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What people might not think about so much is that weight reduction is as important if not more important than the advancements we make in the engine. When Rock

What people might not think about so much is that weight reduction is as important if not more important than the advancements we make in the engine. When Rocky Mountain Institiute was working on their hyper car concept, I believe the researcher said that weight reduction was more important than electric or gas engine. I think he said something like for every pound you save, you actually reduce an extra 2-3 pounds of supporting materials elsewhere. Lighter cars need less HP, you can reduce some of the support bracing as it's not as heavy of a vehicle, etc... Making cars super light would do a lot of good and so every time I see a giant battery for electric cars or a 2nd engine to act as a backup, I wonder how much that is costing in terms of weight and MPG.

wspeirs 12y ago
Along with a weight reduction, they said that, "It can also be run like a diesel, using compression rather than a spark plug to ignite its fuel mixture." This is important as spark plugs require a decent amount of energy to function.
- tnorthcutt 12y ago
  spark plugs require a decent amount of energy to function Are you sure about that? According to [0], "To ignite a stoichiometric air-fuel mixture (14:1) approximately 0.2 milliJoules of spark energy are required. Very rich or lean mixtures can require as much as 3 mJ." [0] http://www.mr2.com/TEXT/DavidKucharczyk/ignition.html http://www.mr2.com/TEXT/DavidKucharczyk/ignition.html
  - schrodinger 12y ago
    (0.2 millijoules * 6 * 3000) / minute = 0.06 watts So yea, not much...
IgorPartola 12y ago
There are lots of designs where the car is significantly lighter than a typical vehicle driving on American or European roads. The problem with them is that if you get in an accident, you are much more likely to suffer much more damage. There are in fact regulations in the US that effectively require you to build heavier cars. Motorcycles and scooters are great examples of personal transportation that are lightweight and can get ridiculous fuel economy, but in a Vespa vs 18 wheeler, the Vespa will lose every time, which is why you don't see them on the freeway.
mikeash 12y ago
One important question is how much you really care about efficiency if you're getting most of your energy from electricity. Electricity isn't free, and it still pollutes depending on what your local generating capacity looks like, but it's a lot better than even the most efficient gasoline. The problem with most electric cars right now is range, which is due to the inherent cost of the batteries. But it's largely psychological, as most people's driving in most situations is within the range of a reasonable electric vehicle. It's just exceptional circumstances when it's not enough. Thus, paradoxically, adding a gasoline range extender to an electric car could really help enable electric driving considerably. And if the car drives 90% on electricity, the efficiency of the gas engine doesn't matter too much. It's just there as a backup. I almost bought a plug-in hybrid last year. A Volt or similar would let me do a ton of pure electric driving, while still having the option to go farther. A Leaf or similar just wouldn't cut it for me, because a car that covers 90% of my driving isn't good enough. But if it can cover 100%, with 90% on electricity, that's a big gain. Ultimately I didn't get one, because they're still a bit too compromised (the Volt only seats 4, others have tiny cargo space), but range extenders could be an important bridge measure as batteries slowly improve, and the extra weight isn't all that important in many cases.

wspeirs 12y ago

Along with a weight reduction, they said that, "It can also be run like a diesel, using compression rather than a spark plug to ignite its fuel mixture." This is important as spark plugs require a decent amount of energy to function.

tnorthcutt 12y ago
spark plugs require a decent amount of energy to function Are you sure about that? According to [0], "To ignite a stoichiometric air-fuel mixture (14:1) approximately 0.2 milliJoules of spark energy are required. Very rich or lean mixtures can require as much as 3 mJ." [0] http://www.mr2.com/TEXT/DavidKucharczyk/ignition.html http://www.mr2.com/TEXT/DavidKucharczyk/ignition.html
- schrodinger 12y ago
  (0.2 millijoules * 6 * 3000) / minute = 0.06 watts So yea, not much...

IgorPartola 12y ago

There are lots of designs where the car is significantly lighter than a typical vehicle driving on American or European roads. The problem with them is that if you get in an accident, you are much more likely to suffer much more damage. There are in fact regulations in the US that effectively require you to build heavier cars. Motorcycles and scooters are great examples of personal transportation that are lightweight and can get ridiculous fuel economy, but in a Vespa vs 18 wheeler, the Vespa will lose every time, which is why you don't see them on the freeway.

mikeash 12y ago

One important question is how much you really care about efficiency if you're getting most of your energy from electricity. Electricity isn't free, and it still pollutes depending on what your local generating capacity looks like, but it's a lot better than even the most efficient gasoline. The problem with most electric cars right now is range, which is due to the inherent cost of the batteries. But it's largely psychological, as most people's driving in most situations is within the range of a reasonable electric vehicle. It's just exceptional circumstances when it's not enough. Thus, paradoxically, adding a gasoline range extender to an electric car could really help enable electric driving considerably. And if the car drives 90% on electricity, the efficiency of the gas engine doesn't matter too much. It's just there as a backup. I almost bought a plug-in hybrid last year. A Volt or similar would let me do a ton of pure electric driving, while still having the option to go farther. A Leaf or similar just wouldn't cut it for me, because a car that covers 90% of my driving isn't good enough. But if it can cover 100%, with 90% on electricity, that's a big gain. Ultimately I didn't get one, because they're still a bit too compromised (the Volt only seats 4, others have tiny cargo space), but range extenders could be an important bridge measure as batteries slowly improve, and the extra weight isn't all that important in many cases.