tube80z

Yes is the short answer. The assumption is that you are looking at wheel rate when you make the change.

This would be a good start, http://nissanroadracing.com/showthread.php?p=65055&highlight=eppler+wing#post65055 Also take a look at the Selig 1223, it seems a number of people use that too.

What exactly are you looking for? I have all the parts no my bench that I've been measuring but I didn't do any of this yet. I can do that tomorrow if I have a better idea what you're looking for. Cary

This was an autox and hillclimb car. It had a 8 point cage, belts, window net, and 5 lbs. fire extinguisher.

I've never ran higher than 1.3 myself (725 lbs/in). But that was on a really bumpy hill and I was amazed at how stable the car felt. But you can see the trend as you start to look at adding underbody downforce. It does require a really good shock to pull it off. The bilsteins you have didn't work for us once past 400 lbs/in springs.

One-piece nose, full doors, and rear hatch were all FG on the car. The rest of weight was lighter components. Rear diff changed from an R200 to an alloy Ford 8.8, steel driveshaft changed to an aluminum one. And so on and so on. I helped a friend put together another 71 240Z that was 1840. It used many of the same parts but had a Rebello KA24 and an R180 rear end. Very fast but very peaky. Quite a few of my friends are laughing at me when I told them I'm going to have a sub 1900 lbs. LS powered autox car. Cary

That was the complete engine.

Not trying to derail this thread but a number of us in the NW were running around 3 hz with the front 5 to 10% higher. What was odd to me was that as we started to develop setups that were mostly spring and little to no bar we didn't need to change much with grip changes. When we ran more bar and a lot softer in the springs we'd have to chase the track. And when it was cold or wet the bars had to come off and often the car wasn't very much fun to drive. I got this chart from Eric Purcell a number of years back. When I first heard about it I thought people were smoking something. But having tried this it's worked very well for me. Spring rate based on corner weight. Sedans and radial DOT tires -- .5 to .7 Production and light GT cars -- .8 to 1 Medium weight, 200 to 300 HP cars GT cars -- 1 to 1.3 (FP) Heavy high HP GT cars -- 1.3 to 2 (XP/EM) Hope this helps, Cary

1970 240Z, SUs, light flywheel (weighed 369 lbs.), 4-speed, R200, full cage. No interior, 25 lbs. battery, very light wheels/tires/brakes (13 inch). 0.125" lexan windshield, FG door skin, one-piece FG nose Weight with 3 gallons of gas was 1850. I had probably another 100 to 125 lbs. that could have been removed. Keep in mind this is an autox car and not a track car. It's very easy to add weight in wheels, tires, and brakes. Changing to 15 inch wheels and tires added 75 lbs. Cary

I think more than anything it's the rear percentage. On my FP autox car it was faster with ballast than without. I tried changing springs, played with shocks, etc. to compensate and it didn't seem to change much on putting power down. When I took Rouelle's seminar I asked this question. The short version he gave was that you need rear percentage to help put power down. He also reiterated that the tire has a traction allowance. If you use all of it for lateral traction you have none for longitudinal. So setting a car up if you can get the front to take more roll resistance you can free up some for the rear. You can do this a number of ways but for me I found lowering the end of the car not working was better than changing springs or bars. The downside is if you go too far the you lose turn in. Taking this to the extreme of the EM monsters. A friends LS2 powered locost (used to be a 260Z) is always faster running rear ballast (0.8 seconds on a 44 second course). Lower CG the more weight percentage you're going to need on the rears. While it's true that a lighter car will always be faster for courses where acceleration and braking are important you may find that the added weight will improve the times. The new car will be built to take this into account. For the shocks you'd be better off dropping some compression rather than adding rebound. That may sound backwards but my experience has been adding rebound often reduces traction but often feels better. My advice would be to try dropping the rear ride height 2 to 4 turns on the rear perches and see if that helps. Or if you are too low in the rear possibly raising the nose. Hope this helps, Cary

It's a nice concept but for the $12K asking price I'd rather have an enclosed trailer, although there are pros and cons to those as well. One thing I thought I saw was the video of one of these towing looked like the rear wheels were wobbling. If that's the case I wonder how the tires will deal as well as long term life of the trailer. One thing to keep in mind on many trailer tires is you need to keep the speed down. Many of them tend to get hot easily and wear, chunk, or generally shred themselves to death. Cary

I've never worried about side to side much on my car. It's more important to get the car balanced so it corners the same both ways, unless you have a specific reason to try asymmetry. I had a sports racer for a brief amount of time and it could be balanced side to side with ballast but I found that it worked better using the ballast for setting front to rear balance and allowing it to be uneven side to side. Even with same size tires front and rear it is better to have a slight rear bias if you can get it. As the power goes up you'll get faster running more rear weight and tire if you can add it. The Camaro is cool but it's like bringing a plastic spork to a machine gun fight. It's too big and way to heavy. There's already a really cool corvette that's built the same way (Sam Platt) and it's miles off the leaders times. But I'm sure it will put a smile on the owner's face and maybe that's all they wanted. Cary

Thanks Chris for sharing the setup and data. Very few have ever done this. best, Cary

Some sad news passed on from Chris Billings of the shock shop. On January 17, 2014, William C. Mitchell passed away suddenly at his home in Mooresville, NC. He was known to his friends as Bill. He graduated from CalTech in 1967 with a degree in Mathematics specializing in numerical analysis, or how to perform difficult calculations. This was followed with a Masters from Stanford University in 1969. His interest in auto racing began while watching a Can-Am race in Edmonton, Alberta in 1969. In 1972 he began serving as a SCCA flagman in the San Francisco region. He was soon working at 20 - 30 races a year up and down the west coast as well as the SCCA Runoffs at Road Atlanta. In the 80’s, he began covering races for the San Francisco Region publication, “The Wheelâ€. The race reporting soon expanded to the magazines, “Autoweek†and “Formulaâ€. He began following the Trans-Am series when Ford returned to professional motorsports in the mid-80’s where he met the engineers and team managers. Tom Gloy was driving Mustangs, Jack Roush was running a Mercury Capri for Greg Pickett, John Dick was leading the DeAtley Motorsports team of Chevrolet Camaros driven by David Hobbs and Willy T. Ribbs with Dennis Fischer building the motors. When IBM released a personal computer, complete with 5.25†floppy disks holding 360kb of data, he needed a project where he could learn to program on the new computers. He had heard of “camber curves†so decided to write a program about suspension. With the advent of affordable and portable computers, data acquisition began to be used by the motorsports industry. It was at this time that Bill began working on the Debrief series of data acquisition analysis programs. Bill is generally considered to be the first programmer to begin the development of serious data acquisition software designed specifically for the motorsports industry. In fact, many of the screen graphics and methods of analyzing data originally developed by Bill are still being used by virtually all of the current data acquisition software developers. This includes the basic algorithms used to construct an accurate track map. This led to spending the 1991 and 1992 seasons with Chip Ganassi’s CART team. The drivers were Eddie Cheever and Arie Luyendyk. The 1993 season was spent with the Roush Racing GTS effort where Tom Kendall returned to racing and won the Driver’s championship. In 1994 Roush and Kendall switched to the Trans-Am series and won three driver’s championships and several manufacturer titles from 1994 to 1997. In 1997 the Roush team won eleven consecutive Trans-Am races, marking the end of factory involvement. 1998 was spent with Huffaker Engineering in the Trans-Am. Bruce Qvale competed for Rookie-of-the-Year. In 1999 Bill worked with Bruce Barkelew’s RaceWerx team where Brian Simo finished second in the Driver’s Championship and GJ Mennen was second in Rookie-of-the-Year points. In 2000 he worked with Ruhlman Motorsports in the Trans-Am and DSTP in the Formula Atlantic series. The DSTP effort was limited to testing, but Buddy Rice won the Driver’s Championship with five wins in twelve races. Bill presented SAE papers at the Motorsports Engineering Conferences in 1998 and 2000. The 1998 papers were “Asymmetric Roll Centers†and “A Method for Data Alignmentâ€. The 2000 paper is “Training Test Drivers with Data Acquisitionâ€. This describes a training project with the Transportation Research Center in Ohio. He was still writing technical articles for Racer Magazine in their Tech Trek series. For over a decade, he was also a sponsor and judge for the Formula SAE competition. Bill's greatest contribution to the motorsports and automotive industry was the development of his kinematics (geometry analysis) software packages known as WinGeo3. Bill pioneered this type of software which allowed the user to study how a suspension system would move under dynamic conditions. Bill's Premier/Data WinGeo3 version allows the race engineer to download track data directly into the program, allowing the engineer to look at step-by-step suspension motion throughout each portion of the track. Bill was a visionary in that the development of this type of software was years ahead of any other kinematics software system. Aside from giving the race engineer intimate knowledge of how the suspension was moving, (camber, castor, bump steer, scrub, changes, etc.), it also allows the engineer to view and record side and rear view instant center motions, which, in turn, can be used to determine the proportion of forces moving through the suspension components versus the springy bits. Bill's software and his personal genius were never fully recognized because Bill was primarily interested in one thing -- the mathematics of motion. As the eccentric that he was, he had little time for promoting himself or his software; however, those designers who took the time to learn and use his software were rewarded with a one-of-a kind program that still outperforms all other kinematics software today. Many companies tried to copy Bill's software but none, to date, have come close to duplicating what his WinGeo3 programs can do. Once a user showed that they had put the time in to learn and use his software, Bill was always happy to tailor new software to their particular suspension system needs. As an example, a UK based race team running several BMW M3 touring cars wanted to analyze that car’s suspension kinematics but the factory race team indicated there wasn't any software that could do that type of analysis. Within a week, Bill had provided the team with a M3 WinGeo3 model. Bill never stopped working at improving WinGeo3 and had just recently developed a series of equations that would automatically change the length of the upper control arm so that the suspension system would maintain a constant moment arm length underneath the center of gravity throughout any realistic combination of ride and roll. This, in turn, produced very stable camber, caster, scrub motion, etc. throughout the suspension’s operational range. Bill was a mathematical genius who was able to retain very complex and lengthy algorithms in his head. He once rattled off 47 pages of hand-written vehicle dynamics algorithms completely from memory that he and two other people had developed over a series of weeks. Sadly, at the time of his death, Bill no longer had any living relatives. However, through the years, he built his own close-knit family of friends. He was dearly thought of and will be greatly missed by all who knew him. He will be remembered for his brilliance, gentleness and generosity.

Congrats. Would love to be able to get in a magazine some day. Cary

That's a great plan. I built a perfect tube frame replica of a bent car once. had thought since all the body lines were straight and the car drove nice it was okay. Always measure first. Never will make the mistake again. I'm also very curious about the panels and the roof. Would love to know how much weight that can drop. Cary

If you're looking for easy things to do to increase torsional strength try gluing in the windshield. We did that to a chump car to save a gasket and I was amazed at the change in handling. It was similar to what you'd see with a strut tower bar. For fun windshield related trivia, aluminium and glass have almost identical Young's modulus and density. Glass has a yield strength about 10 times higher than plain aluminium and obviously less allowable plastic strain. A 5 mm windshield is equivalent to an almost 2 mm thick steel sheet. Cary

Good to know. As others have asked did you measure down the length of the car? I measured a 510 years ago and with a strut bar it came in at a whopping 1500 lbs.

Seam welding is more for being able to fix crash damage. If the car is old and many of the seams are split you may see an improvement but I wouldn't expect it to help and now there's hard data showing that. My only complaint with your fixture is loads should be put in via the strut towers with the suspension. Take a look at this post for what I'm talking about. http://www.locostusa.com/forums/viewtopic.php?f=36&t=3241&start=75 Thanks for the work. I will do the same on my shell when it's done (240Z with full cage). Cary

It looks like you have the ducting covered. Forget the comments on the sharks teeth. Serrated gurneys were darlings in the wind tunnel but never panned out, although everyone had them on there cars at one point. In the tunnel they reduced drag by half at the same downforce level. For the splitter take a look at Loeb's Pug. Rather than a curved splitter blade you can run if straight across the front to gain more area for the pressure to work on. Since you don't have the SCCA 6 inch rule you can make it as long as you want. I'd guess 10 to 12 inches is about the max that would work. On the sides you can add fences, also like the pug. And then on the fenders you have add s-flaps. For the wheel wells my comments were to make sure there's no opening into the engine compartment above the splitter. On the top of the fender you can add louvers and all this should make the diffuser ramps much more effective. The ones in your image can get a lot larger. Take a look at some of the P2 DSR front ramps for ideas. Max angle is around 14 degrees. A more difficult to build splitter would be a large wing section for the front. On the ends use a foot plate so that it won't completely stall when it hits the ground. The Reynard inverter had a small version of this. A few older legrand DSRs have used this and needed to double front spring rate to keep it from dragging. The downside is a lot more work than a flat panel with some ramps. Perhaps an upgrade for the future. Hope this helps, Cary

In the January RCE there's some additional data from the Pikes Peak electric Toyota that is helpful. This shows the rear s-flap better but there's also a front one just as large. For your base setup I would cover both the front and rear tires so you don't see any tread from the front. Then for the flap you can have it extend at least one inch. For Max downforce more may be better and sharks teeth may allow that to work with less drag. For your splitter you haven't mentioned what is allowed in the rules. For more downforce you may be able to extend further out. A lot of the Pikes Peak cars in the open class use 10 to 12 inch extensions. You can also add end plates to the splitter to help. But getting back to max front downforce I think you'd want to first make sure the radiator is ducted and then seal the wheel wells. On top of the fender add very aggressive louvers and cut out the back of the fender. Search for time attack aero, splitter, fender vents, etc. and you'll get some decent examples. At this stage then you have enough low pressure to help drive splitter ramps (diffusers). And if rules allow you can make the splitter a large wing section and run footer plates on the end. From looking at a number of the time attack cars that are doing heavy CFD footer plates are starting to show up on them. Hope that helps, Cary

Let's be a little more civil towards each other here. I don't want to send you to your rooms but if you insist it can be done.

It depends on how you replace it but I'd guess somewhere in the 20 to 40 pound range unless you get really creative. This is assuming a 240. On a 280 you can probably double that number if you don't replace any of the bumper reinforcements. Not something I'd probably do outside of an all out race car. Cary

Thanks for the pic. I was trying to figure out if I could get away with mounts like that in SCCA XP where the wing would be reverse swan neck mounted. The rules specify the wing location but don't really talk about the mounts at all. For those interested here's a thread about the aero development of the red Z we're talking about. http://www.viczcar.com/forum/index.php/topic,9059.0.html Cary

Is there anymore info on the red Z in the pics? It looks like an interesting car. Cary