Gas direct-injection engines

这是GDI发动机进化和基本护理的指南。

Discussions of direct fuel injection are almost entirely focused on diesel engines. Increasingly, however, direct injection is being utilized in gasoline engines ranging from the one in the family car to pickups and now to smaller engines. Yet, gas engine fuel injection is completely different from the diesel pump-line nozzle systems.

20世纪70年代中期目睹了在此进口的许多欧洲汽车上引入了博世机械燃料喷射系统。线上金沙赌城网站在20世纪80年代,GM和FORD推出了一种称为节流阀注射(TBI)的混合燃料系统。它包括油门板和上方的喷射器。在大气压下在环境中引入燃料。

Ford was the first to bring true fuel injection to the pickup truck market in 1986. That innovation was the port fuel-injection system (PFI). With this design, there is a fuel injector for each cylinder that is mounted at the junction of the intake manifold to the cylinder head (located approximately 100 mm or less than 4 inches from the intake valve).

端口注射优势

虽然通用电机TBI在低燃料压力(9至13psi)上操作,但福特系统在45 psi下运行。一旦行业转移到PFI,操作燃油压力范围就在45到60 psi之间。

The need to meet stricter emissions and fuel economy standards brought the introduction of gasoline direct injection (GDI).

这个设计,特别设计的喷嘴placed in the combustion chamber of the cylinder head similar to that of a fuel injector in a diesel. This device injects gas directly into the combustion chamber at pressures up to 2,200 psi.

与PFI相比,GDI的益处是,由于乳化混合物通过气缸盖的进气流液而在运输中没有燃料。主要优点在于气缸中的气体发生的相变。由于蒸发潜热,这为燃料 - 空气混合物提供了冷却效果,因为热量用于将液体汽油转化为稀土状态。

来自GDI的冷却器充电的空气温度然后允许发动机的压缩比在许多应用中增加到几乎柴油样值14:1。提高内燃机中燃料经济性最有效的方法是增加压缩比。

多个注射器

Yet, the evolution of these systems did not stand still. The latest trend is the combination PFI and GDI engine. With this design, the number of injectors is double the number of cylinders. There is a PFI injector at the cylinder head end of the intake manifold runner and an injector in the combustion chamber. The engine controller toggles back and forth between these two fuel injectors.

传统上,当在空闲或怠速时和在非常轻的载荷时,通过PFI喷射器燃料通过PFI喷射器来燃料。在其他操作状态期间,发动机由GDI系统提供。同时使用两个系统时,没有运行状态。

Problems with Valve Deposits

As many manufacturers do real-life testing before a design goes into production, they cannot duplicate every scenario that leads to GDI’s pitfalls. With GDI, there is no fuel wetting on the back side of the intake valve. Yet, during cam overlap, combustion gases are reverted there and turn into carbon deposits. These deposits tent-up on the intake valve and block airflow into the cylinder.

当发动机冷或在中间温度阶段并且以低转速驱动并在中等负载下驱动时,可能发生称为低速预点火(LPSI)的现象。

在最佳情况下,LSPI将导致燃烧噪声或裂开火花塞。然而,在许多情况下,它是如此严重的是,它将取下活塞的环或弯曲连杆。

The series of events that can produce LSPI are too technical and in-depth to cover here. It has been determined that the engine oil is a huge contributor, though. It was found that engine oils with a high level of calcium are very prone to cause LSPI.

因此,如果您正在操作使用制造商指定的精确油,则必须执行GDI引擎,这将是一个低钙混合。例如,通用电机标记其低钙油作为葡萄糖。

照顾阀门沉积物

随着PFI / GDI系统的就业,可以通过PFI系统引起带LSPI的发动机运行状态,不再是一个问题。请记住,一旦发动机保修期满,就没有一家汽车公司将有义务尊重LSPI销毁的发动机的索赔。

如果您只有单独的GDI发动机,则需要使用优质的燃料系统和注射器清洁剂来保持喷射器的轴合清洁。然而,由于燃料在气缸孔中引入,罐内清洁器不会从进气门中除去沉积物。

现在市场上有许多优质的清洁产品,可以通过发动机以高怠速引入感应系统,这将在松开阀沉积物,以便它们可以烧坏。

它是一个合理的协议,每5,000到7,000英里执行每5,000到7,000英里。一旦碳变得太厚或厚,就不可能化学去除它。在这种情况下,需要去除气缸盖。

If the engine is a PFI/GDI system, its care doesn’t require much more than using the specified engine oil and a good in-tank fuel system cleaner every 3,000 miles. The chemistry will keep the valves clean along with the PFI and GDI injector pintles and make the system carefree.

不要担心自己的GDI发动机。但我强烈建议您遵循我在这里概述的维护步骤进行无故障服务。如果没有,你可能会把一个新的发动机放在车辆上。

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