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Old 08-20-2014, 08:33 AM   #1
AVANTI R5
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Default 2015 Corvette will get 29 mpg highway



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DETROIT -- An 8-speed automatic transmission debuting in the 2015 Chevrolet Corvette boosts fuel economy by 3.5 percent over the six-speed it replaces and gives the General Motors long-running sports car an EPA highway rating of 29 mpg, its highest rating ever.

Tadge Juechter, the Corvette’s chief engineer, said a few more pounds of air pressure in the tires would have bumped the EPA rating to 30 mpg, but affected the car’s ride and handling. “We’ll be back next year and we’ll get to the 30,” he said Tuesday at a media event at GM’s proving grounds west of Detroit.

The GM designed-and-built 8-speed automatic, the 8L90, is also scheduled for installation in the certain 2015 models of the Chevrolet Silverado and GMC Sierra pickups and will likely see duty in Tahoe and Yukon SUVs.
Because of the Corvette’s limited space, GM engineers had to keep the 8-speed the same size as the six-speed. They did that in part by moving the electronic controls off the transmission and by relocating the oil pump to the transmission’s sump. The new transmission, which is built in GM’s Toledo, Ohio plant, also uses lightweight components.

“GM’s new 8L90 eight-speed automatic represents a rare win-win-win scenario for customers,” said Kavoos Kaveh, global chief engineer for 8-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, he said.”

The Corvette is equipped with paddle shifters and fast-acting electronic solenoids that enable faster shifts than most dual-clutch transmissions used in sports cars such as the Porsche 911 Turbo. The 2015 Stingray with the 8-speed automatic is faster to 60 MPH than the manual transmission-equipped Corvette, Juechter said.

Long production life?
Though the transmission is just now starting production, it may not have a long production life. A new 10-speed automatic transmission, under development in a joint venture with Ford, is due out in about 18 months. It’s unclear if the 8-speed will remain in production once the 10-speed arrives.

For 2015, GM will install the 8-speed in the Corvette Stingray and Corvette Z06, as well as Silverado and Sierra trucks with 6.2-liter V-8 engines.
GM and Ford are working to boost the fuel economy of their pickups -- not only to meet tougher fuel economy standards, but to catch up with Chrysler’s Ram 1500 Ecodiesel, which carries a 28 mpg highway fuel economy rating. GM officials say they will release the Silverado 8-speed fuel economy figures later this fall as the truck gets closer to production.
Juechter said production of the 2015 Corvette began a few days ago at GM’s plant in Bowling Green, Ky. GM built just over 37,000 2014 Corvettes and still is working to clear a backlog of orders.
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Old 08-20-2014, 10:57 AM   #2
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no manual, no care
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Old 08-20-2014, 11:02 AM   #3
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First Drive:
2015 Chevrolet Corvette Stingray Eight-Speed Automatic
By Nate Martinez | August 20, 2014 |
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We know, we know. Manuals rule. Automatics drool. It’s one of the core arguments among the purest of the purists. But for GM and its crown jewel, the Corvette Stingray, this dispute is not if an automatic will be offered, but rather, which automatic will be offered. Facts are facts: 63% of the 37,000-plus 2014 Corvettes sold had a six-speed automatic. The rest, well, you know what they had.
More on Motortrend.com:2015 Chevrolet Corvette Gains New Valet Mode
Such telling data is precisely why GM is sinking copious time, money, and effort into an updated eight-speed gearbox. It’s dubbed the Hydra-Matic 8L90 and it’s all GM, baby. More than 24 patents were awarded to the company’s brainiacs during its creation. It’s more efficient and more capable than the current six-speed 6L80 it replaces. But, before we get into its specifics, there’s another reason why the 8L90 came to fruition: Z06. Yes, if you haven’t heard by now, the forthcoming Z06 will have a torque-converter-packing, planetary automatic transmission option.


“Really, this transmission was engineered around the upcoming Z06,” admitted Tadge Juechter, Corvette chief engineer. “Corvettes are extremely tightly packaged with the transmission in the back, so we’re bearing-limited in longitudinal space. So essentially, this transmission is custom designed for our package space, as well as the performance capabilities of the car. Our priority was that it had to be able to withstand the 650 foot-pounds of torque and 650 horsepower.”
More on Automobilemag.com:The 2015 Chevrolet Corvette Can Spy on Valet Parking Attendants
Juechter and his team turned to Kavoos Kaveh, global chief engineer for GM’s eight-speed automatic, to take on the task of building not just a gearbox for the Z06 and its crazy power, but a gearbox for the Stingray, other Corvette variants, and GM’s 6.2-liter-powered SUVs and trucks.
Kaveh’s goals were simple, at least on paper: It had to be more efficient; it had to fit inside the Corvette chassis’ already extremely cozy constraints; it had to be lighter; and, if that wasn’t enough, it had to withstand all the stresses that come with the various applications.
More on Automotive.com:2015 Chevrolet Corvette Receives New Options


Amazingly, Kaveh and his team worked within the 6L80’s existing space. They gave the 8L90 smaller step sizes (for better off-the-line go); four simple gear sets with a 7.0 overall gear ratio spread (4.56:1 first gear); a chain-driven, off-axis, binary vane pump (high output for performance, low output for fuel economy); synthetic Dexron 6HP fluid; and a torque converter turbine damper (to improve low-speed clutch smoothness). Just two open clutches reduce power flow losses now.

Its updated Gen II controls include a T87 electronic control module (four times faster than Gen I), three speed sensors for more accurate multi-step shifts, and high and low variable force solenoids to better the accuracy of clutch pressure. The gearbox is eight pounds lighter due to its liberal application of magnesium and aluminum. Its piston housing and channel plate are made of the former, pricey metal; its case with bell housing, clutch pistons, input carrier, and rotating clutch housings are all aluminum. Its input carrier shell uses high-strength low-alloy steel to shed mass.

The end result is a Stingray that is up to five percent better on GM’s highway fuel economy test cycles in Tour mode (not Eco mode). That means 29 mpg — or 29.4932 mpg, if you want to get exact — compared to this year’s 28 mpg EPA rating. “We have an Eco mode in the car, and you have an Eco mode on the label, but we expect more people to drive in Tour, Sport, Track, so we label the car based on the Tour mode,” explained Juechter.
He says that with additional fine tuning and testing, they’ll get to 30, no problem. “We’re going into production, so we don’t have time to tweak or retest for this year, so we’re going in with a 29 (mpg) label. In Eco Mode, it would do solidly in the 30s. And probably next year, we’ll come back and tweak the calibration of the transmission to (officially) get to 30 miles per gallon. In Corvettes, you can actually get the number that’s on the label.” Still, as is sits, that means it’s as efficient as its EPA-rated 2015 counterpart having a seven-speed manual.
But get this: It’s also quicker. In fact, the 8L90-equipped Stingray is quickest Corvette in a straight line (until the Z06 arrives) with a 0-60 mph dash in 3.7 seconds and quarter-mile run 11.9 seconds (no word on trap speed). Added Juechter: “(Those times) should be easily replicated. We’ve had cars in the 3.6s — even some cars in the 3.5s, but we’re going to market with the 3.7 as the performance (figure).”

Wide open throttle second-to-third upshifts are 0.08 seconds quicker than those of its benchmark, Porsche’s seven-speed PDK, says Kaveh (0.45 vs. 0.53). Downshifts from WOT at 60 mph in Sport mode are just as quick (0.95 seconds) too. The PDK also nips at the Hydra-Matic’s heels during WOT first-to-second upshifts (0.49 vs. 0.52). To experience the gearbox’s character, Chevrolet set us loose on its 2.9-mile twisty, undulating, blind-corner-filled track at the Milford Proving Grounds. Nil-to-wee sprints in Track mode, automatic shifts, were quite telling: The gearbox knocked off gears at its indicated 6500 rpm abruptly, spectacularly, with an accompanying violent explosion that only a 6.2-liter V-8 with quad pipes could produce. As corners neared, downshifts were again crisp. Deep inside corners, gears held with no moments of confusion or hesitation — it was as if the CPU was more intuitive than reactive; more organic than robotic — which ballooned my confidence and allowed me to pinpoint the longish nose.
While Chevy’s numbers beg to differ, the 8L90 in Track mode simply didn't feel as quick as the PDK when operated via its plastic paddles. Don’t get me wrong, clicking off a WOT upshift is a glorious, stupidly fast affair. It is much the same for downshifts. Yet, Porsche, with its well-honed cohesion of an extra clutch and different structural packaging, still has the upper hand in smoothness and feel while on track. Even still, the 8L90 was impressive, especially when off the track. We drove more than 40 miles in highway and city settings around Milford. Smoothness was the name of its game. Intuitiveness was too. Multi-step highway passes in automatic mode required no pauses on its part. The ‘Vette just flew. Then it calmly upshifted into a gear best suited for casual cruising. So, you may be thinking, why no dual-clutch? There were a few reasons why, says Juechter: Structural tunnel packaging, vehicle balance, durability, and fuel economy. It needed to be shared within General Motors as well. “There was no DCT or advanced transmission in the world that would just fit in that package and that would live behind the upcoming Z06 with 650 horsepower. So we were faced with a conundrum: We could have designed our own DCT, which could have worked for us, but it would not be useful anywhere else in General Motors. It wouldn't be good for heavy duty trucks and things like that. DCTs are great for some things, but they’re not great for a lot of clutch slipping.

One of the big fuel economy advantages of this car is being able to run in four-cylinder mode. DCT are not terribly compatible with AFM (Active Fuel Management). So having a torque convertor as a torsional damper in the system actually helps to use four-cylinder operation. That’s a big fuel economy enabler. Between those two factors, we, GM, elected to say ‘Ok, were going to do a planetary eight-speed transmission with a torque convertor, but we’re going to model it after DCT performance characteristics.’’ That election resulted in a very stunning, very capable, lightning-quick automatic transmission. It is gearbox that will surely have potential buyers scratching their heads, wondering if a five-, six-, or seven-speed manual is their way to go. Now, that’s saying something.

2015 Chevrolet Corvette Stingray, Eight-Speed Automatic
BASE PRICE $55,500 (est)
LAYOUT Front-engine, RWD, 2-pass, 2-door hatchback, convertible
ENGINE 6.2L/455-hp/460-lb-ft OHV 16-valve V-8
TRANSMISSION 8-speed automatic
CURB WEIGHT 3450 lb (MT est)
WHEELBASE 106.7 in
LENGTH x WIDTH x HEIGHT 177.0 x 73.9 x 48.6 in
0-60 MPH 3.7 seconds
EPA CITY/HWY FUEL ECON 16/29 mpg (est)
ENERGY CONSUMPTION, CITY/HWY 211/116 kW-hrs/100 miles (est)
CO2 EMISSIONS 0.97 lb/mile (est)
ON SALE IN U.S. Fall 2014



Read more: http://www.motortrend.com/roadtests/...#ixzz3Awddnog2
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Old 08-20-2014, 11:19 AM   #4
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no manual, no care
Perfect transmission for the customers taking the initial depreciation on these.
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Old 08-20-2014, 12:31 PM   #5
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NOt sure, but something seems funny about the same transimssion being used on the Vette and on heavy duty trucks...

I kwow it is not uncommon, but for some reason I want the vette to have something more 'unique'

I should know better by now, I know.
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Old 08-20-2014, 12:46 PM   #6
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Originally Posted by SCRAPPYDO View Post
NOt sure, but something seems funny about the same transimssion being used on the Vette and on heavy duty trucks...

I kwow it is not uncommon, but for some reason I want the vette to have something more 'unique'
Yeah, the Corvette would certainly benefit from a transmission made of pure unobtanium running angel tears for lubrication.

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I should know better by now, I know.
Or maybe you should know that it all comes down to the programming.
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Old 08-20-2014, 02:58 PM   #7
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Well if Dodge can use a truck engine in the Viper...

huehuehue
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Old 08-20-2014, 07:39 PM   #8
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Originally Posted by OrbitalEllipses View Post
Well if Dodge can use a truck engine in the Viper...

huehuehue
Corvette engine is more closely related to the truck engines than the Viper V10 is to the truck V10 (is that still a thing?).


Also, Corvette has been getting 30+mpg real life since the late 90's. I wonder why they keep getting ratings below 30mpg.
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Old 08-21-2014, 11:02 AM   #9
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Originally Posted by SCRAPPYDO View Post
NOt sure, but something seems funny about the same transimssion being used on the Vette and on heavy duty trucks...
The fact is drivetrain components in any modern car are very close to the limits of production technology. When you make as much torque as the 'Vette does, you have to have a truck transmission, like it or not. I'm pretty sure the Tremec is lighter than any DCT capable of taking the torque.

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Also, Corvette has been getting 30+mpg real life since the late 90's. I wonder why they keep getting ratings below 30mpg.
Because the EPA highway test doesn't actually resemble how many of us drive on the highway, or rather how we drive on the freeway. Very little time in the test is devoted to constant-speed cruising. Lots of changes in speed. The average is something like 48 mph IIRC.
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Old 08-21-2014, 11:06 AM   #10
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Given the capability of the cars, who cares? Way better MPG out of a performance car than I'm used to.
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Old 08-21-2014, 11:49 AM   #11
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Given the capability of the cars, who cares? Way better MPG out of a performance car than I'm used to.
I bought mine because of mpg. Seriously.
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