在汽車行業(yè)，“運動”是一個已經(jīng)過于泛濫的字眼。在廣告中，常會看到將“轎跑”和“GT”湊在一塊，試圖用類型化的手段給給產(chǎn)品增光的做法，“運動”一詞也經(jīng)常被這樣濫用。
因此，當捷豹的高級工程主管試圖告訴《汽車工程雜志》，他們將在2016年全新推出的輕量級、高性能高端中型XF是一輛“運動型轎車”時，他們其實想說的是：這輛車不僅能在西班牙北部的高難度路面上行駛，而且還能在納瓦拉賽車場上馳騁。
XF搭載著從F-type繼承而來的279 kW (374馬力)， 460 牛·米 (339-磅·英尺) 4.0 L V6渦輪增壓發(fā)動機，即便駕駛員不是專業(yè)賽車手，只是本文的記者而已，這輛車也能夠在高速行駛的狀態(tài)下完美展現(xiàn)“轎車”與“運動”是如何完美結合的。這輛車以沉著冷靜的表現(xiàn)出色地完成了試駕任務。
新款XF（查閱）同樣可以搭配捷豹全新的Ingenium 2.0 L四缸柴油發(fā)動機，其中采用的是博世1800bar（26.1 ksi）的共軌噴射系統(tǒng)，它的功率輸出范圍為120-132 kW（161-177馬力）。第二種配置的XF名為“R-Sport”。
如果撇開名字不談，僅從工程角度考慮，這輛車是否真的可以被稱為運動型轎車？盡管下定論仍需謹慎，但答案是偏向肯定的。
必須達成的要求
當捷豹決定研發(fā)這款新車的時候，工程師們面對的“必須達成的要求”看上去的確令人望而卻步。但正如汽車工程主管Ian Hoban和發(fā)動機規(guī)劃與策略高級經(jīng)理John Pepperell所說的那樣，最終結果達到了他們的預期。
與2007年推出的風格張揚的XF相比，新XF呈現(xiàn)出以下變化：用鋁合金制作的車身框架，使整車質(zhì)量輕了190 kg （419磅）；抗扭硬度提升了28%；空氣動力效率達到0.26Cd；軸距加寬51 mm（2.0英寸），車身總長縮短7 mm （0.3英寸），因此車身包裹性更出色；最后還有彰顯高端本色的車內(nèi)與車外設計。機械方面的改動包括：一體化連桿后懸架；可提供雙輪驅(qū)動和全輪驅(qū)動兩種模式；電動助力轉向系統(tǒng)（EPAS）；多種發(fā)動機可供選擇，其中包括一臺最高扭矩為700 牛·米（516 磅·英尺）的3.0L V6柴油發(fā)動機。
在全車3194個部件中，有2669個是經(jīng)過全新設計的。
“新XF和XE使用的基礎底盤是相同的，”Hoban表示。“我們認為，雙叉骨前懸架和鋁合金一體化連桿后懸架是保證操控性能與高端駕乘舒適感的最佳組合。”
捷豹在車輛上運用鋁材料的經(jīng)驗已累計超過15年。“在鋁材料的設計和制作方面，我們總是在挑戰(zhàn)極限，”Hoban解釋道。“A面是用鋁蒙皮板制作的，車窗使用的是鋁沖壓件，還有車輛基底上采用了厚度各不相同的鑄鋁件，如前懸架的基座等。技術上難度極高的鋁制車身側圍是一整片板材，每片重量不足6 kg。”
高強度鎂鑄件被用于制作XF的前架和橫梁，在B柱等抵御側面碰撞的關鍵部位還使用了超高強度硼強化工藝。
捷豹每次推出新傳動系統(tǒng)的時候，Pepperell都從最初階段就開始參與，在XF項目中也是如此。在初期工程規(guī)劃中，他就將生產(chǎn)與制造策略納入了考慮。
“在這一階段，我們需要為發(fā)動機設定技術目標，其中包括動力、扭矩、細化、耗油量、排放等。我們會研究現(xiàn)有的技術，并思考還需要哪些新技術，”他闡述道。“我們有一個團隊負責監(jiān)控外部市場，評估競爭對手可能發(fā)展的方向，根據(jù)這些信息來決定我們的定位。接著我們將定位轉化為工程規(guī)范，尋找一個全面綜合的解決方案，并在此過程中思考各方面的問題，如設計的復雜性等。”
這一階段完成后， 在捷豹路虎已工作了27年的Pepperell就會和團隊一起將方案轉移給項目實施團隊，后者負責產(chǎn)品的具體工程設計：“對一臺Ingenium這樣的全新發(fā)動機而言，這一階段將花上3-4年的時間。”此后便是一個接一個的研發(fā)階段了。
在捷豹，開發(fā)一款新型發(fā)動機時還需考慮一個極其重要的方面：標志性聲音。而且Pepperell堅定地認為，這項工作十分重要，馬虎不得。在大多數(shù)情況下只要設計好排氣系統(tǒng)就行了，但他也承認，小型柴油發(fā)動機比較困難，需要大量的實踐：“坦白說，最小型的柴油機就是達不到這個效果。”
采用主動電子聲音系統(tǒng)是否能解決這個問題？捷豹路虎已經(jīng)在探討這一可能性了。但如果聲音聽起來不夠真實，那他們是不會使用的，Pepperell解釋道。
XF具有具有一個形狀可以改變的渦輪增壓器（三菱MHT）、功率為132 kW的Ingenium柴油發(fā)動機。確實，這些特點有時候聽起來與XF這樣的車不太匹配，好在轉速為1750-2500 rpm時最高可達430牛·米（317磅·英尺）的扭矩能幫上一點忙。與這臺發(fā)動機搭配的是ZF八速自動變速箱。
700牛·米發(fā)動機
然而在XF的柴油發(fā)動機選項中，有一臺V6發(fā)動機。它由Ford/PSA研發(fā)，不僅聲音“恰當”，而且峰值扭矩可達700牛·米，它在新XF所有動力系統(tǒng)中給人留下了最深刻的印象。新XF的V6發(fā)動機的輸出功率從202提升至221 kW（271至296馬力）。在歐洲混合循環(huán)測試中，XF只需5.8秒就能加速至97 km/h（60 mph），此外它的燃耗僅為5.5 L/100 km，二氧化碳排放為144 g/km。
標準極高的駕乘和操縱方案，是幾十年來多款捷豹車型的重要賣點，而XF在這方面取得的成績比以往還要出色許多。
汽車動力工程經(jīng)理John Darlington將XF的一體化連桿后懸架設計（為F-Type研發(fā)并被XE沿用）稱為駕乘/操縱方面的“一顆明珠”。
此外，他還強調(diào)了在XF上使用的“下一代”減震技術的重要意義。在城市中駕駛時，一個額外的閥門可將部分機油繞過活塞中的主閥門，以減少阻尼力并使駕駛更為順滑。當車輛在城外高速公路上行駛時，這個額外的閥門將閉合，讓所有機油流經(jīng)活塞，使駕駛更為穩(wěn)健。
在XF的V6柴油發(fā)動機中安裝了一個可調(diào)節(jié)的動態(tài)系統(tǒng)（定制的油門映射、變速箱換擋策略、轉向感覺和適應性動態(tài)性能設置等），而且能通過觸屏進行控制。
捷豹的所有這些努力，都讓XF足以當?shù)闷?ldquo;運動型轎車”這一美譽。
作者：Stuart Birch
來源：SAE《汽車工程雜志》
翻譯：SAE上海辦公室
Jaguar’s making of a sports sedan
“Sport” is a much abused word in the automotive industry. Like “coupe” and “GT” together with other attempts at glorification through categorization, it is open to abuse.
So when Jaguar’s senior engineering executives wanted to demonstrate toAutomotive Engineering that its new, mid-size, lightened, aerodynamically efficient, premium 2016MY XF really is a “sports sedan,” they illustrated the point not only on very demanding roads in northern Spain but also on the fast Circuito de Navarra racetrack.
With the supercharged 279-kW (374-hp) 460-N·m (339-lb·ft) 4.0-L V6 engine from the F-type tucked under its hood, the XF was able to show how to convincingly link, at high speed, the words “sedan” and “sport” even with this editor (with no race driver pretensions) in control. It tackled the task with a composed and tidy aplomb.
But the new XF (previously described at http://articles.sae.org/14038/) is also available with Jaguar’s new 2.0-L four-cylinder Ingenium diesel—using Bosch 1800-bar (26.1-ksi) common-rail injection system—with power outputs from 120 to 132 kW (161 to 177 hp), the latter offered in “R-Sport” configuration.
In engineering terms could that, despite its nametag, also be termed a sports sedan? The answer, with one caveat, is in the affirmative.
“Must” list
When Jaguar set out to create the new car, the “must” list of criteria that its engineers had to meet may have seemed daunting, but the result, explained Vehicle Engineering Director Ian Hoban, and Senior Manager Engine Planning and Strategy John Pepperell, is in line with expectations.
Compared to the outgoing XF introduced in 2007, these include a weight loss of up to 190 kg (419 lb) thanks to an aluminum-intensive architecture; torsional stiffness up by 28%; aerodynamic efficiency of 0.26 Cd; improved packaging on a 51 mm (2.0 in) longer wheelbase but 7 mm (0.3 in) shorter overall length; and external and internal design that marks it out as a premium product. The mechanical side includes integral link rear suspension; two- and all-wheel-drive versions; EPAS (electrical power assisted steering); and a very broad engine spread—there is also a 3.0-L V6 diesel with maximum torque of 700 N·m (516 lb·ft).
Of the car’s 3194 part numbers, 2669 are new.
“The new XF shares its fundamental chassis aspects with the XE," said Hoban. "Double wishbones front and aluminum integral link rear suspension we believe are the best combination for handling and premium-level ride comfort.”
Jaguar has accumulated 15 years’ production experience of aluminum throughout its vehicles. “We work at the limit of what is feasible in regard to design and manufacture using the material," said Hoban. "Aluminum skin panels are used for A surfaces, aluminum extrusions for sills, and aluminum castings of varying thicknesses for the foundations of the car such as its front suspension mounts. Technologically challenging aluminum bodysides are single panels, each weighing less than 6 kg.”
High-strength magnesium castings are used for the XF’s front-end carrier and cross-car beam, with ultra-high-strength boron reinforcement, in particular its B-posts for side-impact protection.
Pepperell begins his involvement with all the company’s new powertrains at a very early stage—as he did with those for the XF. That involvement concerns the embryo engineering programs in terms of production and manufacturing strategy.
“It includes technical target setting for the engines in terms of power, torque, refinement, economy, emissions—looking at what technologies there are and what we need,” he explained. “We have a team monitoring the external market place, assessing where we think competitors are going and where we consider we should be positioned. Then we have to translate that into an engineering specification, while considering aspects including complexity as we find the holistic, overall solution.”
That accomplished, Pepperell, who has 27 years’ experience across JLR, and his team hand over to a program delivery team who are responsible for the detailed engineering of the product: “Which for a brand new engine such as the Ingenium will take three to four years.” After that comes the serial development phase.
At Jaguar, another significant element in the development of a new engine is its aural signature, something that must never be subject to palliative action, insisted Pepperell. Much can be done by engineering the exhaust system but he admits that is difficult when developing a small diesel and there is a need for pragmatism: “Frankly, the base diesel will not achieve it.”
Could an active electronic sound system provide a solution; it is something that has been discussed within JLR. If it isn’t authentic it won’t happen, he explained.
Experienced in 132-kW form, the Ingenium diesel, with variable geometry turbocharger (Mitsubishi MHT), does sometimes sound a shade out of place in such a car as the XF, although maximum torque of 430 N·m (317 lb·ft) from 1750 to 2500 rpm helps. It is complemented by a ZF eight-speed auto transmission.
700Nm
However, one of the XF’s diesel engine options is a V6 diesel. Developed from aFord/PSA unit, it does make the “right” sound, and with 700 N·m on tap is a very impressive part of the new model’s powertrain repertoire. For the new car, the V6’s performance has been upped from 202 to 221 kW (271 to 296 hp). It gets the XF to 97 km/h (60 mph) in 5.8 s and achieves a fuel consumption of 5.5 L/100 km and 144 g/km CO2 emissions on the European combined cycle.
Ride and handling solutions that provide very high standards for both have been major selling points for most Jaguars for many decades, and the XF achieves that target far more convincingly than its predecessor.
John Darlington, Vehicle Dynamics Engineering Manager, regards the XF’s integral link rear suspension design (developed for the F-Type and also used in the XE) as “our jewel in the crown” with regard to ride/handling.
He also underlines the significance of the XF’s “next-generation” damper technology. For city driving, an additional valve permits some fluid to bypass the main valve in the piston, so reducing the damping force and smoothing the ride. As vehicle speed builds away from the city, the valve closes, forcing all of the fluid to pass through the piston to firm the ride.
On V6 versions of XF, a configurable dynamics system (tailored throttle mapping, transmission shift strategy, steering feel, and adaptive dynamics settings) is fitted and controlled via a touchscreen menu.
All of this is part of Jaguar’s determined aim to create a car that can carry convincingly the appellation: sports sedan.
捷豹新車型XF可能只是一款標準型的高級轎車，但捷豹缺選擇了在西班牙納瓦拉賽道上向《汽車工程雜志》展示它的性能。圖為V6S。
在捷豹每次推出新發(fā)動機時，發(fā)動機規(guī)劃與策略高級經(jīng)理John Pepperell都會從最初階段就開始參與項目。
75%鋁合金車身架構，有力地確保了新一代捷豹XF的靈活性。
XF中牢牢固定的V6增壓發(fā)動機是由F-Type賽車沿用而來。
捷豹XF的2.0 L柴油發(fā)動機可能將成為R-Sport的配置。
捷豹還使用西班牙北部的高難度道路來證明其賽車和包括新XF在內(nèi)的“運動型轎車”的強大實力。