Improviz

Aerodynamics on the SL would have been MUCH worse than the Z06 in this race due to his running the SL with the top down, so that doesn't explain it.

The Z06 runs great at high speed. Car & Driver ran 0-150 in 17.5 seconds in this one. They also hit 120 in 10.7, 130 in 12.7, and 140 in 14.8. Since its picking up about 10 mph every 2 seconds between 120 and 140, it'd be hitting 0-125 mph (0-200 km/h) in about 11.7 seconds, and 0-135 mph in about 13.7 seconds.

How does this stack up against an SL600? I remembered that I'd looked at SL600 performance in these forums before, and had found the following two tests:

As tested in Sport Auto, 4/2003:
0 - 80 km/h 3,5 s
0 - 100 km/h 4,6 s
0 - 120 km/h 5,9 s
0 - 140 km/h 7,6 s
0 - 160 km/h 9,2 s
0 - 180 km/h 11,4 s
0 - 200 km/h 13,9 s

As tested by AMS, 8/2003:
0 - 80 km/h 3,0 s
0 - 100 km/h 4,1 s
0 - 120 km/h 5,4 s
0 - 130 km/h 6,2 s
0 - 140 km/h 6,9 s
0 - 160 km/h 8,9 s
0 - 180 km/h 10,8 s
0 - 200 km/h 13,5 s

So, the 'vette is about two seconds or faster to 125 mph. Looking up again at the interpolated results from above, we see that when the SL600 hits 125, the 'vette would be hitting 135, about 10 mph faster, pulling away at about one carlength (14.66 ft) per second.

And these are numbers obtained when the SL600 is run with the top up. If it's down, these numbers would go up dramatically, meaning that a well-driven, well-running Z06 should have assassinated a stock SL at these speeds.

With the top up, this might be plausible, but with the top down this frankly doesn't sound very realistic, unless the 'vette had his windows down, which would give him a pretty bad hit drag-wise, *and* the SL got a good jump, *or* if the SL was modded pretty heavily in a previous life.

jmf003

Improviz, based on what I've read, the SL has a .29 Cd with the top up, .34 with the top down. C6 Z06 is .34, the same as the SL with the top down. GM increased drag on the Z06 to reduce lift at high speeds; stock C6 is .28.

The SL's frontal area is 2.34 m^2 while the C6 Z06 is 2.07 m^2.

The corresponding CdA numbers are .68 for the SL top up, .80 for the SL top down, and .70 for the C6 Z06. As a result, the Z06 has a 14% CdA advantage over the SL top down.

However the SL600 has 830 nm torque while the C6 Z06 has 637 nm. That's a 30% torque advantage for the SL600 to offset the 14% CdA disadvantage. That's peak torque, of course; average torque would be less but probably still in favor of the SL600.

Unless I'm missing something, though, based on engine torque pushing CdA, the SL600 has the advantage, even with the top down.

Also, the run wasn't from 0-150 MPH, it was from 60 MPH (or somewhat higher) to 150 MPH. We also know that the Z06 wasn't at max throttle when it caught up to Exodus, otherwise it would have been traveling at 190 MPH. Also, based on Exodus' report his SL600 went full-throttle first.

So what would have happened then? The Z06 would downshift and hammer the accelerator. But would a stock C6 Z06 catch and blow past a stock SL600 under those conditions?

Your figures show the Z06 picking up 10 MPH every two seconds from 120 MPH to 140 MPH. We don't have the same figures for the SL600 but guess what? For the highest figures you do have (180 KPH to 200 KPH) the SL600 is also gaining 10 MPH every two seconds (20 KPH in 2.5 seconds = 10 MPH in 2.0 seconds). If the SL600 can maintain that rate of acceleration through 140, the Z06 won't be catching it.

As you pointed out, the SL numbers were run top-up and would be slower top-down because of the extra air drag. But we also know the Z06 numbers were run with AC off and I'd expect the Z06 AC on since its windows were closed.

Under those conditions I'm thinking it's a neck-and-neck run with Exodus having the edge since he got the jump.

From 0-150 would be a different story, of course.

Exodus

Excellent contributions Improviz & JMF003.

Nice to see some numbers and coherent theories, instead of "impossible" comments.

JAYCL600

This is the "Kill Stories" forum. I guess its not impossible to "beat" someone because you had the jump and "then he engaged" as you outline. Thats just not something most consider a "kill"

Exodus

Of course.

Improviz

OK, now that we have (I assume) accurate numbers for drag with top down for SL600, we can figure out net forces acting on vehicles including drag.

Drag force is -0.5*p*Cd*A*v^2. Let's look at 100 and 150 mph, or 44.704 and 67.056 meter/second respectively.

Z06:
Fdrag(100) = 0.5*1.3*0.34*2.07*44.704^2 = -914N
Fdrag(150) = -2057N

SL600:
Fdrag(100) = 0.5*1.3*0.34*2.34*44.704^2 = -1033N
Fdrag(150) = -2325N.

Net force:
Z06: 100 mph = 5200 rpm, just past peak of 470 lb-ft--close enough, so wheel force = 637Nm*1.30*3.42/0.2286 = 12389N, giving Fnet of 11475N after subtraction of drag force. 150 mph is 6700 rpm, just above power peak of 6300 rpm/421 lb/ft. So I'll figure 410 or so absent a graph, or 556Nm, giving wheel force = 556Nm*1.00*3.42/0.2286 = 8318N, giving net of 6261N with drag force subtracted out.

SL600: 100 mph = 5200 rpm, just shy of peak horsepower, rated at 493, but more like 530 or so. For grins, use 540, at 5200 rpm torque and horsepower are about equal, so call it 540 lb-ft or 732Nm. So wheel force = 732Nm*1.41*2.65/0.2286 = 11964N, giving Fnet of 10931N after subtraction of drag force.

At 150 mph engine is turning 5500 rpm, drop it down to 520 lb-ft or so giving 705Nm, so you get 705Nm*1.00*2.65/0.2286 = 8173N, leaving net of 5847 with drag force subtracted out.

So we have:
Z06: F(100 mph) = 11475N
SL600: F(100 mph) = 10931N

Z06: F(150 mph) = 6261N
SL600: F(150 mph) = 5847N

f=ma, so a = f/m.

Dividing by mass to get acceleration gives:
Z06: a(100 mph) = 11475N /1449kg = 7.92m/s^2
SL600: a(100 mph) = 10931N/2010kg = 5.44m/s^2

Z06: a(150 mph) = 6261N /1449kg = 4.32m/s^2
SL600: a(150 mph) = 5847N/2010kg = 2,91m/s^2

Yes, I didn't do the rolling resistance, but this would hurt the SL more than the Z06 as the SL is much heavier, which would only make matters worse. Bottom line is that, as the numbers show, the huge disadvantages in mass and gearing take the SL out of the running unless it's making waaaaay more than rated horsepower/torque, or as mentioned previously the Z06 driver screwed up (in wrong gear, missed shift, etc), had his windows down which would have hurt his Cd (not sure if it would have hurt it by *enough*, but it would definitely slow him down bigtime especially at very high speeds), or if SL got a really really good jump....too many intangibles, but well-driven, a Z should definitely come out on top vs a stock SL600.

Tried to double check these, but it's late and I'm tired, so hopefully this all gels. Anyway, jmf003, you are correct about the SL600's higher torque, but forgot to take into account the higher multiplication of the Z06's gearing and final drive (and its substantially lower mass, given that Cd is equal and A of Z06 is smaller).

Also, if anyone can give me the torque numbers for these motors in 500 rpm increments, I can plug them into a spreadsheet and see how this comes out overall, but given we were at peak torque in some of the calculations above, it won't change the outcome substantially...

HLG600

Stock Dyno Chart Z06:


The only stock M275 chart I found didn't have the torque rating, only horsepower, which is a bit odd...all others are modified motors. Then again, this is from quick google browse. Any of you M275 guys have a baseline dyno chart lying around?

jmf003

Here's an SL600 dyno from Dragtimes. I believe the lower curve is for a stock motor. More comments in a moment....

jmf003

Iproviz, I think your Fd numbers are spot on. I think your Ft calculation is off, though.

Total force (Ft) = force to accelerate (Fa) + force to compensate for drag (Fd)

If a C6 Z06 runs 0-100 mph in 7.9 seconds and 0-150 mph in 17.5 seconds, then it would take 9.6 seconds to run from 100-150 mph. That's an acceleration from 44.7 meters per second to 67.1 meters per second in 9.6 seconds, or 2.33 m/s2. Since F=MA, 1,421 Kg of mass * average acceleration of 2.33 m/s2 = 3,310 average newtons of force to accelerate the Z06 from 100 mph to 150 mph.

Average Fd is a bit more problematic to calculate because Fd increases geometrically with velocity but acceleration is decreasing so time is increasing as velocity increases. Calculus can produce the answer but my calc skills are more than a little rusty. But we also know the Z06 took about 5 seconds to accelerate from 100 mph to 130 mph and about 5 seconds to accelerate from 130 mph to 150 mph, so the Fd at 130 mph should put us in the ballpark for an average Fd. That number is 1,538 N for the Z06.

In total, then, the Z06 needs something like an average force of 3,310 N + 1,538 N = 4,848 N to accelerate from 100 mph to 150 mph.

The SL600 has a 41% weight disadvantage and would require 4,667 N to match the Z06's acceleration. With the top down it also has a 13% drag disadvantage, so its approximate Fd would be 1,738 N. Ft for the SL would be something like 6,405 N, which is 32% more than the Z06.

If we look at the rear wheel torque figures from the two dynos, the SL600 has about a 25% advantage over a fairly broad range. At least that's my quick take. The dyno numbers also have the advantage of factoring in the different axle ratios and wheel sizes but the disadvantage that different dynos produce different results. Net-net, I think it's close enough.

Since the SL needs 32% more force and has only 25% more torque, that's not enough. Except that's not our race; Exodus got the jump on the Z06.

So imagine the Z06 cruising along. Exodus hits the gas. The Z06 driver sees the SL accelerate, decides to respond, depresses the clutch, downshifts, releases the clutch, then hits the accelerator. How much time has passed?

The "magic" number is 0.6 seconds. A 6% time advantage coupled with a 25% torque advantage gives the SL600 the 32% it needs to keep the Z06 at bay from 100 mph to 150 mph. 6% = 0.6 seconds off 9.6 seconds.

Now these figures are for a run from 100 mph to 150 mph and would be somewhat different for a 60 mph to 150 mph run but even with a longer run, if the Z06 takes a mere second or two to notice the SL, decide to act, then act, the run would play out like Exodus described. At least I think so.

Good chatting with you on this one, Improviz.

JAYCL600

I cant believe you guys have taken it to this level with respect to the data above, and im not faulting either of you as I am one for data, trust me I live by it as I have been an avid drag racer in the past. But there is no reason to go this far, bottom line is he got the jump, end of story. If you want to call that a race then glorify it, personally i think this thread is complete BS that we are arguing whether or not a stock SL600 is faster then a Z06, borderline comical. Are you guys serious, do you actually get to the drag strip or spend anytime street racing? Did you notice the OP said a Carrera GT only beat him by one car length and you want to take this story as credible? Stop sopping this crap up with a biscuit, a freaking truck can get the jump on you and you could lose......sorry to vent

Exodus

You jackass, where did I ever say Carrera GT?

Hazy1

I believe it was the gentleman from Dubai with a Z06 that stated the CGT beat him by a car length.

JAYCL600

i wont stoop to your level and call you names directly, but I will apologize for thinking that was you as I was clearly wrong after reviewing the thread.

blackbenzz

I feel like I'm in friggin physics class WTF!

Stock SL600 is NOT going to beat a stock C6 Z06. Doesnt matter how many calculations you do. Unless the C6 Z06 is being driven by a chimpanzee

HLG600

There is a difference between controlled environment magazine tests and these day to day encounters. All these guys are doing (albeit to infineon) is analyzing a simple race from several technical perspectives, and putting it in layman terms. I'm not doing the math, so I'll just hang back and read their results.

Exodus

Maybe your anger got the best of you, realize some people can't even break a 5 second 0-60 with a Carrera GT

A lot of **** can happen on the street, so don't label me a liar because the scenario didn't play out to your liking. Or the way a magazine says it should.

F**king sensitive morons around here.

Exodus

Yeah, I made it up just to start an argument on MBWorld and have people do massive amounts of calculations to disprove my argument.

JAYCL600

I am far from angry and the last thing I do is quote magazines, to be honest i didnt even read one bit of that data above because i dont need to. We have the same freakin platform my man so why would I personally care, wouldnt i want you to beat the Z06? I wouldnt call you a liar, slightly delusional maybe but not a liar because you actually think your car is "that" fast. I bet youre the type of guy who would never take his car to the dragstrip to see what it actually can do. Id go so far as to say youre the type of guy that would come to the "kills" section of an internet forum and say "hey my stock SL600 just beat a ZO6"

HLG600

E55Jay, Exodus acknowledged the power of the Z06, accrediting it for the performance he witnessed himself. He realizes that stock for stock the anorexic Z06 is quicker than the tank-like SL. However, is this not one of many times such the opposite happened on the street?

Exodus, E55Jay made a simple mistake and apologized for it immediately after he realized this. Relax man, this is just a buncha' car guys on a website killing time. Some read for entertainment, others propose a physics thesis, contributing to an already interesting thread.

The C6 overall is a stellar performance value, and lightly modded can hang with the best and outrun most. This is all result of the rudimentary formula of a low weight being pulled by an absurd amount of thrust. Still, the cost is such minute things like the fact that you can push in the rear panel with little effort from a single finger. So...it's not the safest car in the road to be in, but a friggen' rocketship nonetheless.

Cheers

Exodus

Let's put it this way, on the track in optimal conditions a Z06 will beat me. On the street, where there are numerous variables the scenairo can and DID play out differently.

So do me a favour and explain how I'm slightly delusional? Because I posted the result of an encounter? Because I beat a "faster" car?

To answer your question, no, I would never take my car to the strip because frankly I don't care that much. If I ever would go, I would go make a run or two, hang with the other guys around, have a fun time and go home happy no matter the end result. I didn't buy my car because it's the fastest, if I wanted that I would've invested the 100K in a 25Cent machine, took out a Honda Civic, dropped a B18 in it and rape Lamborghini/Ferrari/Porsche/McLaren's left and right... but honestly... I don't care.

Exodus

I realize that, and I would like to also apologzie for jumping on him for that. I suppose, I had to vent-- I'm sure he knows where I was coming from. Thanks for your insight HLG.

Improviz

I don't. That's a textbook calculation using the force of the engine as supplied by the manufacturers, the cars' gearing, and wheel diameters. The numbers are probably off given that the SL seems to be underrated by a bit more than I was estimating, and of course I was using lossless drivetrains, but Mercedes' drivetrains are afaik roughly 83% efficient (based upon dragstrip results and dyno numbers for cars I've run numbers for), but the methodology is sound. The difference comes from the SL's higher-than-expected underrating in horsepower/torque. I figured them to be similar to the S/SL/E/CL55, but it seems that the xx600 cars are underrated even more.

But the calculations themselves are sound.

Less rolling resistance for the SL, which would be about 43% higher than the Z06 due to 43% more mass, and would not be unsubstantial.

I'll snip the computations for brevity, but don't disagree with your basic conclusions, except that I think that if we look at, say, Ben Treynor's results with a stock S600, where he was running mid 12's at 114, and compare these with the plethora of results showing Z06s trapping in the mid-to-high 120's, it is blatantly obvious that a well-driven Z06 will run away from a stock SL600.

I will also say that if anyone disputes this, then by all means, let's line 'em up; I'd be happy to wager that we can easily find someone on the 'vette forums to volunteer their time.

I think the jump would have to be much larger than 0.6 seconds for cars that trap 11-13 mph apart in the 1/4 mile. A second or so at minimum, possibly more....but I do agree with you here, it was the jump, and possibly errors on the Z06 driver's part, which won the race.

Not to take anything away from the OP (a kill is a kill, and I for one have beaten several cars which should be faster, and conversely have lost to cars which are slower), but the gap between these cars' performance stock to stock is pretty substantial, which was, I think, the source of some understandable skepticism.

But a jump can and will make a big difference; truth be known, I did the reverse to an SL55 a few years ago, with the same results: he couldn't catch up. Of course, I knew good and well that if we'd have both hopped on it at the same time he'd have killed me, but it was still fun!

And similarly, a guy in a 350Z got a jump on me a while back, and it took a while to catch & pass him, whereas when I've run them getting on it at the same time, it's bye-bye Z...

So yeah, if he got a one second jump (which isn't much if you think about it) before the Z06 guy managed to react, downshift, and nail it, badda-bop, badda-bing, that explains it easily.

Exodus

It's kind of hard to argue with these cars considering they all put out different amounts of power. I mean, I've seen E55s run 13s--even close to 14s-- and then you see some breaking into 11s.

So if one of the 11s beats a say M5 (clocking 12.5), are we not to believe it because others are running different times, greater then one second of a difference?

Also, it's hardly fair to compare one racers result (with a different car no less) to my car. Also, we don't know my car is stock.

Ah... forget it. There are so many variables here we could go on all day. In any case, I just might throw my car on the dyno to see what I got. Like one of the previous members said, I might be pleasently surprised.

Improviz

Well, this is why I chose Ben Treynor, as he's got lots of drag strip time and is very consistent. Also because he dyno'd his S600 at about 481 rwhp, or about 580 crank...so if he's trapping 114 tops stock, I doubt anyone else is going to beat this by a substantial margin, certainly not in trap speed.

Well, I'm not saying that I don't believe you; I just needed a convincing explanation of how a car which traps 115 or so could beat one which traps at 125 plus. A big (i.e., a second or thereabouts) jump could do it, or if you allude to below, if it turns out that your car has had its ECU flashed, that could do it too.

Wrt an E55 beating an M5, well, that's much less likely to raise any eyebrows, simply by virtue of the fact that the two cars are both in the 12.3-12.5 range stock, and trap within a few mph of each other. Now, if you have an E55 saying he'd pulled a Z06, again, people would be more skeptical simply due to the much larger difference in the two cars' trap speeds.

I'm not going by only this example.

Absolutely, and I've mentinoned this in previous posts. If you've got an ECU flash, then that too explains it well.

Sure. To be honest, if it was a 0-80 run it wouldn't even have caught my eye, but from 60 up if he can drive a manual at all, driver error is less likely....from a stop, otoh, he'd have to be a pretty good driver to get that thing launched well, time the 1-2 shift w/o hitting rev limiter, etc., so the SL would have a big off the line advantage unless the guy was really good...still, even in a rolling-start race he could've hit third instead of second, etc., so as you said any number of variables could have produced such an outcome.

Indeed. Go for it!

JAYCL600

damn man you have all the fast cars