering was also very difficult.
Odd - I'm 9" shorter, 90 pounds lighter and only in average shape. I've been EOC'ing traffic for a couple of years now and don't find it that bad - with the Focus and my old Peugeot 306, things do load up but not to a dangerous extent as long as I pay attention to when the brake assist runs out of vacuum. With the Colt, I barely notice as it has electric steering assist and the brakes are much lighter.
aristide1 wrote: :idea:
How many white LEDs to equal a headlight :?:
:idea:
High power LEDs are problematic for focussing since the source is spread rather than a single point. The HT guys have had problems with this for projector technology. The heatsink needed is also sizable for high intensity LEDs so there is a limit to how many can be crammed together.
aristide1 wrote:Drivers who routinely turn off the engines of these cars to coast are not playing with an optimum cranial capacity.
It's actually incredibly mentally taxing to EOC in traffic as you need to anticipate light changes and traffic patterns to do it safely and make it worthwhile :? Far, far harder than trying to drive fast (unless you are trying to drift in traffic)
Some Europeans have EOC'd for decades due to the high cost of fuel vs the US.

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Post by independent » Thu Jun 19, 2008 12:39 pm

This is to the OP. We used to have a Toyota Camry (90 same era as your 89). I was really surprised how economical that car was. We got 13km/l easily on most trips (7.6kms per 100km) without even trying. And that was two adults a large dog and the car filled with gear. Surprising for a nearly 20 year old large (in my books ;-)) stationwagon with a 2.0ltr engine.

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Post by NeilBlanchard » Thu Jun 19, 2008 2:54 pm

Hello,

Here's an article in Wired, about hypermiling that gets the spirit without the misnomers that are so common:

http://www.wired.com/cars/energy/news/2 ... ermilers09

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Post by quikkie » Fri Jun 20, 2008 5:45 am

Aristide1 wrote:
NeilBlanchard wrote:....The second type is for when you need to stop anyway: downshift to a lower gear and use the engine to brake the vehicle. This shuts off the fuel (on most cars), so instead of wasting the energy as heat (from the brakes), you can stop using any fuel (while idling the engine and using the brakes).

I have no intention of causing more wear and tear to my clutch, which is a very expensive replacement, compared to my brakes, which can be replaced without dropping the engine.
I was under the impression that clutch wear happened only when you are using the clutch pedal - I thought it didn't (or certainly shouldn't) wear when the clutch pedal is fully depressed or "at rest".

I have to admit I don't see the point of engine braking all the way down the hill, but I guess that depends on the gradient of the hill...

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Post by aristide1 » Fri Jun 20, 2008 2:56 pm

I believe some clutch designs wear even full depressed, but certainly the more shifts the more wear.

There are lots of hills I can coast down in neutral, either maintaining or increasing speed. If I put the car in gear it will slow down. In a lower gear for deceleration it will slow more. With the cruise control engaged down such hills it has to elevate engine speed slightly to maintain speed. I don't see many situations where I could cause deceleration of any kind for any length of time, and this is the first I've heard that fuel is totally stopped under deceleration.

The coasting with the engine business is taking way too many risks. What if something or someone bolts in front of you? A major portion of driving safely is to anticipate sudden unknowns and being ready for them. That said I don't see why more small cars could not be made without power steering.

http://www.wired.com/cars/energy/news/2 ... ermilers09
That's ironic, a Jeep in the background, with the most notoriously bad mileage for a vehicle of its size ever.

I can improve my mileage by leaving the spare tire at home, the back seats, even the front passenger seat.
The U.S. Department of Energy says gas mileage plummets above 60 mph.
Really? I get lower mileage in top gear at 65 than a lower gear at 45? How about when I coast? Is coasting at 80mph worse than coasting at 55?

If I wanted generalities I'd be talking to Carl.

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Post by jaganath » Fri Jun 20, 2008 5:16 pm

The U.S. Department of Energy says gas mileage plummets above 60 mph.

Really? I get lower mileage in top gear at 65 than a lower gear at 45?
it's an undeniable fact that wind resistance increases with the square of your speed, and the engine power required rises with the cube of your speed. think about it; there's absolutely no reason why it should be energetically cheaper for your car to travel at high speed; in fact the forces resisting the car's motion are (exponentially) greater at high speed.

http://driving.timesonline.co.uk/tol/li ... 107764.ece
the study, commissioned by What Car? magazine and based on five cars of different sizes ranging from a 1 litre Toyota Aygo to a 2.2 litre Land Rover Freelander, found that the most efficient speed was below 40mph for all five and as low as 20mph for two.
....
Above 40mph, fuel consumption increased sharply and by 90mph the miles per gallon had halved on average.
...
The average car consumes 38 per cent more fuel at 70mph than it does over the same distance at 50mph. At 60mph it uses 34 per cent more than at 40mph.

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Post by aristide1 » Fri Jun 20, 2008 5:43 pm

jaganath wrote:
The U.S. Department of Energy says gas mileage plummets above 60 mph.

Really? I get lower mileage in top gear at 65 than a lower gear at 45?
it's an undeniable fact that wind resistance increases with the square of your speed, and the engine power required rises with the cube of your speed. think about it; there's absolutely no reason why it should be energetically cheaper for your car to travel at high speed; in fact the forces resisting the car's motion are (exponentially) greater at high speed.
I say I don't challenge the laws of physics and I practice that as well, I don't tailgate.

Gearing plays a huge role as does running the engine in its best rpm range. There are engines so large and powerful that this increase in drag is more than offset by lower engine speeds. The new Corvettes do this all day long. Do I care that my car now requires more power if my engine doesn't? There are people who drive Chevy Suburbans and other huge vehicles, that install larger engines, and get better mileage, because the smaller engine strained much more.

Different car's mileage will peak at different speeds, and yes, most will be at or below 60. But if your car has a tall gear that doesn't even begin to function at a lower speed then I would not bet on it. On a car like the miserable old Chevy Chevette it's best speed for mileage was probably 45mph, the underpowered dog that it was. 50cc mopeds probably do best around 25-30 mph, while 250cc fuel injected mopeds like the Yamaha get the same mileage with much better speeds, because there are more/other factors involved.

Taking the drag and wind resistance factors too far, and you may as well eliminate them by walking. Perhaps a sailboat with wheels? :roll:

I'm sure the statistics you provide are correct for those cars, but people would be shocked at what a larger car with really tall gearing can accomplish on a highway. I get 32mpg in a 3200 pound 3 liter V6 Avalon, and I'm sure most people driving Corollas don't do that well, smaller engines and lighter weight cars though they are.

And my engine speed at 60mph is 2000 rpm. Would I get better mileage if my car had another gear and the engine speed at 60mph was 1800 rpm? Yes. Now would that extra gear allow me to go 65mph at 1900 rpm and get the same mileage as without the extra gear? The answer is - it depends, but there is a good chance of it. (Even at those engine speeds is the engine making substantially more power than is required to move the car?)

This is all no different than riding a 27 speed bicycle. Your best use of your energy is going to be set by what gear you choose for the given conditions, and drag and wind resistance are a subset of those conditions, not the whole formula.

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Post by NeilBlanchard » Fri Jun 20, 2008 6:42 pm

Hello,

There is an optimum speed for any vehicle: at the "intersection" of most efficient engine speed, rolling resistance and aerodynamic drag. The aero drag goes up by the SQUARE of the speed; so 75 is almost 2X harder to push than 55mph. If the gearing is designed right, then the engine RPM's will be at the optimum point for that speed.

A larger displacement engine can provide more torque at a given RPM than a smaller displacement engine, all else being equal -- but if it has excess power (not needed to push the vehicle at the speed), then you just waste the fuel.

To reduce drag, you can either reduce frontal area, and/or reduce the coefficient of drag (the rough edges, as it were) to reduce turbulence.

Weight and rolling resistance also enter into the equation, but they have a (more or less) linear affect on the power need to continue moving at a given speed.

A couple of examples of how things can work: my 1987 Golf (85HP or so) could go ~105mph in fifth gear, with the RPM's at ~4,800 or so. The engine just could push any harder at that RPM -- then I downshifted to fourth and went about 10mph faster; until the engine redlined at ~6,700. That's all she wrote...

On my current car, I would love to have a sixth (and seventh!) gear -- or a taller ratio in the final drive. It spins at ~3,400RPM at just 65mph. It could easily keep the car moving at 2,400rpm.

And yet, with the aero mods I have been trying, I have improved my average MPG from 37 (3 years -- this is already much better than the 30mpg the EPA says...) to almost 41 (90 days) and 45mpg for the last 3 tanks! My previous high was 41.8mpg, and now is 46.4mpg!

Same motor, same gearing; but better tire inflation, much better driving technique, and better aerodynamics make all the difference.

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Post by aristide1 » Fri Jun 20, 2008 7:31 pm

NeilBlanchard wrote: A larger displacement engine can provide more torque at a given RPM than a smaller displacement engine, all else being equal -- but if it has excess power (not needed to push the vehicle at the speed), then you just waste the fuel.
Which is why going from 60 to 65 doesn't matter. You can't make a car with just enough power to keep it moving on flat land. It has to climb hills, sometimes carry extra passengers, and look at the weight of 18 gallons of gas alone.
NeilBlanchard wrote:A couple of examples of how things can work: my 1987 Golf (85HP or so) could go ~105mph in fifth gear, with the RPM's at ~4,800 or so. The engine just could push any harder at that RPM -- then I downshifted to fourth and went about 10mph faster; until the engine redlined at ~6,700. That's all she wrote...
Mine too, higher top speed with the overdrive off. But as you pointed out, I'd get better mileage with an additional gear anyway.

By the way there's another difference. In the lower gear at redline you could probably stay there all day. With the higher gear and your foot to the floor you would probably burn an exhaust valve.

I recall Toyota had engines whose best/longest longevity was at redline. You could run the thing at redline for years if you were so inclined. Just some minutiae.

Neil can you break down your mileage increases per change made?

Thank you.
Aris

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Post by bonestonne » Fri Jun 20, 2008 7:40 pm

hm...topics like this are things i tend to avoid because i have a friend who built a car that sports a 13k fuel injection system in his racecar that helps him keep ~40-42mpg on the track...its all computer controlled, but i couldn't even begin to describe how it works...i don't really even know

we should all just buy 93 octane gas and drive at 32-35mph...that's the sweet spot for every car, any engine whatsoever....it'll give you near 99 miles per gallon almost guaranteed.

been tested and proved, my dads 1996 Dodge Grand Caravan SE gets 99mpg at 33mph regardless of traffic as long as its moving and not sporadic.

but the new "economic gasoline" that's being created, like gasohol, ethanol, and mixtures, hell, even methene based stuff is bad...it causes the carburetors' diaphragm to shrivel up and restrict the intake line. unless the engine is built to run on it, you shouldn't use it. older engines especially. but 87 and 89 octane fuels have similar effects on engines, as well as being rough on the fuel injectors. 93 is really optimal for most cars, it doesn't matter if a car is built to use cheaper fuel, you'll actually end up losing some fuel because the engine doesn't use it all. that liquid that comes out of a tail-pipe sometimes, that's unused gasoline. i don't really think that a new driving technique can really change the design flaws of engines today.

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Post by wim » Fri Jun 20, 2008 8:50 pm

iirc you get best fuel economy for the rpm which your engine provides peak torque. so for most cars i would expect best fuel efficiency will be in the highest available gear traveling at whichever rpm hits the peak torque, and what speed this is depends on the geometry of your car (the gearing ratio, diameter of tires, etc). this will be different for every car and to work it out accurately you'd need to get your car on a dynamometer and obtain one of those charts with engine speed [rpm] on x-axis, torque and power on y-axes.

my previous car (ford festiva) was tuned for best fuel efficiency at about 100kph in 5th gear. note the manufacturer is able to tune engine in order to obtain best fuel efficiency at the speeds they expect the customer to be driving most of the time. in fact they probably choose the gearing ratios based on the torque-rpm line in the first place..

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Post by NeilBlanchard » Sat Jun 21, 2008 4:36 am

Hello,

Of course it is better to drive 60 than 65!

30 * 30 = 900
35 * 35 = 1225
40 * 40 = 1600
45 * 45 = 2025
50 * 50 = 2500
55 * 55 = 3025
60 * 60 = 3600
65 * 65 = 4225
70 * 70 = 4900
75 * 75 = 5625
80 * 80 = 6400

This is ~17.5% increase in drag (from 60 to 65), so say it takes 20HP to push the vehicle at 60, then it will take 23.5HP to push it at 65. Now how your engine and gearing work, that can hurt or maybe help, but no matter what, you need more power -- and therefore more fuel is burned, to go from 60 to 65mph.

It all about the whole "system" of the car in the environment -- the aerodynamic drag SWAMPS any other factor, internal or external!

For any doubling of the speed, there is a 4X increase in drag.

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Post by quikkie » Sat Jun 21, 2008 4:39 am

the liquid that comes out of the exhaust is water - water being one of the by-products of combustion. If it was petrol/gasoline it would flame as soon as it hit the hot exhaust pipe. Remember the Ferrari F40? on a downshift the overrun was so bad the fuel went straight through to the exhaust and that's what caused the flash of flame from the exhaust pipe.

Oh and in the UK we get a choice of 95 (regular) or 97 (premium) - none of that anaemic stuff you Americans can get ;)

As for running at peak torque I think I'd cry if I had to do that... on my car that works out as 5K rpm! Granted it's a lot more "fun" but a lot less silent 8)

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Post by NeilBlanchard » Sat Jun 21, 2008 6:06 am

Hello Aris,

To your other question: my best estimate of the benefits of the three aero mods:

Covering the upper grill was the biggest improvement: ~2-3mpg.

Covering the fog lights was also quite helpful: ~2mpg.

Smoothing out the A-pillar rain gutter is not as noticeable, and I've only had this for half a tank, so I can't put a number on it.

My next mod will be to put a deflector so the air flows up and over the wipers -- and so I can get better air flow in the vents.

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Post by aristide1 » Sat Jun 21, 2008 7:01 am

Neil,

1. What happened to your coolant temps when you blocked the grill?

2. Would you rather be coasting at 60mph or 80mph?

Aris

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Post by NeilBlanchard » Sat Jun 21, 2008 9:03 am

Hello Aris,

There was no appreciable change in coolant temp -- I don't have my ScanGage II yet, so I don't have the actual numbers, but the electric fans still only come on when I'm sitting still in traffic for an extended period (i.e. in a traffic jam). This is what they have always done.

I coast at 55mph, 'cuz that's how fast I drive, and I coast at any speed possible on hills on backroads. I have one spot where I can coast a mile, starting at the top of the hill at ~35mph. Before I did any aero mods, I could NOT COAST ABOVE ~70mph -- because that was th "terminal speed" for my car. The drag was too much for even the HUGE hill going east on Route 2 from Belmont into Cambridge.

Cruising at 80mph would suck down the gas -- I doubt I would get 33-34mpg at that speed...

Question to you: what is your average fuel mileage? How do you drive, and what are the driving conditions? Have you tried some "hypermilage" techniques?
http://ecomodder.com/forum/EM-hypermili ... riving.php

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Post by aristide1 » Sat Jun 21, 2008 10:05 am

NeilBlanchard wrote: Cruising at 80mph would suck down the gas -- I doubt I would get 33-34mpg at that speed...
Who said anything about cruising?

Most of my driving:
1. Highway, 62-65mpg, flat and straight with some hills.

Prior roads allowed for some coasting, I seldomed bothered less than 1/2 mile, and 99% were less than 4 miles. Never with the engine off, need quick and responsive steering. The longer ranges were made possible by allowing the car to proceed, often above 75mph, and then climbing hills in neutral, which used up the excess speed rather quickly. My 7 mile stretch was made possible by taking turning turns way beyond their posted limit, which made coasting somewhat less boring. :shock: 8)

I had one coast that allowed me 80mph for about 30 seconds and then to climb 2 small hills in neutral. The tractor trailers did the same thing. I wonder why. 8)

2. Also back roads, slightly hilly and curved. About 60mph, no coasting here as conditions make it impossible. Coasting at anticipated stops and lower limits.

3. I still coast on off-ramps, and use the energy to turn the ac compressor. If I wanted to save gas, sweat, and smell bad I'd ride a camel. 8)

My EPA rating is 21/29. I can achieve 32 on the highway, but in town only is as bad as 21. Stopping and starting mass takes energy.

I use Mobil 1.

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Post by alphabetbackward » Sat Jun 21, 2008 12:35 pm

At 55 MPH, the best I've ever gotten is 39.2 MPG. Although, I'd say my average is around 36. It's a big improvement over the 28-ish I've been usually getting prior to hypermiling.

I drive an automatic Toyota Camry rated for 24/33 or 21/30 depending on whichever EPA year rating you'd want to look at.

I drive 95% highway and I usually get to 55 MPH, then let off the gas ever so slightly and let my speed slowly bleed off to ~50 before I accelerate back to 55 and depending on the terrain, I can keep that speed for a while. Letting off the accelerator increases the instantaneous MPG from 35-40 to about 50. I wouldn't know that if I didn't get the ScanGauge. But at the same time, prior to getting the ScanGauge, I did manage to get 36 MPG and after getting the ScanGauge, I've gotten a couple 34 tanks.

At lights, I put the car in neutral and at extended lights, I turn the car off. I let off the accelerator completely at exits to engage the fuel cut off.

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