Login


10282012, 09:15 PM  #23  
New Member
0
Rep 11
Posts 
Quote:
All of the most recent tests (last few years) have focused on late model fully optioned Z06s with abysmal production rates and a little extra pork (3300+ lbs). The vast majority of Z06s out there are actually 20062009 models which weighed 31303200 lbs and dominate the fast lists; excluding the weight factor for some reason(s) unknown they're faster than later models. So statistically speaking if you run into a Z06, odds are pretty good it's going to be a 20062009. When you look at (in my humble opinion) the single most important indicator of straightline acceleration, 0150 MPH time, for one of those models it's 17.7 seconds [1]. Same spec. for the new GT500 is 17.6 seconds [2]. I don't think it can get any closer than that. Two professional drivers wouldn't be capable of consistent wins for one car over the other. That's pretty conclusive evidence that at least in a straight line it's a toss up and not an easy win. So that really just leaves track performance. As good as the GT500 is, with an extra ~700 lbs it's just not going to keep up with the Z06 through the twisties. Similar deals for the CTSV and ZL1  both awesome cars as well but you can't overcome the body roll and understeer etc. with near 4000 lb curb weights. Now all that being said, if you can really drive and you go up against a stereotypical garage queen vette owner, absolutely you'd probably beat a Z06. Just enjoy the new car; the most important thing is that it puts a smile on your face. [1] http://media.caranddriver.com/files/...orldcup2.pdf [2] http://www.caranddriver.com/reviews/...00testreview 

Appreciate
0

10282012, 09:57 PM  #24 
Captain
15
Rep 900
Posts 
Is the new GT500 a lot more aero dynamic than the previous model? I've seen (actually rode in) my buddy's stock Vette vs a pulley/tuned '11 cobra and the Vette had the advantage as the speeds climbed. Not sure what the exact power the cobra was making but he sounded like he could drive and the Vette had an extra 220lbs in the passenger seat opposed to only the driver in the cobra. I know it's hard to compare since I'm not sure the exact power but I know it was on the stock blower, stock intake and stock exhaust,aside from the tune/pulley.

Appreciate
0

10292012, 02:47 PM  #25  
New Member
0
Rep 11
Posts 
Quote:
Estimating the aerodynamic characteristics of any car is a huge challenge. Typically we're talking absurdly expensive computer models, wind tunnels, and a lot of man power and time. But there are simpler models that can usually give us the "90% answer". In this case we want to look at drag force. Like others have said, the drag coefficient is just one part of this equation. The other critical piece is crosssectional area; imagine putting a 5 ft by 5 ft piece of cardboard against the wall and swinging it outward as fast as you can; going to be a lot more difficult than the same with a 1 ft by 1 ft piece of cardboard (and this is basically independent of drag coefficient since it's the same for both cases, same material and shape). To estimate a car's crosssectional area we can multiply width and height. Attachment 1 has the formula for drag force (think that's actually from one of my old papers); ignore the wind velocity part  that application was crosswind induced lateral movement of aircraft; in this case velocity of the car plugs right in assuming no head wind. From there we need the drag coefficients and dimensions for both cars. Couldn't find a reference for the GT500 drag coefficient so I just went with the value (0.35) that Peteypab listed. Everything else was easy to locate. I plugged everything into Excel (attachment 2). Looking at attachment 3 (plot of drag force vs. speed up to 160 MPH for both cars), there doesn't appear to be a huge difference. At 160 MPH the difference between the two cars is less than 100 lbs of air resistance. You can definitely see the effect of velocity squared in the equation though. Here's where it gets interesting. Looking at the difference in drag force (attachment 4), it also seems negligible, e.g., 30 lbs of difference at 100 MPH. That's deceptive though. What really matters is the area under this curve  that's the cumulative amount of air resistance that a GT500 accelerating from 0 to 160 MPH will experience beyond that of the Z06 doing the exact same thing. To estimate that I just did a polynomial regression curve fit in Excel (top equation in plot, to define the curve) and then calculated the integral (area under the curve, bottom equation). So how much more cumulative drag force will the GT500 experience from 0 to 160 MPH? Roughly 4000 lbs. Or to imagine it another way, lifting a CTSV. You can look at that two ways though. The Z06 is more aerodynamic, experiencing 4000 lbs less drag force over the course of a 0 to 160 MPH run, enabling it to be almost equally as fast with less power. Or alternatively, that the GT500 is such a brutal monster it plows through an extra 4000 lbs of force against it and ends up being as fast at the Z06. 

Appreciate
0

10302012, 04:36 PM  #28 
Captain
15
Rep 900
Posts 
Impressive man! For shits and giggles where dues the M3 fit in with regards to aero compared to these two. My car is pretty much as modded as it can get short of a built motor and I hang with my buddies Z06 until about 4 when he starts to pull.

Appreciate
0

10302012, 09:03 PM  #29  
Private
0
Rep 97
Posts 
Quote:


Appreciate
0

10312012, 09:11 AM  #30  
New Member
0
Rep 11
Posts 
Quote:
Not surprisingly, it did pretty damn well. With respect to drag force it's literally right on top of the Z06; had to use some formatting trickery to distinguish the two. That's pretty impressive given that the Z06 is four feet tall. The one big thing I would infer from this is that drag can probably be tossed out when comparing the M3 and Z06. So in theory if the two cars have the same power to weight ratios and other effects (like gearing and traction) are negligible the two should be very close. What kind of power are you putting down? Take a look at the attached wind tunnel test of the M3 (why I went with coupe dimensions). It shows that any one method of testing or modeling isn't 100% accurate. What I'm guessing is the derived drag coefficient (0.33) isn't what BMW listed for the M3 coupe (0.30). Another thing it shows is that my model isn't 100% accurate because using width and height to estimate frontal area ignores the fact that the bottom of the car is several inches above the ground. They listed frontal area as 2.17 meters and based on width and height I calculated 2.57 meters. Of course when we're comparing different cars and each one has a different height above ground, even more accuracy is lost. This is a perfect example of why bench racing is never accurate. Results of any one run are based on so many variables it's insane. Drag force varying between cars and getting even more complicated when winds are included. Driver skill, transmission type (shift speeds), gearing (number of shifts), power to weight, torque to weight, traction (in every gear), tires, it goes on and on. http://media.caranddriver.com/files/...toryfinal.pdf 

Appreciate
0

11012012, 11:18 PM  #32  
Captain
15
Rep 900
Posts 
Quote:


Appreciate
0

11022012, 03:49 AM  #34  
Lieutenant
17
Rep 571
Posts 
Quote:
We both dyno'd our cars twice...on Dyno Dynamics i put down 446 Shelby put down 546...on a what appeared high reading dyno i put down 486 and he had 603 that day... I also have another friend with a 560whp Shelby that i pull on as well. Im convinced thats it the aerodynamics plus weight that helped me.
__________________


Appreciate
0

11022012, 06:49 PM  #35 
New Member
0
Rep 11
Posts 
Wow, those are pretty insane numbers. What's your setup?
The torque difference probably throws in some interesting twists. You may be able to get the jump on a Z because the lower torque helps you grip in low gear, but then when the higher torque of the Z kicks in after traction is established, could start to pull. So did you and Mookster run each other or are you guys talking about different events (M3 vs. Z06, Z06 vs. GT500)? You guys should seriously consider some Michelin PSS tires. They're incredible. As fast as your cars are, they'll only get faster. The PSS use 4/5 winter compound; warm they can support 1st gear full traction with ~500 whp from a dead stop in 45 deg. F, pretty crazy, I've seen it. 
Appreciate
0

11022012, 09:25 PM  #36 
Captain
15
Rep 900
Posts 
Mookster is talking about his Z vs the cobras and that's the out come
I expected. Just blows my mind how bad ass the Vettes are. My buddy out here in SoCal has his own shop and he was pissed when I beat him when he had just basic bolt ons (fast intake, throttle body, long tubes, tune and catless exhaust going into corsa mufflers) so he went all out and did the heads and cams and that was the last result I spoke of in the earlier post. My M has the Gintani stage 2+ supercharger, catless exhaust and reprogrammed DCT. My hats off to Chevy for their small block tht has stood the test of time over and over again, but I did post a faster time than my buddy at the track haha 
Appreciate
0

Post Reply 
Bookmarks 
Thread Tools  Search this Thread 

