08-20-2014, 07:30 AM | #1 |
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GM Releases Details for New 8-Speed 8L90 Hydramatic Automatic Transmission
New 8-Speed Enables Quicker, More Efficient Corvette
GM-designed, patented paddle-shift gearbox rivals dual-clutch performance General Motors 2014-08-20 DETROIT – The all-new, GM-developed Hydra-Matic 8L90 paddle-shift eight-speed automatic transmission offered in the 2015 Corvette Stingray and Z06 enhances performance and efficiency, while delivering exceptional refinement and world-class shift responsiveness that rivals the world’s best dual-clutch transmissions. In fact, in the 2015 Corvette Stingray, it enables a class-leading 29-mpg EPA highway estimate – a 3.5-percent increase in fuel economy over the previous six-speed automatic – and a quicker 0-60 time of 3.7 seconds, all while delivering wide-open-throttle upshifts quicker than those of the dual-clutch transmission offered in the Porsche 911. “GM’s new 8L90 eight-speed automatic represents a rare win-win-win scenario for customers,” said Kavoos Kaveh, global chief engineer for eight-speed automatic transmissions. “It offers greater performance and efficiency, while weighing less than the transmission it replaces. That’s a rare accomplishment in the industry today – and one for which GM has been awarded more than two dozen patents.” With four simple gearsets for optimal efficiency and five clutches (two brake clutches and three rotating clutches), creative packaging enables the new eight-speed automatic to fit the same space as the previous six-speed automatic – and the powerflow only uses two open clutches for low spin losses, which enhances efficiency. Extensive use of aluminum and magnesium also make it more than eight pounds (4 kg) lighter than the six-speed. The greater overall performance and efficiency enabled by the 8L90 in the Corvette is due primarily to a new, wider 7.0 overall gear ratio spread, which enhances off-the-line performance with a more aggressive first gear ratio – 4.56 vs. 4.03 on the six-speed – helping achieve the quicker 0-60 time. The top gear ratio is 0.65 vs. the six-speed’s 0.67. Combined with a new, numerically lower 2.41 rear axle ratio in the Stingray vs. the 2.56 gear used with previous six-speed automatic models, engine rpm is reduced by 8 percent (123 rpm) on the highway at 70 mph. The lower engine speed reduces fuel consumption, while a new torque converter design enhances refinement, particularly during low-speed gear changes. Stingray models equipped with the Z51 Performance Package feature a more aggressive 2.73 axle ratio, while the Corvette Z06 features the 2.41 axle ratio. World-class performance Designed and built by GM, the paddle-shift 8L90 transmission delivers world-class shift times that rival the best dual-clutch designs. “The Corvette’s new eight-speed automatic delivers the comfort and drivability of a true automatic transmission, as well as lightning-fast shifts and the manual control that enhance the performance-driving experience,” said Kaveh. “It was designed to enhance the driving experience, with performance on par with dual-clutch designs, but without sacrificing refinement.” For performance driving, the transmission offers full manual control via steering wheel paddles. A new transmission-controls system and unique algorithms deliver shift performance that rivals the dual-clutch/semi-automatic transmissions found in many supercars – but with the smoothness and refinement that comes with a conventional automatic fitted with a torque converter. In fact, a new, Gen II transmission controller analyzes and executes commands 160 times per second, and wide-open throttle upshifts are executed up to eight-hundredths of a second quicker than those of the dual-clutch transmission offered in the Porsche 911. Smaller steps between gears, compared to the previous six-speed automatic (see chart above), keep the engine within the sweet spot of the rpm band, making the most of its horsepower and torque to optimize performance and efficiency. Additionally, a torque converter design with a turbine damper complements performance with excellent refinement at low engine speeds. Unique clutch and torque converter specifications matched to the torque capacity of the Stingray’s LT1 6.2L naturally aspirated engine and the Z06’s LT4 supercharged engine distinguish the applications for the different Corvette models. Architectural and design features More than 550 computer-aided engineering analysis were made during the development of the 8L90 to ensure strength, durability, performance and refinement. The architecture features a one-piece case with an integral bell housing for enhanced powertrain stiffness, as well as a detachable extension for the Corvette’s rear transaxle arrangement. Similar to GM’s six-speed automatic design, the eight-speed’s architecture locates the grounding clutches rearward of the middle of the structure, outside the gearsets. However, the grounding clutches are splined to the case, eliminating the center support, which reduces weight. This architecture also features a turbine shaft node that reaches to the outside of the barrel, enabling easy execution of a high-resolution magnetic speed sensor. The turbine shaft itself is very short, keeping oil channel drill lengths to a minimum. The rotating clutches are located near the front of the transmission, with short oil feed channels, supporting the transmission’s very fast shifts. Additional design and performance features include:
Shift time quickness and improved responsiveness are accomplished with the new Gen II controls system. VFS solenoid technology and three internal speed sensors give the 8L90 the capability for world-class shift performance. The new transmission controller is mounted external to the transmission and has a processor that executes hundreds of calculations and commands every 6.25 milliseconds. The 8L90 is built at GM’s Toledo, Ohio, transmission facility.
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08-20-2014, 08:25 AM | #2 |
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I was really hoping, as I'm sure GM was, that they would be able to knock down 30MPG highway for the auto Stingray. That is a very minor disappointment compared to everything else this tranny can do, and it's still an improvement over the six speed. Nicely done.
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08-20-2014, 01:30 PM | #3 |
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I wonder if the 6th gen Camaro will get this tranny. I kinda think it will since it doesn't come out for over a year.
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08-20-2014, 01:51 PM | #4 |
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Should also point out that automatic Corvettes are now faster than the manuals.
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08-20-2014, 02:13 PM | #5 |
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08-20-2014, 02:27 PM | #6 |
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I thought the vette had an eco mode that allowed over 30mpg's?
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08-20-2014, 02:29 PM | #7 |
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It does but the EPA requires them to list it in Touring mode, the mode that is most used by customers. Like the 7 speed manual, it will achieve 30MPG hwy very easily.
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08-20-2014, 05:26 PM | #8 | |
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Quote:
The countdown begins Fen....
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08-20-2014, 06:06 PM | #9 |
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Popular Mechanics did over 37 MPG hypermiling a C7 so...
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08-21-2014, 07:45 AM | #10 | |
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(Motor Authority)
2015 Chevrolet Corvette 8-Speed Automatic First Drive Quote:
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08-21-2014, 07:50 AM | #11 | |
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(Motor Trend)
2015 Chevrolet Corvette Stingray Eight-Speed Automatic First Drive Quote:
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08-21-2014, 09:05 AM | #12 | |
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That's insane if true! I remember reading that the 6L90 in the ZL1 was supposed to have shift speeds "close" to the PDK, but for them to out shift the PDK is pretty darn impressive.
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08-21-2014, 09:11 AM | #13 |
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Its cool that Gm I kinda sticking with the "old school" approach with certain things on cars OHV big displacement Engines Vs. OHC smaller more technical engines and regular auto Vs. Dual clutch tranny's that match and or beat the competition.
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08-21-2014, 10:27 AM | #14 |
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Just too beautiful a thought. Not sure if this is nationwide, but where I'm at Corvettes get dumped on by the import crowd who claim American cars can't perform/keep up with imports. |
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