2014 C7 Chevrolet Corvette

[ZDan]

Originally Posted by Dimman

Because I feel they 'believe' in the OHV setup, but not the springs.

??? I honestly don't know what to make of this statement. Large-displacement OHV V8 is a valid approach to engine performance. Leaf springs are a valid method to get force/distance restoring force in the suspension.

Both are valid engineering approaches. And you're talking about what you "feel"? About what the engineers might (or might not) "believe in"? Funny!

Ducati didn't just shrug at engine development because they had a displacement advantage. They believed that the desmo was best.

Worth noting that desmo was legacy for them. For sure they had a very good appreciation of the advantages *and the disadvantages* of desmodromic valve actuation. They had experience with desmo, they exploited that. The didn't/don't have as much experience with non-desmo, so they probably would take some time to get up to speed if they abandoned desmodromics.

It's a practical choice between two valid approaches. No one can say one is "better" as both have been proven effective.

For what it's worth the 750cc L4s still raped them on the straights, and the V2's advantages were it's low-end response, packaging, low CoG, and balance that allowed them to put power down out of the corners.

The FIM giving them a weight break as well certainly helped them a LOT in braking/cornering!

(Sounds rather familiar, including the displacement advantage, heh...) They needed power up top, and felt desmo would be their best option. Not to be different.

Similarly, leafs were the best option for the production Corvette.

Then Honda brought out the RC51.

No desmo, playing to the same rules as Ducati, and beat them. Which, again, doesn't really say non-desmo is "superior".

So saying that Ducati didn't have to put a world class attempt-to-be-the-best effort in because of displacement advantage is a bit rude to their engineers, and by logical association, to GM as well.

Where in the hell did I say THAT?! Of course their effort WAS world class. They came from nowhere to beat the 4-cylinders. They *were* given huge displacement and weight advantages, that's a simple fact. I certainly don't hold it against them that they capitalized on them.

... So there will probably soon be a point where a DOHC will be smaller and lighter, with a smaller displacement that still outperforms the OHV in every category.

Still thinking in terms of absolutes, that there MUST be exactly ONE "best" way...
DOHC has inherent advantages and disadvantages. Ditto OHV. AT the moment, I don't see a clear advantage one way or the other. Other than that GM's OHV V8s are a much easier fit into smaller/lighterweight cars

*IF* regulations or taxes were applied based on displacement, DOHC multivalve wins. IF they continue to be based on fuel economy, however...

[ZDan]

An aside related to the Ducati vs. RC51 conversation:
Several years back, on of the mags interviewed professional riders, having them talk about "body steering" vs. "countersteering" motorcycles. Many riders were religious devotees of the one method or the other.
Colin Edwards said something like: "Body steering, countersteering, there's no one way, you just ride the shit out of it!".

That's how I see these different approaches. DOHC multivalve works. larger-displacement OHV V8 works. Coil springs work. Leaf springs work. Desmodromics work. Non-desmo works. Hell, even rotaries work (sort of)!
I'm for continuing development of all of them.

It will be a sad world when the absolutists take over and variety is forbidden...

[Ryephile]

Originally Posted by vtmike

The complaint of the leaf springs stems from the handling of the Corvette. I understand there are more things at play than the leaf spring set up alone. I'll admit I can not conclusively say the leaf spring plays a roll just as much as you can't make the claim that it doesn't. Maybe the spring rate is a limitation of the leaf spring? I don't know.

Let's just drop it then, since nobody can prove one way or the other.

:happy0180:

Let's also not pigeonhole the C7 before anyone even drives it. Handling dynamics are a very complicated subject and must be understood as a holistic system. That starts at the chassis and ends in the tires, and literally every piece of hardware in the middle makes a marked and important impact on the overall dynamics of the handling.


Just a quick story. I was at the NAIAS yesterday for Industry Preview. That means that most of the attendees are automotive industry professionals that are supposed to know what they're doing and saying. For the handful of minutes I spent studying the design of the Corvette, I heard significantly more ignorant things than intelligent things...and these are the people behind the cars we drive! GM smartly positioned a Camaro in front of the Corvette, so you can easily compare/contrast the rear ends. Only a moron would conclude their taillights are identical...and yet there were many people making such comments. The Camaro has rounded trapezoidal bezels and a half-circle illumination pattern for each of its 4 taillights. The Corvette has a polygonal bezel for each pair of taillights and a 3-sided "italic" rectangle outline for it's illumination pattern on each of the 4 taillights. The less attentive people are confusing the Camaro bezel for the Corvette illumination pattern. More attentive people understand that the Corvette's taillights are an interpretation of Chevrolet's current "rear face" design language and are not a direct facsimile of any car. Our brains like to make correlations and "connect the dots", even when it's not accurate. I can imagine Dark Helmet sitting behind GM's CEO desk and yelling "FOOLED YOU!".

As for the C7 in the flesh, it looks stunning. It'll have awesome presence when rolling down the road.

[vtmike]

Originally Posted by ZDan

WTH?! I never said it was! I specifically said I didn't read the article! I said that *if* it had posted a slow lap, then you would be on that. In your post, you said it did post a "fast lap".

I never said or implied that the Corvette was "fastest".

And this says absolutely nothing about whether coils are better than leafs as springs. Or, indeed, whether struts are better than double-wishbones...

You mean "fared well".
Anyway, you must surely admit that it is a little bit nutty to look at a comparison of cars that are ALL on coil springs, and suggest that the results imply coil superiority over leaf springs!

You *really* think that the above referenced comparison tests say anything at all about leafs vs. coils? HA!

You're playing a funny game here. When presented with emperical evidence (fast lap times) that doesn't agree with your preconceived notions, you dismiss it with statements like this. You're all about "emperical evidence" when it's negative SUBJECTIVE impressions ("unrefined"), though!


The springs are the simplest, dumbest part of the suspension. They provide a restoring force pretty much linear with deflection. You can design in progressive rates with either coils or with leafs, but usually straight rates are preferred for serious performance cars.

Handling feel is going to be VASTLY more affected by all the factors I mentioned in my last post than by whether the springs are coils or leafs.




Extrapolating a curve based on a single point?

It is worth noting that while giant sticky front tires provide more grip, they can hurt handling feel quite a lot. Both the Corvette and Viper suffer from this.

But in the Viper's case it can't be due to leaf springs, now can it?

Actually I happen to have a new Viper/C6 ZR1 comparison test in front of me (Feb Car and Driver). Similar power/weight, ZR1 2 seconds(!) faster at Laguna Seca. AND they liked the Corvette's handling feel a lot better.

Is the difference down to leafs vs. coils? Of course not. Tires and dampers? More likely...

If you look at those 2 handling comparisons they try to put data to generally an objective thing that is handling. Measuring things like steering angle, slip angle, body roll to name a few. Generally the cars that were said to handle well showed similar trends in data gathered.

The only reason I mentioned lap times was to show that in one instance the fastest car won and in another a significantly slower car won, and in general lap times had nothing to do with the results.

You can have a car that posts a fast lap time that is light, powerful, and has a lot of sticky tire that many people would consider lacking in the handling department. Example: Corvette, viper

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[Dimman]

@ZDan Don't you dare bring magical triangle, spontaneously seizing, beer kegs into this argument!

Also (serious now) I would like your opinion on what I feel may be the practical displacement limits on an OHV V8. Actually any V8 really.
@Ryephile I came to a similar conclusion about industry people over Christmas. I was actually in your neck of the woods (Novi) and met two of the 3 Denso sales managers responsible for Ford. Electrical products (alternators etc...) and thermal products (AC, etc...) and was kind of disappointed with their depth of general automotive knowledge.

[Ryephile]

Originally Posted by Dimman

@Ryephile I came to a similar conclusion about industry people over Christmas. .....and was kind of disappointed with their depth of general automotive knowledge.

I work in Novi! Next time you're in the area give me a heads up and we'll do lunch.

There are a bunch of brilliant minds in the industry. It's just too bad the idiots usually have a louder voice. That goes all the way from entry level to executive. With the companies as big as they are, a lot of the amazing innovators get frequently lost in the noise. Just like most industries, management often confuses political posturing for actual productivity.

[n2oinferno]

Originally Posted by vtmike

I have yet to see a review (from reputable 3rd party neutral source, not gm/Corvette magazines) of any factory Corvette that has all good things to say about the handling without major negative caveats.

Have you driven one? I wasn't sure if this was answered yet, but I did skim back to see if it was asked.

[SubieNate]

I see a lot of subjective, "the handling isn't GOOD, it's just fast because x,y,z..., fast doesn't mean good handling..." going on here on the anti-leaf spring side, and almost no empirical evidence or engineering oriented reasons why the spring type is to blame for those issues. It could all be a combination of spring rate, bushing stiffness, steering linkage slop etc. that cause the softer feel Pobst mentions.

The bottom line is that the Corvette has a double wishbone suspension with springs providing the restoring force. Whether those springs are leafs or coils is really a non-issue as far as the chassis dynamics go. The chassis only cares how hard the springs are pushing back when a force is applied to them, how hard/soft the bushings and joints in all the components are, and how the geometry of the suspension combined with that hardness/softness in the bushings and springs combines to keep (Or not keep) the rubber planted effectively and communicating that information to the driver.

Everything else is a load of verbal (written) diarrhea until some direct comparison evidence is shown with an identical suspension setup with everything about the car held identical except for the spring type. That means the only thing changing is the type of spring providing the restoring force.

Until that type of comparison is made, any comment to the effect of, "the suspension design is sloppy because it has leaf springs" or "the leaf springs are holding back the suspension and responsible for the poor handling." or, "leaf springs are worse than coils" is completely meaningless and solely keyboard jockey conjecture.

From a logical engineering perspective there isn't any major indicator that the springs are worse or better. So until that is proven, those saying, "It's no worse or better, it's just different" are correct. Because that's the only conclusion we have the evidence to make at this point.

Cheers
Nathan

[vtmike]

Originally Posted by n2oinferno

Have you driven one? I wasn't sure if this was answered yet, but I did skim back to see if it was asked.

C5 z06 405hp.

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[n2oinferno]

Originally Posted by vtmike

C5 z06 405hp.

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Ok, so you've got about the same experience in one as I do, down to the model.

I thought it was a really enjoyable car to drive when I had some time with it though. Not just because "go fast = fun" since I've driven faster. But looking at what they achieved going from the C5 to the C6, I can't imagine that the C7 will be anything less than great. Just my opinion though.

[kask2_6.0]

Originally Posted by Ryephile

I work in Novi! Next time you're in the area give me a heads up and we'll do lunch.

Where at?! I live in Novi!.

Unfortunately I can't contribute to this thread but I will follow

[zoomzoomers]

Really enjoying this thread.

The C7 just say me to buy an American car yet.

[Dimman]

Originally Posted by Ryephile

I work in Novi! Next time you're in the area give me a heads up and we'll do lunch.

There are a bunch of brilliant minds in the industry. It's just too bad the idiots usually have a louder voice. That goes all the way from entry level to executive. With the companies as big as they are, a lot of the amazing innovators get frequently lost in the noise. Just like most industries, management often confuses political posturing for actual productivity.

I'd like to but it's not going to be a regular trip. Also, I've never seen so many Lincolns on the road in my life.

The thing that was disheartening was that these guys were no different than the guys I work with. One was a casual enthusiast at best, and the other was about the job/benefits. Kind of the same effect as when my old boss, who was a brilliant engineer, sold to a bigger company with 'normal' engineers. Very disappointed in their capabilities, but I guess there will always be people that just fill chairs, who coast on the work of others. Everywhere.





Bringing the above back to GM/Corvette, despite my opinions of the OHV (slightly inferior) and leaf springs (not necessary), it's clear that GM throws some very serious engineering talent at the Vette.

But GM, unlike the Ducati desmo example, is more than just the Corvette. And as ego-boosting as the Corvette is, why the Hell can't GM manage the same things with EVERY SINGLE OTHER model? That is where they need the brilliance now. For my general dislike of the Vette, it's pretty much impossible to argue that it isn't the best dollar for dollar supercar currently available. On a sheer performance/money-no-object scale, it is still in the shortlist of best supercars.

However, the rest of their lineup could REALLY use that talent.




PS, I share a similar complaint with the LFA/Toyota, but I see more relevant tech transfer across the lineup. Minus the bazillion dollar CNC carbon fiber looms.

[Ryephile]

Originally Posted by kask2_6.0

Where at?! I live in Novi!.

Unfortunately I can't contribute to this thread but I will follow

Just sent ya a PM