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I'm really curious to see how the new car drives and the dynamics of it. Making sure they're ahead of the C7 platform isn't easy as that platform is quite capable. I hope the improvements aren't just a tire upgrade.
While the variants will be faster, the C7 Z51's overall performance will give us a good indication of the potential of the platform.
The dramatic shift might also reset the aftermarket tuner pecking order also as it's not just another iteration of tried and tested platform.
That literally confirms what I said, so it provides the same answer (unless that’s what you meant).
The C7 had a disastrously low 14,500 deg/nm target and GM stated they came within 5% of said target. So it’s even flimsier than a paltry 14,500 deg/nm. Seriously, find one car on sale today with a lower rigidity figure. You’ll find it hard to impossible. Clearly this is a massive area where “pennies saved for faulty life threatening ignition switches” GM has been able to keep costs down.
Sure, the new 992 might have a nubbin, a luxury sedan like interior that’s feels more designed for calm Sunday cruises than spirited track romps, and a soulless sounding turbo motor, and costs a lot more, but if you’re in a pileup where other cars are putting every area of your cars structure to the test, you’ll appreciate the detailed engineering Porsche puts in that GM doesn’t (which thus provides you a better bargain).
I don’t even have a dog in this race as I can’t stand the bland sound of the 9A2 turbos, and admire an N/A 6.2L (sure, I’ll even accept the ancient pushrods) hulking at the mid of an attainable car, but let’s be objective here. The C8 isn’t magically supplying a potion that no car manufacturer could crack. They literally bolted the structure together which provides statistically fragile resistance to bending. Maybe that doesn’t matter to many shoppers, maybe it does, but it’s important to note.
If really concerned about being safest on the road, you're better off driving something other than any sports car when you're looking eye level at someone else's bumper.
Hmm. Did you miss the point about the car been designed to be a targa top? instead of a coupe? And how that affects torsional stiffness?
What used to be the delta between a Boxster and a Cayman in regards to torsional stiffness?
Would you call the Boxster a deathtrap? Since the 987 Boxster S probably had about the same chassis torsional stiffness as the targeted torsional stiffness of the C8.
But the 718 Boxster has a 19,000Nm/degree torsional stiffness number which is significantly higher than the C7. The 718 Cayman set the sportscar benchmark for structural stiffness, with an incredible 40,100Nm/degree.
I've never been a Vette fan but I must say there's nothing out there that comes close to this for 60K! Nothing!
Saw it up close yesterday, Probably impossible to get one at 60K at first much like getting a 35K Tesla. Front end is Ferrari derivative, not bad. Back end is terrible, too much like previous models. They have a brand new platform and had the chance to start a new look and blew it.
That literally confirms what I said, so it provides the same answer (unless that’s what you meant).
The C7 had a disastrously low 14,500 deg/nm target and GM stated they came within 5% of said target. So it’s even flimsier than a paltry 14,500 deg/nm. Seriously, find one car on sale today with a lower rigidity figure. You’ll find it hard to impossible. Clearly this is a massive area where “pennies saved for faulty life threatening ignition switches” GM has been able to keep costs down.
Sure, the new 992 might have a nubbin, a luxury sedan like interior that’s feels more designed for calm Sunday cruises than spirited track romps, and a soulless sounding turbo motor, and costs a lot more, but if you’re in a pileup where other cars are putting every area of your cars structure to the test, you’ll appreciate the detailed engineering Porsche puts in that GM doesn’t (which thus provides you a better bargain).
I don’t even have a dog in this race as I can’t stand the bland sound of the 9A2 turbos, and admire an N/A 6.2L (sure, I’ll even accept the ancient pushrods) hulking at the mid of an attainable car, but let’s be objective here. The C8 isn’t magically supplying a potion that no car manufacturer could crack. They literally bolted the structure together which provides statistically fragile resistance to bending. Maybe that doesn’t matter to many shoppers, maybe it does, but it’s important to note.
The engineering team had no choice:
"GM got zero bids from suppliers to produce the C8's six high-pressure diecast aluminum structural parts. Those parts are too exotic and will be required in too much volume for anybody to handle. So they learned to produce them themselves."
This makes me think Porsche had the same constraints in their strut top hat design, that part should have been high pressure die cast, but Porsche production volume is lower than c8
That literally confirms what I said, so it provides the same answer (unless that’s what you meant).
The C7 had a disastrously low 14,500 deg/nm target and GM stated they came within 5% of said target. So it’s even flimsier than a paltry 14,500 deg/nm. Seriously, find one car on sale today with a lower rigidity figure. You’ll find it hard to impossible. Clearly this is a massive area where “pennies saved for faulty life threatening ignition switches” GM has been able to keep costs down.
Sure, the new 992 might have a nubbin, a luxury sedan like interior that’s feels more designed for calm Sunday cruises than spirited track romps, and a soulless sounding turbo motor, and costs a lot more, but if you’re in a pileup where other cars are putting every area of your cars structure to the test, you’ll appreciate the detailed engineering Porsche puts in that GM doesn’t (which thus provides you a better bargain).
I don’t even have a dog in this race as I can’t stand the bland sound of the 9A2 turbos, and admire an N/A 6.2L (sure, I’ll even accept the ancient pushrods) hulking at the mid of an attainable car, but let’s be objective here. The C8 isn’t magically supplying a potion that no car manufacturer could crack. They literally bolted the structure together which provides statistically fragile resistance to bending. Maybe that doesn’t matter to many shoppers, maybe it does, but it’s important to note.
Neither the C7 (and I assume C8) or 911’s get crash tested. For a reason. Want safe get a Volvo
Sure, the new 992 might have a nubbin, a luxury sedan like interior that’s feels more designed for calm Sunday cruises than spirited track romps, and a soulless sounding turbo motor, and costs a lot more, but if you’re in a pileup where other cars are putting every area of your cars structure to the test, you’ll appreciate the detailed engineering Porsche puts in that GM doesn’t (which thus provides you a better bargain).
I don’t even have a dog in this race as I can’t stand the bland sound of the 9A2 turbos, and admire an N/A 6.2L (sure, I’ll even accept the ancient pushrods) hulking at the mid of an attainable car, but let’s be objective here. The C8 isn’t magically supplying a potion that no car manufacturer could crack. They literally bolted the structure together which provides statistically fragile resistance to bending. Maybe that doesn’t matter to many shoppers, maybe it does, but it’s important to note.
BTW: Are you correlating torsional stiffness to accident survival rates? Just because the chassis structure has high torsional stiffness doesn't mean that it can dissipate energy from the point of impact away from the passengers sitting in the vehicle.
the 63 photos of c8 cutaway illustrate the beefiness of frame, it may not translate to stiffness, but the heavy gage section and gussets imply strength, i cannot envision frame damage from hitting curbs , particularly due to the torque to yield bolted connections acting as springs that distribute loads over a larger area avoid concentrated loads and stress risers from a chassis being too stiff thus in case of c8 metal fatigue and stresses due to wheel impacts absorbed throughout frame not all at the initial load transfer point of bottomed out strut to top hat mount on gt4.
adhesive connections have no elasticity thus are stiff till point of catastrophic failure
Die casting usually requires much greater parts volume to justify the hardware and bring the cost savings. Forging would work but that drives up cost. Perhaps they could have instead compromised to use simpler shapes, maybe they ran out of time and weren’t expecting the no bids.
Die casting usually requires much greater parts volume to justify the hardware and bring the cost savings. Forging would work but that drives up cost. Perhaps they could have instead compromises to use simpler shapes, maybe they ran out of time and weren’t expecting the no bids.
GM had the c8 5 years in development, the current frame they have does the job for them in the current NA 6.2 vette at a lower cost and huge production flexibility, 100's of fabricators can do the required notching and press brake forming that some of the frame parts require, even at low volume and a constant design change iteration. Genius
IMO this kind of frame and production method will disappear for the 2023 4-cam 5.5L, 760hp TT, it has to in order to make space for the turbos and wider engine.
Frame development is likely ongoing on 2023 TT since current frame flexes too much with the high torque 5.5 TT as reported 3/12/19 in early testing.
"one prototype equipped with a particularly powerful, 900-1,000 hp version of the supercar’s new twin-turbocharged V8 engine experienced “structural distortion of the aluminum spaceframe,” upon acceleration which even broke the rear engine compartment glass. This has sent Chevy back to the drawing board for the new MR platform, although it’s not clear if this problem has been solved yet." (as of 3/12/19)
Good see that DCT can take that kind of power
I expect fixed roof, bonded and riveted T7 extrusions with forged parts at critical nodes, perhaps even at spring perches ; no way GM would want GT4 type issues once the chassis stiffness is ramped up.
BTW: Are you correlating torsional stiffness to accident survival rates? Just because the chassis structure has high torsional stiffness doesn't mean that it can dissipate energy from the point of impact away from the passengers sitting in the vehicle.
Torsional stiffness is all about handling, so its benefit would be in preventing an accident. If cars collide torsional stiffness isn't much of a factor, There are lots of reviews for the safest cars on the internet, and I didn't find a Porsche on any of the lists that I viewed. Below is just one of many, but it is one of the most comprehensive. https://elmersautobody.com/safest-ca...auto-accident/
I’ve looked into *TORSIONAL RIGIDITY* and this is what I’ve discovered:
The C7 has about 14,000 deg/nm of torsional rigidity (GM set a “target” of 14,500 and said they got within 5% of that.... i.e they couldn’t even accomplish such a flagrantly low target). That is HORRENDOUS
Less than I would have guessed, but what makes you say it is "horrendous"? How much do you think you NEED? IMO, as long as the first mode is 20 Hz or so, that's plenty stiff enough for a very high-performance production car and there's very little if any to be gained from going stiffer than that as it's a factor of 10 or more over suspension natural frequencies.
If I remember correctly, someone above noted that GM says the C8 will be 20% stiffer. That’s also embarrassingly atrocious and puts it at well under 20K. This explains why Vettes feel famously flimsy.
I seriously doubt you would be able to feel the difference between 15kN/deg and 20kN/deg, at least at street car or street/track compromise spring rates...
Compare to the 991 which Porsche stated is 30% stiffer than the 997, which was 33,000 deg/nm. Putting the 991 at around 40,000 deg/nm. And the 992 is even stiffer.
Chevy’s “all bolts and no welds” clearly are destroying the cars rigidity figures.
C8 is stiffer than C7 despite being more "bolted-joint" intensive. I believe they went to bolted joints to avoid totaling cars from them barely bottoming out and cracking an aluminum weldment with no way to repair/replace the damaged portion. For sure it is possible to design bolted joints that are plenty stiff. Likely to be a weight penalty vs. welded though...
Would you rather be in a car with 40,000 degrees of withstanding force, or a paltry 17,000 (C8 approximate figure), which is lower than a 2014 Cruz, in an accident? GM are famously the WORST at torsional rigidity while VAG are about the best.
Stiffness is NOT the same as strength, or crashworthiness! In fact it is possible to be *too* stiff for safety, you definitely want the structure to have crumple zones.
Worth noting that some German cars with exceptional stiffness have had issues with primary structures cracking and failing over time...
Ya get what ya pay for. At least somewhere.
And sometimes you pay more and still have structural failures, despite higher chassis stiffness...
Originally Posted by K-A
But we’re stuck with the targa top. I’d much prefer a solid roof to get tons of rigidity back.
So would I. It's too bad they've stuck with this design since the C3, with the only exception being the rather grotesque-looking C5 hardtop/Z06...
So even the coupe Corvettes are essentially roadsters/convertibles. Compared to other convertibles, they are in the ballpark for stiffness. C8 will apparently be stiffer than the 992 convertible.
EDIT: Somehow i forgot that the C6 Z06/ZR1 did have a fixed roof! Which allowed it to be about the same stiffness (slightly stiffer) but *lighter-weight* vs. base and GS coupes. They kinda skipped this approach for the C7 and went with more power over lighter-weight for the Z06. Doh...
FWIW I am an aerospace structural engineer, and have designed and/or analyzed structures for space, air, and road vehicles. Lately I've been working on a bonded carbon fiber spectrograph for the biggest telescope ever built by humans. ~2600 lb., 13' x 3' x 4', first mode > 50 Hz. Now that is stiff! For good reason...
IMO sports cars don't need to have bank-vault levels of rigidity to be good at what they do. There's a point of diminishing returns on chassis stiffness for sports cars, and honestly I think even my 987.2 Cayman is already beyond it. It feels much stiffer than my BRZ. But it's 250 lb. heavier BRZ is nearly as fast at slower tracks (did 1:23.1 at Thompson in the BRZ last Friday, vs. 1:22.7 in the Cayman the next day in similar conditions). I would be willing to trade some of the Cayman's stiffness for less weight...
All that said I have always been more a fan of fixed-roof sports cars over roadsters/convertibles, partly due to more efficient structure with greater stiffness/weight.
Who knows, maybe the Z06 or ZR1 version of the C8 will have a fixed roof?
I can see GM doing things like using a less expensive water pump housing or radiators or things like that .
But I can not see them having things like frame breakage or having these cars twist and shear and beat themselves to pieces.
Im Old School as y'all know. I haven't been a fan of the adhesive bonding Porsche frame bits either but they say it works and is an improvement so Ill have to go with it.
Porsche has been very diligent about keeping these cars on a diet and keeping the weight down though and I have to believe GM looks at that too.
07-29-2019, 09:19 AM
BRZ is nearly as fast at slower tracks (did 1:23.1 at Thompson in the BRZ last Friday, vs. 1:22.7 in the Cayman the next day in similar conditions). I would be willing to trade some of the Cayman's stiffness for less weight...