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View Full Version : Mark Stielow's Red Devil '69 Camaro vs. 2012 Chevy Camaro ZL1



MAP
12-07-2012, 12:56 PM
Hi Folks,

Continuing the thread of the same name from the "Open (Pro Touring) Discussion" forum, where in my ignorance of its rules (my apologies again,) I had started to post questions of a technical nature.

That thread started with a video showing the Red Devil (which I will abbreviate "RD" going forward,) versus the Camaro ZL1, being driven full-out by Mr. Mark Stielow at Gingerman racetrack. The video includes a depiction of transverse acceleration and longitudinal velocity for both cars througout the course. An article about this same event was written by David Freiburger in December 2012 "Hotrod" magazine. Here is a link to that article:

http://www.hotrod.com/featuredvehicles/hrdp_1212_built_vs_bought_1969_chevy_camaro_versus _2012_zl1/viewall.html

To give the appropriate background to start things here, I started with this statement over there:

"I'm puzzled as to why Mark's car didn't do somewhat better compared to the ZL-1 in transverse acceleration. The location of both car's COM's in relation to their respective tire patches may be at the root of this, but this is only conjecture on my part. Or, it may be rooted in both car's non-linear handling responses near the edges of traction."

To which Mr. Stielow replied:

"The ZR-1 has a much wider track width so its max lat capabiliy is a little better due to the way it can load the tires. The CG and track width help define the work the tires can do cornering. Because both cars are on Goodyear Super Car II tires that is fairly equal. So chassis tuning and geometry make up the rest of it."

To which I then replied:

"Mark - many thanks for your reply. Briefly for now: the pictures in the Hot Rod article seem to indicate roughly 8% narrower track width for the RD re the ZL1. But my guess is that the height of your COM may be roughly that same fraction lower too, but I have almost no data to go on. The ZL1 has a very high belt line, and I'm also guessing, lots of weight in the superstructure to meet rollover standards. This argues for a high COM. But the RD has a roll cage and heavy (1-2lb/ft^2?) noise barrier treatment on the roof (in addition to the rest of the cabin) which may also push its COM higher. Ditto the LS7/9 motor - I'm guessing maybe 530 lb and a high COM for the motor considered in isolation because of its SC? These would tend to point to a COM that's rather high in the RD relative to the car's original design, but maybe not so much so as to give the ZL1 an advantage here in relation to track width. I'd imagine you'd like to reduce some of the inertia terms, especially I zz, and pull the COM (= high-frequency yaw center, presumably,) more rearward in the car. (For this reason I'm pondering an LS7 with a Squires-like rear mount turbo for my mid-80's G-body project.)

Also, if the comparative drawing was really done to scale in the article, you seemed to be running more static negative front camber (-2 deg?) than the ZL1, and the video seemed to hint that you reduced the ride height beneath your book's claim of minimum 4" ground clearance.

Anyway, my point is that I remain somewhat puzzled about how the cars compared in transverse acceleration. Longitudinally - if I read the velocity graph correctly, and you had both cars at WOT in the final straightaway, then the RD had an average of 58% higher acceleration than the ZL1 - amazing - and, if I use the SAE numbers of 580-ish hp at the rear wheels for the ZL1, then the RD would map to roughly 780hp. If the graph were calibrated for velocity and time, then I could calculate mechanical power more directly from the derivative.

This is just scratching the surface...

Questions notwithstanding, the RD is an absolutely amazing accomplishment!"

It would be nice to continue the discussion here, and by no means am I implying that the discussion must depend on Mr. Stielow's engagement (I'd imagine he's quite busy and probably has far more important things to do.) Also, because of my nearly boundless curiosity, it's very likely I'll ask questions of a proprietary nature (e.g., x,y,z location of ZL1 Camaro's COM,) if I think there's the slightest chance that such knowledge might be in the public domain. If not, however, I'll most certainly understand if answers may not be forthcoming.

Thank you,
MAP

exwestracer
12-08-2012, 05:37 AM
I had to pop in on this one because I FINALLY get to give a short answer to a LONG question, instead of the other way around! :idea:

IRS.

There. Now that that's out of the way, there's a pretty good lesson in the data provided in the HOT ROD article...
68472

Note how the red line (2012 ZL1) is much "squigglier" (gotta love those technical terms) around the area of max lateral acceleration. That's driver feel. The Red Devil was easier for the driver to hold on the corner line (most of the time) than the new car. The (bottom) speed graph shows the 69 having an advantage in almost every corner, and a smoother transition from cornering to acceleration to braking. Bottom line: The STOPWATCH tells you what the right setup is, not the G meter....

MAP
12-08-2012, 10:54 AM
Greetings Ray,

Thanks for your answer. I'm short on the practical side of this, so your perspective is most helpful. About "squiggliness," I try to understand that by mentally taking the time derivative of the top curve (which amounts to "jerk." This is where that I zz term is likeliest to manifest.) As far as I can tell, I see different behaviors in different turns for both cars (I'm guessing that the range of the graph might be +/- 1g.) I honestly can't say that the average between the two cars in the turns is significantly different judging by eye; it looks like factors other than the cars per se may be dominating this sporadic difference signature.

You're saying that based on what you think is smoother behavior with the RD, that is was, "...easier for the driver to hold on the corner line (most of the time) than the new car." But Dave Freiburger said in the video (I don't know how to copy that here,) that the RD clearly required more "muscle" to drive around the track. Dave's comment, plus my somewhat different interpretation of transvserse jerk, seem to suggest either an ambiguous conclusion, or some overall advantage to the ZL1. If the IRS is making a significant difference, then we would expect the ZL1 to gain dominance here (except for limited anti-squat,) and so your opening claim of the IRS being the main difference, isn't supported by your succeeding observations.

If I misunderstood anything of what you wrote, please correct me.

Thank you.

Best,
MAP

exwestracer
12-08-2012, 11:04 AM
Freiburger's a wuss... ;-). I have no doubt it took more effort to turn the 69, as I'm sure it has much more aggressive alignment settings than a stock 2012 production car.

I'm not reading anything into the data posted above. Just look at the average amplitude of the G load changes as the cars went through the corners shown. The 69 has a little less variation in G loading through most corners. All that means is the driver was having an easier time at the limit of adhesion. They are very close, though; and that could come down to something as simple a 5lb of air pressure in the tires (really).

What I like to see is a graph of steering wheel input angle laid over the lateral G chart. That would really tell us something!

MAP
12-10-2012, 01:08 PM
Hi Ray,

Thanks again. I agree that it would be nice to see the steering wheel angles, or ultimately, the tire slip angles. My guess is that Mark's car might have had more understeer than the ZL1.

Best,
MAP

MAP
12-12-2012, 09:12 AM
Hi Ray,

I think your post deserves a second dive. "...it took more effort to turn the 69..." to me means two things: physical effort, and mental effort of concentration to know when, and how much, physical effort to apply. About alignment spec's bieng more agressive for the 69: I take it to mean that the 69 might have had neutral toe or possibly even some toe-out? Possibly reduced caster? We know it had lots of static negative camber if the article drawing was rendered accurately. Often a system with faster transient response tends to be less stable, and such systems tend to be more difficult to control (fighter planes react so quickly that without real-time active control assistance of all control surfaces, the average pilot would crash in their first turn.)

But again, I'm somewhat left scratching my head. If the 69 used all of these tricks to do as well as it, and it had a 500-ish lb weight advantage over the ZL1, and if we can imagine that the height of the COM in relation to track width might have been roughly the same for both cars, then why didn't the 69 emerge as the clear winner in transverse acceleration? I could imagine that if the driving surface were bumpy, then the lower unsprung mass in the rear of the ZL1 from the IRS would figure prominently, but my guess is that Gingerman's pavement was smooth.

Maybe some factors that would explain the near parity might be:
1. The SC'd LS7/9 motor in the 69 probably shifted the COM up and forward, so that F/R weight distribution might have been biased more heavily in the front than in the ZL1 (claimed to be 52%/48% F/R.)
2. The 69 probably had much less in the way of mechanical low-pass filtering in the form of suspension/body bushings, interposed between the road and the cabin and the steering wheel. The result efficiency of transfer of high-frequency mechanical "noise" to the steering wheel, reduces the driver's tactile perception of "signal", making it more difficult to discern how to react to the low-frequency information which is so vital to judging appropriateness of steering inputs. (If this guess is correct, then despite the heavy acoustical noise-barrier treatment in the 69, the "VH" part of "NVH" might have been considerably worse for the 69 than the ZL1.) On the other hand, typical bushings tend to have insufficient loss factor and thus tend to create high-Q resonances, and these can add to the "noise" side of the equation as well. I presume the bushings used in the ZL1 therefore have very high loss factor.
3. If the pavement was rough, then no question that the IRS would maintain better control through turns due to lower unsprung mass. However, the 69's aluminum central housing section for the 9" rear, probably kept the live axle mass on the low side of typical.
4. The active magnetorheological aspect of the ZL1's shocks is an unknown factor to me. I'm guessing that one aspect designed into this action amounts to the equivalent of high shock valving divergence, to reduce the high-frequency side of NVH. But what's good for driver comfort might be bad for handling over sharp bumps in the ride surface.
5. The high roll center of the 69's rear (12"?) might be good for roll-axis yaw dampening, but bad for handling over rough surfaces (once again.) It can be shown that with a high roll center, a portion of the car's sprung mass is reflected back to wheels for any difference-mode inputs. The higher the RC, the greater the reflected mass. This has to be accommodated by transverse tire sidewall flexure in the high-frequency regime. This flexure, in turn, is created by a reaction force which "competes" with the tire's traction circle, which we would like to have wholly devoted to accelerating the car.
6. The distinctive body lines of the 69, in conjunction with the desire to have the front wheels "wink" through the wheelwell openings, unfortunately create a very tight constraint for maximum front track width. If function wins over form, then the obvious solution would be to create generous fender bulges for the 69. Or, transgress the body lines. My guess is that either option was one bridge too far for Mr. Stielow, which may help explain the change to the '67 body for "Mayhem," where fender bulging might be much easier to disguise.

Best,
MAP

exwestracer
12-12-2012, 10:32 AM
It's quite possible to write a vehicle dynamics treatise in response....

The short version is, automobile handling has WAY to many variables to be governed by an engineering textbook. Even F1 teams (with multi-million dollar shaker rigs) have to take the car out ON THE TRACK to see exactly what it will do. We can math it to death, predict it just so far, ...but then we have to race it and see what happens.

Besides, if we could predict the outcome 100%, what fun would it be to pull beside somebody? :)

MAP
12-12-2012, 10:44 AM
Hi Ray,

You're exactly right, and that's why I appreciate your posting here (and anyone else too - hopefully including Mr. Stielow himself if he should be so inclined.)

But, are we really at the point where nothing further is to be gained by theoretical conversation? And, can't we add to the practical conversation aspect too?

Thanks,
MAP

MAP
12-18-2012, 11:45 AM
Greetings,

Maybe the onslaught of questions and ideas here is too much for this type of venue, so to break things down into bite-size chunks, how about the following as a start:

Is there any information about the location, fore-aft and height (I will assume reasonable left/right symmetry,) of both cars' COM's? The only data I have is that the ZL1 is 52%/48% F/R weight distribution. For the '69, in the absence of further data, I'm guessing its COM is fractionally closer to the front axle. Concerning height of COM, I'm guessing that the '69 might be an inch or two lower than the ZL1.

However, I know that getting COM height isn't trivial, and especially if done with high accuracy (say, a tolerance of better than 5%,) where you need to lock the suspension and prevent tire deflection for the tilted condition measurement.

Thanks!

Best,
MAP

Kenny
01-09-2013, 11:28 AM
One thing that stands out in all this math is that some of the most relevant predictors are missing from these equations. The ultra expensive test equipment does not take into account road surfaces, minute elevation changes, banking etc.... To give an example, we have very fast switchbacks on our country roads that are banked for neutral handling(for the average driver at legal speeds) and what you end up with is something more akin to jumping a diagonal speed bump when attempting a "good line". Two wheels on opposing corners a very heavily loaded while the others can be totally unloaded. It is not unusual to see a big bar car lift a wheel, or a big spring car dislodge a spring on these very well maintained roads. Same goes with that washboard effect on many back roads in VA,NC and TN. This is the beauty of the active suspension and the ability to differentiate between body motion and wheel motion.

I do love RD, and it is a marvel, but I feel certain it would be chasing tail lights on the more compliant ZL-1 in short order on our mountain roads. With that being said, the math used to figure out why RD is superior in this scenario would likely be incomplete for other conditions. Road courses and auto-x have always seemed way too 2-dimensional to come up with good mathematical predictors for a good pro-touring car.

I would also suggest the factory bushings loading and unloading may contribute to the squiggly nature

MAP
01-21-2013, 11:25 AM
Greetings Kenny,

Sorry to have taken so long to reply - I thought the thread wasn't going to attract any more responses, so I neglected checking back here until now. Thanks for replying.

Kenny, I have to admit that since my background is in physics and EE, and since I only dabble in cars once in a while, that I'm not well versed in the terminology used by the practitioners of the trade, nor am I fully up to speed (pardon the pun) in the practical aspects of this. I suppose it was for this reason that I somewhat struggled with understanding your response, so let me try to understand it piece by piece:

1. "...some of the most relevant predictors are missing from these equations." Which, in particular?
2. About road surfaces, this is a big unknown for me regarding Gingerman. I presume, but don't know, that the surfaces are smooth, so things like rear unsprung mass and roll dampening would be rather unimportant.
3. I see what you mean about switchbacks, banked turns, and diagonal loading with very sharp transitions. But, the transitions ought to occur with low centripetal acceleration, so I wonder whether this would have a significant impact on speed of negotiation.
4. "This is the beauty of the active suspension and the ability to differentiate between body motion and wheel motion." This is rather unclear to me - would you elaborate? Again, if the aspect of active control only relates to the rheology of the dampening fluild, which in turn is controlled in response to relative motion between the wheel and body, then it would seem that this is at least one DOF short of true active control, but I don't have a good sense as to the practical consequences of this shortcoming. (My employer has worked on fully active suspensions for years now, but I post here strictly as a hobbyist.)
5. "I do love RD, and it is a marvel, but I feel certain it would be chasing tail lights on the more compliant ZL-1 in short order on our mountain roads." Then why not make the RD more compliant too? Is it the roll aspect again? Is it the higher mass reflected to the rear due to the high (11-ish inches) roll center height? If we recognize these as shortcomings of the live rear axle and its method of roll-center constraint, then why didn't Mark use an IRS too? Could it have been the low rear anti-squat limitation? This is one of many areas where it would indeed be wonderful if Mr. Stielow would engage the conversation, but once again, it's quite understandable that he probably has higher priorities.

Best,
MAP

RSX302
01-22-2013, 09:39 PM
Personally I think this test is moot...cool to see the difference between the two, but still irrelevant.

Stielow's Camaro's are bad to the bone no doubt and takes older technology to a higher level, but this is far from apples to apples test. If one was looking for a daily driven street car, I'm going for the ZL1 hands down. Yes the 69 could be driven daily, but I wouldn't want too.

If you want apples to apples, put and additional $40k into the ZL1 to match the $100k price tag of Stielow's and put on a diet. I would put money that the ZL1 would smoke the 69.

But then again if I was looking to put 100k into a newer car, I would look at the ZR1 instead of a Camaro. I sat in a new Camaro, my head hits the roof. :hammer:

Kenny
01-24-2013, 09:05 AM
Greetings Kenny,

Sorry to have taken so long to reply - I thought the thread wasn't going to attract any more responses, so I neglected checking back here until now. Thanks for replying.

Kenny, I have to admit that since my background is in physics and EE, and since I only dabble in cars once in a while, that I'm not well versed in the terminology used by the practitioners of the trade, nor am I fully up to speed (pardon the pun) in the practical aspects of this. I suppose it was for this reason that I somewhat struggled with understanding your response, so let me try to understand it piece by piece:

1. "...some of the most relevant predictors are missing from these equations." Which, in particular?
2. About road surfaces, this is a big unknown for me regarding Gingerman. I presume, but don't know, that the surfaces are smooth, so things like rear unsprung mass and roll dampening would be rather unimportant.
3. I see what you mean about switchbacks, banked turns, and diagonal loading with very sharp transitions. But, the transitions ought to occur with low centripetal acceleration, so I wonder whether this would have a significant impact on speed of negotiation.
4. "This is the beauty of the active suspension and the ability to differentiate between body motion and wheel motion." This is rather unclear to me - would you elaborate? Again, if the aspect of active control only relates to the rheology of the dampening fluild, which in turn is controlled in response to relative motion between the wheel and body, then it would seem that this is at least one DOF short of true active control, but I don't have a good sense as to the practical consequences of this shortcoming. (My employer has worked on fully active suspensions for years now, but I post here strictly as a hobbyist.)
5. "I do love RD, and it is a marvel, but I feel certain it would be chasing tail lights on the more compliant ZL-1 in short order on our mountain roads." Then why not make the RD more compliant too? Is it the roll aspect again? Is it the higher mass reflected to the rear due to the high (11-ish inches) roll center height? If we recognize these as shortcomings of the live rear axle and its method of roll-center constraint, then why didn't Mark use an IRS too? Could it have been the low rear anti-squat limitation? This is one of many areas where it would indeed be wonderful if Mr. Stielow would engage the conversation, but once again, it's quite understandable that he probably has higher priorities.

Best,
MAP Good deal..... I don't think you are lacking terminology as much as my hillbilly"ese" leaves most people grasping for anything coherent in my replies. Your skills in physics are perfectly suited to this conversation, the application comes with learning to let go of the "paper tiger" theory that confounds most of us in real world applications. If you can look at this like martial arts, knowing that overall balance is everything, then throw in a heavy dose of chaos theory (butterfly effect), you will be faster.

If you take the width of both cars and are able to set the cg height at the same percentage of there respective track width, keeping the same roll centers, they would more or less see the same dynamic loading. You are absolutely correct in your assumptions. When you are looking at tracks that are smooth and have turns as wide as a walmart parking lot it is pretty straightforward to predict a winner by using factors such as hp/wt, G's and braking distances. All of the math we commonly use can be used to great effect to gain advantages in these instances. Where all of this gets fuzzy is when you run into surface irregularities or even high traffic. If you are between a bunch of cars, or trying to make a clever pass, the wider car can quickly lose it's advantage.

More to the point of suspension design, let's say you have a car with less than optimum rear suspension travel so it goes into snap oversteer in a turn that has a rise or bump on entry that bottoms the suspension. Now we have to deal with a traction problem on that turn. The track day fix would be more compression damping or spring rate at the rear....... that fixes the bottoming, but changes everything at every other point on the track like trail braking, or having too much oversteer when everything was fine before. So added travel was the real answer. Consider the same condition with a different problem, but with the distinction of having too much sway bar rate or linear valved shocks that have a big spike in wheel rate on the same section causing the issue. The logical answer would be a digressive valved shock. The point being that the car that should be faster by all common measure, that has these limitations, is no longer such a foregone conclusion.

Let's take another scenario where there are two identical cars with the exception that one has some anti-dive geometry in the front that allows less front spring or compression damping while keeping the same amount of control on turn in, but possibly making for better control on a bumpy track. At the same time it could cause understeer on a smooth track because anti-dive geometry does create some bind. Chaos theory, one small change can affect every behavior.

With just those two scenarios you can see that finding the most balanced approach is the answer. At the same time, active suspension can effectively deal with both problems without adverse effects on the rest of the course, especially when we throw in other things like getting forced off the track or overshoot a turn. Where this will make one of the biggest differences is the driver fatigue level on the track, reducing driver mistakes. Active suspension uses all kinds of input like braking, speed, steering angle, and G forces in every direction....... It knows when one wheel falls into a pothole and can adjust accordingly. Conventional shocks don't differentiate body motion vs wheel motion.

If you dig beyond the surface in that test (like you are), what happens when you throw a race day alignment on the ZL1? How much of that lead disappears? Does that mean that the ZL-1 is actually faster through the turns? While they made the assumption that the higher tire temps were due to weight, I would not be so quick to judge, it could just mean it is working the tires harder for whatever reason. It is possible that track alignment could have totally negated that difference. Measuring street tire temps for "distribution" after a 2 mile jaunt don't mean a lot unless you have some severe alignment issues (mainly toe settings). There is just too much time for temps to equalize across the tread surface. Looking at the lower weight is another indicator, but I would suggest that RD has lower weight in the right places. Tire/wheel weight, lighter flywheel, driveshaft etc are obviously a bigger bang than just removing static weight. Did you know that replacing a Gen 5 Camaro 2 pc driveshaft with a one piece is worth around 8hp to the rear wheels? The carrier bearing and extra joint have some frictional penalties across the entire rpm range.......

The biggest challenge to finding answers is the pre-formed opinions and assumptions by internet racers. I actually saw where someone on another post said that the ZL-1 is a wallowing pig...... another has said that the ZL-1 was harder to drive... which is the exact opposite of the statements made by the guy that actually drove the car.

None of this is meant to diminish RD. It is truly the best of the best. It is to demonstrate how astonishing the technology is in the new breed of muscle.

High Plains Mopars
01-24-2013, 02:29 PM
You know Stielow is a semi regular poster over on lateral-g.net. You might try contacting him over there and see if he has the info you are seeking.

Link to his latest build that started just last month and is already up to 23 pages; http://www.lateral-g.net/forums/showthread.php4?t=39584

MAP
01-29-2013, 10:42 AM
Greetings Kenny,

Thanks for that response - I thoroughly enjoyed reading what you shared. About chaos versus determinism: as one digs deeper and gains further understanding, the more likely it is that something which seems chaotic is really deterministic. But then again, there is genuine chaos. About active suspensions, I'm not close to the department in our company that has done extensive development here, but I'm sure that what you're saying about how GM is executing it is correct: using my own words, they are using sensors to determine body kinematics as distinct from wheel kinematics, which takes control a significant step above simply responding to relative motion between the body and wheel, as "dumb" shocks do. (The chassis had better be quite rigid, however...) But, GM's execution remains an active control over a passive resistive element: that is, ignoring minor inertial and compliance effects, the dampening dissipates energy; it doesn't add energy. This is the one key DOF in the design that I think is missing in the ZL1. Of course, having said that, adding it can be enormously difficult, expensive, and heavy. But then again, full active control where energy flow is bidirectional, can do absolutely amazing things for vehicle ride and control. Now all we need is cheap neodymium...

What is unknown to me is the efficacy of GM's active system from a driver's perspective - I've never had the pleasure of riding, let alone driving, one of these cars.

Anyway, zooming back out to the whole car comparison:

I think your post comes back to the key missing ingredient in the consideration so far, which is how both cars respond to bumpy surfaces, and how bumpy Gingerman may or may not be.

Greetings High Plains,

Thanks for that tip. I'm a bit perplexed to see his sticking to the same basic formula as the RD (supercharged LS7, 9" Ford rear, etc.) The addition of carbon fiber elements in the front and in the brakes is interesting, but it seems there are far cheaper ways to chase lower mass: foregoing some noise control in the cabin alone might save as much weight as many cubic dollars of carbon fiber substitution, for example (and granted that saved mass counts more in the unsprung assembly.) Even so, I'm sure he has good reasons for sticking with this formula, but it would be nice to gain further insight. I infer that Mr. Stielow is an infrequent poster here?

Best,
MAP

Kenny
01-31-2013, 11:14 AM
I thoroughly enjoyed reading what you shared. About chaos versus determinism: as one digs deeper and gains further understanding, the more likely it is that something which seems chaotic is really deterministic. But then again, there is genuine chaos.

Anyway, zooming back out to the whole car comparison:

I think your post comes back to the key missing ingredient in the consideration so far, which is how both cars respond to bumpy surfaces, and how bumpy Gingerman may or may not be.

Greetings High Plains,

Thanks for that tip. I'm a bit perplexed to see his sticking to the same basic formula as the RD (supercharged LS7, 9" Ford rear, etc.) The addition of carbon fiber elements in the front and in the brakes is interesting, but it seems there are far cheaper ways to chase lower mass: foregoing some noise control in the cabin alone might save as much weight as many cubic dollars of carbon fiber substitution, for example (and granted that saved mass counts more in the unsprung assembly.) Even so, I'm sure he has good reasons for sticking with this formula, but it would be nice to gain further insight. I infer that Mr. Stielow is an infrequent poster here?

Best,
MAP That first statement "as one digs deeper and gains further understanding, the more likely it is that something which seems chaotic is really deterministic. But then again, there is genuine chaos." is where there seems to be the true difficulty. Personally, I believe that almost everything deemed "chaos" is just due to incomplete data, insufficient measurement techniques, or incorrect projections. Let me make a disclaimer up front: I do not do this professionally (maybe one day), I am nearly completely self educated, and have a hideous case of ADD. All this stacks up to the fact that I see things completely backward from normal folk. Most of the people that know me give praise for my ability to apply "outside the box" solutions to complex problems. I can assure you that this ability comes from the inability to figure my way into "the box". I am keenly aware that the answers are sometimes actually in that damn box. Apply my musings accordingly.

I am of a completely different school of thought than most when it comes to data acquisition. More is better.While you can take a look at the data log files posted, they are very near worthless, but not completely. If you take the acceleration curve where there is a sawtooth pattern upon shifting, there is time being lost. To get better times we kind of have to extrapolate, or make assumptions by comparing it to the other car that is equipped with a manual trans that does not have the same problem except in slower portions...... looks to be wheelspin by investigating the available information. The driver would have complained if it were clutch slippage, and if it was the driver being a lazy shifter, both cars would have shown the same behavior having the same driver. So there is our most basic input. Of course there are many adjustments we could make to reduce the time lost through wheelspin, whether it be more anti-squat, less rear compression/front rebound damping, or even going into the ecm and dropping timing at the affected area...... easy stuff. The point is that you have to on driver input etc and make assumptions. So if we use a few more channels on the DA equipment to utilize engine rpm/wheel speed/suspension position/steering position/ brake line pressure, we would probably find many areas that could use improvement that aren't even perceiveable to a good driver.

I think the biggest improvements to be had would come from the use of real time thermal imaging on the tires. I have heard of guys making substantial improvements by making small adjustments to geometry that were not indicated as problematic with traditional temp measurements. While there was mention of the ZL-1 tires being hotter due to weight, there is also a case to be made that RD is not using the tires full potential. I would be willing to bet there is a lot of potential left in RD with changes being applied from data aquired in 1 track session using a fully loaded DA system, not just G's vs time.

The latest Camaro? It seems to me that the last couple of Mark's Camaro builds have been of the showcase variety being used as sales tools to show his preffered vendors wares rather than pushing the technological envelope

j-rho
02-01-2013, 09:35 PM
MAP,
You seem able to construct some well-written sentences and questions; you ought to use your full name instead of an acronym. :) What do you do for a living?

The data is fun to look at, and I've been using the DL1 software in amateur racing for years - but you can't assume the cars were necessarily driven to their limits. If we had TPS data and in-car video showing steering input, that'd give us a better idea of how hard he was really pushing. But really, it's a question of how far from the limit Mark chose to be in each car for the laps in question. It's possible a relative underperformance in your view of RD could be attributed not to physics but to the differing risk:reward equation Mark would have been doing in his head; wadded up ZL1 = not that hard to replace; wadded up one-of-a-kind RD = very hard to replace.

All these little things (geometry, shock technology, etc.) assuming they're at least in the ballpark on both cars, are orders of magnitude less important than weight, tires, and how hard the driver was pushing. RD is 570 pounds lighter! It's actually embarrassing how heavy the ZL1 is, and makes me wonder how close I could get with my stock 302, stock-chassis'd '67 on a handling track.

Also don't forget who employs Mr. Stielow. A really unfavorable outing for the ZL1 might not be in his own best interest - remarkable how this outcome lets him keep his pride as an amazing builder of Camaros, but keeps it close enough a ZL1 buyer can know his new car not only comes with a warranty but is "almost as fast" as the fastest unlimited-$ P-T car out there. :)

MAP
02-28-2013, 02:52 PM
Hi Kenny and Jason,

Once again I haven't checked here in a long time and am far behind in responding. My apologies for not answering sooner. Treating the points in reverse order - Jason, I'm just a rank amateur in the world of cars. I design loudspeaker transducers for a large company, and some of these go into GM vehicles. Thank you for asking, however.

Jason and Kenney, what I seem to get from both of your interesting posts, is that we need more data directly from the cars, as well as from the driver. Unfortunately, since we can't get inside Mr. Stielow's head so to say, and since it would be completely unreasonable to expect him to be able to be 100% forthcoming in a public forum like this given his associations (even assuming he may have the time and the interest to post,) I think we're likely to stall at roughly the current level in this thread. We're simply too deep in conjecture and too shallow in hard facts to make certain progress, so I agree with you both. Plus, on the ZL-1 side of the equation, we're probably delving into off-limits IP to get a full understanding.

Thanks,
MAP

Kenny
03-01-2013, 07:45 AM
That is the nature of magazine features. It is too hard to keep the attention of readers when you throw too much data at them..... Their primary goal is to sell product, and therefore advertising, while keeping the reading audience entertained. Unquenchable curiosity is not something that is shared by most.

If you look at what you do for a living..... The constant struggle to find the most rigid, lightest material with the best internal damping, then designing the most balanced motor structure for it's intended application.....Of course there have been people devoting their lives to finding the most perfect balance for about a gazillion years.... Now someone as smart as yourself will nearly lose your mind every time someone is impressed by a woofer because of the size of the magnet or a giant surround that takes up 1/3 of the potential cone area. Most guys are judging by the "magnet size" rather than transient behavior and application suitability.

It is clear that the time gained by RD was in acceleration (HP/LB). What you will do to gain an advantage is take the true empirical evidence that is available in this very limited test, get rid of the "noise" , and pack the usable stuff to extrapolate to other information you pick up in other experiences. One of the things that RD has over most PT type builds is the ABS. I would be curious to see how many times the ABS was activated....... This is no small advantage over the average PT build.

The trick to driver input is making the changes without specifying what was done, though you obviously let them know changes were made, then get their input. One example would be if you added more front caster gain for "theoretical" perfection for tire contact, but it feels less confident on turn-in to the driver, he slows down. Now we find other corrective measures for the new problem, or find the best compromise......