“搭载1.0L EcoBoost三缸发动机的福特蒙迪欧”听起来可能有点别扭，那么想想看，现在福特正在为这个小小的三缸发动机开发停缸技术, 是不是很让人惊异。

福特公司正在与欧洲合作伙伴携手对这台最小的点燃式乘用车发动机展开测试，测试内容包括单次和“滚动式”停缸技术的应用。在B级嘉年华和C级福克斯上成功通过测试后，这台比许多汽车发动机更小（92kW，69hp，1.0L）的发动机现在正式用于欧洲的D级蒙迪欧身上了。

当三个汽缸同时工作时，这台迷你发动机是怎样在宽敞的轿车中运作的？作为《汽车工程杂志》的编辑，我亲自在英国大街上用一辆已经上市的三缸蒙迪欧进行试驾，试驾结果有效地打消了公众对其是否能驾驭这辆重达1455 公斤（3207 lb）的汽车的疑虑。从0加速至100km/h总共耗费12秒，而其官方公布的最高速度为200km/h（124mph）。此外官方还公布了1.0L蒙迪欧的燃油经济性数据，100公里油耗为5.1L（约46mpg），二氧化碳排放为119g/km。

此外，无论在通常状态还是巡航状态下，本次试驾的NVH（噪声、振动和不平顺性）水平都给我留下了极深刻的印象。在巡航状态下，蒙迪欧也可以使用两缸模式，就像体型更小的嘉年华和福克斯车型一样。

两种停缸技术策略

三缸发动机停缸技术的可行性是由福特公司内部的一个高级团队着手研究的，该团队的领袖是研究与高级工程部门全球传动系统主管Andreas Schamel。他表示，如果该发动机安装在福克斯上且开启666 cm³两缸模式，那么在各种因素的影响下，整体燃耗可减少4%-6%。

整体停缸系统还有待后续技术的补充与完善，其中包括一种专门开发的摆式减震器。在2015年维也纳汽车论坛上发布的一篇技术报告中，Schamel表示这个整合进传动系统的减震器，可使发动机在低速停缸状态下延长行驶里程。

报告中提到了研究的合作方是舍弗勒集团（M. Scheidt）与其LuK分部（由H. Faust博士领导）。福特克隆公司的Dipl-Ing C. Weber也是研究团队中的重要成员。

除了摆式减震器外，使用停缸技术的福克斯的原型车上还装有舍弗勒双质量飞轮（DMF）和一个经过调试的离合器片，用以隔离变速箱和发动机之间的振动。

研发中所设定的硬性指标都已成功实现，而测试结果表明，与标准版的1.0L EcoBoost相比，使用停缸技术的车型，其NVH性能丝毫不逊色。

福特对两种停缸技术策略进行了测试，一种是单缸停缸，而另一种被称为“滚动缸”停缸。后者可以有效地将EcoBoost三缸发动机切入“发动机半运转”模式，使停缸的数量与顺序可以自由改变。

Schamel解释道，在一个三缸发动机上可以应用多种不同的停缸策略。一种策略是“对一个汽缸应用合适的阀门失活技术，”该技术可以有效地实现666cc两缸模式，但缺点是会导致点火顺序不均。福特正在研究可自由改变停缸数量与次序的其他技术。

Schamel在报告中指出，这种技术为滚动式停缸成为了可能，而且可以在半发动机模式下运行发动机。这相当于一个500cm³的主动排量，但同时具备了点火顺序均等的优势。

研究团队发现，在半发动机模式下，负载极低时油门损耗更容易避免，但与二分之三模式相比，总体负载限值更低。Schamel补充道：“在两种停缸技术策略都可使用的区域，在全发动机运行状态下，滚动停缸技术节约燃油的潜力比固定停缸技术更大。”

在低负载驾驶循环中，1.0L发动机在滚动停缸期间的的燃油经济性比固定停缸期间更高，但这一额外优势的程度取决于汽车的应用和循环。小型汽车轻负载阶段的优势最明显，而大型车在中高负载阶段的优势最微弱。因此，在新欧洲驾驶循环NEDC中，对搭载1.0L发动机的福特嘉年华车型而言，在通过固定停缸技术已提升的燃油经济性的基础之上，它经济性评估还能再提升1.2%。但在更能代表真实的驾驶情况WLTP（全球轻型车测试规程）循环中，搭载该发动机的蒙迪欧所提升的燃油经济性便微不足道了。

攻克NVH难题

尽管降低燃耗是停缸技术的一大显著优势，但它同时也会对NVH性能造成负面影响。

Schamel表示，“一方面NVH的要求限制了低速状态下的最高扭矩，而另一方面，人类更容易感觉到低频率的震动，这一特点又不允许发动机在低速下运作。车型设计中的NVH性能目标就是将停缸对发动机低速运转顺序启动造成的影响降至最低。”

 “通过传动系统的优化和新技术的引入，保持NVH目标性能所需要的扭矩限值将会更高，而发动机低速限值将会更低。”他指出。

福特公司的测试结果显示，带有经过调整的离合器片和双质量飞轮可以抵消0.5阶次或0.75阶次发动机振动，摆式减震器可减少90%以上的1.5阶次的发动机振动。

基本配置的双质量飞轮和离合器，可将2档时的1500rpm提升至6档时的2000rpm以上，从而实现提升巡航舒适度的目的。减振系统可使所有档位的低速限值“显著降低”，而可接受的最大扭矩则可提升至双质量飞轮的机械设计极限，使得NEDC燃油经济性评估提高1%。若使用滚动停缸技术，该数值还能再提升0.5%。

在对单缸停缸和滚动停缸的优缺点进行总结时，Schamel与其同事这样说道：“所有停缸策略都能实现硬性开发指标，且NVH性能不会下降。在不显著影响燃油经济性的条件下，单缸停缸策略在复杂性、控制难易度和成本效益方面更加优秀。”

福特的计算结果显示，与滚筒停缸相比，单缸停缸技术的总运行成本及优势更加明显。一张高级示意图显示，用40%的成本便能实现90%的燃油经济性优势，“实在是太划算了。”研究团队总结道，“即便超小型发动机也能从停缸策略中获益，而且还能在全球的各种行驶工况和真实的驾驶体验中看到燃耗的降低。”

If the words “Ford Mondeo powered by 1.0-L 3-cylinder EcoBoost engine” sound a bit incongruent, now consider that the company is researching cylinder deactivation for its little triple.

Ford, working with European partners, has examined both single and “rolling” deactivation strategies for its smallest spark-ignited passenger car engine. After proving itself in the B- and C-segment Fiesta and Focus models, the 92-kW (69-hp), 1.0-L—smaller than many motorcycle engines—is now also available in the D-segment Mondeo in Europe.

How does this diminutive engine perform in the roomy sedan when all three cylinders are on the job? A test drive in the U.K. by this Automotive Engineeringeditor of the production version of the Mondeo triple largely dispelled doubts of its general suitability to propel a 1455 kg (3207 lb) curb weight car. Acceleration from zero to 100 km/h takes 12 s and claimed top speed is 200 km/h (124 mph). Official economy figures for the 1.0-L Mondeo include a combined figure of 5.1 L/100 km (about 46 mpg) with CO₂ emissions of 119 g/km.

My test drive was particularly impressive regarding NVH levels both generally and in the cruise. And it is in the cruise that two-cylinder operation for the Mondeo could be viable, just as it may be for the smaller Fiesta and Focus.

Two deactivation strategies

Research into the feasibility of cylinder deactivation for a production triple has been carried out by a high-level Ford team led by Dr. Andreas Schamel, Director, Global Powertrain, Research and Advanced Engineering. He said that when installed in a Focus and dependent on various factors, a fuel consumption reduction of between 4% and 6% is achievable when operating in 666-cm3 twin-cylinder mode.

The general deactivation system would be complemented by further technology that Ford has now researched, including a specifically developed pendulum absorber. Integrated into the driveline, the absorber enables a broader operating range during cylinder deactivation at lower engine speed, explained Schamel in a technical paper he presented during the 2015 Vienna Motor Symposium.

The paper notes Ford's collaboration with Schaeffler Group (Dr. M. Scheidt), including Schaeffler's LuK division (Dr. H. Faust). Dipl-Ing C. Weber of Ford Cologne is also a key member of the research team.

As well as incorporating the pendulum absorber, a cylinder deactivation Focus prototype was also fitted with a Schaeffler dual-mass flywheel (DMF) and a tuned clutch disc, to achieve vibration isolation between transmission and engine.

Mandatory development targets were met and results noted no NVH deterioration compared to the standard production 1.0-L EcoBoost.

Two different cylinder deactivation strategies were examined: deactivation of a single cylinder, and what is termed a “rolling cylinder” deactivation, which would effectively run the EcoBoost triple in a “half-engine” mode, with freedom to vary the number and sequence of deactivated cylinders.

Schamel explained that on a 3-cylinder engine, different strategies for cylinder deactivation are applicable. One "is to apply an appropriate valve deactivation mechanism to one cylinder," effectively creating a 666-cc twin but with the disadvantage of an uneven firing sequence. However, Ford has investigated other technologies which provide the freedom to vary the number and the sequence of deactivated cylinders.

Such a set-up offers the opportunity for a rolling cylinder deactivation and could be used to run the engine in half-engine mode, corresponding to a 500-cm3 active displacement but now with the advantage of an even firing order, he noted in the paper.

The research teams found that the half-engine mode offered a greater potential of avoiding throttle losses at very low loads, but at an overall lower load limit compared to the two-thirds mode. Schamel added: “In the operating area in which the two deactivation strategies overlap, the rolling cylinder deactivation shows a bigger fuel saving potential related to the full engine operation compared to fixed cylinder activation.”

The fuel economy for the 1.0-L engine during rolling cylinder deactivation would be better than that for the fixed cylinder deactivation in low load drive cycles, but the magnitude of the additional benefit would depend on vehicle application and cycle. A small car at light load would get the biggest potential benefit, with smallest achieved by a large car during mid to high load cycle. So a Fiesta with a 1.0-L engine would be able to gain another 1.2% fuel efficiency benefit in NEDC compared to the improvement already achieved with fixed cylinder deactivation. But for a Mondeo using the engine the gain would be negligible in the WLTP (Worldwide Harmonized Light Vehicles Test Procedure) cycle, considered to be more representative of real-world driving.

Conquering NVH

While fuel consumption reduction is the salient plus factor regarding the general application of cylinder deactivation, the downside can be negative NVH effect.

Schamel explained “On the one hand, NVH requirements constrain the maximum torque at lower engine speeds and on the other, the human perception of low frequencies does not allow the operation at very low engine speeds. The NVH objective is the minimization of low engine order excitations caused by cylinder deactivation.

"The NVH limits can be moved to higher torque levels and lower engine speeds by optimization of the powertrain and introduction of new technologies,” he noted. 

The use of the dual-mass flywheel with tuned clutch disc counteracts the 0.5th or 0.75th engine-order excitation and the pendulum damper reduces the 1.5th engine order by more than 90%, according to Ford testing.

The baseline production DMF flywheel and clutch facilitates comfortable cruising from 1500 rpm upwards on 2nd gear and above 2000 rpm in 6th. The absorbing system allows the lower speed limit to be “significantly” reduced in all gears and maximum acceptable torque to be increased close to the mechanical design limit of the DMF, bringing a 1% NEDC fuel economy benefit. The rolling mode deactivation would see an extra 0.5% achieved.

Summing up the pros and cons of single or rolling cylinder deactivation, Schamel and his colleagues reported, “The fulfillment of the mandatory development target, no NVH deterioration, is achievable for all cylinder deactivation strategies. Without a significant compromise regarding fuel economy, the single cylinder deactivation strategy is preferred regarding complexity, controls efforts, and cost effectiveness."

Ford calculations show the ratio of total functional benefit and cost to be "advantageous" for the single cylinder deactivation strategy versus the rolling approach. A high level contemplation shows a 90% fuel economy benefit for 40% of the cost—good "bang for the buck." The research team concluded that "even highly downsized engines can benefit from a cylinder deactivation strategy, with fuel consumption reduction gained in various global drive cycles – and under real conditions.”