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How the C8 Corvette’s Dual-Clutch Has Changed Since We Drove the Car

The new Corvette has an eight-speed Tremec DCT. We weren’t crazy about it in the pre-production C8 we drove, but engineers tell us the final version will be better.

For the C8 Corvette, Chevrolet abandoned the traditional manual and torque-converter automatic for a new, eight-speed Tremec dual-clutch. And in our Performance Car of the Year testing, the gearbox was the weakest component in the pre-production C8 Stingray we had on hand. It’s part of why the Corvette didn’t win.

In automatic mode, the DCT dolled out nice, snappy shifts, but when using the paddles, it could be clumsy. Too often we found ourselves running into the rev limiter, or having downshifts denied after a paddle pull. But, the C8 we drove wasn’t a finished product. There’s been development work since we drove the car, and that work will continue for the foreseeable future. At a powertrain engineering seminar held by Chevy last week, we asked Glen Hoeflinn, controls program manager for the DCT, what will change from the car we drove.

“Maybe you get some humpy-bumpy shifts here, you get a little bit of that there. That all gets refined out,” Hoeflinn said. “It’s in final refinement, and then it’s in final checks and looking what we’re doing and making sure that it’s behaving exactly [how] we want.”

“That’s what we’ve done since the car that you had. Doing all that refinement and making sure it’s ready to go for everybody across the all the cars.”

A dual-clutch presents unique challenges, no matter what sort of car it’s in. “There’s a lot of pre-selection interaction that goes on in the background,” Hoeflinn said. “It’s the same choreography” between the engine and transmission, he added, but without the “luxury” of a torque converter, there’s a lot more programming work involved.

As you’d expect, the transmission has different automatic shift strategies for the various drive modes, which adapt in real time. The more aggressive, the more spirited you drive, the more aggressive the car’s going to respond,” Hoeflinn said. “As you start to relax, the car’s going to start to relax.”

The DCT uses latitudinal and longitudinal accelerometers, and looks at information like throttle position and steering angle to gauge how the car is being driven, and react accordingly. For example, in Track mode with the transmission set to automatic, the car will downshift aggressively when the driver is braking hard into a corner, and hold upshifts until corner exit.

The C8 has two manual modes. If you pull a paddle while in Drive, you get a temporary manual mode, which automatically times out, or can be exited sooner by holding the upshift paddle. In this mode, the car will automatically upshift at redline. If you press the M button in the center console, you get full manual mode. There’s no time out, and the car won’t upshift at redline.

There are two other neat tricks available for drivers to exploit. First, if you hold the downshift paddle, the DCT will serve up the lowest possible gear. Do that while braking, and the transmission will keep downshifting as engine speed allows. And second, pulling both paddles at the same time is equivalent to pushing in the clutch pedal on a manual car, which allows you to rev the C8’s new V-8 as much as you want.

In the C8, the paddles are directly wired to the transmission control module (TCM) for quicker response times. “In other applications, from the paddle, the wire will go to the body control module and then from the body control module back over to the transmission. You have obvious latency there,” Hoeflinn said.

“It could be 25, 30, 40 milliseconds from the time you pull, to the time that transmission actually got the message. When you wire them directly from the paddle straight to the TCM, we’re getting the message instantaneously.” This doesn’t mean the paddles will give you a downshift that over-revs the engine—the TCM prevents that—it just helps reduce delay.

One of the headline figures of the C8 Corvette is its incredible acceleration. We timed a pre-production Z51 Stingray as hitting 60 mph in 2.8 seconds and running the quarter-mile in 11.2 seconds at 122 mph. With the C8’s Performance Launch mode, the car will actually use the inertia of the engine coming down between revs to propel the car forward. Chevy calls these “Boosted Shifts,” and they’re only used with a Performance Launch. In any other mode, they make the car feel unsettled.

From a mechanical standpoint, this new Tremec transaxle isn’t a radical departure from other DCTs. There are concentric clutches and input shafts for the odd and even gears. The even gears and reverse live near the front of the transmission, while the odds are at the back. A limited slip-differential is integrated within the unit. Base Stingrays get a mechanical diff with a 4.89:1 final drive ratio while Z51-pack cars get an electronic LSD with a 5.17:1 ratio. The overall gear ratio spread of 8.8:1 is the same regardless of differential.

The packaging of the transaxle is such that there’s a common oil sump—filled with 11 liters of Pentosin FFL-4 fluid—for all components. A cooler mounted to the top of the transaxle assembly means there’s no need for additional hydraulic lines, while two filters keep things clean. An externally mounted pressure-side filter requires replacement every 20,000 miles, while the internal suction filter mounted to the sump is a lifetime part.

We asked about why the C8 team didn’t try to do a manual. Hoeflinn and the other engineers present gave us a similar answer to Corvette chief engineer Tadge Juechter, when we interviewed him before the car debuted. They’d need to develop a new manual just for the C8, and considering the stick-shift market is shrinking, it would be an expensive endeavor seemingly without much reward. There are packaging constraints with the Corvette’s central backbone tunnel, too, which would require a hole to accommodate the shifter and gear linkage, hurting structural rigidity. Juechter also said the pedalbox would be cramped with a clutch.

Our first experience with this DCT was less than positive, but this is a gearbox that shows a lot of promise. We look forward to driving the finished product.

Originally written by Chris Perkins; Road&Track


Highlights of the 2019 SEMA Show in Las Vegas

SEMA is the United Nations conference of all things aftermarket, and here’s some of the best stuff we spotted there.

1.Quintin Brothers Dodge Challenger

This 1000-hp Dodge Challenger went on a wild adventure after it arrived in Las Vegas. Vermont-based Quintin Brothers Auto & Performance had their truck and trailer stolen days before the show. Their custom Challenger was inside. Video surveillance helped track down the perp, but when Nevada state trooper Adam Whitmarsh tried to block the stolen Challenger into a parking space, the suspect rammed the Trooper’s Ford Explorer and escaped. After exiting the parking structure, the suspect smashed through a fence and drove the stolen Challenger across a nearby karting track—during a karting event. He eventually ditched the car and was later arrested. The Quintin Brothers and their Dodge Challenger arrived at the SEMA show wearing battle wounds from the wild chase.

2. Chevrolet E-10 Concept

It’s not an engine, it’s a motor. The Chevrolet E-10 concept is a 450-hp electrified C-10 pickup. Typically the only time a 1970s Chevy pickup is plugged into anything, it’s connected to a trickle charger. The E-10 has its batteries in the bed. The two electric motors seen here are called eCrate motors, a nod to the popular Chevy crate engines that can be found swapped into just about anything. GM claims the E-10 can complete a zero-to-60-mph run in about five seconds with a quarter-mile time in the high 13s. A Tesla P100D might be quicker, but it doesn’t look as cool.

3. Vibrant Performance Titanium Chair

Had Game of Thrones producers used Nissan Skylines or Toyota Supras instead of dragons as source material, this might be the Iron Throne. Vibrant Performance didn’t have to vanquish their enemies to build the thing, but they did use more than 50 pieces from their lineup of titanium exhaust products to construct what’s likely the most uncomfortable Adirondack chair on the porch. But it’s fun. Feeling exhausted? Have a seat.


4. Hyundai Veloster Grappler Concept

You’re unlikely to see a Hyundai Veloster on an off-road trail, let alone a dirt road, but this overland concept is out to change that. The Veloster Grappler concept is equipped with typical in-car camping accessories like a rear-hatch tent, solar panels, LED light bars, big all-terrain tires, and a roof basket to carry a spare. It’s still pretty low to the ground, and the tire clearance isn’t ideal for crawling, but it’s a concept. We’d pitch a tent with this thing.

5. Toyota Supra Wasabi Concept

Toyota’s Genuine Accessory Team cooked up a color for this concept that we hope will soon find its way onto a Camry. This Supra’s paint mimics wasabi paste and features white accents on the brake calipers, mirrors, stripes, and spoiler. The forged-aluminum wheels were designed at Toyota and have center caps with the original Toyota emblem. Ohlins coil-overs drop the Supra concept two inches. This was one of many Toyota Supras at the show.

6. AEV Jeep Gladiator

This Jeep Gladiator is equipped with all the proper get-dirty-quick gear. It has tough Bilstein dampers, a lifted suspension, and 37-inch tires. American Expedition Vehicles (AEV) is known for swapping big engines into off-road vehicles and then adding lift kits and other off-road accessories. They’re also responsible for the coolest parts of the Chevy Colorado ZR2 Bison. This year AEV brought three green machines to show off their latest accessories.

7. 1999 Honda Civic Si Super Street Build

Was this the car that sparked the movie The Fast and the Furious in 2001? It sure looks like it. Honda brought a handful of concepts to the show in celebration of its 60th year in North America, and what better way to do it by showcasing the Civic Si Super Street magazine modified for the Civic Si Challenge in 2000. If you collected buckets of Mattel die-cast cars as a kid (or shamelessly as adults, like us), this car might look familiar.

8. Nissan Frontier Desert Runner

The current-gen Nissan Frontier might be 16 years old, but this concept proves that Nissan knows what people at SEMA want in a truck: tons of suspension, awesome off-road tires, some type of light bar, and a 600-hp 5.8-liter V-8. In the meantime, we can only hope one of these ingredients get put to use on the upcoming Frontier refresh.

9. RTR Rambler Ford Ranger Concept

The RTR Rambler Ford Ranger does everything right without going too far. Ford chose 33-inch Nitto Ridge Grappler tires with custom RTR Tech 6 wheels, because they know anything bigger than that will be unnecessary in most cases. Three LED light bars are tastefully tucked into a custom front grille to complete an almost Ranger Raptor–like appearance. A two-inch suspension lift is installed as well as heavy-duty rock sliders, which act as both a step and as extra protection against rocky terrain. It’s a simple package done well, saving the flashy stuff like wild paint for the Insta-campers.

10. 1972 Honda N600

If it looks like this 1972 Honda N600 has a motorcycle engine under the hood, it’s because it does. This oddball is powered by a Honda VFR 800-cc V-4 motorcycle engine that puts power to the rear wheels. Although the car itself predates the era of high-revving VTECs, with the bike motor installed, this is likely the only N600 with a 12,000-rpm redline. This was one of several cars Honda showcased at the SEMA show.

11. Honda Civic Si Drift Car

This is a peek under the hood of a 926-hp Honda Civic Si. The engine is turned longitudinally and transforms a front-wheel-drive coupe into a rear-wheel-drive drift-spec machine. The work was done with help from Jeanneret Racing and Olson Kustom Works.

12. Chevrolet Silverado ZR2 Prototype

We saw this Chevrolet Silverado Desert race truck back in early October, when it competed in the Laughlin Desert Classic, a 17-mile race event in Nevada near the Arizona border. It was there for “engineering development,” but we still think it’s a preview of an upcoming Silverado Z

13. Honda Rally Passport

Honda R&D in Ohio built this rally-ready Honda Passport in their spare time. It has already survived a handful of rally competitions, finishing second in its class at the Southern Ohio Forest Rally. It has had typical safety additions like a roll cage, but other than that it’s unchanged except for tires, brake pads, wheels, and skid plates. Oh, there’s also the addition of a hand-operated hydraulic brake, for epic drift action.

14. 1968 Ford Bronco

There’s been plenty of buzz lately about the upcoming Ford Bronco, which is expected to debut in early 2020. A collaboration between Jay Leno and Ford, this Bronco has a supercharged 5.2-liter V-8 from the Ford Mustang Shelby GT500 and a five-speed manual transmission. The restoration maintained the simple beauty of original Bronco. The 18-inch steel wheels by Detroit Steel Wheels are a great combination of old style and modern needs. The Bronco’s Tonight Blue color would look great on a Mustang or F-150 Raptor.

15. Hyundai Veloster N Performance Concept

The Veloster N is quick, but this Veloster N Performance concept is quicker. Hyundai modified its hot hatch with carbon fiber for the front splitter, side skirts, rear diffuser, and spoiler while adding carbon fiber to each wheel’s center caps. The suspension is made up of Extreme Racing coil-overs and H&R coil springs with aluminum chassis bracing to add rigidity. Orange-accented interior bits stand out among more carbon-fiber pieces and an Alcantara dashboard.

16. SpeedKore Dodge Charger

Routed through the front fender of a 2019 Dodge Charger Pursuit is the exhaust from a 1525-hp Dodge Demon V-8. This project, put together by SpeedKore Performance Group and MagnaFlow, began as a police car. After fitting a carbon-fiber widebody kit, they turned it into something that would outrun police cars. The stock supercharged 6.2-liter V-8 was transformed into a twin-turbo engine and received an upgraded upper intake manifold designed to withstand the 26 psi of boost.

Written by: Austin Irwin, Car&Driver


2020 Corvette Stingray Shown at Spring Mountain’s SEMA Display

Spring Mountain Motor Resort and Country Club, home of the Ron Fellows Performance Driving School, is located less than hour from Las Vegas and they bring a continent of cars and people to the annual SEMA Show at the Las Vegas Convention Center.

Drivers for Ron Fellows School provide hot laps for the attendees which is hella fun if you have ever had the opportunity to catch a ride in one of the ZR1s they have. In addition to the hot laps, Spring Mountain also has booth display at SEMA and featured prominently is the 2020 Corvette Stingray wearing the Ron Fellows Driving School livery.

We asked Spring Mountain’s Todd Crutcher send us some photos of the 2020 Corvette on display as it’s the only place at SEMA outside the Chevrolet display where you catch the C8 Corvette in the flesh.

Chevy had displayed a C8 Corvette with the Ron Fellows door stickers at both the Woodward Dream Cruise and Corvettes at Carlisle, but the car on display at SEMA is much more representative of the Ron Fellows livery that also features the No. 01 car number on the front and back while Michelin stickers are also featured. A windshield banner completes the look.

This C8 Corvette is a Z51 model and 3LT trim package and inside is the two-tone Blue leather interior. The Stingray also shows off the visible carbon fiber roof panel that’s only been spotted a couple of times.

There has yet to be any kind of announcement regarding a driving school for owners of the C8 Corvette at the world-class driving school, but we’ve been told to stay tuned as things are progressing. We do know that a continent of cars will be built for the school and that they will be used as part of the official GM training for dealerships who are selling the new sports cars. While the strike has messed up the original timeline for the school to receive their cars, we expect some sort of announcement will be made in the near future.

If you have purchased a C7 Corvette in the last year, your time is limited to take advantage of the 2-day Corvette Owner’s School that’s heavily subsidized by Chevrolet. To find out more information about the Corvette Owner’s school, visit SpringMountainMotorsports.com or call Melinda or Donna for details 1-800-391-6891. All Corvette enthusiasts are invited!

Spring Mountain / Ron Fellows Driving School


OFFICIAL: The 2020 Corvette Stingray Goes 0-60 MPH in 2.9 Seconds; Runs Quarter Mile in 11.2 @ 121 MPH

OFFICIAL: The 2020 Corvette Stingray Goes 0-60 MPH in 2.9 Seconds; Runs Quarter Mile in 11.2 @ 121 MPH

Chevrolet today revealed the long-awaited performance figures for the 2020 Corvette Stingray. While the various magazines and websites have been releasing their numbers, we’ve finally gotten the official word straight from Chevrolet.

The 2020 Stingray with the Z51 package will hit 60mph in 2.9 seconds and run the quarter-mile in 11.2 seconds at 121mph. The base Stingray without Z51 performs the 0-60 sprint in 3.0 seconds and covers the quarter-mile in 11.2 seconds but at 123 mph. That’s a whole lot of boogity, boogity, boogity for just $60,000. But why is the base car faster than the Z51 in the 1,320? It’s the same reason the Z51’s top speed is lower than the base car – aerodynamics. All that aero that keeps the car planted in the corners holds it back at high speeds in a straight line.

“The performance of the 2020 Stingray has far exceeded our expectations,” said Alex MacDonald, Chevrolet vehicle performance manager. “Moving more weight over the rear wheels helps us get off the line quicker, but it’s the integration between the powertrain and chassis that really takes the performance to new levels.”

The 2020 Corvette Stingray Goes 0-60 MPH in 2.9 Seconds; Runs Quarter Mile in 11.2 @ 121 MPH

All that performance is the result of harmonization between the 495hp LT2 engine and the 8-speed Tremec DCT. The transmission is built at Tremec’s Wixom, MI facility utilizing components produced Belgium, Mexico, and other locales. The DCT itself is a complex unit that contains the rear differential, final drive unit, its controls system, various sensors, its lubrication system, and the cooling hardware. It’s a combination of all these items in addition to the inherent advantages of mid-engine architecture that allow the C8 to achieve its mighty performance.

“The goal from the beginning was to design a transmission worthy of an exotic supercar that is fun to drive everyday,” said Terri Schulke, GM global chief engineer of transmissions. “We achieved that goal by combining the best attributes of the LT2 and the DCT, and I think the impressive performance numbers speak for themselves.”

We expect to hear more details, including official fuel economy ratings, now through the car’s February start of production.

The 2020 Corvette Stingray Goes 0-60 MPH in 2.9 Seconds; Runs Quarter Mile in 11.2 @ 121 MPH

Chevrolet Confirms 2020 Stingray Quickest in its History
LT2 V-8 engine and dual-clutch transmission combine for unprecedented performance

DETROIT — Jaws dropped when Chevrolet first announced the 2020 Chevrolet Corvette Stingray coupe would accelerate 0 to 60 mph in less than three seconds with the available Z51 Performance Package. Today, the brand confirms the sportscar with the available Z51 Package can reach 60 mph in 2.9 seconds and cross the quarter-mile mark in 11.2 seconds at 121 mph.

Even without the available Z51 Package, a base Stingray, starting at $59,995 (including destination charges, excluding tax, title, license, and dealer fees), can reach 60 mph in three seconds flat and cross the quarter mile mark in 11.2 seconds at 123 mph. Performance numbers may vary, as different climates, tire conditions and road surfaces may affect results.

“The performance of the 2020 Stingray has far exceeded our expectations,” said Alex MacDonald, Chevrolet vehicle performance manager. “Moving more weight over the rear wheels helps us get off the line quicker, but it’s the integration between the powertrain and chassis that really takes the performance to new levels.”

A full chart of the above performance specs is listed below:


This groundbreaking performance is achieved through a formula of rear weight bias, tire technology, aerodynamics, chassis tuning and of course, the powertrain. The 6.2L LT2 Small Block V-8 engine and eight-speed dual-clutch transmission are in many ways the stars of the show.

Chevy’s Small Block Hits the Gym

The LT2 is the only naturally aspirated V-8 in the segment and is SAE-certified at 495 horsepower (369 kW) and 470 lb.-ft. (637 Nm) of torque when equipped with performance exhaust, making it the most-powerful entry Corvette ever.

“The LT2 is one of our best efforts yet in Corvette’s history of naturally aspirated high-performance Small Block V-8 engines,” said Jordan Lee, GM’s global Chief Engineer of Small Block engines. “This engine is incredibly powerful and responsive. Power is readily available when the driver needs it.”

The standard engine-mounted dry sump oil system boasts three scavenge pumps, which help make this the most track-capable Stingray in history. The LT2’s lubrication system keeps oil in the dry sump tank and out of the engine’s crankcase. It provides exceptional engine performance even at lateral acceleration levels exceeding 1g in all directions. The low profile oil pan is high-pressure die-casted – similar to some of Corvette’s large body structure parts – to reduce mass and is only 3.5 mm thick. The LT2’s pan-mounted oil filter and cooler assembly has cored oil and coolant passages, allowing for a 25 percent increase in cooling capacity over the LT1.

Much of the LT2’s additional power can be attributed to how much better it breathes. The intake system is a low restriction design and incorporates identical 210mm length intake runners and an 87mm throttle body. The performance header exhaust manifolds are also low restriction and feature a stylized four-into-one design with twisted runners to allow for thermal expansion. The camshaft now has 14mm gross lift on the intake and exhaust with an increased duration for both profiles, which helps the combustion system take advantage of the extra flow capacity. The LT2 retains variable valve timing, with 62 crank degrees of cam phasing authority.

The LT2 has a very low-profile oil pan. This allows the engine to be mounted low in the vehicle for a low center of gravity and improves handling and track performance. The DCT’s flywheel dampener was even reduced in diameter to allow for the lower engine position.

Bespoke DCT Puts the Power Down

Chevy’s first eight-speed dual-clutch transmission was designed to do two things – put the LT2’s power down and put a smile on every driver’s face. The bespoke, transaxle transmission was developed with Tremec to provide uninterrupted torque delivery whether setting a new lap record or heading out on a roadtrip.

“The goal from the beginning was to design a transmission worthy of an exotic supercar that is fun to drive everyday,” said Terri Schulke, GM global chief engineer of transmissions. “We achieved that goal by combining the best attributes of the LT2 and the DCT, and I think the impressive performance numbers speak for themselves.”

Engineering decided to use a dual-clutch design because it better supports the Stingray’s new mid-engine architecture and desired performance. The DCT aids vehicle performance with a very low center of gravity, enables desired weight distribution and offers maximum traction under acceleration. It is a highly integrated system, as it houses the differential, final drive, controls system, sensors, lubrication and cooling hardware.

The heart of the DCT uses dual concentric wet clutches that are opened by springs and closed by hydraulic pressure. The two clutches work in tandem for uninterrupted torque delivery as they toggle between gears. A separate lube circuit is used for on-demand clutch cooling to reduce parasitic losses. Holes in the outer housing allow for the wet clutches to operate moist instead of submerged. Gear ratios were engineered to be incredibly low-end biased for maximum acceleration. First gear takes advantage of the additional traction to get off the line quickly and reach 60 mph in 2.9 seconds with the Z51 Performance Package. The Z51’s 11.2 second quarter-mile acceleration is achieved by lightning-fast upshifts and excellent low-end torque. The gear ratios are:


The final drive and differential are integrated for the first time and make for an incredibly efficient package. A mechanical slip differential is standard on all 2020 Stingrays. The mLSD has an effective final drive ratio of 4.9:1 and is intended for straight line acceleration and dynamic handling. An electronic limited slip differential is offered on the Z51 Performance Package and has an effective final drive ratio of 5.2:1. It is intended for ultimate control during track driving and commands more authority than previous generation eLSDs.

Though they have different purposes, the mLSD and eLSD were engineered together. They share a common ring and pinion gear ratio of 3.55:1. Their ring and pinion gears also use a zero offset spiral bevel as opposed to the typical hypoid arrangement, which allows for a common fluid to be used and benefits overall packaging.


Software Plays Key Role

Beyond hardware, the transmission software controls are really where customers will find the most tangible benefits. Most of these will feel familiar when toggling through varying driver modes:

  • Tour: Moves to the background to provide quiet, smooth shifts for optimal ride comfort.
  • Sport: Gives drivers altered up and downshifts for more spirited driving.
  • Track: Maximizes vehicle performance with aggressive gear selection expected to keep the engine in a peak performance window.

A proprietary algorithm will influence gear selection if the car senses spirited driving. The level of aggressiveness will change with modes, but when sensed, the DCT can downshift early on hard braking, hold gears when lifting off the throttle and alter shifts points with lateral acceleration. All behaviors are intended to increase driving enjoyment and avoid unnecessary shifting.

To achieve peak acceleration numbers on the Stingray, drivers must initiate a performance launch. Once in Track mode, double pressing the traction control button will put the vehicle in Performance Traction Management for Magnetic Ride Control-equipped cars or Competitive driving mode for all others. Once prepared, the driver can then fully depress the brake and accelerator pedal together, and then release the brake pedal once 3,500 RPM are reached. Extensive work went into ensuring the DCT felt like the best of both worlds: the spirited, direct connected feeling of a manual and the premium driving comfort of an automatic. The magnesium steering wheel-mounted paddle shifters give a premium feel when pulled. For the most responsive shifts possible, the shift signal is sent directly to the transmission control module the moment the paddle pull begins. This avoids any communications delay through other modules and allows drivers precise control of their gear selection.

Unique features of the ergonomic paddles are:

  • Double paddle declutch – pull both paddles simultaneously to simulate pressing a clutch pedal.
  • Temporary manual – simply use either paddle while in Drive, and the vehicle will temporarily switch to manual mode.
  • Lowest available gear – hold the downshift paddle and the transmission will shift to the lowest available gear for a quick burst of torque.

The 2020 Chevrolet Corvette Stingray coupe and convertible are available to order at certified Chevrolet dealerships nationwide or on Chevrolet.com.

Source:
Chevrolet.com