内燃机照常轰鸣

    各大汽车制造商及驾车者长期以来一直希望在燃油效率问题上得到一个简单的解决办法。曾经有一段时间，这个愿望看起来有可能实现。2009年，《财富》杂志（Fortune）撰文称，由于电动汽车、混合动力汽车及柴油车等技术性的进展，“传统的汽油内燃机似乎可以肯定地说正在日渐式微。”

    事实是，一种颠覆标准发动机、而且可负担得起的技术尚未出现。行业预测机构LMC汽车咨询公司（LMC-Automotive）预测，到2020年，98％以上的车辆将仍然使用某种形式的内燃机。LMC动力总成行业分析师麦克•奥莫托索称，在2020年销售的新车当中，约有72％的新车将只使用汽油，相比今天的84％仅下降几个百分点。（其余大部分是混合动力车、柴油车或乙醇动力车。）

    鉴于在未来几年内还不会出现革命性的突破，从大众（Volkswagen）到宝马（BMW），各大汽车制造商现在正寻找利用现有技术的新方法。鉴于美国燃油经济性标准即将提高——到2025年将达到54.5 英里／加仑（mpg），上述措施正变得格外重要。（美国是世界上第二大汽车市场，仅次于中国。）为了达到新的燃油经济性标准，各大汽车公司目前正在整合一系列现有技术，以期在已有120年历史的内燃机的基础上节约使用任何可能的点滴燃油。

    问及正在大量整合进入标准发动机的各种不同技术时，美国汽车工程师协会（Society of Automotive Engineers）的安德鲁•斯马特这样说道：“展望2025年时，预计不会出现“银子弹”——即能够寄予厚望的新技术，但会出现大量“银弹片”——即会出现大量技术性改进。”

    举例而言，福特汽车公司（Ford）在新推出的、已成为市场热点的EcoBoost发动机上就采用了技术性改进这个方法。福特在四年前推出了EcoBoost发动机，目前各款EcoBoost发动机汽车的销量已超过350,000辆。EcoBoost发动机在传统汽油发动机的基础上进一步汇集了燃油缸内直喷、涡轮增压及可变气门正时等存在已久的技术。其中没有多少是新技术，但汇集在一起，这些递增式的改进与以往的传统汽油发动机相比，在燃油经济性方面实现了20％的提高。（点击此处，了解更多有关EcoBoost的资讯。）

    他们是如何做到这点的呢？首先，EcoBoost重量轻。福特计划明年在美国推出的1.0升三缸EcoBoost发动机将成为这家汽车制造商有史以来最小的发动机。其中发动机重量的减轻一部分是通过在发动机结构中使用铝合金、而不是铸铁实现的。而且发动机的尺寸也较小，这要归功于其他一些调整，使得它在缩小尺寸的同时、仍能保证强劲的动力输出。

    这款发动机的尺寸顺应了潮流。在整个汽车行业里，各大汽车制造商都已把六缸发动机换成四缸发动机。豪华汽车也是如此，对于豪华汽车而言，发动机小于八缸曾经被视为大不敬。现在，甚至连宝马都加入这个潮流。公司将于明年开始销售一款配有小型三缸发动机的汽车。

    汽车制造商有几个办法可以使小型发动机实现高性能。一个办法是燃油缸内直喷。这项技术已经存在有一段时间了，但最近才获得美国制造商的广泛采用。为了避免浪费汽油，发动机内的精密喷射器把燃油喷入气缸中的一个确切位置。这样，燃油就能够更完全燃烧，而所需的确切燃油量及应该击中的准确位置均由电脑来确定。此外，由于燃油没有通过发动机的其他部件、而是直接喷入气缸，因此喷入气缸后燃油温度较低。温度较低意味着汽油与空气混合后产生的油气较为稠密，从而使更多的油气能够在压缩水平较高的情况下在较小的空间里得到使用。最终的结果是输出的动力更大。

    Auto manufacturers and drivers alike have long yearned for a simple solution to fuel efficiency. For a while, it looked possible. In 2009 Fortune wrote that, thanks to advances such as electric cars, hybrids and diesel vehicles, "It seems certain that the traditional gasoline internal-combustion engine is on the wane."

    Truth is, an affordable technology to upend the standard engine still has yet to materialize. Forecaster LMC-Automotive predicts that by 2020, more than 98% of vehicles will still incorporate an internal combustion engine of some kind. And some 72% of new car sales in 2020 will run on gasoline only, says LMC analyst Michael Omotoso, down just a few points from today's 84%. (Most of the rest are hybrids, diesel or ethanol-powered.)

    Absent a revolutionary breakthrough within the next few years, carmakers from Volkswagen to BMW are now finding new ways to work with what they have. That's becoming especially important with a looming hike in fuel economy standards in the U.S. to 54.5 miles per gallon by 2025. (America is the world's second largest car market, after China.) To meet the new standards, companies are combining an array of existing technologies to eke out every possible bit of fuel savings from the 120-year-old internal combustion engine.

    Asked about the disparate technologies being crammed into the standard engine, Society of Automotive Engineers's Andrew Smart puts it this way: "When you look at 2025, the expectation is there is no silver bullet, but there is plenty of silver shrapnel."

    Ford (F), for one, took this approach in its new, much talked-about EcoBoost engine, which was introduced four years ago and has already sold more than 350,000 models. The EcoBoost is a compilation of long-standing technologies like direct injection, turbocharging and variable valve timing. Not much in it is new, but all together, the incremental improvements achieve a 20% gain in efficiency over its predecessors. (For more on the EcoBoost,click here.)

    How'd they do it? For starters, the EcoBoost is light. The one-liter, 3-cylinder model it plans to release in the states next year will be the carmaker's smallest engine ever. Part of the weight loss is achieved by using aluminum instead of cast iron in the engine construction. It's also smaller, thanks to the other tweaks that allow it to downsize and still pack a punch.

    The engine's scale is in keeping with a trend. Throughout the industry, automakers have swapped V6s for four-cylinder engines. That applies to luxury cars, too, where once it was sacrilege to have anything smaller than a V8. Even BMW is joining in, with a tiny, three-cylinder engine slated to go on sale next year.

    There are a few ways carmakers get smaller engines to deliver high performance. One is direct injection. The technology has been around for a while, but it has recently gained traction with U.S. manufacturers. To avoid wasting gas, precision injectors within the engine shoot fuel into an exact location in the cylinder. That allows for a cleaner burn, with a computer determining the exact amount of fuel needed and the exact spot it should land. Also, because the fuel goes directly to the cylinder without passing through other parts of the engine, it's cooler once it gets there. The colder temperature means the gas is denser, allowing for more of it to be used in a smaller space at higher levels of compression. The end result is a bigger punch.