Powertrain Technology: Acknowledging Advances

Gearbox Developments: From the Race Track to the Driveway

Xtrac is a company based in the United Kingdom that specializes in the production of high-performance transmissions, particularly for use in motorsports series including Formula One, IndyCar, Touring Car, and Grand-Am. For the 2011 season, “The requirement for more fuel-efficient engines has increased the demand for new transmissions, leading to our highest-ever order book with more than 60% of our contracts coming from overseas markets. This includes brand new products developed to meet the latest technical regulations in endurance sports car racing and touring cars,” says Peter Digby, managing director of the firm.

So even in motorsports, fuel efficiency is something that is of more than slightly passing interest.

The company has actually developed new transmissions—or “gearboxes,” as they are known in that world—for the 2011 season. Included:

• 1046. This is a front-wheel-drive transverse gearbox specifically designed for the British Touring Car Association (TOCA) regulations for the Next Generation Touring Car. Xtrac was named the official 2011 Dunlop MSA British Touring Car Championship transmission provider and technical partner, meaning that it is the sole provider of transmissions to that racing series. Development on the 1046 began in May, 2010, with the goal of meeting a torque target of 450 Nm (332 lb-ft) for the TOCA requirement. The transmission is a sequentially shifted six-speed. It has a cast-aluminum alloy case. In addition to the front-drive setup, one for rear-wheel-drive applications was also designed at the same time. This transmission uses the same internal components, but the case is different. In addition to the aforementioned series, the transmissions are also available for use in the FIA World Touring Car Championship (WTCC). While there is no spec transmission for that series, there are specific requirements that the transmissions used must meet: for front-drive transmissions, the minimum weight is 35 kg (77 lb); for rear-drive transmissions, the minimum weight is 30 kg (66 lb). The 1046 transmissions hit those numbers.

 

• 1059. This is a traverse six-speed that was developed for the Automobile Club de l’Ouest LMP technical regs. It is housed in a generic main case so that it can be used with various engine and chassis setups. The transmission was designed so that it is short: the input-to-output length (not including the separate bell housing) is just 288 mm (11.34 in), contributing to increased rigidity. Development goals include high reliability, performance, cost-effectiveness, and ease of servicing and assembly. Also, it has been designed for installation with kinetic energy recovery systems, the Flybrid flywheel system (flybridsystems.com).

 

• 600. A six-speed, rear-mounted longitudinal transaxle gearbox with a manual sequential gear change that was developed for GT1, GT2, and GT3 applications. One interesting aspect of the development: the main case and cluster cover are cast aluminum (Xtrac has in-house casting capabilities) to reduce costs. However, the castings can also be done in lighter—but more expensive—magnesium. Also, for those who need to address packaging issues, the two castings are designed so that they can be integrated into one.

 

• 426. This is a rear-wheel-drive six-speed transmission that was developed for GT2 and GT4 endurance sports car racing, based on the 426 front-drive transmission that had been developed for touring car racing. It has an input torque capacity of 650 Nm (480 lb-ft) and weighs 43.5 kg (96 lb). One aspect of the development of this transmission is meeting the strict cost constraints that are characteristic of the series; this meant that value engineering was a paramount concern.

While this may be good and well for those who go racing, what about those who go to work and the grocery store and the like? Well, Xtrac has developed technology for racing that it believes can be deployed in more traditional cars . . . although its initial application area is on electric vehicles.

 

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The Pagani Huayra: Light & Powerful

Pagani Automobili S.p.A. is one of the world’s renowned producers of exotic supercars, such as the Zonda R. The latest vehicle from Horacio Pagani’s studio is the Huayra, a car that was styled during a five-year period. Development included the construction of eight scale models and two 1:1 models before the final shape was realized. There are five copies of the car built, which are undergoing extensive testing by companies including Mercedes-AMG and Bosch Engineering.

Through the extensive deployment of lightweight materials both inside and out—ranging from a carbon-titanium monocoque to chromium-molybdenum subframes—the Huayra is extremely light, with a mass of just 1,350 kg (2,970 lb).

Add in a 6-liter, 700-hp V12 engine from Mercedes-AMG, and you can imagine the power and performance of this car.

What’s connecting the engine to the wheels? A traverse sequential seven-speed gearbox and a dual-plate clutch supplied by Xtrac. This synchromesh transmission setup is light, weighing 96 kg (211 lb). While Pagani—which also uses an Xtrac transmission in its Zonda R race car, which has a similar engine, but one that produces 710 Nm (524 lb-ft) of torque vs. the 1,000 Nm (737 lb-ft) of the Huayra—had considered using a dual-clutch transmission, it determined that that would add an additional 70 kg (154 lb) to the car, so they chose not to go in that direction.

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Durr at Cummins Columbus

Engine manufacturing is a high-precision process, and it goes without saying that the components produced have to be clean. At the Cummins (cummins.com) light-duty diesel facility in Columbus, IN, they’ve installed a comprehensive system from Dürr Ecoclean (durr-ecoclean.com) that integrates the CNC machines with washers, coolant filtration systems, gantries, robotic buffer systems, and conveyors and floor automation.

To transfer the blocks and heads, a modular system, Dürr PZR—Powered Zone Roller—is used along with overhead guided vehicles, which transport parts across main aisles. To manage work flows, there are Robotic Input-Output buffers, which provide automated short-term storage of components—say in the event of a downstream work stoppage.

Cleaning of the blocks is performed in a process that starts with an immersion and rotation. Then there are two stages during which dedicated nozzles aim at specific features on the blocks (e.g., tapped holes). Then there is a drying process that includes rollover, air blow-off, and a vacuum drying station.

The cylinder heads are cleaned in a similar manner as the blocks, with some modifications. For example, there is a third stage during which high-pressure—4,500-psi—nozzles not only clean but deburr features on the heads.

With more than 40 CNC and transfer machines in the system, and the potential for expansion, Dürr also provides a central coolant filtration system that has two 100,000-gal tanks and a pumping capacity of 17,000 gal/minute.

  Dürr EcoCTrans parts cleaner used to clean Cummins diesel blocks and heads.
 

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Compact SCR Urea Pump

To help address the nitrogen oxide (NOx) regulations that diesel manufacturers are facing for both cars and trucks by 2014, TI Automotive (tiautomotive.com) has developed a compact, self-contained selective catalytic reduction (SCR) urea pump motor assembly that the supplier claims is the “smallest and lowest-weight assembly” of its type available today. It is said to be 50% lighter than traditional products. Because of its compact size, it can be deployed with various SCR systems and can be mounted in various positions.  

The system uses magnetic coupling technology so all electrical connections are isolated from the fluid flow (urea is highly corrosive, so this isolation is important); the compact brushless motor and gerotor pump allow controlled flow of 5 to 50 liters per hour.

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Quickly Inspecting Bores

A system for fast inspection of bores measuring from 75 to 110 mm in components including engine blocks, transmission cases, connecting rods, and cylinder liners has been introduced by Hommel-Etamic (hommel-etamic.com). The IPS100 uses CMOS image sensors that capture images from inside the bore surface. Illumination is provided by an internal LED. The system provides a 360° scan of the surface as it is inserted into the bore. Defects including blow holes, scratches, and porosity can be readily detected by the system. Because it operates quickly in a single pass it can be deployed in high-volume inspection operations.

 Internal LED source provides illumination for the IPS 100 bore inspection system.
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Honing for Better Engines

An automated CNC honing system that can handle inline four- and six-cylinder blocks as well as V6 and V8 engines—including high-nickel and compacted graphite iron (CGI) blocks—has been developed by Sunnen (sunnen.com). The SV-410 features a 7.5-kW spindle for fast metal removal with metal-bond CBN and diamond abrasives (as well as standard aluminum oxide and silicon carbide stones); the servo-driven straight line stroke can be performed at rates up to 160 strokes per minute. The servo stroking system allows auto-dwell in any part of the bore to automatically correct any straightness issues.

The system features a servo fixture that rolls the block to provide access to all of the cylinders (then rolls the block to dump oil/coolant); a 500-lb. block can be rolled in one second, bank-to-bank. The system has a work envelope of 36 x 40 in. and can handle parts up to 1,500 lb. Blocks with bore diameters of 19 to 200 mm can be honed (depending on tool options).

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Electric Powertrains & Safety

While many vehicle manufacturers are promoting their electric powertrains, there’s one thing that tends not to be discussed so much in public: the conse-quences of collisions in electric vehicles (EVs). One company that is developing an EV that is putting safety first and foremost is, not surprisingly, Volvo.

The Volvo C30 Electric has an 82-kW electric motor under the hood in place of an internal combustion engine. It has a 400-volt electrical system. It uses lithium-ion battery packs that weigh a combined 280 kg.

 

Part of the issue related to safety is packaging. For one thing, because the electric motor doesn’t have the crash-energy management properties that an internal combustion engine does (due primarily to its size and mass), they’ve had to reinforce the front structure of the C30. Because the overall vehicle weight is heavier than a standard car on the order of 300 lb, there is more energy to manage. The batteries are bigger than a conventional gas tank. Not only do they fill the space where the tank would be positioned, they are also in the tunnel area down the middle of the car. So they’ve added reinforcements around the battery pack.

According to Jan Ivarsson, senior manager, Safety Strategy & Require-ments, at Volvo, “Our far-reaching research emphasizes the importance of separating the lithium-ion batteries from the car’s crumple zones and the passenger compartment. This is the same safety approach we apply with regard to the fuel tank in a conventional car. Another challenge is to reinforce the crumple zones where the smaller motor occupies less space than usual.”

The crash sensor that’s used to send signals to the airbags for deployment performs another function: it controls the fuses so that power is cut in 50 milliseconds in case of a collision. In addition, there are other fuses that are cut in the event that a ground fault is detected (e.g., a damaged cable comes in contact with the frame).

To determine the performance of the C30 Electric they performed a 40% offset collision at the Volvo Cars’ crash test facility in Sweden. The car hit a barrier at 40 mph (64 km/h). According to Ivarsson, “The test produced exactly the results we expected. The C30 Electric offers the very same high safety level as a C30 with a combustion engine. The front deformed and distributed the crash energy as we expected. Both the batteries and the cables that are part of the electric system remained entirely intact after the collision.”

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New Steel for Valve Seats

One of the consequences of downsized engines—yet engines that are still expected to perform—is that they tend to be highly loaded, which has a consequence of running at higher temperatures. These factors can play havoc on the valvetrain, the valve seat inserts, in particular.

So Federal-Mogul (federalmogul.com) has developed a new material for valve seat inserts for these engines (or those that are using high-octane blended fuels). Unlike some other tool steel grade alloys that contain molybdenum and tungsten, which are comparatively costly alloying elements, this “lean” tool steel has an increased amount of chromium in it, as well as carbides that contribute to a multi-phase composite microstructure.

While the material exhibits high wear resistance (the hard phases of the material are >1000HV50 on the Vickers hardness scale), its softer matrix means longer tool life when, say, bevel cutting the valve seats. Which improves productivity in cylinder head machining ops while providing a product that meets performance requirements.

Federal-Mogul is looking into using variants of the tool steel for other applications, like turbocharger components.

New steel alloy meets demands for downsized engine valve seats yet is easy to machine.

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Transmissions by the Numbers

What do the Audi A6, Audi A7, Audi A8, Audi Q5 Hybrid, BMW 5 Series, BMW 7 Series ActiveHybrid, and BMW X3 have in common?

ZF Friedrichshafen AG (zf.com).

Each of those cars is equipped with a transmission from the supplier of driveline and chassis components.

As in, the A6 has a ZF eight-speed; the A7 and A8 have eight-speeds, as well. The Q5 Hybrid has a modified eight-speed for hybrid use (in place of a torque converter there is a disk-shaped electric motor; there is a multiplate clutch operating in an oil bath that couples and decouples the electric motor and the four-cylinder engine). The 5 Series can be fitted with a manual six-speed or an eight-speed transmission. The 7 Series ActiveHybrid also has a modified eight-speed, but in this case there is an electric motor and a torque converter (although it should be noted that there is a V8 involved, as well). And the X3 can be equipped with a six-speed manual or an eight-speed automatic.

While “six” has become something of a default number for automatic transmissions and “eight” still holds the premium position, ZF has announced that it will be putting a nine-speed transmission into production in 2012 in a plant that it is building near Greenville, SC.

Unlike the eight-speeds used in the aforementioned rear-drive vehicles, this new transmission is for vehicles with transversely mounted engines: front-drive vehicles. Among the features of the nine-speed are an advanced shock absorber system in the torque converter to permit fast lockup of the converter clutch for improved fuel economy and lower emissions and control electronics that are said to be capable of accurately selecting the appropriate gear for the driving conditions so that there isn’t the “hunting” sometimes characteristic of transmissions.

And another name needs to be added to the list: Chrysler.

The company will be deploying the nine-speed in a yet-to-be announced application.

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B-Class Goes V8 at Rastatt Plant

The Mercedes Rastatt plant in Germany is the corporation’s center of excellence for compact vehicles. They’ve been building the A-Class there since 1997 and the B-Class since 2005. Of the two cars, the B-Class is slightly bigger than the A-Class, particularly in terms of overall length and wheelbase (168 in. vs. 153 in. and 109 in. vs. 101 in., respectively), with the height and width pretty much a wash (63 in. vs. 63 in. and 70 in. vs. 69 in., respectively).

So maybe it is because the B-Class is a little bigger that gave Rastatt plant manager Peter Wesp the idea that they could put a different engine in that car. While a B-Class normally has a four-cylinder engine—a 1.5-liter or a 1.9-liter—he had something a bit different in mind: a 5.5-liter V8. And while the car is ordinarily a front-drive, this would be a rear-drive car.

The execution was performed by Andreas Würz, a foreman in the plant’s technical vocational training department, Matthias Rieger, a foreman in the electrics/electronics installation section, and a team of 12 second- and third-year trainees specializing in production mechanics and automotive mechatronics.

An additional aspect of the challenge of this task was that they couldn’t change the size of the car.

According to Würz, “The V8 power unit fitted amazingly well, and we were even able to use the original engine mounts.” The rear axle was sourced from previous generation (W 210 series) E-Class. They also used an E-Class prop shaft.

The V8 B-Class weighs 1,620 kg, or about 180 kg more than a typical version of the car.

Würz said, “We have not made any measurements yet, but we should manage a sprint to 100 km/h in under six seconds.”

No doubt.

This is a 5.5-liter, 388-hp V8 fitted into a Mercedes B-Class, which typically is equipped with engines ranging in output from 94 to 138 hp.

 

The Mercedes B-Class compact car.