Lexus 2-Liter Engine ArchitectureThe Lexus in-line, four-cylinder, two-liter engine in the 2015 NX 200t includes a balance shaft with resin gearing. It uses a twin scroll turbocharger. The engine also has an air to liquid intercooler. Fuel is delivered to the engine by both port and also direct injection. The VVT-iW cam and valve timing system can allow the engine to operate in both the Otto and also Atkinson cycles. The exhaust manifold is built into the cylinder head and is cooled to keep exhaust gases from causing too much strain on this super-hot area of the engine. Let’s dive deep into this engine design now and take a closer look at every aspect of what could be the most important Toyota/Lexus engine in a decade.

Lexus 2.0-Liter Engine Turbocharger DetailsTurbochargers compress the intake charge to aid in combustion. The twin-scroll turbocharger on the Lexus 2015 NX 200t is different in many key ways from competitors’ turbos. The first unique aspect is that Lexus is making its own turbo. Most automakers don’t make turbos. They source them from companies outside. This slows development; means automakers are fitting a standard part to their engine, rather than making it a custom fit, and the quality program now involves two corporations. Lexus takes ownership of this turbo and it was designed entirely in-house by Lexus and manufactured in the Miyoshi plant. Lexus controls its turbocharger from raw material processing to installation in its vehicle.

Most automakers are using twin scroll turbos now with aim of reducing complexity (compared to twin turbos), space, and of course turbo-lag. Lexus’ design focused on not just power, but also fuel efficiency and emissions. Lexus and Toyota live and die by QDR, quality, durability, and reliability. By making this turbocharger themselves Lexus controls its own QDR destiny.

Lexus’ new turbo design has a focus on reduced friction, efficiency optimized turbine blades, and a reduction in noise, vibration, and harshness (NVH). This focus on reduced NVH is apparent when one stands outside the car while it runs. The engine is silent. Stand next a BMW 2.0 liter turbo, such as that in the BMW X3 28i and you will immediately sense the difference in Lexus’ reduced NVH.

Lexus’ turbo impeller is forged to near its final shape which helps control distortion. The impeller wheel is electron beam welded to continue this attention to dimensional accuracy. The turbo housing itself is a new cast-steel material with reduced nickel content Lexus says helps the casing deal with and resist heat distortion and wear.

Lexus 2.0 Turbo Intercooler DetailsIntercoolers remove heat from the compression of the air by the turbo and aid in combustion. A cooler air intake charge is more dense, and thus has more oxygen for combustion (PV=nRT). Lexus mounted its intercooler downstream of the turbo (of course), behind the engine and low in the engine bay. This has many advantages including lower center of gravity (radiators are heavy) and to move the weight back toward the centerline of the vehicle.

Lexus Cam and Valvetrain Details Lexus uses an ultra-lightweight valvetrain with sodium filled valves. The variable valve timing (VVT) system now used by Lexus is called VVT-iW. The i stands for intelligent, and the W stands for wide. The upshot of the new system is that it operates over a wider segment of the intake timing. The system can advance and retard timing so much that the engine actually operates at times in the Otto cycle, and at times in the Atkinson cycle. Say goodbye to the debate over whether to use Otto (more power overall) or Atkinson (better fuel efficiency in some circumstances).

Lexus Exhaust Manifold DetailsThe Lexus exhaust manifold is a 4-pipe to 2-pipe to 1-pipe system that is integrated directly into the cylinder head. Lexus uses engine coolant to remove heat from this critical part to prolong life. It also prolongs the range that the engine can be operated in with the optimum air-fuel ratio. Lexus designed the exhaust manifold to work with the turbocharger to reduce exhaust gas pulsing.

http://www.torquenews.com/1083/2015-nx-200t-lexus-2-liter-turbo-engine-companys-most-important-decade

文章有點(diǎn)長(zhǎng)，亮點(diǎn)有點(diǎn)多，我著重介紹幾個(gè)吧：

1）發(fā)動(dòng)機(jī)型號(hào)是8AR-FTS。

2）雙渦管渦輪增壓器。和其它廠商不同，這臺(tái)渦輪增壓器是完全自己生產(chǎn)的。雷克薩斯宣稱各種高大上的技術(shù)運(yùn)用使得增壓器的NVH控制的更好，發(fā)熱控制的更好，磨損更小。

3）電噴+直噴。壓縮比10:1。被黃金動(dòng)力組合長(zhǎng)期譏笑的VVT-i這次多了個(gè)字母變身VVT-iW, W等于wide，表示進(jìn)氣正時(shí)的控制范圍更加寬，可以在低負(fù)荷時(shí)變成阿特金森循環(huán)（雖然這個(gè)技術(shù)也不新鮮了）。

4）4-2-1排氣歧管直接與氣缸連接（區(qū)別于其他發(fā)動(dòng)機(jī)用螺栓緊固？），歧管由發(fā)動(dòng)機(jī)冷卻液冷卻以減少整個(gè)引擎艙的發(fā)熱量（這個(gè)很重要大家都知道。。。）。雷克薩斯宣稱針對(duì)渦輪增壓引擎的排氣脈沖做了針對(duì)性設(shè)計(jì)。

5）中冷器被放在了發(fā)動(dòng)機(jī)的后面，為了改善前后配重（會(huì)不會(huì)降低冷卻效率？畢竟放在前面更容易吃到風(fēng)）。中冷器盡量靠下是為了降低車輛重心（會(huì)不會(huì)更容易被打壞？）。

6）最大功率235匹@4800-5600rpm。最大扭矩350牛米@1650-4000rpm。放進(jìn)四驅(qū)的NX里0—96kmph用時(shí)7秒。雷克薩斯宣稱綜合百公里油耗10L。

從各種參數(shù)看來這臺(tái)發(fā)動(dòng)機(jī)明年放到國(guó)產(chǎn)漢蘭達(dá)里是用來取代現(xiàn)在的3.5V6的（大概也是被排量稅給逼的。。。），而且據(jù)胖哥楊力說會(huì)匹配現(xiàn)在3.5上的那臺(tái)5速手自一體。。。