C7 Weight Issues
Team Owner
Joined: Sep 1999
Posts: 41,732
Likes: 1,718
From: Springfield MO
You cannot win an argument with logic so you resort to insults?
I am quite confident of grasping your point -- interestingly, your own data (which may not be 100% correct based on good analysis by other thoughtful posters, but let's assume it is) illustrates MY point which is correct -- but you clearly did not get. Look at the data in bold red. Is it not obvious from that that as the LT1 sweeps from 4K to 5K that the average HP for the LT1 is very close? (Given that the LT1 is, apparently, 40HP GREATER @ 4K RPM and only 10 HP less @ 5K RPM). Accordingly, it would be very surprising if the LT1 would not stay with the LS7 thru 5K RPM. Further, the 365 HP for the LT1 @ 6500RPM is meaningless in your example becuase by then the LT1 driver would have shifted and put the engine in a more favorable part of the torque curve where the horsepower delta would have been reduced a bit.
So let's state this in a clear way as illustrated by your own data:
1K => 4K RPM LT1 > LS7
4K => 5K RPM LT1 ~ LS7
5K => 7K RPM LS7 >> LT1
So, your LS7 will own the 5K to 7K range, but if the C7 LT1 driver knows when and how to shift they will reduce the advantage somewhat. Meanwhile, they may even own you a bit in the very common street range of 3K => 5K RPM. And none of your bluster or insults means a thing becuase neither of us has seen the final stats on this yet -- when we do, I guarantee you I will know exactly the point at which the LS7 is superior.
Seriously -- what % of the time do you run your Z over 5K RPM? I mean, except for your Talladega triumph...
I am quite confident of grasping your point -- interestingly, your own data (which may not be 100% correct based on good analysis by other thoughtful posters, but let's assume it is) illustrates MY point which is correct -- but you clearly did not get. Look at the data in bold red. Is it not obvious from that that as the LT1 sweeps from 4K to 5K that the average HP for the LT1 is very close? (Given that the LT1 is, apparently, 40HP GREATER @ 4K RPM and only 10 HP less @ 5K RPM). Accordingly, it would be very surprising if the LT1 would not stay with the LS7 thru 5K RPM. Further, the 365 HP for the LT1 @ 6500RPM is meaningless in your example becuase by then the LT1 driver would have shifted and put the engine in a more favorable part of the torque curve where the horsepower delta would have been reduced a bit.
So let's state this in a clear way as illustrated by your own data:
1K => 4K RPM LT1 > LS7
4K => 5K RPM LT1 ~ LS7
5K => 7K RPM LS7 >> LT1
So, your LS7 will own the 5K to 7K range, but if the C7 LT1 driver knows when and how to shift they will reduce the advantage somewhat. Meanwhile, they may even own you a bit in the very common street range of 3K => 5K RPM. And none of your bluster or insults means a thing becuase neither of us has seen the final stats on this yet -- when we do, I guarantee you I will know exactly the point at which the LS7 is superior.
Seriously -- what % of the time do you run your Z over 5K RPM? I mean, except for your Talladega triumph...
That's the whole 100% point of the VVT on the LT1. It was not designed as high RPM high horsepower engine at the sacrifice of low RPM torque.
Tell me. Why does a 1964 327ci Corvette with 350 lbs-ft of torque have 365 horsepower yet the same displacement engine with 360 lbs-ft of torque only have 300 horsepower?
With your beliefs of how engine operate, the 327 ci engine with 360 lbs-ft of torque should have 375 horsepower, not 300 horsepower. Correct? Then what about that other 1964 Corvette engine with 350 lbs-ft of torque and 375 HP?
Explain why three engines with the same displacement range from 300 horsepower to 365 horsepower to 375 horsepower yet their maximum torque only ranges from 350 lbs-ft to 360 lbs-ft, and....surprise...surprise...the engine with the greatest amount of torque has the lowest horsepower. I know the answer...do you?
Le Mans Master
Joined: May 2010
Posts: 7,756
Likes: 173
From: Ventura CA
Team Owner
Joined: Sep 1999
Posts: 41,732
Likes: 1,718
From: Springfield MO
Jawnathin -- my point was not about PEAK HP for the LS6 @ 6300 RPM, nor the 55 ft/lb extra torque the LS7 delivers. It was the way JoesC5's initial post made it seem as though the LT1 simply dies after 4K RPM (it does not, with fairly flat torque through at least 4500 RPM and peak HP @ 5900 RPM) and that the LS7's 55 ft/lb torque advantage is constant from 6300 RPM => 4K RPM (it is not; it grows more gradually). Simply meaning that peak numbers do not tell the whole story.
Lost in all this is that we all agree with what the Chevy folks are suggesting -- that the performance numbers for the C7 base should fall neatly between the C6 GS and the Z06. My provocative thought is: don't be shocked if the C7 winds up VERY close to the Z06 (especially if they were a bit conservative with the 450/450 estimate). Then again, if the C7 really does weigh 3300 lb, the Z06 should remain significantly superior
Lost in all this is that we all agree with what the Chevy folks are suggesting -- that the performance numbers for the C7 base should fall neatly between the C6 GS and the Z06. My provocative thought is: don't be shocked if the C7 winds up VERY close to the Z06 (especially if they were a bit conservative with the 450/450 estimate). Then again, if the C7 really does weigh 3300 lb, the Z06 should remain significantly superior
Race Director
Joined: May 2005
Posts: 11,992
Likes: 1,331
From: Middletown, DE
Actually I spend very little time above 5000 RPM with my Z06. I seldom go above 2,000 RPM in normal driving as the LS7's torque is great enough so I can shift early and not bog the engine and still accelerate quite briskly.
That's the whole 100% point of the VVT on the LT1. It was not designed as high RPM high horsepower engine at the sacrifice of low RPM torque.
Tell me. Why does a 1964 327ci Corvette with 350 lbs-ft of torque have 365 horsepower yet the same displacement engine with 360 lbs-ft of torque only have 300 horsepower?
With your beliefs of how engine operate, the 327 ci engine with 360 lbs-ft of torque should have 375 horsepower, not 300 horsepower. Correct? Then what about that other 1964 Corvette engine with 350 lbs-ft of torque and 375 HP?
Explain why three engines with the same displacement range from 300 horsepower to 365 horsepower to 375 horsepower yet their maximum torque only ranges from 350 lbs-ft to 360 lbs-ft, and....surprise...surprise...the engine with the greatest amount of torque has the lowest horsepower. I know the answer...do you?
That's the whole 100% point of the VVT on the LT1. It was not designed as high RPM high horsepower engine at the sacrifice of low RPM torque.
Tell me. Why does a 1964 327ci Corvette with 350 lbs-ft of torque have 365 horsepower yet the same displacement engine with 360 lbs-ft of torque only have 300 horsepower?
With your beliefs of how engine operate, the 327 ci engine with 360 lbs-ft of torque should have 375 horsepower, not 300 horsepower. Correct? Then what about that other 1964 Corvette engine with 350 lbs-ft of torque and 375 HP?
Explain why three engines with the same displacement range from 300 horsepower to 365 horsepower to 375 horsepower yet their maximum torque only ranges from 350 lbs-ft to 360 lbs-ft, and....surprise...surprise...the engine with the greatest amount of torque has the lowest horsepower. I know the answer...do you?
So, you went into some insulting diatribe about what I do and don't know simply because your original oversimplified (not an insult; a fact) post neglected to look at the FULL torque curve for both engines in question BETWEEN 4K and 7K. Which is all I pointed out in my original post.
Then, you pulled out more detail on the torque curves and (inadvertantly, I assume) proved my point!
Read my original post again, and again, and again so you may gain understanding, grasshopper.
Race Director
Joined: May 2005
Posts: 11,992
Likes: 1,331
From: Middletown, DE
I never said, not did I imply, that the LT1 simply dies after 4,000 RPM. What I did say, is that the torque doesn't continue to climb and then I does drop off quite rapidly at the top end compared to the LS7. The LT1 is not designed to move enough air in the upper RPM range to go above approximately 450 HP. Without increasing the amount of air, the engine can't produce more horsepower. Why should the LT1 produce 500 HP at 5,900 RPM when it can't move anymore air then the LS3 with it's 436 HP at 5,900 RPM?
Back to the OP's issue -- all this will be moot if in fact the C7 is as much heavier than the C6 Z as it looks like it will be...
Racer
Joined: Nov 2012
Posts: 288
Likes: 0
The C7's ability to launch has just as much to do with its ability to squat and hook up as it does power.
The C7 has launch control and I'm sure it's a better system than the one the C6 has.
The C7 could have the same power as the C6 and sprint better if it hooks up more effectively.
Good drivers in the C6 were getting 4.1 give or take a tenth. Is it really hard to believe that a car with more power and torque and a better chassis can hit 3.9 or better?
The numbers haven't been released so the C7 may very well hit 3.8, but it's at least 3.9 as of now.
Z06 owners need to stop scratching their heads. It's 2013. A sub 4 second 0 - 60 time ins't that difficult for a car of the C7's caliber. Forget comparing Z06 and C7 dyno numbers.
The C7 has launch control and I'm sure it's a better system than the one the C6 has.
The C7 could have the same power as the C6 and sprint better if it hooks up more effectively.
Good drivers in the C6 were getting 4.1 give or take a tenth. Is it really hard to believe that a car with more power and torque and a better chassis can hit 3.9 or better?
The numbers haven't been released so the C7 may very well hit 3.8, but it's at least 3.9 as of now.
Z06 owners need to stop scratching their heads. It's 2013. A sub 4 second 0 - 60 time ins't that difficult for a car of the C7's caliber. Forget comparing Z06 and C7 dyno numbers.
Safety Car
Joined: Dec 2006
Posts: 4,642
Likes: 9
From: Dalllas/Ft Worth Area TX
Various car weight notations!
As of late, the last year or so, I have closely looked at the ET's AND the WEIGHT of the car to make my impressions.
Even the type of platform: RWD; AWD; front, mid or rear engine. It is interesting to note the ET's compared to the xWD setup, engine setup, etc (substitute R or A for "x" for type of wheel drive). In looking at ALL of the different exotics, you begin to recogonize the limits of all types of cars.
HP/TQ, tires, and type of platform (front, mid, rear engine and xWD) make the determination of ET's and their limits to each type of setup. GM must make radical changes to their platform in the near future because these limits are being rapidly approached.
HP/TQ, weight, and design are big factors in determining the agility and straight line responses, but they all have physics limitations. 
This C7 is beginning to approach limits and GM is realizing this in trying to reach their targeted numbers, a real challenge at this level of competition. We will just have to wait and see. I don't see much radical weight reduction at this point, GM has been chopping and the gains now are small.
Even the type of platform: RWD; AWD; front, mid or rear engine. It is interesting to note the ET's compared to the xWD setup, engine setup, etc (substitute R or A for "x" for type of wheel drive). In looking at ALL of the different exotics, you begin to recogonize the limits of all types of cars.
HP/TQ, tires, and type of platform (front, mid, rear engine and xWD) make the determination of ET's and their limits to each type of setup. GM must make radical changes to their platform in the near future because these limits are being rapidly approached.
HP/TQ, weight, and design are big factors in determining the agility and straight line responses, but they all have physics limitations. This C7 is beginning to approach limits and GM is realizing this in trying to reach their targeted numbers, a real challenge at this level of competition. We will just have to wait and see. I don't see much radical weight reduction at this point, GM has been chopping and the gains now are small.
Somba master
Joined: Mar 2005
Posts: 10,554
Likes: 63
Cruise-In 7, 9 & 12 Veteran
Wounded Warrior Escort '11
St. Jude Donor '07-'08-'09-'10-'11
Well, they started off badly by making it BIGGER. Then added the AFM, which necessitated the extra weight of the steel torque tube, exhaust flap, and more insulation....
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VETERAN
Joined: Aug 2005
Posts: 512
Likes: 114
From: Owings Maryland
C7 performance still in testing...allot can change over 7 months
I have a distant family member (cousin) that works for GM and was able to see several C7 mules test at the proving grounds. Once the C7 started matching the times on the track to the C6 Z06 times is when Ed Welburn accepted the "stingray" name plate. My cousin still maintains that the C7 has more hp/tq than the estimated 450 number that is being used. He also said that from the beginning of the project that one of the priority issues was weight reduction. Tadge hammered everyone on the requirement/need to find the best ability to drive the car fast on a track with better precision and steering feel. Obviously weight, balance & suspension was key and this is a significant improvement over the C6.
The C7 is only going to get better. By summer we will all want one.
Cheers, Way to go GM. The C7 looks awesome in Cyber Gray and RED.
The C7 is only going to get better. By summer we will all want one.
Cheers, Way to go GM. The C7 looks awesome in Cyber Gray and RED.
Racer
Joined: Apr 2008
Posts: 270
Likes: 8
From: Michigan
Amazing how many people have opinions on the C7's final weight and power when they don't know either number. Have faith guys; would it make ANY sense for GM to bring out a new Corvette that was slower than the previous Corvette of equivalent trim level?
Le Mans Master
Joined: Jul 2005
Posts: 5,328
Likes: 405
You have this backwards...squatting means less traction/hook up. All Corvettes since the C4 have rear suspensions with anti-squat geometry. If squatting was a good thing, they would've stuck with the de Dion rear suspension from the C2/C3. Lol
Safety Car
Joined: Dec 2006
Posts: 4,642
Likes: 9
From: Dalllas/Ft Worth Area TX
How GM tamed the ZR1 rear end wheel hop.
On the powerful ZR1, "squat" is back in and was used to tame the rear end on the ZR1. The biggest thing that the "squat" does is to LESSEN wheel hop on the powerful ZR1. GM did several things to lessen this disasterious effects of wheel hop which broke or destroyed rear ends. It programed the magnetic ride suspension (MRS) computers to cause "squat" down to lessen the wheel hop on WOT. In addition, different sized diameter half shafts were also installed on each side to prevent harmonics. The result was the controlling of the rear end and prevented 638HP from destroying the differential, etc.
Le Mans Master
Joined: Jul 2005
Posts: 5,328
Likes: 405
On the powerful ZR1, "squat" is back in and was used to tame the rear end on the ZR1. The biggest thing that the "squat" does is to LESSEN wheel hop on the powerful ZR1. GM did several things to lessen this disasterious effects of wheel hop which broke or destroyed rear ends. It programed the magnetic ride suspension (MRS) computers to cause "squat" down to lessen the wheel hop on WOT. In addition, different sized diameter half shafts were also installed on each side to prevent harmonics. The result was the controlling of the rear end and prevented 638HP from destroying the differential, etc.
Squat on launch is bad for traction on any car. The 4-link drag race rear suspension has two jobs...prevent squat and transfer weight to the rear. Squat on a road race car at any time is a bad thing since the main task of the driver is to not upset the chassis...anti-squat geometry in the rear suspension relieves the driver of that task, weight transfer still has to be managed by the driver.
Thread Starter
Le Mans Master
Joined: Oct 2004
Posts: 6,813
Likes: 287
From: Toronto Ontario Canada
As of late, the last year or so, I have closely looked at the ET's AND the WEIGHT of the car to make my impressions.
Even the type of platform: RWD; AWD; front, mid or rear engine. It is interesting to note the ET's compared to the xWD setup, engine setup, etc (substitute R or A for "x" for type of wheel drive). In looking at ALL of the different exotics, you begin to recogonize the limits of all types of cars.
HP/TQ, tires, and type of platform (front, mid, rear engine and xWD) make the determination of ET's and their limits to each type of setup. GM must make radical changes to their platform in the near future because these limits are being rapidly approached. HP/TQ, weight, and design are big factors in determining the agility and straight line responses, but they all have physics limitations.
This C7 is beginning to approach limits and GM is realizing this in trying to reach their targeted numbers, a real challenge at this level of competition. We will just have to wait and see. I don't see much radical weight reduction at this point, GM has been chopping and the gains now are small.
Even the type of platform: RWD; AWD; front, mid or rear engine. It is interesting to note the ET's compared to the xWD setup, engine setup, etc (substitute R or A for "x" for type of wheel drive). In looking at ALL of the different exotics, you begin to recogonize the limits of all types of cars.
HP/TQ, tires, and type of platform (front, mid, rear engine and xWD) make the determination of ET's and their limits to each type of setup. GM must make radical changes to their platform in the near future because these limits are being rapidly approached.
HP/TQ, weight, and design are big factors in determining the agility and straight line responses, but they all have physics limitations. This C7 is beginning to approach limits and GM is realizing this in trying to reach their targeted numbers, a real challenge at this level of competition. We will just have to wait and see. I don't see much radical weight reduction at this point, GM has been chopping and the gains now are small.
. I don't undertstand why some of you take every word spouted from GM as the unvarnished truth. If they were to announce right now that the C7 is slower than the C6 there would be an uprising from the Corvette faithful which would make the tailight issue seem like small potatoes. It is not a given that each succeeding generation of Corvette will be faster than the previous. There are diminishing returns. At some point you are not going to get much better in flat out acceleration unless you strap a rocket motor onto these cars. Every spec GM has mentioned so far is not cast in stone. Until the first production C7 is out there and there is some real world testing with it all numbers quoted are just marketing spin. That is what the word prelminary specification means.
Le Mans Master
Joined: Jul 2005
Posts: 5,328
Likes: 405
I never said, not did I imply, that the LT1 simply dies after 4,000 RPM. What I did say, is that the torque doesn't continue to climb and then I does drop off quite rapidly at the top end compared to the LS7. The LT1 is not designed to move enough air in the upper RPM range to go above approximately 450 HP. Without increasing the amount of air, the engine can't produce more horsepower. Why should the LT1 produce 500 HP at 5,900 RPM when it can't move anymore air then the LS3 with it's 436 HP at 5,900 RPM?
Safety Car
Joined: Apr 2010
Posts: 4,231
Likes: 451
From: Maryland
Unlike man's law, the law of physic's cannot be bend or broken. 
My understanding is that the C7 LT1 engine has more compression than the LS3; all things being equal that means more power for the LT1. Oh, and lets not forget the electric steering which also adds to the power output that I said the Corvette would/should have months ago and should of had years ago. A lot on here boo-hooed that and said no way in a sports car!
Last edited by C7/Z06 Man; Jan 27, 2013 at 11:59 AM.
Team Owner
Joined: Sep 1999
Posts: 41,732
Likes: 1,718
From: Springfield MO
Unlike man's law, the law of physic's cannot be bend or broken. My understanding is that the C7 LT1 engine has more compression than the LS3; all things being equal that means more power for the LT1. Oh, and lets not forget the electric steering which also adds to the power output that I said the Corvette would/should have months ago and should of had years ago. A lot on here boo-hooed that and said no way in a sports car!
Safety Car
Joined: Apr 2010
Posts: 4,231
Likes: 451
From: Maryland
So, when GM dropped the compression ratio from 10.9:1 on the LS2 to 10.7:1 on the LS3, the horsepower dropped from 400 all the way down to 436? Or did other factors come into play, such as larger displacement, high flow heads, larger intake valves, high flow intake manifold and new exhaust manifolds?
The point of my post is that the compression ratio of the LT1 also adds to it's higher output.
Last edited by C7/Z06 Man; Jan 27, 2013 at 12:59 PM.
Team Owner
Joined: Sep 1999
Posts: 41,732
Likes: 1,718
From: Springfield MO
Do you believe that all things are equal between the LS3 and the LT1 other then the bump in compression?
I don't believe they are equal, so your assumption that the horsepower will automatically increase on the LT1 because of a bump in compression isn't correct. To many differences between the two engines that have to be taken into consideration.
I don't believe they are equal, so your assumption that the horsepower will automatically increase on the LT1 because of a bump in compression isn't correct. To many differences between the two engines that have to be taken into consideration.
Safety Car
Joined: Apr 2007
Posts: 4,458
Likes: 325
From: Houston TX
To the OP, what you say may very well be true. I don't believe for a second that the C7 will weigh less than the C6 at comparable trim levels. That said, I'm sure the car will still be fantastic.