JoesC5

So, C&D has been 100% correct in their predictions 100% of the time for the past 50-60 years? Same with the other rags?

dar02081961

Joe I agree with you on this. I think much of the weight increase in the C7 comes from interior quality upgrades, and increased crash standards for 2016 and beyond.

More concerning is the discussion of polar moment of the rear engine compared to the Corvette. The modern Vette has the transmission in the rear which changes the ball game significantly. Folks will try to tell you that having 60+ percent of the weight in the middle and rear of the car is better than having 50% of the weight distributed evenly.
All the information and discussions used to bolster this argument is based on the older Corvette layout prior to the C5.

I don't think this is true for the newer layout. If we took a clean slate and designed a mid engine car the exact same weight as a Corvette with the exact same horsepower I would venture to say the current 50/50 configuration would be better than the mid engine layout.

In other words any gains or claims of higher handling capabilities of mid engine cars over the current Corvette layout are in my opinion due to a superior power to weight ratio or all wheel drive.

I'm sure someone will find an example but at first glance anything I see that beats a Z06 around the track is doing so because of a better power to weight ratio not because the engine is located 2 feet behind the drivers head. That being said the Viper ACR is a more conventional layout with the transmission directly behind the engine and last I checked it was holding its own as well.

I get it, many folks like and prefer the mid engine layout.
But for mass produced street cars this insistence that mid engine cars are superior, simply hasn't proven out to be a fact in the real world.

tbrenny33

[QUOTE=SBC_and_a_stick;1593884817]The C7 puts power down via long wheelbase. Mid-engine can get away with a much shorter wheelbase. Look at what's already made on the market ME, at least 2 inches shorter. The hood line will be low since no engine has to be fitted upfront, and the overhang is smaller as well. Add up the driveline and pipe reduction. Easily 250lbs reduction going to M
Porsche 918 battery and electric motors alone weigh 692 lbs. It is obvious to me you don't understand how much the hybrid power train adds to kerb weight. This estimate doesn't even account for the extra heat exchangers or wheelbase you need to carry the battery pack and electric /QUOTE]

I have to agree with you. You're telling me a $1 million Porsche has 700 pounds of electricity but a car that's a 10th of the cost with a very similar system only weighs 250 pounds! I'm looking at this layout of the NSX and based on the motors and batteries not to mention the wiring probably additional heat exchangers and the modifications to support that I highly doubt it weighs anything less than 450 to 500 pounds. Comparing a Camry to this, is like comparing a V-6 no optioned Camaro to a fully optioned Z06.

http://www.caranddriver.com/features/2016-acura-nsx-dissected-powertrain-chassis-and-more-feature

SBC_and_a_stick

Yes boys, you heard it here first. A mid engine Corvette, all things equal, will share more components with a Camry hybrid than a performance car.

Let me remind you of where earth is. The discussion is about going from FMR to ME ALL THING EQUAL. You brought to the table a discussion about one of the most complicated hybrid supercars on the market just to prove the point that ME can be heavy. Wow, touche. Everyone will tell you that the NSX hybrid drive is closer in construction to a 918 than any other car on the planet. I gave you statistics about how much the 918 hybrid drive adds to the car to give you a clue. You don't have statistics about how much the NSX hybrid drive weighs because you just don't. Instead you bring the Camry as a comparison to try to salvage a point. Well guess what Joe, the Camry is not a mid engine car. You can't have your cake and eat it too. What do you want? A hybrid ME comparison or a Camry comparison. Neither makes any sense.

But, I will indulge.

Problem number 1. You forgot at first that the NSX has a battery pack. Guess what, the plug on the 918 is irrelevant. What is relevant is that they both drive on battery only, and both have all wheel drive based on electric motors. That's going to weigh a lot and your Camry can't do hybrid drive AWD.

Problem number 2. The NSX actually has a third electric motor. If the 918 has more battery weight to go over longer distances (not sure that it does just giving you a bone here) then it also has less mass because it's a simpler design with only two electric motors.

Problem number 3. Cooling adds weight at this point. NSX's three-motor Sport Hybrid power unit is cooled through 10 heat exchangers and that doesn't even include the A/C cooled batteries! compare that to C7's 2 heat exchangers.

If you think NSX's hybrid drive weighs as much as a Camry's you've lost your mind. In either case, it's the wrong comparison. NSX's wheelbase is shorter...talk about a straw man. Isn't that my point? Acura packed all of that in an ME and still has a shorter wheelbase. ME for the win. How much longer do you think the C7 would be if it had three electric motors and a battery pack on top of a DOHC turbo? C'mon...

Higgs Boson

I don't think I would classify it as "confusion."

I might however call it on your end, "delusion."

Bwright

Terrific question.

To look at Car and Driver's Lightning Lap test results and the place of both the C7 Z06 and the Grand Sport it certainly does beg askance on what one gets exactly, outside of a whole different look, for going mid-engine. Either that or the fact that GM's engineers can do what they do with a front/mid-engine platform makes them geniuses.

At the 2016 Lightning Lap, the performance of the $92,060 Grand Sport was instructive. Just look at the cars that relatively humble 460 hp V8 beat for less than a $100K:

2017 Acura NSX: $203,100 - 573 hp
2016 McLaren 570S: $219,670 - 562 hp
2016 Audi R8 V10 Plus: $202,750 - 610 hp
2015 Lamborghini Huracán LP610-4: $274,120 - 602 hp
2014 Ferrari F12 Berlinetta: - $437,844 - 730 (!) hp
2012 Ferrari 458 Italia: $333,376 - 562 hp

All but one of the cars listed above was mid-engined (supposedly the only way to build a sports car) and not one cost less than 2X the Grand Sport's as tested price. To top it all off the Grand Sport wasn't within 100 hp of any of those esteemed competitors all of whom it proceeded to eviscerate.

If great engineering is indeed doing more with less, then in the Grand Sport we may have seen a command performance from probably the best engineered performance car on the road today.

If the Grand Sport was instructive then the Z06 before it (Lightning Lap 2015) was coldly so. After its test, only one car stood above it on the all-time leaderboard. The $875,175 Porsche 918. That car has been shown elsewhere to only be able to complete a lap in anger before its batteries died causing its times to fall off dramatically.

Today, among roadgoing cars, second and third place on CD's leaderboard are held by the Viper ACR and the Z06 respectively. The two are separated by 4/10ths of a second. A total of 201 cars have been tested.

If mid-engine is the only thing to be effective then someone should be sure to relay that message to the Viper and Corvette teams. They could probably use the heads up not the least reason to allow their esteemed competition to catch up.

Like I said, terrific question.

Over the course of this thread you will no doubt get a lot of interesting theories. Look to see how many of them can explain the above realities.

SBC_and_a_stick

First, the Corvette team has known for decades mid-engine is superior from a performance point of view:
http://kinja.roadandtrack.com/making...tte-1679942984

Second, cars are optimized for certain performance metrics. ME will always put the power down better and you will see this clearly in 0-30 mph runs. The GS and Z06 come with insanely wide rubber optimized for dry tracks. That is part of the trick, and also the reason why if wet, those track laptimes are actually upside down with Z06 on the bottom. Second GM is saving money and weight by designing the car with minimal cooling. It does great for a fast lap but heats up big time for continuous lapping. Top speed? Z06 Z07 pack is the slowest in that group again.

So what is your performance test? Pick the right one and the Z06 is fastest in the group, pick a different one and it might be last in that group. Once you see how cars are optimized you realize there are few heroes to speak of.

Bill Dearborn

I didn't imply that but just like the Government leaks info to determine impact automakers and other companies do the same thing. As I said things change so the statement just represents the thinking at the time the leak was released.

Bill

JoesC5

I wonder how a 2017 Cayman GT4 S would have stacked up against those cars on the Lightning lap.

dar02081961

Amen Brother....time to pass the collection plate.

JoesC5

SAE paper on the 1963 Corvette, with it's 47/53 % weight distribution(better than the 50/50 % of the C7) and it's 16.5" CofG(1" lower than the C7's 17.5")

http://www.corvetteactioncenter.com/...3/1963-SAE.pdf

Notice that GM addressed the mid engine concept and the front engine rear transaxle setup and why they were not chosen for the new 1963 Corvette.

SBC_and_a_stick

Where does it discuss it? I'm not going to read 3 dozen pages from 55 years ago to find it.

dar02081961

Last paragraph of page 2 and first few paragraphs of page 3.

Good stuff. Gotta be careful though. The industry has learned a whole bunch of stuff since this was written.

SBC_and_a_stick

Ok, read those bits. Not sure what Joe was trying to prove with this old piece.

The subject matter "cost" is all to prevalent in the article which goes to show just how much of the final design was driven by it and not performance maximization.

Maybe Joe wanted to show the line that says midengine would have required a longer wheelbase, which is not applicable to the C7. The point of comparison is front engine with front mounted transmission, not the rear mounted trans design of the FMR C7. Clearly ME would increase the wheelbase compared to an FR design, but that's not the important point of discussion. You have to take into account the car's ability to put the power to the ground, in which case ME will give you the best traction 40/60 distribution while having the shortest wheelbase. It won't however be the shortest wheelbase design of all designs but it will be the one with the highest performance with a minimal wheelbase penalty.

If you believe the thinking of this 55 year old piece, mounting the transmission in the rear is actually only a cost increase and worth nothing in terms of driving dynamics. I think this is obviously false, and the main reason why Corvette is ahead of Mustang, Camaro, and the Jags. This is what puts in the category of AMG GT S and Aston Martins, and not in the cheap muscle car group. Clearly the guys who wrote the piece wanted to sell the 60s design, it reads as a marketing piece sprinkled with a few numbers. I don't believe even for one second that even at that time placing the trans in the rear wouldn't have helped. It was clearly a cost cutting decision.

Finally, remember that in the 60s folks knew/cared little about aerodynamics. The emphasis back then was more on power to weight ratio, and driving dynamics if cheap to build in. Nowadays the Viper is ruling on the tracks for the very fact that it has 5 times the aero the 'Vette does. A midengine goes a long way to improving front downforce which is hard to achieve with high ground clearance street cars. See for example the large shovel that has to be removed on the ACR. With midengine you can design the front of the car to produce massive downforce without sacrificing ground clearance. Rear downforce is relatively easy to achieve with a wing on any car.

dar02081961

I read the article. I didn't see where it said the mid engine layout was superior? It did reiterate the well known fact that during acceleration the mid engine layout was better for traction purposes due to rear weight bias. However what many neglect to tell you is that same advantage is a liability when decelerating or during a decelerating turn.
Admittedly on the track a decelerating turn isn't encountered as much as on street. But in the real world of daily driving where you are likely to hit a decreasing radius off ramp....well you get my point.

Its physics. You can bias the weight to the rear (which all modern behind the pilot mid engine cars do) and get better traction for acceleration. But the design has its disadvantages during other phases of the performance envelop. Its just that few folks are willing to discuss them.

SBC_and_a_stick

This gem?

"Instead of the old strategy, which was to replace the front-engine car, you'd do the Corvette in a mid-engine version. You'd price that at about $120,000, half that of the European stuff, and then suck the doors off everybody."

Or this gem?

"Problem is, lap times would be no better using the same architecture, even with, say, 750 hp." and that by contract they found the ME proposal from Tadge "convincing" as an alternative.

Everything in that article points to superior ME except cost. A ZR1 rolling out with 750hp is irrelevant (as explained in the article) in comparison to ME.

Deceleration will be better overall due to two reasons:
1. There will be less work to do for the front brakes, which we can already see get devoured on the track. Even CCBs die quickly and stock iron cracks.
2. mid engine will have higher amount of front downforce. This will help high speed breaking by a lot and improve stability under breaking. Ask the Viper guys how nice it is to brake with loads of front downforce. The snake was never more tame.

Poor-sha

To add to the weight savings discussion. Ford just released the weight for the new GT. 3173 lbs without fuel. Figure it's probably ~3300 lbs with a full tank of fuel compared to 3559 lbs for my 2015 C7 Z06 3LZ with stock run flats and wheels.

The GT also has a carbon fiber monocoque instead of a frame but also adds in the adaptive aero that certainly adds weight.

Higgs Boson

only an incremental upcharge of $675/lb of weight lost.

not bad.

jvp

Come on Sean...

This is the biggest contributor to the lighter weight of the new Ford; it has nearly nothing to do with the drive train layout. Any thoughts to the contrary are just silly.

Hardly enough to make up for the significant loss due to the monocoque.

Thanks for my morning giggle. I needed that. Time for my third cup of coffee.

Poor-sha

That was my point. I was just trying to present the facts and let folks draw their own conclusions.