In most segments, chances are the transmission was developed and manufactured by the same company that built the rest of the car. Some are made by independent suppliers like Borg-Warner, Getrag or ZF. But at the top end of the market, where exotic supercars roam, a disproportionate share of the high-performance gearboxes come from Graziano.
The Italian company – part of Oerlikon since 2007 when it merged with Fairfield – has built the transmissions in countless Ferraris, Lamborghinis, Aston Martins and Maseratis, to name just a few. That new-fangled seven-speed Independent Shifting Rod transmission in the new Lamborghini Aventador? Also Graziano's. But before that project, Graziano developed the clever gearbox in the McLaren MP4-12C.
The Sequential Shift Gearbox developed for McLaren, as you may be aware, takes the dual-clutch transmission to a new level by allowing the driver to pre-select the next gear and load it onto the second clutch before engaging it, reducing shift times to practically nothing while engaging the driver in a way lost on many paddle-shift transmissions.
In an apparent nod to the clairvoyant siblings in Minority Report, Graziano and McLaren dubbed the system "pre-cog," but that's not the extent of the transmission's advances. It's also said to be the lightest, most compact, most refined and most durable gearbox of its type, while capable of keeping its fluids pumping at extreme levels of multi-directional loading. Want to read more? Follow the jump for the full press release.
New double-clutch transmission for McLaren is the lightest and most compact in its class
Innovative 'pre-cog' feature allows near-instant gear changes
Torino – Italy, May 4th 2011 – The McLaren MP4-12C's new Sequential Shift Gearbox (SSG) is not only the lightest and most compact in its class; supplier Oerlikon Graziano says it also sets new standards for the refinement and durability of a Dual Clutch Transmission (DCT).
"McLaren has a very clear understanding of its brand and of the type of cars that it should make. This is reflected in the technologies and innovations that are chosen for their powertrains," explains Oerlikon Graziano head of automotive transmissions Paolo Mantelli. "As well as being immensely fast and dynamically capable, the cars must be comfortable, refined, efficient and a pleasure to drive every day. We worked closely with McLaren Automotive's engineers to develop a new transmission that would help them meet these targets."
A DCT-type transmission was the natural choice as it combines smoothness and refinement with the possibility to change gear quickly with no torque interruption and therefore no reduction in acceleration. It also allowed a highly sophisticated control system, developed in conjunction with world-leading DCT controls specialist Vocis (a subsidiary of Oerlikon Graziano), whose UK-based team has managed some of the world's most challenging and prestigious DCT programmes.
The compact dimensions were driven by McLaren's desire to maximise passenger space without compromising dynamics. A three shaft architecture was chosen because the parallel secondary shafts help to minimise gearbox length, allowing the engine to be mounted further back. All eight ratios use Oerlikon Graziano's high-performance synchronisers, further optimised to allow substantially faster changes without compromising durability.
"We wanted to achieve genuinely fast, smooth shifting without any of the 'tricks' that can be employed to make a DCT feel fast," says Vocis managing director Mike Everitt, who's team also calibrated the transmission.
"The secret is to get the very best out of the whole control system with a highly-optimised interaction between the software and the hardware. This ensures that the responses are not just quick and accurate but are also consistent and progressive. That means rigorous attention to the fluid dynamics and to the design and calibration of the control algorithms, which are constructed using our proprietary architecture."
An unusual feature of the McLaren transmission is a 'pre-cog' facility that can make the already class-leading change time feel almost instantaneous. The driver can pull the gear up/down paddle to the first detent position, commanding the transmission to engage the next gear and preparing the oncoming clutch. When the paddle is pulled to the second detent, the gear shift is completed in a fraction of the time required by a conventional DCT. The system also makes the shift more engaging than typical DCTs with single-pull paddle shifts.
McLaren's passion for weight reduction led to extremely sophisticated analysis of the transmission hardware with numerous iterations so that the maximum amount of material could be removed without compromising strength or stiffness. "McLaren set very high standards for durability too, so everything was tested in a virtual environment, then on purpose-designed rigs at our laboratories before whole-vehicle testing," says Mantelli.
Rig testing was also used to validate the designs for the very high dynamic loads that the car can deliver. "At 1g, the oil will be at 45 degrees to the horizontal. The McLaren can significantly exceed 1g both cornering and accelerating and substantially exceed it under braking. Its dynamic performance is phenomenal, which makes managing oil flows critically important," explains Oerlikon Graziano's DCT programme manager Alberto Noto. "As the world's leading supplier of transmissions for high-performance vehicles, Oerlikon Graziano has developed specialist test techniques that provide insights into these challenges and allow a high level of design refinement, helping us to improve performance and durability while also reducing weight."
The very low weight is also important in reducing vehicle CO2 emissions, which were further cut by meticulous attention to the efficiency of the overall SSG system. Low friction bearings were specified and fluid thermal management was optimised. The result is a significant contribution to the vehicle's ground-breaking CO2 performance.
The new transmission is manufactured at Oerlikon Graziano's plant in Luserna, Italy, using a combination of precision automation and traditional craft skills to allow consistently high-quality manufacture in low volumes. Comprehensive end-of-line functional testing, using custom-built automated systems, ensures that every transmission delivered to McLaren meets their demanding requirements for Britain's newest supercar.
Oerlikon Graziano has also recently started production of transmissions for the new Lamborghini Aventador and for the new Aston Martin Vantage S, each one using a different technology carefully matched to the character and technical requirements of the vehicles.