“Mules,” or engineering prototypes, are where all cars begin, and the 2020 C8 mid-engine Corvette Stingray is no different. But here’s the story behind the three generations of mule cars.
Corvette fans worldwide have two dreams. The first is to find the yet-to-be-found 1970 Stingray equipped with the ZR2 package and coupled with the LS7 engine. It’s reported that this combo made it to the order guides but never became a reality. The second, of course, is to squirrel away one, or possibly one each, of the three generations of “mule” cars used in the development of the 2020 C8 mid-engine Corvette Stingray.
During a recent trip, editorial speak for playtime, we had the opportunity to drive Corvettes on the docile city streets and highways surrounding Las Vegas followed by a day at Spring Mountain Motorsports Resort for the singular purpose of scarin’ the livin’ daylights out of ourselves. The disguise of the event was to prove the 2020 C8 Corvette mid-engine Stingray is a world class sports car. And also to prove we aren’t world-class sports car drivers! It all ended well, and the new C8 is everything that’s promised and then some. But how did the mid-engine C8 get to this point? Well, here’s a walkaround of each of the three generations of mule cars under the watchful eye and explanation of Mike Kociba, the lead development engineer for the mid-engine Corvette project.
Kociba began by pointing out one of each of the three generations of mule cars was under one roof. And, as luck would have it, we found ourselves with camera in-hand and Kociba standing by—ready, willing, and more than enthusiastic to tell us a little something about each of these cars.
We started our tour standing next to Blackjack. In the VIN, DX3044EX, notice the EX at the end of the string of letters and numbers, which denotes experimental. As such, this car is never to be sold or released to the public. Odds are these EX cars will be crushed, with a few kept for one of the GM museums. The initial, one-of-a-kind prototype was built to show “engineering proof of concept.” According to Kociba, this vehicle is extremely early on in the development phase. He continued to tell us that even before this unusual looking mule car came into being, 100,000 man hours of computer aided engineering work were needed to get to something like this.
With their homework well underway, the next phase was to begin. Blackjack represents the next phase. The idea is to learn about certain things: Can the body structure handle the loads introduced from the suspension? Is the suspension in the right place? And especially, does the kinematic (the motion of objects without reference to the forces that cause the motion) make sense? According to Kociba, everything else doesn’t matter at this point.
Development is akin to a large funnel. In the end, you want the final product coming out of the small opening at the bottom. At this point, the Corvette engineers are at the wide opening at the top, with lots of data to deal with but focusing in on the proof of concept. If you look deep down into this mule car, you will see lots of billet machined parts, lots of hardware, and multiple mounting points. Components are moved around, all the while diligently working toward proof of concept.
The Blackjack project started with 7,000-plus pounds of billet material. Not one big piece, but multiple pieces. From this, almost 90 percent of the billet was flung into chips after the componentry was made. Each piece on Blackjack was made in a GM facility.
What you see in the photos, ostensibly, represents where the C8 design was at the time—not much. However, the suspension components that you can see show there’s several bolt-on parts because interchangeability is required. Kociba wanted to be able to drive some of these different kinematic configurations to see if this is how he wanted the car to behave in specific conditions. Everything else beyond this point he didn’t care about, at least not now. At this point, he needed the car to weigh what he wanted, is the mass distribution what’s required, and he needs the driver in the correct spot, plus the C8 goodies underneath.
At this point, a C7 was gutted and given to the advanced vehicle integration staff, AVI, out of Warren, Michigan, which is located at the GM Tech Center. The AVI staff was instructed as to what matters mechanically and what design elements that matter. Everything else, Kociba didn’t care about. In the end, the car was to look like an El Camino. Why? The shape and styling on the outside was the camouflage. Kociba likes to tell us that the new C8 was “hiding in plain sight.” The truck mule looks like a Holden Ute, and if you look closely, the only parts on this truck that are from a Holden are the headlights, the facia (note the badge in grille), the mirrors, and the taillights. Everything else on this mule is handmade.
Because Kociba was still at a point that the interior was of little consequence, you will note that everything is C7. As a Corvette enthusiast, you will undoubtedly notice the C7 roof, C7 glass, and C7 doors underneath the exterior panels. Mechanically, you will also notice the use of C7 brake booster, radiator fan, and several other C7 parts.
Interestingly, when one looks at the back of the car you will notice that the engine is a LT1. Kociba broke out his saw and began making parts so that the conventional LT1 front engine would work in a mid-engine configuration. For instance, the intake manifold was turned around, a special bellhousing was created, and custom headers were made to allow the exhaust to exit out the back. But as many C7 parts that could be used were retained during this phase.
You are looking at Blackjack, a one-of-one C8 Corvette. At this point, the LT1 was mated to a ZF seven-speed DCT. Here, this engine/trans combo required handmade provisions in the rear cradle to accept the mounting. This isn’t the intended transmission, but it was a transmission that would mate to the engine at hand. It took Kociba’s staff about eight months to build this car. When asked if this mule would be destroyed, Kociba was excited to tell us that he hopes that it will have a long life in the GM Heritage Center.
From here, his staff moved onto an architectural mule (VIN #1G1YK2D6XKX4510EX), the second of three engineering mule vehicles. At this point, the car underneath has true high-pressure die castings, true extrusions, and there isn’t much in the way of one-off components. During this phase, Kociba is doing representative processes, as well as design iteration of the key body structure elements.
Back again, is the funnel analogy. Kociba’s staff is a little further down the development funnel. There are more things that his staff cares about, but there are also many items they don’t. The interior of this car its Spartan to say the least. Note the use of black tape and cardboard to cover the dash. A press-brake piece of aluminum represents a dashboard that components are mounted to.
The suspension kinematics at this point are correct, and so are the brakes. Now is the first time the LT2 engine is in the car and mated to a Tremec DCT. It’s also the first time that the new electrical and cybersecurity architecture that was developed for GM is integrated into the vehicle. But the mule still has some exterior design elements from the old car, such as the C7 windshield, C7 roof, and C7 doors, so the interior can be sealed. Underneath the camouflage are several hand-built parts that are stuck together to cover the tires and so on.
We were told 11 of the second-iteration of the C8 mules were built, and five were crashed. These were barrier facility crashes and not crashes that occurred on a test track or open roads. Kociba told us the one thing they were super proud of through the entire development process was this: “We never crashed a car, pre-production, during any of the development as an accident.” The barrier tests we did crashing five of these cars were to determine if the design elements and load paths in the body structure were going to get the Corvette engineers to where the car could be certified across the globe to fulfill all the requirements that every region has.
Because it’s the first time Kociba had a GM small-block “talking” to a Tremec DCT, there was lots of learning going on. They knew that when you get a shift wrong, or a launch, you telegraph that directly through to the driver because you’re fully coupled with a clutch. They wanted to make sure that the Corvette owner was used to an automatic transmission when driving casually would experience those buttery smooth shifts. He wanted the same expectation of the DCT. It was reported that likely the hardest part of this entire development was getting that right. They knew how to get the DCT—all of the full throttle shifts, track driving, and other parameters—to perform and had been doing so for years. The subtleties were things that had to be learned during this phase. There were elements that they needed to add to the control logics to be able to get the car ready to drive nicely.
Next up, vehicle dynamics. His team needed to focus on how well the car would ride. Does the car handle and steer like a Corvette should? Taking the knowledge already in hand and designing representative elements was next. His staff would make the first pass at what a Stingray wants to be, as well as what the Z51 want to be in regard to steering and handling elements. From this phase, one of the 11 was built.
Next up is the integration vehicle phase. About 100 of these were built. You can look inside this mule (1G1YM2D62LX5895EX) and see design-representative interior and design-representative exterior. Across the board, the glass is right, the doors are right, other aspects are correct. This is the first time the entire collection of parts is built into a Corvette. These are the C8 roof and doors shown for the first time. This is the first time the pile of parts comes together and are then integrated together to make it into the new car. Kociba’s staff learned a lot along the way, as you can imagine. Everything had to be done here, from figuring out how to make this car truly into the final stages of a Corvette, then to run emissions testing along with engine and trans calibration.
More barrier testing was done for very specific tests. Of the 100 Phase 3 mules made, more than 30 were crashed. At the end of this integration vehicle phase, his staff handled the certification and validation. The team was now done, having tuned all the parts and put the parts onto a “golden” vehicle. They confirmed that they have what they wanted to get out of it before moving into a pre-production car at the Bowling Green plant. This is still a hand-built car out of Warren, Michigan. This creates the target that the staff needs to move onto a pre-production Bowling Green-built car. Next step is to figure out how to make sure you can build X cars per hour, while ensuring that every car is perfect, and every car is the same.
In this last iteration of the mule cars, you can begin to recognize items such as the center console and the dashboard. One of the things you don’t see in this car post-reveal is the camouflage covering throughout the interior and the tape over the logo. Look at the steering wheel, where there’s another piece of camouflage. The hood would be covered over along with the instrument cluster, center console, and seat covers trying to make sure that as the vehicles were taken into the outside world for final development, Kociba and his staff weren’t giving away things that they didn’t want us to see just yet.
In the end, nearly every one of the C8 engineering vehicles (mules) will be crushed. Exceptions will most likely be mule No. 1, Blackjack, and possibly one or two from the final 100. The hope and wishes are that they will end up in the GM Heritage Center for fans of the Corvette to see for years to come.
For fun, we also included some final photos of an early production 2020 C8 mid-engine Corvette Stingray. This will give you a chance to see the evolution from the earliest days right through to a final production model. By years end, some 30,000 lucky hot-rodders will have one parked in their garage and enjoying those fun-filled drives.