2020 Mid Engine Corvette Tech
Making Sense of all the mid-engine Corvette leaked pictures, details, and info
Rumours of a mid-engine Corvette have been around basically since the C2 Corvette, the first Stingray. The current Corvette engine does sit more or less entirely behind the front axle, making it mounted mid-ship. But a true mid-engine layout has a lot more traction - all else being equal - than a front-midship mounted engine like the current Corvette, no matter how far back it is mounted. Chevy knows this, and there has been no shortage of Corvette mid-engine concepts for decades, like the CERV III Concept below revealed during the fourth generation C4. This time, however, looks like it's finally for real.
Mid engine Corvette Engineering Research Vehicle (CERV) III - GM
There has been many spy shots and a few spy videos of mid-engine prototypes tested on the street and on track - the Nürburgring, of course (enjoy video below of a prototype running on the street and at the 'Ring). There are also technical details and technologies that point to a redesigned 'Vette. If Chevy is working that hard on a mid-engine prototype (i.e. on public roads and tracks outside of GM's proving grounds) and it is not showing it to the world, the only conclusion is that this time, it is meant for production.
As a result, the automotive society - journalists and fans - are collectively convinced that this time, it's for real. The next Corvette will be mid-engine, or at least a variant will be. With plenty of articles floating around, publications/patents, spy shots and videos, and even some (supposedly) leaked documents, I figured I'd make a post summarizing what is known about it and provide a bit of technical background where I could.
Chassis & Suspension
You can't tell much about the suspension from spy shots but, luckily, leaked CAD images that were posted a few months ago show some important bits - assuming they are accurate and reflect the design of this car.
Leaked mid engine Corvette CAD image of rear sub frame and engine/transaxle - Corvette Forum
The rear sub frame is large and not meant for only holding the suspension like on a traditional unibody chassis. It clearly has engine and transaxle mounts, suggesting that the car might be built around a centre tub or chassis with front and rear sub frames bolted to it. It isn't immediately clear from just the CAD images what it will have for rear springs but the structural members and drivetrain near the rear lower control arm/wishbone suggest little room for a transverse leaf spring like the current Corvette, so this could finally use coil springs all around.
Front and rear suspension designs appear to still be unequal length double wishbone. I was expecting to see pushrod suspension or something to move components inboard but it doesn't look that way. There is a traditional coil-over spring setup up front, albeit steeply raked inwards as you'd expect but certainly nothing like the Ford GT's unique inboard double-spring system with pushrod torsion bars.
Leaked mid engine Corvette CAD image of front suspension - Corvette Forum
Brakes are visible in the spy shots. There aren't much details on the front brakes from the leaked CAD images, just a fixed calipers and a large disc/rotor. GM has been offering carbon ceramic brakes on its highest performing Corvettes since the C6 ZR1, so it's probably a safe bet to be offered here, at least as an option. There are no brakes shown on the rear axle in the leaked CAD. However, a spy shot not too long ago revealed not one, but two brake calipers on the rear axle. It's not clear why.
Spy shot of mid-engine Corvette prototype testing in public showing dual caliper rear brakes - Automobile Magazine
It could be to increase stopping power by increasing the clamping force over a larger area. Race cars in the past such as the Porsche 956 have used dual brake calipers in the back. With the engine in the middle, rear wheels should have more available grip, while simultaneously taking away some from the front. That, in turn, would increase the rears braking capacity and therefore increase heat generated there. Unlike front brakes, however, which have the entire front fascia to utilize for some air inlets/intakes to duct air for brake cooling, the rear is more restricted, especially as you move the engine to the back because the engine will be fighting over every inch of surface area to gain as much air as possible for combustion as well as cooling.
Another possibility is much simpler; it's a parking brake. Cars that have used a second brake caliper as a parking brake are Ferrari F430, Lamborghini Murcielago, Aston Martin Vantage, McLaren Senna, and probably others. Judging by the size, I'd say it's just a parking brake.
Engine & Transmission
Leaked mid engine Corvette CAD image of rear sub frame & engine/transaxle- Corvette Forum
The engine is clearly longitudinally mounted. If it is a complete engine, it doesn't look like there are any turbos or supercharges. We also know from the recently revealed Cadillac twin-turbo 5.5 litre DOHC V8 that the engine uses a "hot-vee" turbo arrangement with the turbos mounted in the space between the cylinder banks and GM certainly won't change that arrangement for the Vette (assuming it will likely end up here). With this engine height being as tall as it is and the exhaust piped directly towards the back, it doesn't look like there is room for vee-mounted turbos. The height also makes it very unlikely that there is a top mount supercharger as is usual for Chevy engines, suggesting that this is likely a naturally aspirated engine with no "external" turbos/superchargers.
Chances are, it will be the next gen 6.2 litre OHV V8 which is anticipated to be the base engine to the optional twin-turbo Cadillac LT7 V8 recently revealed. Horsepower figures aren't known for the base engine. The Cadillac engine was confirmed to be making at least 550 hp and 627 lb-ft of torque. I suspect it will make more here to the tune of something north of 600 hp (IMO) and the base naturally aspirated 6.2 litre will certainly make more than the current one in the base C7 Stingray. I suspect anywhere between 480 hp and 500 hp. I’m sure a new car developed for this market will be designed to allow future integration with a hybrid system, but I suspect it will be launched without hybrid tech.
Tremec TR-7007 and TR-9007 family of dual clutch transmissions - Tremec
For a transmission, there is already a very strong dual clutch transmission candidate by Tremec, which makes the manual transmission in the current Vette (the current auto is a GM unit). Seemingly an unlikely DCT manufacturer and much better known for its manuals in Mustangs, Camaros, Challengers, Corvettes, and Vipers, Tremec actually owns Hoerbiger Drivetrain Mechatronics. In an attempt to expand and reach broader markets, Tremec acquired Hoerbiger to help develop DCT's instead of, presumably, starting from scratch. The result? Tremec’s TR-7007 and TR-9007 family of 7-speed dual clutch transmissions. TR-7007 has a torque capacity of 516 lb-ft so we (hopefully) don't have to worry about that one. The TR-9007, though, has a torque capacity of 664 lb-ft. That's a lot more like it.
Although it is not confirmed to be used in a mid-engine 'Vette, it can be used in RWD and AWD layouts, including trans-axle configurations according to Tremec's own product literature and it was developed for "products characterized by high-torque applications in sports cars, SUVs and diesel vehicles that demand performance and refinement." But wait, there's more! It is good for 10,000 rpm. It's probably a safe bet that it will make its way in the new mid engine Corvette. It weighs 198 lb. according to Tremec, whereas the current 8-speed GM 8L90 weighs between 211-218 lb., so the DCT should actually be a little lighter.
C7 Corvette rear transaxle - GM
As for manuals, I personally wouldn't be surprised to see a manual on the base engine. I haven't found any publication confirming or expecting that so I could be out to lunch, but Chevrolet already has a manual rear transaxle to work with the current 6.2 litre LT1 V8 in the C7 Corvette. Gear ratios, rpms, and torque capacity of that transaxle are already compatible. I don't see an upgraded version of the LT1 being so far improved/changed that the current transaxle doesn't work anymore. The only potential issue is that the current rear transaxle is obviously separated from the engine in the front by a torque tube so the only limitation could be incompatibility to bolt directly to the engine, but for an OEM manufacturer, that should be fairly simple to get around (if there is a problem to begin with).
Chevy hasn't shied away from big aero recently. Splitters, canards, dive planes, big spoilers, vents, the lot, even on the Camaro. It should be no surprise to see big aero elements and devices used, especially in top versions. One major new tech, however, is active aero. GM recently filed a number of patents covering active aero elements. A lot of the devices described in the patent filings are shown on a C7 Corvette. Since the C7 Corvette is nearing the end of its life and there is a brand new extremely high performing Corvette just released - the ZR1 - this is almost a guarantee that they are meant for the next generation Corvette, be it front or mid engine.
GM Patent Filing Showing Active rear spoiler
Active spoilers are commonplace now on high end sports cars and super cars. This takes it a step further, though. Whereas most active spoilers vary height and tilt (angle of attack), this one can also move front and back. The first two are obvious. The higher the spoiler, the further it is from air flowing over and around the car (which is more turbulent, less effective) and the better it is at generating downforce.
The tilt angle of an airfoil spoiler is directly related to its ability to generate downforce, just like an airplane wing angle of attack - except it's inverted so it generates downforce instead of lift, plus adjusting tilt angle could also be used to an extreme angle as an airbrake. The last one - the ability to move front and back - could have two benefits. Just like spoiler height that allows it to move further away from turbulent air, moving the spoiler towards the front of the car brings it closer to the cabin, where air is even more turbulent. This could result in a wider range of adjustability. Moving it to the front could also have some effect on front-to-rear aero balance.
GM Patent Filing Showing Active side skirts
The other active aero elements are active side skirts. The patent filing covers active side skirts, allowing the effectiveness of those skirts to be varied by raising or lowering them closer to the ground, as well as extending them outwards or retracting them. Moreover, the filing includes individual control mechanisms for side skirts on each side of the car allowing the car to vary downforce side-to-side, so the car could optimize downforce for left and right hand corners. Side skirts serve to keep air flowing where you want; air flowing outside and around the car stays there. This has two benefits. First is reducing drag by preventing air flowing around the car from getting disrupted by going underneath the car. The second is, by doing so, you can also increase (effective) downforce in aero-optimized performance cars.
In aero-optimized performance cars and especially race cars, there are passages under the car designed to speed up the air as it passes underneath the car. Air pressure is inversely proportional to speed, meaning that as air speed increases, pressure decreases. Low pressure underneath car has the same effect as downforce, except that it doesn't push the car down so much as it "pulls" it down by creating a relative vacuum. The challenge is that a relative vacuum wants to also suck air in from around the car, not just the car itself. By minimizing the amount of air that gets sucked in from the sides, side skirts allow undercar passages to maintain their relative vacuum/low pressure and increase effective downforce, which takes us nicely to the last active aero tech filing; Downforce Generating Ducts.
GM Patent Filing Showing effective under-car aero ducts
This is already explained to an extent above, but aero optimized cars often use underbody ducts or passages to control airflow. Those are used for two benefits. First of which (already discussed) is to speed up airflow. Faster moving air has lower pressure (Bernoulli's principle), effectively increasing downforce. Another function for underbody passages is directing air towards a rear diffuser. Rear diffusers increase downforce by expanding the volume of the exit passage for air moving underneath the car. In other words, air moving underneath the car has to "exit" from the back. The volume of passage underneath the car is smaller than that of where it exits; the diffuser. By expanding the volume, you require more air to fill the newfound volume, resulting in more flow and faster moving air at the inlet (throat) of the diffuser underneath the car, which creates downforce.
Another benefit of rear diffusers is slowing down the air at the trailing edge where air from underneath the car (fast) needs to meet air from above car (relatively slow). This reduces turbulence at the back of the car and therefore drag. GM's patent includes ducts from the top and bottom of the car (C7 Corvette pictured). Although there is no mention of them being active, there is potential to make them active by varying the volume of the "throat" of the duct or varying airflow to the diffuser, reducing or increasing its effectiveness.
GM Patent Filing Showing frontal and top mounted air inlets
Finally, a previous patent preceding all those filed by GM last year describes "a method or apparatus" to tie everything together. The intent is to use input about what the car is doing such as yaw, steering angle, tire pressure, speed, lat-g, and others to control all active systems simultaneously and optimize performance. The current Corvette already does this and can vary damping rates (if equipped with magnetic shocks), differential lock (e-LSD), and brake activation through Performance Traction Management (PTM). Adding active aero will only enhance and vastly expand the ability of the car to optimize grip for any particular scenario where it's needed. This is what Lamborghini is doing with the Aventadpr LP 770 SVJ, the one that broke the Nurburgring lap record this year in July.
Pricing & Release Date
Who knows? Pricing is perhaps the biggest unknown (by far IMO). I don't see this car costing more than $200,000 and I don't see it under $100,000. I think a base price around $120,000 is not too unreasonable, with options taking it towards $180,000. This is pure speculation, though. I would be very surprised if it cost anywhere near the Ford GT but I wasn't expecting the GT to cost that much either, so take that for what it's worth.
As for reveal, I read an article from end of last year (2017) where the writer was expecting the car to be revealed at the Detroit Auto Show in January of this year (2018). Here we are almost a year later and it is still not revealed. Judging by the stage of development apparent from the spy shots and videos, we are likely not too far away, though. The Detroit Auto Show is one of the biggest for Ford and GM. Ford decided to reveal its GT in the same show three years ago in 2015 along with the Shelby GT350R and the current F-150 Raptor. GM revealed the current CTS V that year and a year prior (2014) revealed the C7 Corvette Z06 and the C7.R Corvette race car. I would be surprised if we have another 1+ years until the reveal (i.e. 2020) so perhaps this January is a safe bet. If that's the case, we should be no more than 1 year from on-sale date so I would expect deliveries to begin in 2020, if not very late 2019 as a 2020 model year. If revealed this January, there's a decent chance publications will begin testing or at least first drive reviews next summer. I can't wait!
Do you think that the mid engine Corvette is real this time and are you looking forward to it? Let me know below!
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