Well, we had a source of clean energy that emited not a single gram of Greenhouse gasses- but the Luddites and the Stupids out there have basicly blocked it. It was called Nuclear.
If you can get dudes from blocking stuff because they just don’t understand it, then us scientific types can solve the problems. But we can’t solve the problem of Stupidity.
Oh, and once you stop dudes from blocking stuff just because they don’t understand it, then we’ll have to work on NIMBYISM and general Luddite problems. For example- some dudes don’t want Wind turbines as they “block the view” :rolleyes: . Hydroelectric is the cleanest energy out there, but still the morons at the Sierra club want to dynamite all the damns.
(That’s not to say Nuclear doesn’t have some problems, but it doesn’t go “BOOM”, and it doesn’t contribute Greenhouse gasses).
That’s absolutely true, and I fully understand that it’s necessary to travel further in the course of every day life in the US than it is in Europe generally and in the UK in particular (I spend a lot of time in the US, and generally cover insane distances on what would be considered local trips while I’m there). I even accept that it is unreasonable to expect Americans to adopt the tiny “sub-compact” hatchbacks that we are so fond of, given how miserable they are to travel in over any distance. But taking that aside, is it really necessary to consume so much more gas per mile than we do? Why do you need family cars with 5 or 6 litre engines? Why do people moan about $3 gas, and then knowingly buy a vehicle that gets less than 30 miles to the gallon?
Probably because $3 gas is still really cheap. People complain about it because that’s what people do, but it’s not expensive enough to make them change their behavior.
It’s common knowledge that driving more conservatively (accelerate gently, keep speed down) saves gas. And that’s a much less drastic step than trading in your pickup truck for a Prius. Yet I still get passed by impatient drivers when I accelerate slowly from a stop light. I lost count of cars that passed me on a recent road trip, where I was driving at the 65mph speed limit. I can only assume that those people aren’t really affected by gas prices, at least not to the point where they’d do anything about it other than complain.
Speaking as one of those who accelerates and stops quickly (not to mention carefully timed lane changes, fuel-sapping 80mph speeds, etc), I agree with you. Gas prices are cheap enough that the time I save by driving in a gas-inefficient way is worth significantly more than the cost of the gas I lose. I don’t complain about the price either; I understand the choices I’ve made.
I hope that gas prices continue to increase (slowly, though) to encourage better transportation options.
Accelerating quickly does not use more gas. It uses less. So long as you’re accelerating to the correct speed - not accelerating hard and then braking hard. But if your objective is to get to 60 mph, it’s more efficient to do a fast, short acceleration and then cruise than to do a longer acceleration.
I’ve long held this to be false, but based on little evidence. In fact, I once had a screaming argument about it with my buddy (a Physics PhD) that was never resolved. Do you have any math or empirical research to back this up? I am genuinely interested in being proved wrong, so I can apologise to my friend.
I too would like to see some cite or reasoning behind this, as I find this very hard to believe.
I accelerate very gently - usually taking 15 seconds to get up to 45mph. I consistently get 30 mpg in city driving. This car only gets 24 mpg on highways (where I always keep it under 65 mph) so I must be doing something right, no?
We can get clean energy now, but we wont. We’ll pull a Y2K and put it off until the last minute. A 1000 MW nuclear plant costs about $2 billion (newer models should cost less, pebble bed reactors do not need a containment dome for example and are modular). Wind power is cost competitive with fossil fuels. The reality is 25-50 billion a year in investment and implementation in the US could probably almost totally stop global warming from the grid in the next 10-20 years, and 25-50 billion is only 0.5% of the economy (about 40-70 cents per household per day). In the US 103 plants provide about 20% of our energy. In Russia 30 plants provide 14%. So an extra 200-300 plants at a cost of 400-600 billion (over 15 years, it is 25-40 billion a year) would make 70% of our energy non-polluting. And nuclear is expensive as hell, but that is still affordable.
sadly there will be no ‘manhattan project’ in regards to actually implelmenting this stuff. What do you do with all the old coal plants? what do you do with all the engineers and factory workers who work in coal plants? How do you explain an energy project that costs 50 billion a year?
Do you know what a green certificate is? It is a certificate you can use to purchase wind power to contribute to the electricity grid (basically it offsets the cost of putting wind energy into the grid). It costs about $5-10/month in certificates to provide wind energy for a household.
if you guys are worried about energy there are a few things you can do that are cheap and easy.
Ask your power company to switch you to the ‘green option’ which means you get your energy from clean sources instead of coal.
Buy about $5-10/month in green certificates to offset the pollution your own energy usage is causing.
As far as car energy, no clue. We can get gasoline from biomass, shale and other sources but it is still polluting. Hydrogen wont be cost effective until mid next decade from what I read in scientific american.
Anyway, sadly, the point is that an investment of two quarters a day per american household could do alot to prevent global warming. So it isn’t like the science is unattainable, we just aren’t using it.
in retrospect too bad this thread is about cars and not grid electricity and most of this post is off topic. Happens I guess.
Engines are most efficient with the throttle wide open. A partial closed throttle leads to ‘pumping losses’. From this cite:
Pumping loss is significant. When you take your foot off the gas and let the engine ‘brake’ your car, that’s the pumping force doing that for you. It’s also why big engines are less efficient than smaller ones. Big engines have more energy lost due to pumping when they are at partial throttle than smaller engines do. Small engines are more efficient because they spend more of their time at wide-open throttle. If it requires 70HP to maintain highway cruising speed, then the most efficient engine will be one that makes 70HP at wide open throttle.
In WWII, Charles Lindbergh made a major contribution to the war effort by teaching pilots to run their engines ‘oversquare’ (max throttle/high manifold pressure with low RPM) to extend their range. Conventional wisdom was that this was bad, but Lindbergh showed that it was a highly efficient mode for the engine to be in, because max throttle minimized pumping losses and low RPM minimized frictional losses.
Now, as usual, your mileage may vary. This is really going to depend on the car and the current conditions. And we’re assuming the RPM is the same. If you floor an automatic, two things happen that increase fuel consumption - the first is that the transmission will usually downshift to increase engine revs, and another is that the accelerator pump will engage and the engine will be fed a richer mixture to prevent detonation. Under those conditions, you’ll almost certainly consume more fuel than you would with a more leisurely acceleration. The computer controlled fuel system in some cars may richen the mixture at higher throttle settings as well for the same purpose.
And also, if you accelerate to a higher speed and then brake hard so that you waste more energy overall, you will obviously use more fuel than if you accelerated slower to a lower speed and braked less.
Here’s what I’m saying - Let’s say your objective is to get your car to 55 mph. Choice one is to accelerate slowly, gradually building up to speed. The other is to accelerate hard, without shifting, until you hit 55, and then maintaining a constant speed. The second option causes the engine to operate more efficiently, and will burn less gas getting you to 55.
Of course, if by ‘hard acceleration’ you’re thinking of launching off the line and revving to 6000 rpm in first, then shift to second and accelerate to 6000, etc., then yes this will burn lots of fuel.
But if you think that consciously accelerating very slowly will save you fuel, it won’t. Other than that your average speed will be lower because you spent more time at lower speeds. But you could achieve the same thing by accelerating harder to a lower top speed, and be even more efficient.
The conclusion: The most fuel efficient way to drive is to keep the engine RPM as low as you can (don’t lug the engine), and the throttle as open as you can without causing the fuel system to richen the mixture. I think a good rule of thumb would be to accelerate using maybe 75% throttle, and shifting as soon as you can. If you have an auto transmission, something else you have to worry about is that if the transmission detects you accelerating hard, it may go into ‘sport’ mode and let the engine revs build up higher before shifting. That defeats the purpose. If you have a manual, you could try ‘skip shifting’ from first to third - you’ll have to use a more open throttle to maintain the same acceleration than you would if you shifted 1-2-3, so your engine will be running more efficiently.
Don’t drive like a maniac, and don’t drive like a granny. If you want to drive efficiently, pay attention to upcoming stoppages and slowdowns and use the opportunity to not build up speed in the first place. Shift early, keep your tires inflated and your engine tuned up, and relax. Being the pokey guy who crawls to cruising speed buys you nothing and annoys the people behind you.
OK pretend that I am an idiot. (Not hard trust me) on an engine with a carb (all they had in WWII) how do you keep the throttle WFO (wide fucking open) AND keep the RPM low? The more air that flows into the engine, the more fuel. The more fuel/air the higher the RPM. I don’t get it. Not calling you a liar, I just don’t understand how to do this.
Yes you will
Yes it will.
Not for long. I was just reading the '07 New car features info from my company. We will have a new engine that runs at close to WOT when below about 3,000 RPM. It relies on cam timing to maintain engine speed. This was done to reduce pumping losses, and improve gas mileage.
Your original assertion was that “accelerating quickly uses less gas,” but now you’re saying there’s an optimal point somewhere. Seems to be contradictory, but I assume your earlier statement was an over-simplification.
Which raises the question: do most people accelerate at or below this optimal acceleration, and therefore accelerating more gently would reduce fuel consumption? When I accelerate at the same rate as the cars around me, I usually end up getting the engine up to 3500 rpm or so. When I accelerate much slower than other cars, I can keep the engine under 2000 rpm, and when I reach the cruising speed of 45 mph or so, the engine cuts back to 1700 rpm or so. Would you say I’m using more gas by doing this, or less?
WWII fighters (and most larger propellor airplanes) have a ‘constant speed propeller’. A constant speed prop uses an hydraulic or electric hub that adjusts blade pitch to maintain a constant RPM, which is set with a control in the cockpit. You can fly at any combination of power settings and RPM, so long as you stay within the design limits of the powertrain. When you set the blade pitch for low RPM, the blades are adjusted so that each revolution of the prop takes a bigger ‘bite’ of air, which puts more of a load on the engine. Similar to switching to a higher gear in a car, where every rotation of the crankshaft moves the car farther down the road.
Cool. BTW, a CVT transmission gets its efficiency from the fact that it can keep the engine in a more efficient, low RPM range as well. This requires a more open throttle for the same acceleration, which reduces pumping losses.
scr4: I can’t answer for your specific car. And yes, my first message was an over-simplification. I threw it out there to refute the point that a long, gradual acceleration is necessarily better on gas than a normal acceleration to cruising speed. You might be using marginally less gas, but my guess is that the difference one way or the other isn’t much, except for the times when your very slow acceleration in stop and go traffic significantly reduces your average speed.
I just don’t think your refutation is very convincing. On the contrary, it seems to be saying that if you are revving up your engine to accelerate from a stop (which everyone does), you probably benefit from accelerating slower.
Ignoring the fact that A) it’s possible to accelerate harder without increasing revs, and B) at some point the increased efficiency of the engine will compensate for the frictional loss of higher RPM. This means that there is an optimum acceleration point, below which you gain nothing and even hurt performance by accelerating slower.
And that point is surprisingly high. I don’t have a cite, but BMW did some tests around this and concluded that their vehicles were most efficient accelerating at about 75% throttle. Above that, and the computer systems would richen the mixture and change the shift points of the transmission.
BTW, the ‘hard acceleration’ efficiency gain is well known to drivers of cars equipped with continually-variable transmissions like the Prius, because those transmissions can keep the RPM constant regardless of throttle input, and it becomes much clearer that harder acceleration is more efficient.
In your case, it seems that your car automatically delays the shift point of your transmission when you accelerate at what you say is a ‘normal’ acceleration, and shifts earlier if you accelerate more gradually. If that is the case, then you should do some experimenting and find out what the maximum throttle input is that you can give the car before the transmission starts shifting higher. THat would be your most efficient acceleration, I’d guess. You might also try accelerating harder, then taking your foot off the gas when you get the point where it would normally shift, to see if the tranny will shift up when you do that, then pressing the accelerator again to add power with the tranny in a higher gear. You might be able to increase your overall acceleration while improving economy.
But my guess is that none of this is going to make a lot of difference, and the fuel savings you are seeing from your very gradual acceleration are actually because you are driving at a lower average speed.
My personal opinion as well is that if you aren’t accelerating with the flow of traffic, you are impeding it every bit as much as if you drive 40 in a 50 zone.
The more air that flows into the engine, the more fuel. The more fuel/air the higher the RPM. I don’t get it. Not calling you a liar, I just don’t understand how to do this.