Dodge scrapped its plans for a long wheelbase Viper and the new 2013 Viper has a 98.8" wheelbase.

The C3 Corvette has a 98" wheelbase.

So what wheelbase length is expected of the C7 Corvette ?


The next subject is roof height:

C5 Corvette:

47.7" height


C6 Corvette:

49.1" height


And so does the C5 Corvette look more exotic than the C6 Corvette ?
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I think I read somewhere that the C6 is taller than the C5 due to a federal regulation regarding the A-pillar. So, fed regs can influence styling.

 

Even though I wasn't all that happy with the increased height of the C6 over the C5, I was VERY happy with the decrease in overall length.
I prefer my sports car to be smaller (and lighter), not extra long/stretched out.
On the C7, I'm hoping to see the same wheelbase or even shorter than the C6's and I would even LOVE to see the car lose an inch or too in overall length as well with no changes in height or width.
Though I'm certainly not counting on any of that.
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The mules look to have fairly long wheelbases. If there's a pool, I'm guessing ~108".
Wonder if CAFE fleet averages using footprint sizes might be a factor, plus possibility of shifting the weight balance toward the rear.

 

I hope this isn't much of a factor driving the C7 wheelbase or other features, but as a reminder: The new CAFE rules specify target mpg for each model based on that model's footprint (average track X wheelbase). Models with smaller footprints have higher mpg targets. Of course, by definition, CAFE is an average. So (to oversimplify) GM can sell more Corvettes that don't quite meet their targets (about 35 mpg for 2014 MY to 47 mpg for 2023 MY if C7 has the same footprint as C6) if they sell more Volts that exceed their targets.

So as I posted in another thread, I think we should hope that GM sells lots of Volts and other high mpg vehicles.

 

Problem is, Volt sales are not exactly shocking, you know? It's such a bland-looking vehicle, they may be all over the place, but you just don't notice them. I see Prius everywhere!

 

Now, of course, the Prius OWNS the market it created...but did not sell well in the first few years. The Volt will do fine but has a lot more competition than the Prius did in those days. How many Volts have to sell before it helps the GM/Corvette CAFE situation, I have absolutely no idea.

 

It doesn't help the Volt that you can buy a Cruze and have a better looking car that's less expensive now and later, with very good efficiency.

I see the Volt doing what the early Prius' did for that platform - i.e. prove out its utilized tech and serve as a "baseline" for future iterations that will continue the development/improvement of the model.

As to the C7 footprint, CAFE will impact it as noted, and hopefully it doesn't have the front overhang that some angles of the spy shots depict (which seems to be more overhang than current - which improved over C5 - but some of that could be camo/subterfuge).

 

Gents, I don't think we have to wring our hands over the Corvette mileage, footprint, etc. There is no need to as the Corvette's impact on GM's CAFE results is very minor indeed.

According to Cars.com, GM's 2011 CAFE was 31.7. That was driven by about 12,000 'vettes at 18 MPG and about 2.5 million other vehicles at a calculated average of 31.8 MPG. I assumed 12,000 miles annually per vehicle.

I won't say my calculations are 100% exact, but it does give some food for thought.

For example, if the Corvette's MPG dropped to 17 MPG, GM's CAFE would move from 31.7 to 31.69! If the car's mileage increased to 20 MPG, GM's CAFE would improve from 31.7 to 31.73. It's rather clear that for GM's CAFE to improve to the proposed 35.5 MPG by 2016, the results will be driven by many models other than the Corvette.

Please don't tear me apart now. I just had a little time on my hands to play with Excel.

 

This is what I have been saying for a long time. Corvette is fairly CAFE neutral...very little improvement is needed given GM's fleet average improvements.

 

I know.

I just never thought it through, analyzed it before tonight.

 

Truth is that if CAFE was such a huge deal, ALL carmakers selling in the U.S.A. would be making a LOT more noise about it than they are.

As opposed to the 70s/80s, carmakers are far more technologically advanced in dealing with efficiency and pollution reduction. The horrible Corvette/muscle car years were that way because GM never really had to give much of a crap about efficiency before and didn't know how to approach it without just dropping engine power. They didn't know how to make performance and efficiency co-exist.

The Arab oil embargo and small Japanese cars changed all that.

 

I'd like to see the front wheels pushed forward 2-3 inches,shifting the F/R weight bias slightly rearward, plus shaving 2-3 inches off the F/R overhangs keeping the overall length the same.

 

There is a new twist to CAFE -- the average that must be met is based on the average vehicle footprint for the manufacturer's cars.

http://www.hybridcars.com/incentives...explained.html

This takes away the pressure to downsize cars irrespective of market forces.

Though I do wonder if this will make small cars suck more -- it seems to me they're paying more of a weight penalty for the sake of safety standards, proportionally. (Look at the change in curb weights of subcompacts since the mid-80s, versus the change in curb weights of midsize sedans, for example. Little cars are really porky these days.)

Anyway, this ought to make Corvette's impact on CAFE even smaller.

.Jinx

 

jackall99;

I think your basic point is absolutely correct. And as you acknowledge, your calculations are not 100% exact. Apologies if I'm sounding like a smart-***, but the the CAFE isn't based on an arithmetic average, it's based on a so-called harmonic average that makes it slightly harder to offset a few low FE cars with many high FE cars. If we have two models sold in numbers N1 and N2 having mpg FE1 and FE2:

CAFE = (N1+N2)/((N1/FE1)+(N2/FE2))

Also, I think but I'm not certain that the FE numbers used in the CAFE calculations are the EPA test numbers weighted like:

FE = 1/((.55/CityMPG)+(.45/HwyMPG))

The "Sticker" FE numbers are adjusted downward from the actual EPA test numbers by 10% for city mpg and 22% for Hwy mpg, I think.

So, by my calculations, which could be wrong, the number used in the CAFE calculation for a 2012 base M6 is 22.5 mpg (which, if I'm right, means they just missed the gas guzzler tax by a hair).

The thing that admittedly worries me is how much more stringent the CAFE requirements get over the likely lifetime of the C7. For example 2014 + 7 years = 2021, when the CAFE target for a 45 sq ft footprint car (C6 & Volt, I think) is about 47 mpg. Seems to me that unless folks are buying lots of EVs and Volt-type PHEVs, GM is going to think hard about the economics of selling any vehicles that miss their target by a factor of two.

BTW, my 45 sq ft is based on GM sites' reported front and rear "tread" (and wheelbase) for a base C6. Are tread and track the same thing, or are they different?

 

I'd guess that "tread" in this case refers to track width.
"Under Reformed CAFE, fuel economy standards are restructured so they are based on a measure of vehicle size called 'footprint,' the product of multiplying a vehicle's wheelbase by its track width."
http://www.nhtsa.gov/fuel-economy/


If more Corvettes are sold than the Volt (which could very well happen with the C7), does that mean the Volt's gain in contributing to CAFE might be offset by Corvette sales? Volt looks to be on target for 17-20k units this year and if past Corvette intros are anything to go by, the C7 should comfortably match this if not exceed it, at least for a couple of years.
I'm sure the Corvette by itself won't drag down GM's CAFE, but combine it with some heavy-duty trucks or large sedans and we could see the numbers head down. If these models combined contribute to GM missing its target by, say, 0.2 mpg, then GM could be looking at fines of $27.5M. (Based on the $5.5 penalty per 0.1 mpg under the target and US sales volume of ~2.5M; could be wrong on that though.)

 

True, and that's good to know ...but what if it was driven by closer to 30k units (a potentially safe estimate for the first full model year of C7 at least) instead of only 12k? That might skew the averages a bit more I'd assume.

 

Carbon-fiber unibody C8 in 2020

 

Moves it from 30.7 to 31.53, all else being equal. By the same token, I used 2.5MM total GM vehicles, although GM unit sales are increasing which would offset that to some degree, actually swing the results better for GM.

 

Thanks.

I was doing a very high-level executives 'quick what-if' analysis. The exact calcs are left to the worker bees.

No apology needed.

No comment.

I knew that! I did a three minute exercise and debated even posting the numbers, ergo my comment "Please don't tear me apart now."