在研發(fā)凱迪拉克ATS-V高性能版時，通用汽車的工程師遭遇到了一個不尋常的問題——這款基礎車型的重量有些太輕了。
雖然這樣描述并不準確，但也已經能夠大致描述核心問題了。在通用汽車多年的汽車開發(fā)歷史中，給汽車減重似乎是后來才出現(xiàn)的想法。最近一些用Alpha平臺開發(fā)的型號（如ATS），其基礎車型上都能體現(xiàn)通用公司對重量優(yōu)化理念的貫徹。然而，直到工程師在ATS-V上加大發(fā)動機功率和牽引力后，才發(fā)現(xiàn)他們需要一個更強壯的車身。
凱迪拉克首席工程師Dave Leone表示，無論是雙門轎跑版還是四門轎車版，都必須對ATS-V的底盤進行大量加固，才能將扭矩強度提升25%。首先，工程師們在車輛前部安裝了一個連接沖擊塔與集氣室的支架，以輔助引擎蓋下的V型支架，共同起到加固作用。此外他們還對以下三個平臺進行了加固——包括搖桿隔板，后懸掛托架與單片式車身底板之間用螺栓緊固的沖壓鋼支架，以及前懸掛子結構下方的大型鋁制平臺（升級用的中央部件）等。通用汽車將該平臺稱為“剪力板”，其作用是將前懸掛和托架更穩(wěn)固地與單片式車身相連。
Leone表示，大型鋁制加固板的作用在車輛轉彎時體現(xiàn)得最為明顯，因為ATS-V的轉彎表現(xiàn)非常干脆利落，而且車身并未發(fā)生扭曲。
繼平臺加固之后，通用汽車的工程師還將懸掛部件進行了加固。首先，他們將多連接雙樞軸麥弗遜柱懸掛上的支架避震組替換為零壓順應球形接頭、更堅固的前部彈簧以及更厚實的防傾桿，三者相加可提升50%側傾剛度。此外，他們還將普通ATS上的轉向齒條替換為更堅固的ZF Servotronic II轉向齒條，這也提升了轉向表現(xiàn)。
后方的支架避震組、彈簧、防傾桿和托架基座也同樣得到了加強。工程師還對后懸架的形狀進行了改進，增加了其抗后座力性能，并減少了后部側傾中心的移動。
工程師用一個標準的電子限滑差速器降低出彎時的動力，此外還利用不同直徑的半軸對扭矩反應的頻率不同這個原理，抑制加速時發(fā)生的車橋跳動現(xiàn)象。由GKN提供的左半軸是一個帶有恒速接頭的總成件，長度為55毫米（2.2英寸），而右半軸則是標準規(guī)格，為30毫米（1.2英寸），兩軸剛度比為2.6:1。
制動器均為布雷博產品，前制動器為六活塞單件制動鉗搭配14.5英寸（368毫米）轉子，后制動器為四活塞制動鉗搭配13.3英寸（338毫米）轉子。該配置同樣用于重量級更高的戶外型CTS-V，不僅能夠提供不會衰退的強大制動力，還能在得克薩斯奧斯汀美國跑道（Circuit Of the Americas）的牽引力測試中增加踏板行程。
減震系統(tǒng)使用的是京西重工（BWI）的主動式電磁懸掛技術（MRC），該系統(tǒng)由凱迪拉克首先使用。該技術最近一次迭代時，將兩個減震模式進行了更明確的區(qū)分。ATS-V項目工程師經理John Barrick表示，“現(xiàn)在我們有兩個真正的減震模式了，之前頂多是一個半。”高檔減震模式的性能比舊版高出了40%。
新系統(tǒng)更快的反應時間意味著當車速為60 mph（97 km/h）的時候，ATS-V每行駛1英寸，減震系統(tǒng)都能進行一次自我調節(jié)，而舊系統(tǒng)為3英寸，Barrick補充道。
18英寸鋁制車輪不僅重量輕，而且還能用三個截然不同的區(qū)域牢牢地固定米其林PSS（Pilot Super Sport）輪胎。外輪唇經過硬化處理，可以更好地承受因輪胎周圈的沖擊而造成的側向反力，而且不會對輪胎表面的橡膠造成磨損。中間層經過了濕地牽引力優(yōu)化，而內層則是具有粘性的賽車級橡膠。
轉彎時，該輪胎可以提供驕人的1.25g橫向加速度。
正如工程師們?yōu)楸砻嫦路降募毠?jié)傾盡全力，設計師們對表面本身同樣不遺余力。“所有設計元素都有其目的，”凱迪拉克全球設計執(zhí)行總監(jiān)Andrew Smith表示。“它們可以減小升力、加強冷卻、為車身減重，或兼具多個功能。”
其中最引人注目的是碳纖維引擎蓋及其不加裝飾的碳吸熱口。首先，碳纖維引擎蓋比鋼制引擎蓋更輕巧。第二，吸熱口不僅能為發(fā)動機區(qū)域降溫，而且從引擎蓋上逸散的空氣也有助于降低車輛在高速行駛下產生的升力。
車輛前臉上擴大的敞口可讓更多空氣進入到其后方的眾多熱交換器，而底部的分流器也可以對來自路面上的空氣進行引流，減少升力。ATS-V的擋泥板也經過了加寬處理，可以覆蓋更寬的車輪和輪胎，而門檻和后擾流板則為車輛升力的整體平衡提供了最后的輔助。用戶還可以選擇配置更大尺寸的分流器、引擎蓋吸熱口、后擾流板、門檻和后部空氣擴散器。
經過改善的不僅僅是空氣動力設備。工程師使用塑料對車身下方的后控制臂進行包裹，Barrick說這樣做可以將拖曳力降低兩成。
自然而然，在加裝完所有必要的輔助設備之后，這款高性能ATS-V一定需要一個更強大的傳動系統(tǒng)。
ATS-V的發(fā)動機為獲得SAE認證的雙渦輪直噴3.8升V6發(fā)動機，功率為464 hp（346 kW），扭矩為444 lb·ft（601 N·m）。變速箱可選擇6速手動或8速自動變速箱進行搭配。該車加速至60mph需要3.8秒，最高車速為189mph（304公里/小時）。
這臺發(fā)動機由低慣量鈦鋁合金渦輪與真空作動廢氣閥組成，不僅可以降低拖力，還能增強低轉速時的反應。渦輪增壓器的壓縮器專為匹配峰值功率時的峰值效率而設，可將賽車性能發(fā)揮至最佳水平。
工程師們使用了一種正在申請專利的小容量增壓冷卻技術對發(fā)動機的反應性能進行增強，該技術可以在發(fā)揮出最大升壓的同時提高封裝效率。而發(fā)動機本身則可受益于鈦制連桿，降低慣量。
Hydra-Matic的8L90八速自動變速箱的速度更快，效率更高，因此受到了工程師的青睞。盡管駕駛員可用方向盤上的撥片完成手動變速，但只要切換至沖刺模式，當他在圓形賽道上飛速馳騁時，變速箱的計算機便可自動做出完美的換檔決策。從多方面考慮，這種方式都具有明顯的優(yōu)勢。
然而，對那些不滿足于這種方式的駕駛員來說，凱迪拉克還提供Tremec TR6060六速手動變速箱。我們曾在其他車型上（包括通用汽車的雪佛蘭Corvette）看到過降檔時自動匹配轉速的功能，但ATS-V將其加入無升力的升檔中。當駕駛員腳踩離合器時，可用H模式換擋器完成手動升檔，然后像平常一樣松開踏板。但加速器踏板安裝在車輛地板上，且車輛會自動降低動力，直至升檔完成。
盡管這種方式與擅長手動變速的駕駛員長期積累下來的肌肉記憶背道而馳，但它能夠以驚人的速度完成升檔。因此，計算機匹配的降檔和自動削減動力的升檔可讓駕駛員不再費心于手動換擋，而且它們都能使換檔變得更流暢、更迅速。
搭載自動變速箱的ATS-V的EPA燃油經濟性評估結果為16 mpg城市和24 mpg公路，手動版的結果分別是17 mpg城市和24 mpg公路。
一個電子控制的限滑差速器可將動力高效地傳至路面。多虧極其豐富的齒輪比以及非常低的第1檔，手動版的主減速比為3.73:1，自動版為2.85:1。
可以預見，狂熱的汽車愛好者們還需要進行一番自我調整，才能適應運動型自動變速箱理念和這款運動緊湊型凱迪拉克。
In developing the Cadillac ATS-V high-performance variant, General Motors’ engineers were faced with an unfamiliar problem; a base car that was a little too light.
Not exactly, but that was the gist of the issue. After years of developing cars in which mass reduction was a seeming afterthought, GM has with recently developed models such as the ATS, on its Alpha platform, so thoroughly optimized on mass for the base model that the car was left needing a stronger foundation when more power and traction were added for the ATS-V model.
In both its two-door coupe and four-door sedan variants, the ATS-V received a raft of needed chassis reinforcements that produce a 25% increase in torsional rigidity, reported Cadillac Chief Engineer Dave Leone. This improvement was achieved through the installation of a front shock tower-to-plenum brace along with underhood V-braces, reinforcement to the rocker bulkhead, stamped steel bolt-on braces between the rear suspension cradle mount and the floor of the unibody, and (the centerpiece of the upgrades) a large aluminum platform beneath the front suspension subframe that the company terms a “shear plate” that connects the front suspension and its cradle more securely to the car’s unibody.
The effect of that huge aluminum reinforcement plate is felt primarily on corner turn-in, where the ATS-V responds crisply rather than by twisting the car’s structure, according to Leone.
With the platform suitably braced, GM’s engineers beefed up the suspension components too. That includes replacement of bushings in the multi-link double-pivot MacPherson strut suspension with zero-compliance ball joints, stiffer front springs, and thicker front anti-roll bar that combine to produce a 50% increase in roll stiffness. The ZF Servotronic II steering rack is also stiffer than that on the regular ATS, which also contributes to improved steering feel.
At the rear, there are stiffer bushings, springs, and anti-roll bar along with stronger cradle mounts. Revised rear suspension geometry incorporates more anti-squat and has less migration of the rear roll center.
A standard electronic limited-slip differential helps put the power down on corner exits, while different-diameter halfshafts suppress axle hop under acceleration by not having the same frequency response to torque. The left side shaft, which is provided by GKN as an assembly with its constant velocity joints, is 55 mm (2.2 in) compared to 30 mm (1.2 in) for the standard-issue right shaft, for a 2.6:1 difference in rigidity between the two.
Brakes are the same Brembo six-piston one-piece front calipers with 14.5-in (368-mm) rotors at the front and four-piston rear calipers with 13.3-in (338-mm) rotors at the rear as were used on the heavier outgoing-generation CTS-V, which provided impressive stopping power without fade or increased pedal travel during track testing at the Circuit of the Americas in Austin, TX.
Damping is by the BWI Group’s Magnetic Ride Control that Cadillac brought to market. This latest iteration of the technology provides improved differentiation between its two modes, according to John Barrick, Program Engineering Manager for the ATS-V. “Now we have two true modes,” he said. “Before it was more like one and a half modes.” The increase in maximum damping is 40% greater than before.
The new system’s quicker response time means that the damper adjusts itself for every inch the ATS-V travels at 60 mph (97 km/h), while the previous system covered three inches between adjustments to settings, Barrick added.
The 18-inch forged aluminum wheels help reduce mass and mount Michelin Pilot Super Sport tires molded with three distinctly different zones of compound. The outer shoulder is hardened to withstand the cornering force of hammering around tracks without burning the rubber off the outside of the tires. The middle section is optimized for wet traction, and the inner portion is sticky race-ready rubber.
On the track, the tires contributed to an impressive 1.25 g lateral acceleration in the turns.
Just as engineers attended to every detail under the skin, so did the designers when working on the skin itself. “All of the design elements have a purpose,” said Andrew Smith, Executive Director of Cadillac Global Design. “They contribute to lift reduction, enhanced cooling, reduced mass, or all of the above.”
Most obvious is the carbon-fiber hood, with its bare carbon heat extractor vent. The hood saves weight compared to a steel hood, and the extractor not only helps hold down engine bay temperatures, but the air exiting it atop the hood reduces lift at speed.
The enlarged openings in the front fascia feed more air to the various heat exchangers behind it, and the splitter on the bottom scrapes directs air from the road surface, minimizing lift. The ATS-V’s fenders are widened to cover the wider wheels and tires, and the rocker panels and rear spoiler provide the final touches on overall balance of lift on the car. The optional carbon-fiber package provides enlarged splitter, hood air extractor, rear spoiler, rocker panels, and rear diffuser.
Those aren’t the only aerodynamic devices. Under the car, the lower control arms at the rear are sheathed in plastic covers that Barrick says reduce drag by two counts.
Naturally, as a high-performance variant, once the necessary supporting infrastructure was established, the ATS-V needed a suitably more powerful powertrain.
It is an SAE-certified 464-hp (346-kW), 444-lb·ft (601-N·m) twin-turbocharged, direct-injected 3.8-L V6 engine matched to a six-speed manual or eight-speed automatic transmission. The car accelerates to 60 mph in 3.8 s and reaches a top speed of 189 mph (304 km/h).
The engine features turbocharges with low-ineria titanium-aluminide turbine and vacuum-actuated wastegates for reduced lag and stronger low-rpm response. The turbos’ compressors are matched for peak efficiency at peak power levels, providing maximum on-track performance.
The engine’s response is augmented by a patent-pending low-volume charge-cooling system that improves packaging efficiency while permitting maximum boost pressure. The engine itself enjoys some reduced inertia courtesy of its titanium connecting rods.
The Hydra-Matic 8L90 eight-speed automatic is the faster and more efficient transmission choice. The car features steering-wheel-mounted paddles for manual shift actuation, but when the ATS-V is switched to attack mode, the transmission’s computer makes flawless shift decisions while the driver hammers the car around a circuit. In most respects, it is the better way.
However, for those drivers who think it is not the fun way, Cadillac offers theTremec TR6060 six-speed manual transmission. We’ve seen automatic rev matching on downshifts elsewhere, including GM’s own Chevrolet Corvette, but the ATS-V adds to that no-lift upshifts. The driver depresses the clutch, makes the manual gearchange using the H-pattern shifter, and releases the clutch pedal all as usual. But the accelerator pedal stays on the floor throughout and the car automatically cuts power just long enough to compete the shift motion.
Though this defies the accumulated muscle memory in anyone able to operate a manual transmission, it makes upshifts shockingly quickly. So, maybe computer-matched downshifts and automatic power-cut upshifts leave the driver doing less of the manual shifting job, both ensure that the shifts are smoother and faster.
The EPA fuel economy estimates for the automatic transmission-equipped ATS-V are 16 mpg city and 24 mpg highway, while the manual gets 17 mpg city and 23 mpg highway.
An electronically controlled limited-slip differential helps the power get to the road effectively, with a 3.73:1 final drive ratio for the manual transmission and a 2.85:1 for the automatic, thanks to its abundance of gear ratios that permit a very low first gear.
Apparently, enthusiasts will have to accustom themselves to both the notion of sporty automatic transmissions and sporty compact Cadillacs.
ATS-V擁有頂級運動型轎車級別所需的優(yōu)秀賽道平衡性能。
“書頁式匹配”碳纖維部件不僅更輕巧，而且它的鏡像紋理就如同攤開的書本一樣，更為美觀。
ATS-V的雙渦輪3.6L V6發(fā)動機可以輕輕松松地達到464hp。
穩(wěn)固連接子結構和單片式車身的巨型鋁板可讓ATS-V的轉彎表現(xiàn)更加干脆利落，因為底盤是通過轉向而非彎曲來吸收慣量的。
相對便宜的沖壓鋼角板可以加強后懸掛與單片式車身的連接，這可增強ATS-V的反應表現(xiàn)。