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Old 08-28-2007, 08:24 PM   #1
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Next Corvette (C7) MID-Engined

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AN AUTOEXTREMIST EXCLUSIVE: The Mid-Engined Corvette is not only back on the front burner - it looks to be a certainty. 2007 Autoextremist.com Detroit.

It was already supposed to be a done deal that the seventh generation of the Corvette would arrive in its current, front-engined, rear-wheel-drive configuration - albeit slightly smaller, lighter and with two engine choices. There was serious talk of an extremely limited production mid-engined "super" Corvette (fewer than 500 units), which would be built as an adjunct program to the traditional car, but that had not been decided. That's the way we reported it many weeks ago, and that was the assumption by many in the business as to how it was going to go down - until now. But after my conversations late last week with executives at the top of the company (who shall remain nameless for obvious reasons), I can tell you that the "idea" of a mid-engined "C7" Corvette has not only progressed far beyond the initial planning stages, the engineering on the car is well underway. What brought on this monumental philosophical shift? Read on...

1. Cost. Up until this point, the argument that the Corvette's fundamental high-performance-for-the-money equation - one that has been a hallmark of the car since Zora Arkus-Duntov took over the program in the mid-50s - would be compromised with a mid-engined car has held sway over every future Corvette product discussion/decision. That's no longer the case, apparently. The two key stumbling blocks for a mid-engined Corvette that have always put a damper on previous discussions were the sophisticated, complex and highly expensive transaxle required, and the extremely difficult cooling challenges. The transaxle in particular has a heavy cost-per-piece price that cannot be subjected to shortcuts due to the engineering requirements necessary to accommodate the high horsepower output of a proper Corvette. GM has found a way to solve these issues while still maintaining the Corvette's fundamental value proposition and while still delivering the kind of high performance expected of a car that wears the famed Corvette name. I have it on impeccable authority that as a result of the intensive engineering push on the C7 in the last five weeks, the new car will have a target base price that's very close to a loaded Corvette convertible of today, a number that will keep the future mid-engined Corvette well within reach of its core buyers at current volume levels. This would also obviously allow the Corvette to remain true to its raison d'etre - and continue to outperform cars costing thousands upon thousands more. Judging by the digital images I have seen, the new mid-engined Corvette is sensational looking, which, given GM Design's roll of late, certainly shouldn't be a surprise. Futuristic, purposeful and bristling with exquisite "signature" Corvette design elements - with no "blades" and no bullshit gimmicks - the new Corvette is everything the Corvette faithful could hope for. But an interesting sidebar? Judging by the reactions of people I have spoken to who have seen it, the Cadillac XLR variant of the mid-engined car is drop-dead gorgeous too.

2. The Technological Imperative. There has always been a passionate group of True Believers within General Motors, Chevrolet and GM Racing that wanted to push the Corvette envelope further and aggressively present and promote the sports car as a technological showcase for the entire corporation. This group has always believed that GM has squandered the success of the Corvette - not only failing to use the power of the Corvette brand in corporate image advertising but failing to let the car's significant achievements in racing in recent years speak forcefully on behalf of the corporation in terms of technical ability. This is a belief I share, by the way, because in an era when GM - and the rest of Detroit - is literally and figuratively on the ropes and has become the favorite punching bag of the anti-car, anti-Detroit "intelligentsia" (and I use that term derisively) in the media and in Washington, here is a car that not only humbles cars costing thousands more on the street, it regularly competes and wins against the best that the competition has to offer on racetracks around the world. And its success goes largely unnoticed and unappreciated both within and outside the corporation. The mid-engined configuration will not only propel the Corvette to the next level in terms of performance - giving cars such as the new Audi A8 and any future Porsche 911 fits, by the way (not to mention making Ferrari and Lamborghini very uncomfortable) - it will finally be able to assume the role as a global technological showcase for the corporation, something that it couldn't quite accomplish as long as it was hamstrung with its traditional front-engined configuration, even though the current Z06 already humbles some of the world's most expensive exotic sports cars. Rick Wagoner got up in front of the media at the L.A. Auto Show last November and touted that GM was going to become a technological leader. But being a technological leader is about much more than producing plug-in electric cars - it's about demonstrating passion for the product and in your products - and the willingness to put your technological stake in the ground on all fronts. A mid-engined Corvette will help deliver Wagoner's positioning in spades.

3. The Competitive Imperative. Right now, GM's Corvette Racing program exists for one simple reason: to win the premier GT1 class in the 24 Hours of Le Mans - the world's greatest sports car race - every year. Everything else Corvette Racing does revolves around that single quest, which is why they find themselves running without competition in the American Le Mans Series this year. The ALMS' connection to the world's most prestigious sports car race requires that Corvette Racing wins over here in the GT1 class first, even though no worthy competitor (other than the occasional Prodrive Aston Martin effort) runs consistently against the Corvette in the series, which makes for some less-than-ideal "We beat ourselves - again" headlines. But a mid-engined production Corvette changes everything. Remember the first scenario that I mentioned? That the next-generation Corvette would be in its current front-engined configuration with the possibility of a ultra-limited-production mid-engined "super" variant? The decision to go with a mid-engined configuration for the Corvette alters the landscape significantly. First of all, it eliminates the expense of developing (and paying for) two separate cars, which was something that the GM brass was not jumping up and down with joy about, understandably. Secondly, it allows GM and Corvette Racing to do something that is long, long overdue, and that is to become the second American automobile manufacturer to go for the overall victory at the 24 Hours of Le Mans - something that hasn't been achieved since the glory days of Ford's four-year winning onslaught in the 60s - some 40 years ago. As you read this, GM's senior brain trust is contemplating every facet of this mid-engined scenario down to the last detail for the seventh-generation Corvette. The facts of the matter are hard to deny: The technical issues are on the way to being solved, the classic Corvette high-performance value proposition would remain intact, and GM's drive to establish itself as a global technological leader would be enhanced and embellished, especially with a mid-engined Corvette Racing prototype going for the overall victory at Le Mans. I strongly believe that Corvette's True Believers out there - some of whom have been wishing and hoping for a mid-engined Corvette since the early 70s - are finally going to have their prayers answered - and very, very soon. The word from inside sources intimately familiar with the next-generation Corvette is that a final "go" decision for the mid-engined C7 will be made by the first week in September, and given everything I've learned and everything I've pieced together on the timing, I'll bet the farm right now that the next-generation mid-engined Corvette will make its debut - on the street and at Le Mans - in 2010. Thanks for listening, see you next Wednesday

This isn't a guarantee, but what if this came to be? Good idea? Bad idea?

Someone at GM has been wanting to do this for a long time.


Last edited by What : 08-28-2007 at 08:26 PM.
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Old 08-29-2007, 10:57 AM   #2
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Certainly different, but Corvettes have always been front engined, so it could spark some controversy between enthusiasts....
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Old 08-30-2007, 01:02 AM   #3
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Eh I don't like the reasons for the shift really. I think they should stick to the corvettes front engined setup unless going mid engined results in gains. Im not sure it would, it very well could though. I like the looks of a long hood, that looks right to me. Maybe they could just move the driver and passenger and engine back to achieve the same result.

I think they should move the engine back and make the driveline more of a stressed structural components to save weight. I like where they were going with the engine solid to the rear of the car. Great idea. I think they should build on it.
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Old 08-30-2007, 01:41 AM   #4
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Quote:
Originally Posted by rudypoochris
I think they should move the engine back and make the driveline more of a stressed structural components to save weight.
come again?
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Old 08-30-2007, 02:27 AM   #5
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Quote:
Originally Posted by windsonian
come again?

Well if you look at the driveline of a C6 it is solid from engine to rear axle. The driveshaft is inside a metal case that bolts to the engine which bolts to the transaxle. This helps keep good balance and provides rigidity. I was suggesting they slide the engine even farther back and go with a longer hood and make the driveline more of a structural member to save weight elsewhere.
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Old 08-30-2007, 03:10 AM   #6
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I don't really believe any of it.
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Old 08-30-2007, 03:52 AM   #7
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Quote:
Originally Posted by rudypoochris
Well if you look at the driveline of a C6 it is solid from engine to rear axle. The driveshaft is inside a metal case that bolts to the engine which bolts to the transaxle. This helps keep good balance and provides rigidity. I was suggesting they slide the engine even farther back and go with a longer hood and make the driveline more of a structural member to save weight elsewhere.
So you want to use the drivetrain to take the stresses of the car's weight and inertia?? Don't you think you're going to drastically reduce the life of your drive components doing that? Can you imagine the cyclic stresses/strains? The necessity to over-design to remain under infinite fatigue life would hugely increase the weight of the drivetrain, thus defeating the purpose.

[Disclaimer]: obviously I'm making these comments without any calcs, but intuitively it seems (to me) crazy to use your transmission components for transferring non-drive related stresses.

Out of curiosity, by using this method, where would you make the distinction/joint between suspended and non-suspended transmission components?
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Old 08-30-2007, 02:24 PM   #8
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Quote:
Originally Posted by windsonian
So you want to use the drivetrain to take the stresses of the car's weight and inertia?? Don't you think you're going to drastically reduce the life of your drive components doing that? Can you imagine the cyclic stresses/strains? The necessity to over-design to remain under infinite fatigue life would hugely increase the weight of the drivetrain, thus defeating the purpose.

[Disclaimer]: obviously I'm making these comments without any calcs, but intuitively it seems (to me) crazy to use your transmission components for transferring non-drive related stresses.

Out of curiosity, by using this method, where would you make the distinction/joint between suspended and non-suspended transmission components?

The transmission in the C6 is mounted in the rear and connected to the engine via "torque tube". It was designed to keep the 50/50 weight ratio to the front and rear. The torque tube is mounted to the the engine much like the manner of a bell housing would be. A ball and socket type of joint called a "torque ball" is used at one end of the torque tube to allow relative motion between the axle and transmission due to suspension travel.



The torque tube is hollow and houses a more traditional driveshaft. There is consequently no stress on the "drive line". The design has been used in Porsche 944 if you're somewhat familiar with that setup.
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Old 08-30-2007, 11:50 PM   #9
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Quote:
Originally Posted by DSMer
The transmission in the C6 is mounted in the rear and connected to the engine via "torque tube". It was designed to keep the 50/50 weight ratio to the front and rear. The torque tube is mounted to the the engine much like the manner of a bell housing would be. A ball and socket type of joint called a "torque ball" is used at one end of the torque tube to allow relative motion between the axle and transmission due to suspension travel.


The torque tube is hollow and houses a more traditional driveshaft. There is consequently no stress on the "drive line". The design has been used in Porsche 944 if you're somewhat familiar with that setup.
Ummmm... I know exactly what he was talking about... but it seemed from his post that he wanted the driveline to be structural..... In fact, that's exactly what he said.
Quote:
Originally Posted by rudypoo
make the driveline more of a structural member
So, saying "There is consequently no stress on the "drive line"." contradicts what he said.

Chris, I'm interested to hear your ideas. Were you, in fact, referring to what DSMer's talking about, and maintaining the rigid shaft housing, but using it for structural reasons? Or did you actually want to transfer structural stresses through the drivetrain components?
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Old 08-31-2007, 12:45 AM   #10
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Quote:
Originally Posted by windsonian
Ummmm... I know exactly what he was talking about... but it seemed from his post that he wanted the driveline to be structural..... In fact, that's exactly what he said.
So, saying "There is consequently no stress on the "drive line"." contradicts what he said.

Chris, I'm interested to hear your ideas. Were you, in fact, referring to what DSMer's talking about, and maintaining the rigid shaft housing, but using it for structural reasons? Or did you actually want to transfer structural stresses through the drivetrain components?

Stop attempting to be a stickler. If you knew what he was talking about then you would have assumed that he was not using proper terminology. Its a bit too semantical to get hung up on a phrase of words that are so closely related together.

Unless you didn't know what he was talking about to start with. Somehow I find the latter of the two to be more probable. "What do you mean stress on the driveline, thats dangerous!"

No shit sherlock. Congratulations for pointing out the obvious.

*EDIT*
In case you didn't read this.

"The driveshaft is inside a metal case that bolts to the engine which bolts to the transaxle. This helps keep good balance and provides rigidity."

That SHOULD have cleared up any doubts you may have had.
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Last edited by DSMer : 08-31-2007 at 12:48 AM.
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Old 08-31-2007, 01:12 AM   #11
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Quote:
Originally Posted by DSMer
Stop attempting to be a stickler. If you knew what he was talking about then you would have assumed that he was not using proper terminology. Its a bit too semantical to get hung up on a phrase of words that are so closely related together.

Don't try to answer for him. I wasn't being a stickler. He's talking about a proposed new design.... not the old one.

I don't assume he's not using proper terminology. I assume he knows what he's talking about, and I want to discuss it with him.

Quote:
Originally Posted by DSMer
Unless you didn't know what he was talking about to start with. Somehow I find the latter of the two to be more probable. "What do you mean stress on the driveline, thats dangerous!"

No shit sherlock. Congratulations for pointing out the obvious.

You make a "quote" that I didn't say, then say "no shit sherlock" ??
You sure showed me not to make a point .... that I didn't make.

Quote:
Originally Posted by DSMer
*EDIT*
In case you didn't read this.

"The driveshaft is inside a metal case that bolts to the engine which bolts to the transaxle. This helps keep good balance and provides rigidity."

That SHOULD have cleared up any doubts you may have had.

duh..... like i said, I knew exactly what he was talking about. But my doubts are not with the OLD design. He was talking about a NEW design. Extend your quote to read this (in case YOU didn't read it)
Quote:
Well if you look at the driveline of a C6 it is solid from engine to rear axle. The driveshaft is inside a metal case that bolts to the engine which bolts to the transaxle. This helps keep good balance and provides rigidity. I was suggesting they slide the engine even farther back and go with a longer hood and make the driveline more of a structural member to save weight elsewhere.
I'm not arguing what they DO do, because that would be kind of stupid. Notice that he's proposing that they do something different?? I'm discussing/debating HIS design, not the old C6 design.
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Old 08-31-2007, 03:58 AM   #12
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Ugh why do these threads degenerate so. The torque tube is part of the drivetrain. I wrote driveline, sorry. I used incorrect terminology since I interchanged the two although they probably are interchangeable, whatever). Yes I do mean increase the rigidity through modification of drivetrian components (such as the torque tube, obviously not the prop. shaft). Basically make the drivetrain double back as more of a spine of the car. No I haven't thought about all the details or the best way to do it. Yes I realize minimal torsional gains are to be had. I think its a good idea thats all. Whenever you can kill two birds with one stone you gain.
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Old 08-31-2007, 04:25 AM   #13
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Quote:
Originally Posted by rudypoochris
Ugh why do these threads degenerate so. The torque tube is part of the drivetrain. I wrote driveline, sorry. I used incorrect terminology since I interchanged the two although they probably are interchangeable, whatever). Yes I do mean increase the rigidity through modification of drivetrian components (such as the torque tube, obviously not the prop. shaft). Basically make the drivetrain double back as more of a spine of the car. No I haven't thought about all the details or the best way to do it. Yes I realize minimal torsional gains are to be had. I think its a good idea thats all. Whenever you can kill two birds with one stone you gain.
ok ok....
so you want to keep the idea of a "shaft within a pipe".
So, as you understand it, the current design uses the "torque tube" for stiffness / rigidity, but not for structural strength??

If you're using it as a structural "spine" of the car, the whole thing would have to be suspended, would it not?
If so, then you'd have to either suspend the diff (or gearbox if it is in fact in the rear also) and put a couple of CV's on the axles, or have a break in the drive shaft just before the diff/GB.
I suspect you would go with the latter, which seems to be pretty much what they're doing with it now.

I guess it sounds (in general) pretty much exactly what they're doing with it now. If you're going to strengthen the spine, you just have to make sure your 1 stone is killing your birds. Where can the weight then be eliminated i guess? Is a structural member down the guts of the car the best chassis design? Because if it's not, are we really making any gains by using it that way? I understand you just want to give something 2 uses, but if it's not the most efficient chassis solution, then are we just doing it for the sake of it??

hmm.... a lot of questions .. not too many hard and fast answers yet. Interesting concept though.
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Old 08-31-2007, 05:51 AM   #14
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Quote:
Originally Posted by windsonian
ok ok....
so you want to keep the idea of a "shaft within a pipe".
So, as you understand it, the current design uses the "torque tube" for stiffness / rigidity, but not for structural strength??

If you're using it as a structural "spine" of the car, the whole thing would have to be suspended, would it not?
If so, then you'd have to either suspend the diff (or gearbox if it is in fact in the rear also) and put a couple of CV's on the axles, or have a break in the drive shaft just before the diff/GB.
I suspect you would go with the latter, which seems to be pretty much what they're doing with it now.

I guess it sounds (in general) pretty much exactly what they're doing with it now. If you're going to strengthen the spine, you just have to make sure your 1 stone is killing your birds. Where can the weight then be eliminated i guess? Is a structural member down the guts of the car the best chassis design? Because if it's not, are we really making any gains by using it that way? I understand you just want to give something 2 uses, but if it's not the most efficient chassis solution, then are we just doing it for the sake of it??

hmm.... a lot of questions .. not too many hard and fast answers yet. Interesting concept though.


The torque tube ALREADY acts as a main part of the Corvettes structure. The rear end pushes on the torque tube, which in turn pushes on the engine which is mounted to the subframe that is a part of the cars frame.

The structural rigidity of the frame is already taken care of with the seamless tubes on the C6. Over engineering an already simple design won't fix anything.
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Old 08-31-2007, 06:07 AM   #15
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Quote:
Originally Posted by DSMer


The torque tube ALREADY acts as a main part of the Corvettes structure. The rear end pushes on the torque tube, which in turn pushes on the engine which is mounted to the subframe that is a part of the cars frame.

The structural rigidity of the frame is already taken care of with the seamless tubes on the C6. Over engineering an already simple design won't fix anything.
why are you telling ME this?
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