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73-530: Originally implemented in the Acura RL, SH-AWD allows torque to be continuously distributed between front and rear wheels from 70% front/30% rear to 30% front/70% rear, with up to 100% of the rear power being distributed to the outer left or right wheel to assist in cornering and dramatically reducing understeer . For example, in straight-line, full-throttle acceleration, the RL is capable of distributing 40% of torque to

146-411: A Bundorf analysis . Great care must be taken to avoid conflating the understeer/oversteer behavior with the limit behavior of a vehicle. The physics are very different. They have different handling implications and different causes. The former is concerned with tire distortion effects due to slip and camber angles as increasing levels of lateral acceleration are attained. The latter is concerned with

219-530: A transverse engine , either a turbo-charged in-line four-cylinder Honda K-Series engine in the case of the RDX, or naturally aspirated V-6 versions of the Honda J-Series engine. The engines are mated to a front-wheel drive transaxle without a center differential. The transaxle is bolted to torque transfer unit that spins a center drive shaft that powers the rear differential unit. The rear differential

292-403: A 2005 model, was the first production implementation of SH-AWD. It is the most mechanically complex, and probably the heaviest implementation of SH-AWD. This RL is powered by either a 3.5L 300 horsepower VTEC (variable valve timing and lift) V-6 (2005–2008), or a 3.7L 300 horsepower VTEC V-6 (2009–2010) transverse mounted in the manner of a typical Honda front-wheel-drive car. In fact, the RL uses

365-574: A 2009 model has two major trim levels, a front-wheel-drive version, and an upmarket SH-AWD version. Similar in layout to the Acura RL, the Acura SH-AWD TL features a 3.7L 305 horsepower VTEC V-6, transversely mounted front engine in the Global Midsize Platform. The 2009 model uses a five-speed automatic transmission, but Acura has also promised a new six-speed manual transmission for the 2010 model year. It remains to be seen if

438-518: A 30 kW electric motor which could operate independently of the V-6, unlike earlier mild hybrid Honda IMA configurations. In addition, each rear wheel would have a 20 kW electric motor that would operate independently, varying torque as conditions demand. On a turn, the electric motor would apply torque to the outside rear wheel, while the inside rear wheel motor would drag, amplifying the SH-AWD effect. At

511-491: A constant 1.7% with respect to the speed of the front wheels. The Acceleration Device was first introduced in the flagship Acura RL sedan, and continues in the MMC versions of the Acura RL sedan. This more complex configuration appears to be unique among Acura vehicles equipped SH-AWD. This more complex RL configuration could be considered an exclusive flagship vehicle feature, and not specified for vehicles with lower price points. On

584-416: A cornering situation, the output shaft spins up to 5.7% faster than the input shaft, effectively speeding up the rear wheels. The electromagnetic clutch packs, based on sensor inputs, will vary the torque sent to the rear differential from side to side providing constant and dynamic balancing of the car handling characteristics. The SH-AWD configuration with no acceleration device overdrives the rear wheels at

657-415: A default power split of 90% to the front and 10% to the rear. Like the unit in the RL, both can power the rear wheels with various amounts engine torque. The power split under straight-line, high-speed acceleration varies from vehicle to vehicle. In addition, in cornering situations, dependent on the specific vehicle balance and dynamics, the rearward power transfer ratios in the RDX and MDX differ greatly from

730-589: A given steady state operating condition by the Society of Automotive Engineers (SAE) in document J670 and by the International Organization for Standardization (ISO) in document 8855. Whether the vehicle is understeer or oversteer depends on the rate of change of the understeer angle. The Understeer Angle is the amount of additional steering (at the road wheels, not the hand wheel) that must be added in any given steady-state maneuver beyond

803-696: A high-powered audio system with CD player, AM/FM/ XM Satellite Radio and USB audio interface with iPod integration. Sales began in winter 2009. The Technology Package adds the Navigation System with voice recognition , an Acura/ELS Surround premium audio system and a new multi-view rear camera. Advance Package adds blind spot monitoring system, Collision Mitigating Braking System (CMBS), Adaptive Cruise Control (ACC) and Integrated Dynamics System (IDS), which brought multiple modes of suspension firmness and response using electronically controlled Magneto-Rheological shock absorbers. For 2013, in

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876-537: A highly modified version of the Honda Global Midsize platform, versions of which exist for the Honda Accord, Acura TSX and Acura TL. However, the front transaxle is directly coupled to a torque transfer unit. Two identical clutch/planetary gearsets power each rear wheel. The rear wheels are always overdriven with respect to the speed of the front wheels. The Acceleration Device can variably overdrive

949-542: A last ditch attempt, Acura sold the ZDX in only one trim level. Acura cut costs by eliminating CMBS, ACC and IDS and replaced them with Forward Collision Warning (FCW), Lane Departure Warning (LDW), redesigned front grille, integrated parking sensors, power-folding auto-dimming side mirrors, and new dark accents for the wheels. This resulted in a MSRP ($ 51,815) over $ 5K less than the previous year advance model. The 2013 ZDX has one well-equipped trim level. Standard features include

1022-476: A mechanically similar fixed 1.7% over driven rear differential configuration to the other Acura SH-AWD equipped vehicles. Acura announced in late 2008 that the 2010 Acura TL SH-AWD would be implemented with a six-speed manual transmission. Previous implementations of SH-AWD had all been with five-speed automatic transmissions. On July 20, 2009, Acura announced the Acura ZDX four-door sports coupe, equipped with

1095-449: A navigation system with an 8-inch screen, satellite radio, USB input, Bluetooth, dual-zone automatic climate control, leather upholstery, ventilated and heated seats (front), cruise control, keyless entry, power-folding side mirrors, an auto-dimming rearview mirror, power tailgate, moonroof, and auto on/off headlights. Standard safety features include forward collision warning, lane departure warning, blind spot monitoring, parking sensors, and

1168-491: A new six-speed automatic transmission and SH-AWD. This would be the first time a six-speed automatic transmission would be mated to SH-AWD, as well as being the first six-speed automatic transmission introduced in either the Acura or Honda line up. One week later, Acura announced a similar six-speed automatic transmission and SH-AWD with the 2010 Mid Model Change (MMC) refresh for the second generation Acura MDX. In December 2010,

1241-462: A rearview camera. The ZDX has 27.5 cubic feet of cargo space behind its 60/40 split-folding rear seats and just 57.3 cubic feet with them folded flat, which is very small by class standards. United States Environmental Protection Agency (EPA) fuel consumption estimates for all models are 16 mpg ‑US (15 L/100 km; 19 mpg ‑imp ) in the city, 22 mpg ‑US (11 L/100 km; 26 mpg ‑imp ) on

1314-642: A significantly higher 544 lb⋅ft (738 N⋅m) of torque. All versions use GM's 102   kWh lithium-ion modular Ultium battery, which is also used in the Cadillac Lyriq. It allows the single-motor A-Spec model an EPA range of 313 miles (504 km), while the dual-motor version achieves 304 miles (489 km). The Type S, which has larger 22-inch wheels, achieves a lower 278 miles (447 km) of range. The ZDX can DC fast charge at up to 190kW, which Acura claims allows single motor models to add 81 miles (130 km) of range in 10 minutes, and can charge

1387-401: A variety of situations. The 2009 RL was updated to have more aggressive intervention of SH-AWD to give the car more rear-wheel-drive-like handling characteristics. The Acura RDX was introduced in mid-2006 as a 2007 model year car. The first generation Acura RDX is a small crossover utility vehicle, and features a simpler implementation of SH-AWD than that found in the RL. The RDX does not have

1460-423: Is a T-shaped device. Power coming from the engine is transferred via a central hypoid gear that delivers power to each rear axle. Power to each axle is modulated by identical planetary gear sets and electromagnetic clutch packs which can vary incoming power side to side. As previously described, SH-AWD can vary torque side to side through the rear wheels. This ability to drive one of the rear wheels with more power

1533-399: Is accomplished through overdriving the rear wheels with respect to the front wheels. The Acura RL is designed with a third planetary gear set and clutch pack that are packaged into a so-called "Acceleration Device", which is bolted in front of the rear differential unit. The Acceleration Device allows torque to be passed to the rear wheels at a near one to one ratio, but in cornering situations,

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1606-485: Is also transversely mounted. The second generation Acura MDX, introduced in late 2006 as a 2007 model, uses a simpler implementation of SH-AWD than that found in the RL, the main difference is that unlike the RL 70% front/30% rear torque distribution, the MDX offers the opposite, having a 30% front/70% rear torque distribution. The MDX configuration is similar to that in the RDX in that there is no Acceleration Device as found in

1679-428: Is broken, they are relatively free to swing laterally. Under braking load, more work is typically done by the front brakes. If this forward bias is too great, then the front tyres may lose traction, causing understeer. Understeer gradient is one of the main measures for characterizing steady-state cornering behavior. It is involved in other properties such as characteristic speed (the speed for an understeer vehicle where

1752-547: Is front-biased (with the exception of the performance oriented UB5 TLX Type S) but Audi's Quattro is rear-biased. SH-AWD is already a torque vectoring system but Audi requires two different packages (Dynamic and Dynamic Plus) in order for Quattro to be a torque vectoring system. SH-AWD technology is deeply integrated with other systems and sensors implemented in Acura vehicles including: These systems and sensors all work together to enhance vehicle handling, and safety. The second generation Acura RL sedan, introduced in late 2004 as

1825-522: Is necessary to specify the speed and lateral acceleration whenever reporting understeer/oversteer characteristics. Many properties of the vehicle affect the understeer gradient, including tyre cornering stiffness, camber thrust , lateral force compliance steer, self aligning torque , lateral weight transfer , and compliance in the steering system. Weight distribution affects the normal force on each tyre and therefore its grip. These individual contributions can be identified analytically or by measurement in

1898-401: Is provided from four driving wheels rather than two front driving wheels. In the dry, this served to reduce front-wheel drive torque steer , and provide more front tire adhesion for cornering. In the wet, snow or mud, power to the rear wheels moves the vehicle from rest with a minimum of wheelspin because all four tires are working together to move the car, rather than just two front tires. VTM-4

1971-409: Is taken to the grip limit of the tyres, where it is no longer possible to increase lateral acceleration, the vehicle will follow a path with a radius larger than intended. Although the vehicle cannot increase lateral acceleration, it is dynamically stable. When an oversteering vehicle is taken to the grip limit of the tyres, it becomes dynamically unstable with a tendency to spin . Although the vehicle

2044-512: Is the base single-motor, rear-wheel drive A-Spec which outputs 358 hp (267 kW; 363 PS) and 324 lb⋅ft (439 N⋅m) of torque. The all-wheel drive A-Spec has an additional motor powering the front wheels and makes 490 hp (370 kW; 500 PS) and 437 lb⋅ft (592 N⋅m) of torque. A higher output version of this setup is used in the Type S, where it produces a slightly increased 500 hp (370 kW; 510 PS) and

2117-423: Is unstable in open-loop control, a skilled driver can maintain control past the point of instability with countersteering and/or correct use of the throttle or even brakes; this is done purposely in the sport of drifting . If a rear-wheel-drive vehicle has enough power to spin the rear wheels, it can initiate oversteer at any time by sending enough engine power to the wheels that they start spinning. Once traction

2190-399: Is what is happening when a car 'spins out'. A car susceptible to being loose is sometimes known as 'tail happy', as in the way a dog wags its tail when happy and a common problem is fishtailing . In real-world driving, there are continuous changes in speed, acceleration (vehicle braking or accelerating), steering angle, etc. Those changes are all constantly altering the load distribution of

2263-460: The 2009 Acura RL. This improved version provided earlier SH-AWD intervention (first gear vs second), and more precise use of the rear differential electromagnetic clutch system. Yet another version of SH-AWD was introduced in late 2008 with the fourth generation 2009 Acura TL . The Acura TL implementation of SH-AWD is mechanically more similar to the SH-AWD layout in the Acura MDX and RDX in that

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2336-668: The 2010 model will also feature the newly announced six-speed automatic transmission featured in the prototype Acura ZDX announced at the April 2009 New York Auto Show. Unlike the Acura RL, the SH-AWD TL does not have the Acceleration Device. The Acura TLX was introduced in April 2014 at the New York International Auto Show . The first generation Acura ZDX was announced on April 8, 2009 at

2409-478: The 2011 Acura RL was announced with a second Mid Model Change, featuring, among other things, a six-speed automatic transmission. On November 30, 2011, as part of the publicity surrounding the 2011 Tokyo Auto Show , Honda announced a new implementation of SH-AWD as part of its "Earth Dreams Technology". The new hybrid electric SH-AWD would be based on an all new 3.5 L V-6 alongside three electric motors and lithium-ion battery technology. The V-6 would be mated to

2482-429: The 3,664 cc (3.664 L; 223.6 cu in) SOHC VTEC V6 all-aluminum engine rated 300 bhp (220 kW) at 6300 rpm and 270 lb⋅ft (366 N⋅m) at 4500 rpm, 6-speed automatic transmission, Super Handling All-Wheel Drive (SH-AWD), 19-inch, 7-spoke alloy wheels, panoramic glass roof with movable sunshades, hand-stitched leather interior, HandsFreeLink Bluetooth connectivity, power tailgate, and

2555-519: The ATTS technology in the 1997 Honda Prelude Type SH. Honda introduced the VTM- automatic all-wheel-drive system in late 2000 on the 2001 model year Acura MDX sport utility vehicle ( SUV ) and later on the 2003 Honda Pilot SUV. The VTM-4 system claimed to be different from other all-wheel-drive systems in that it "anticipated" wheel slippage, rather than waiting for the vehicle to sense wheel slippage, when

2628-432: The Acceleration Device and can be found in: The Acceleration Device allows the rear wheels to be variably overdriven with respect to the speed of the front wheels up to 5.7%. The Acceleration Device in the Acura RL is positioned in front of the rear differential. During normal steady state driving, the Acceleration Device input shaft (from the engine) and output shaft (to the rear differential) spin at almost equal speeds. In

2701-549: The Acceleration Device found in the Acura RL; instead the rear wheels are constantly overdriven at 1.7% higher speed than the front wheels. The RDX is distinguished by a unique 2.3L turbo charged 240 horsepower inline four-cylinder VTEC engine mounted in what is purported to be a unique version of the Honda Global Small Light Truck Platform, a version different from the platform used for the same-generation Honda CR-V and Honda Element. The engine

2774-412: The Acceleration Device variably increases the torque passed to the rear up to 5%, depending on the cornering situation. As of early 2010, SH-AWD has been implemented by Acura in two functionally similar, but mechanically different configurations, with and without Acceleration Device. The more complex SH-AWD version uses the Acceleration Device and can be found in: The less complex version of SH-AWD omits

2847-466: The Ackermann steer angle. The Ackermann Steer Angle is the steer angle at which the vehicle would travel about a curve when there is no lateral acceleration required (at negligibly low speed). The Understeer Gradient (U) is the rate of change of the understeer angle with respect to lateral acceleration on a level road for a given steady state operating condition. The vehicle is Understeer if

2920-534: The Acura MDX V-6. The Acura ZDX SH-AWD implementation description appears to be very similar to the Acura MDX SH-AWD implementation. Understeer and oversteer Understeer and oversteer are vehicle dynamics terms used to describe the sensitivity of the vehicle to changes in steering angle associated with changes in lateral acceleration. This sensitivity is defined for a level road for

2993-435: The Cadillac Lyriq. Compared to the original ZDX, the 2nd generation ZDX has a more traditional roofline. The ZDX gains an A-Spec single-motor configuration, and a Type S performance variant, the latter of which is estimated to give 500hp, making it the most powerful SUV ever produced by Acura. It is the first Acura to implement several technologies and features. The standard 18-speaker Bang & Olufsen audio system marks

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3066-523: The New York Auto Show as a 2010 model, slated for introduction in late fall 2009 as an all new prototype concept car, billed as a luxury four-door sports coupe. The Acura ZDX went on sale December 15, 2009. The car is powered by an all-aluminum 3.7L 300 horsepower, 270 lbs-ft torque VTEC V-6, mated to an all-new 6-speed automatic transmission with Sequential SportShift and Super Handling All-Wheel Drive. The V-6 appears to be mechanically similar to

3139-524: The RL and TL sedans. For example, in comparing the RL to the MDX, in hard cornering, the most power transferred to the rear wheels for the RL is 70%, whereas the MDX is only 50%. In straight line efficient cruising, different model years of the RL can transfer from 70 to 80% to the front wheels, while the MDX can transfer as much as 90% to the front wheels. SH-AWD differs in function from other popular all-wheel drive systems, like Audi’s popular Quattro . For example, when it comes to torque distribution, SH-AWD

3212-657: The RL. The rear wheels are constantly overdriven at 1.7% faster speed than the front wheels. The MDX is powered by a 3.7L 300 horsepower VTEC V-6 engine transversely mounted in a version of the Honda Global Large Light Truck Platform, versions of which are used for the Honda Pilot, Honda Ridgeline, Honda Odyssey, and the 2010 Acura ZDX. As can be seen below, the vehicle dynamics of the Acura MDX require different operating parameters. The fourth generation Acura TL, introduced in late 2008 as

3285-760: The all-electric ZDX in August 2023. The first EV in Acura's lineup, the new ZDX is co-developed using General Motors ' Ultium vehicle architecture that currently underpins the Cadillac Lyriq , Chevrolet Blazer EV and the Honda Prologue , itself slated for a 2024 release. Similar to the Prologue, it shares many components with the Blazer EV, including the steering wheel, climate setting controls, and door handles. Additionally, it shares its powertrain with

3358-415: The best automotive innovations of 2004, and as part of an already tech-filled vehicle helped to earn the 2005 "Tech car of the year" from CNET . Honda has since announced an evolution of SH-AWD using hybrid electric technology. In a 2012 announcement, Sport Hybrid SH-AWD replaces the engine powered mechanical drive shaft and clutch packs by two, 27 horsepower electric motors, one on each wheel, not driven by

3431-418: The center of mass is moved rearward, the understeer gradient tends to decrease. The shifting of the center of mass is proportional to acceleration and affected by the height of the center of mass. When braking, more of the vehicles weight (load) is put on the front tyres and an less on the rear tyres. Conversely, when the vehicle accelerates, the opposite happens, the weight shifts to the rear tires. Similarly, as

3504-586: The center of mass of the load is shifted from one side to the other, the inside or outside tyres traction changes. In extreme cases, the inside or front tyres may completely lift off the ground, eliminating or reducing the steering input that can be transferred to the ground. While weight distribution and suspension geometry have the greatest effect on measured understeer gradient in a steady-state test, power distribution, brake bias and front-rear weight transfer will also affect which wheels lose traction first in many real-world scenarios. When an understeering vehicle

3577-554: The debut of Acura's partnership with the company. The infotainment system has Google Built-in, which is the first implementation of Android Automotive in an Acura, though it is a reskin of GM's version rather than the Honda developed version seen in the Accord . Additionally, the ZDX will debut a new hands-free highway driving assistance system called AcuraWatch 360+ with Hands Free Cruise. The ZDX has three different powertrain options. First

3650-564: The distinction between coupe, sedan and sport utility vehicle." The ZDX features Acura's first six speed automatic transmission , advanced ventilated seats, as well as other luxury appointments. Although the ZDX shares a similar profile with the Honda Crosstour , the two vehicles are not mechanically related: the latter is based on the Honda Accord, while the ZDX is based on the Honda Pilot / Acura MDX . On August 19, 2022, it

3723-404: The front tyres will keep the front of the vehicle on the desired path but the rear tyres will slip and follow a path with a greater radius. The back end will swing out and the vehicle will turn toward the inside of the curve. If the steering angle is not changed, then the front wheels will trace out a smaller and smaller circle while the rear wheels continue to swing around the front of the car. This

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3796-688: The gasoline engine. The first two announced applications of the Sport Hybrid SH-AWD are to be on the rear wheels of the 2014 Acura RLX , and on the front wheels of the second generation Acura NSX . On a very basic level, the SH-AWD system is a combination of the Honda Variable Torque Management 4WD (VTM-4) automatic all-wheel-drive system and the Active Torque Transfer System (ATTS) variable torque distribution system. Honda introduced

3869-506: The highway and 19 mpg ‑US (12 L/100 km; 23 mpg ‑imp ) combined. Discontinuation The ZDX was discontinued after the 2013 model year due to poor sales, and in a statement from Honda, "as the Acura brand sharpens its focus on new models and core products." The ZDX was the rarest of U.S. manufactured Acura offerings, with a total of 7,191 vehicles produced and sold in North America. Acura unveiled

3942-425: The lateral and longitudinal forces, a function of the normal force and coefficient of friction. If the lateral and longitudinal forces presented at the tyre during operations exceeds the tyre's available traction force then the tyre is said to be saturated and will loose its grip on the ground and start to slip. Push (plow) can be understood as a condition where, while cornering, the front tyres become saturated before

4015-406: The limiting friction case in which either the front or rear wheels become saturated first. It is best to use race driver's descriptive terms "push (plow) and loose (spin)" for limit behavior so that these concepts are not confused. Tyres transmit lateral (side to side) and longitudinal (front to back) forces to the ground. The total traction force (grip) available to the a tyre is the vector sum of

4088-409: The measurement methods. Results depend on the type of test, so simply giving a deg/g value is not sufficient; it is also necessary to indicate the type of procedure used to measure the gradient. Vehicles are inherently nonlinear systems , and it is normal for U to vary over the range of testing. It is possible for a vehicle to show understeer in some conditions and oversteer in others. Therefore, it

4161-485: The other hand, the later SH-AWD configuration without the Acceleration Device could just be a simpler and less sophisticated version due to vehicle dynamics and price points, or it could represent a more refined, less complex and inherently more reliable, new standard for the SH-AWD configuration. The rationale for the two distinct configurations has not been publicized by Acura. SH-AWD in the Acura RDX and Acura MDX uses

4234-409: The rear and slip first. Since the front tyres cannot provide any additional lateral force and the rear tyres can, the front of the vehicle will follow a path of greater radius than the rear and if there are no changes to the steering angle (i.e. the steering wheel stays in the same position), the vehicle's front will slide to the outside of the curve. If the rear tyres become saturated before the front,

4307-564: The rear axles. In the North American market, Honda introduced the original SH-AWD system in late 2004 with the second generation 2005 Acura RL. Two other SH-AWD variants were introduced in late 2006 in the then all-new 2007 Acura RDX , and the new second generation 2007 Acura MDX sport utility vehicles. In late 2008, an improved version of the Acura RL SH-AWD was introduced in the significantly revised Mid-Model Change (MMC) of

4380-457: The rear differential is over driven at a constant 1.7% faster than the front wheels. This is unlike the Acura RL which, since its introduction in 2004, added an acceleration device that can over drive the rear wheels up to 5.7% faster than the front wheels. As of 2010, the Acura RL remains the only SH-AWD configuration with the variable speed rear differential acceleration device. The newly introduced 2010 Acura ZDX four-door sports coupe maintains

4453-401: The rear wheel speed up to 5.7%. The 2005 and 2006 system normally sends 70% of power to the front wheels and 30% to the rear under normal conditions but these ratios can reverse according to dynamic driving conditions. The 2007–2008 brochure specification sections indicate that this ratio changed to 80%-20%, and vice versa. The system works because the clutches can slip under circumstances where

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4526-440: The rear wheels and 60% to the front wheels. In a hard turn, up to 100% of the rear wheel power can be distributed to the single, outer rear wheel. This action pushes the rear around the corner, reducing understeer and keeping the car balanced and controlled. The effect is similar to steering a row boat where applying more power to one oar can turn the boat. The SH-AWD all-wheel-drive system was lauded by Popular Science as one of

4599-507: The reduction of oversteer and more balanced handling. In limited situations, the vehicle may exhibit power oversteer, a characteristic of sportier rear-wheel-drive vehicles. While the rear differential also acts like a limited slip differential in spirited driving, SH-AWD is deeply integrated into the Honda Vehicle Stability Assist (VSA) system and various onboard sensors which helps to keep the car under control in

4672-501: The same time, the dragging motor would act as a generator , feeding power to the outside wheel motor. If the lithium ion pack became depleted, the V-6 would power the front electric motor as generator to feed electricity to rear wheels while also charging the battery. A prototype of this system was shown in a test mule using an 8th generation North American version of the Honda Accord . Current SH-AWD configurations are all mated to

4745-404: The steer angle needed to negotiate a turn is twice the Ackermann angle), lateral acceleration gain (g's/deg), yaw velocity gain (1/s), and critical speed (the speed where an oversteer vehicle has infinite lateral acceleration gain). Acura ZDX The Acura ZDX is a mid-size luxury crossover SUV with a sloping rear roofline developed by Honda for its upmarket brand Acura . The car

4818-657: The understeer gradient is positive, Oversteer if the understeer gradient is negative, and Neutral steer if the understeer gradient is zero. Car and motorsport enthusiasts often use the terminology informally in magazines and blogs to describe vehicle response to steering in a variety of manoueuvres. Several tests can be used to determine understeer gradient: constant radius (repeat tests at different speeds), constant speed (repeat tests with different steering angles), or constant steer (repeat tests at different speeds). Formal descriptions of these three kinds of testing are provided by ISO. Gillespie goes into some detail on two of

4891-433: The vehicle ZDX, Acura added the words "Luxury Four-Door Sports Coupe" to the caption for each picture. Moreover, it did not state the vehicle as a crossover or an SUV. The automaker translated the designers renderings almost literally into production sheetmetal. It's all but unheard-of for a rookie designer to have sketches embraced by a car company and put into production with so few changes. The announced version includes

4964-438: The vehicle is turning, thus allowing the rear and front wheels to turn at different rates around a curve. As noted above, the SH-AWD can take 100% of the power shunted through the rear differentials and variably direct power to each wheel, up to 100% of that power to the outside rear wheel. Adding power to the outside rear wheel on a turn has a steering effect on the vehicle which can greatly improve vehicle handling dynamics through

5037-495: The vehicle may already be in trouble. The VTM-4 system consisted of a pair of computer-controlled wet clutches in the rear axle that worked in concert with the front wheels regardless of road conditions. On start-up, the VTM-4 system would send torque (power) from the front wheels to the rear wheels to supplement the normal front-wheel drive mode. With all four wheels being powered on start-up, regardless of conditions, more tire adhesion

5110-412: The vehicle, which, along with changes in tyre temperatures and road surface conditions are is constantly changing the maximum traction force available at each tyre. Generally, though, it is changes to the center of mass which cause tyre saturation and inform limit handling characteristics. If the center of mass is moved forward, the understeer gradient tends to increase due to tyre load sensitivity . When

5183-465: Was announced that the ZDX nameplate would return to Acura's lineup in 2024 for the brand's first electric vehicle . The new ZDX was co-developed with General Motors . Five teaser shots, released by Acura between March 16 and 20, 2009, indicated a coupe-like sloping roofline akin to that of the BMW X6 , which led many observers to believe that is its direct competitor. After the announcement about naming

5256-425: Was designed with a special lock mode to assist when a vehicle is stuck in the snow. This lock mode automatically engaged power to all four wheels at low speeds. As speeds increased, the power to the rear wheel would decrease, and by 18 mph, the system would revert to front-wheel drive. SH-AWD combined both the automatic all-wheel drive VTM-4 system capability with the "super handling" torque shifting ability of ATTS on

5329-455: Was originally planned to be called the "MSX". The ZDX debuted at the 2009 New York International Auto Show on April 8, 2009, as a 2010 model. The vehicle was also the first to be completely designed at Acura's southern California design studio in Torrance. The original ZDX concept was penned by Michelle Christensen who labeled it a "4-door luxury sports coupe" and which Acura says "blurs

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