Mikelly Posted October 24, 2002 Share Posted October 24, 2002 Terry has the magical "Spot" figured out with his ride.... You too cna have it... Search the archives... Mike Quote Link to comment Share on other sites More sharing options...
brokebolt Posted October 24, 2002 Share Posted October 24, 2002 I read a lot of post for tons of good into but never reply. Here goes! I ran the black lawn edging material (mine was brown) for a summer. Excellent for making the car 'stick' at speed. Fuel economy went from 17 MPG to a gas gusseling 12 mpg when used as a conservatively driven daily driver on the freeway at 65 MPH. Unsure how much HP was sucked up, but I was unable to achieve the 120 mark on the cars speedo. Mike Quote Link to comment Share on other sites More sharing options...
260DET Posted October 25, 2002 Share Posted October 25, 2002 My car has a pan from the bottom of the front spoiler to the back of the engine. It is higher from the ground at the front than the rear. The theory for that is the venturi effect, where air is forced into a narrowing space it speeds up and loses some pressure. The front edge of the pan actually projects forward in front of the spoiler to form a horizontal splitter. That, in theory, reduces the amount of air flowing under the car. The less air under the car the lower the air pressure under there. When driving on public roads, the sharp edge of the splitter is covered with a piece of clip on rubber strip for safety reasons. Now I have only reached around 200kph (110mph) or so on the track but the car is rock solid with absolutely no nose lift. There is a bit more detail in what has been done overall, eg spring rates, rear spoiler, but basically thats it for the front. PS Nearly forgot. The bonnet has two air exit vents towards the rear. The reasons for that are to- reduce the amount of air going under the car, to spoil the airflow over the rear of the bonnet and so reduce potential lift there, and, as a engine cooling aid. Quote Link to comment Share on other sites More sharing options...
Mikelly Posted October 25, 2002 Share Posted October 25, 2002 Richard, Do you have pics of that...I'd REALLY like to see the splitter/ belly pan combo! Mike Quote Link to comment Share on other sites More sharing options...
260DET Posted October 26, 2002 Share Posted October 26, 2002 Originally posted by Mikelly:Richard, Do you have pics of that...I'd REALLY like to see the splitter/ belly pan combo! Mike Sorry Mike, someone has borrowed the scanner. But the setup is quite simple. Because the car is also driven on the road, the front air dam is mounted so that its bottom is a bit higher than the front (removable) X member. Which gives the pan a 'down at the rear' slightly convex curved slope when it is attached to those two items and to the radiator support (fixed) X member The splitter, as a horizontal forward extension of the pan, projects in front of the dam by only about 50mm (2") for road safety reasons. The setup is deliberately limited in its design for road clearance purposes eg the pan does not have downward facing lips along the two sides to better contain and channel air flow. One thing not mentioned before is that the adjustable suspension heights are set up to give just a bit of rake, about 20mm (3/4"). Quote Link to comment Share on other sites More sharing options...
Mudge Posted October 26, 2002 Share Posted October 26, 2002 Originally posted by brokebolt:I ran the black lawn edging material (mine was brown) for a summer. Excellent for making the car 'stick' at speed. Fuel economy went from 17 MPG to a gas gusseling 12 mpg when used as a conservatively driven daily driver on the freeway at 65 MPH. Unsure how much HP was sucked up, but I was unable to achieve the 120 mark on the cars speedo. Mike Not sure why your car would do that, I know a guy who hit 197MPH with about a 3200 pound race weight and around 490HP, Silver State Classic 1999 I believe. Quote Link to comment Share on other sites More sharing options...
kalium99 Posted October 26, 2002 Share Posted October 26, 2002 Richard, I would be interested in seeing that setup oneday. Quote Link to comment Share on other sites More sharing options...
Michael Posted November 3, 2002 Share Posted November 3, 2002 The idea of a rigorous test of the Z in a wind tunnel comes up from time to time.... I think that this would be nice, but prohibitively expensive. It’s not just a matter of renting tunnel time. You would have to build and instrument the model, figure out how to spin the wheels (pretty important), how to run the ground belt (very important), how to attach the various removable components (air dams, side skirts, spoilers,…). Figure maybe $300,000 for a decent model, $1M for a short test and maybe $10M for a serious test with multiple entries (pressure-sensitive paint, probe-rake traverse and maybe particle image velocimetry). These are only guesses, of course – but more likely than not, they’re on the low end. NASCAR, F1, etc. perform minor tweaks of proven designs year after year – and spend more. Just imagine the costs of starting from scratch. Big difference! Of course, reasonable qualitative information can be obtained from MUCH cheaper and simpler experiments. Not to toot my own horn, but that’s what I tried to do in my water tunnel flow visualization tests. But these tests are rather useless for vehicle design. At best, they elucidate general trends. As for belly pans and underbody tunnels, the short answer is that these devices have good potential, but only when many, many other factors are just right. It’s a very “peaky” design. As Terry and others point out, blocking off the flow in the front with a good air dam, altering the hood lip and front grill, and following up with a good hatch lid spoiler are a better compromise solution, because it works over a broad range of scenarios, even if it’s not the “ultimate” in performance. Quote Link to comment Share on other sites More sharing options...
Guest Anonymous Posted November 3, 2002 Share Posted November 3, 2002 Here's a link off the Washington Z Club site with a VERY in-depth discussion of early Z-car aerodynamics. Starts 2 feet in front of the car and talks about almost every inch from there to the back bumper...Pretty depressing compared to modern cars, but not bad when compared to 60/70 era domestics and some imports. http://zccw.org/Tech/Body/09-97EarlyZAerodynamics.html Twydog (Give me an air chisel and 135psi and that damn undercoating WILL come off!!!) Quote Link to comment Share on other sites More sharing options...
Guest Anonymous Posted November 3, 2002 Share Posted November 3, 2002 Anyone have any idea what some good software is used for aerodynamics analysis? Will any Computational Fluid dynamics software work (theoretically it should) but perhaps there's something more specialized Maybe there are some done on more of a plug-in basis for existing CAD/CAM programs. I'm sure it's more likely for the high end stuff like ProE, or CATIA if it is a plugin type application. (Hell considering the origin of CATIA I'd hope they have some aerodynamics specific stuff around for it). I doubt there's anything for the lower end stuff like Solidworks and Autocad somehow but ya never know, there's quite a bit of FEA stuff for Solidworks after all so why not some CFD stuff too? Quote Link to comment Share on other sites More sharing options...
260DET Posted November 6, 2002 Share Posted November 6, 2002 Originally posted by kalium99:Richard, I would be interested in seeing that setup oneday. Let me know if you ever are coming to Brisbane. But future changes are possible, there is a Haynes book by Simon McBeath, Competition Car Downforce, which looks interesting. It may be described on www.haynes.co.uk Quote Link to comment Share on other sites More sharing options...
ZROSSA Posted November 6, 2002 Share Posted November 6, 2002 260det, Dont bother with that book unless you know absolutly nothing. It was full of information , but its all general. We have gone into things in more detail on this site. Douglas Quote Link to comment Share on other sites More sharing options...
Drax240z Posted November 6, 2002 Share Posted November 6, 2002 TempeZ, there is CFD available for solidworks. Currently I am using the FlowWorks plugin, which is a pretty rudimentary CFD package, but VERY FAST and can give you some ballpark numbers without leaving your computer processing for hours at a time. The other one I highly recommend is Algor. Its not a plugin for solidworks, but it will import solidworks assemblies and parts without much trouble. It really gives some great results, and its dynamite for FEA as well. Honestly, I'd love to apply this CFD stuff to the Z, but I just can't find the time these days. If someone wants to do an accurate solidworks model of a 240z then I'll happily do the CFD analysis on it. Quote Link to comment Share on other sites More sharing options...
Guest Anonymous Posted November 6, 2002 Share Posted November 6, 2002 Well I'm afraid my skills with actually modeling aren't going to be sufficient to make an accurate one of a Z in Solidworks. Now if I had one of the 3d digitizer things I could probably make one off a franklin mint model or something. Quote Link to comment Share on other sites More sharing options...
Michael Posted November 12, 2002 Share Posted November 12, 2002 Just out of curiosity, what's inside the CFD code that runs "very fast" on a PC? If it's a panel method (vortex and source distribution, with flow-tangency boundary condition on each panel - and possibly vortex particles ejected at specific points in each time step, to simulate the "wake"), I would have to be skeptical. For an example of a state-of-the-art family of inviscid codes (tuned to mimic viscous effects), check out www.consultingaviation.com, or send them e-mail at cascd@mindspring.com – but please, don't mention my name. An erroneous answer is WORSE than a wild guess. A “ballpark” estimate can be worse than having absolutely no clue whatsoever – if the ball is in the wrong ballpark. And aerodynamics "improvements" based on specious analysis are likely to be worse than doing nothing at all. There's a reason that most cars have significant positive lift, and it's not because the OEMs are lazy or stupid. A real CFD analysis would be based on a full 3-D unsteady Navier-Stokes analysis. A full "direct numerical simulation" is currently not possible even with the best of computers and the best, most-motivated minds in industry and academia working on the problem, so we're back to the problem of turbulence modeling. I honestly have no idea what to suggest – what model to use. That doesn't mean that the problem can't be solved, of course - but it does justify tremendous skepticism whenever some one proposes a “solution”. Quote Link to comment Share on other sites More sharing options...
Mikelly Posted November 12, 2002 Share Posted November 12, 2002 Michael, Sorry I missed you while you were in town... Been too busy and had way to much on the plate all weekend... As to the comments made about aerodynamic modeling, I agree 100%. Way too easy to get caught chasing the wrong data in the wrong direction. Bottom line is that the car isn't the best solution for testing speeds above 150mph for sustained periods. The CD data available suggests that the car car suffers in several critical areas. Some data came out of Japan years ago that suggested some band aid fixes, like the G-nose and the solid headlight covers and winglets at the front corners... They helped some of the cars achieve sustained 180mph+ stability, but we're talking factory backed, full on race cars. In the end, none of us is gonna get the kind of monetary support to chase this dream down safely... Mike Quote Link to comment Share on other sites More sharing options...
kalium99 Posted November 13, 2002 Share Posted November 13, 2002 Originally posted by 260DET: quote: Originally posted by kalium99: Richard, I would be interested in seeing that setup oneday. Let me know if you ever are coming to Brisbane. But future changes are possible, there is a Haynes book by Simon McBeath, Competition Car Downforce, which looks interesting. It may be described on www.haynes.co.uk Actually...I live in Brisbane Quote Link to comment Share on other sites More sharing options...
Guest Anonymous Posted November 14, 2002 Share Posted November 14, 2002 Honestly I'd just be happy with a solution that made for nice even downforce up to 120 or so without hanging a big drag inducing whaletail or the like on the back. I do have some 4' sections of assymetrical airfoils that downforce once you get the correct angle of attack dialed in. They're pieces of a rotor blade for experimental/kit helicopters from rotorway intl. if you must know they were slightly out of spec to hold a bird in the air but plenty good for making downforce on a car just couldn't throw em away after all. Only have 2 of em so after making myself a rear and possibly chin spoiler that's it unfortunately. (Sorta like the Primadonna kit but that might look somewhat dated on the front) The problem with that route, is that they fall too much in the direction of the current Honda "Tuner" (as in tune the exhaust to sound like a rusty fart in my book but what do I know) scene which stinks, I've had em for about 7 years now and putting em on at this point would just make me feel like one of the vinyl clad with 500 horsepower worth of stickers crowd. In any case, I wouldn't think it would be too tough to implement, either mount them static or adjustable slightly to get it dialed in. I was thinking what would be really cool is to make them automatically adujstable. It could probably be done with just some sensors that measure the compresson of the suspension and either increase or decrease the angle of attack on the airfoil as needed. It probably would have to include some buffering logic so every time you go over a bump they don't sharply reduce the angle of attack, that could make for some good times. Might be fun and would definitely have alot of geek factor for bragging rights in any case. The only problem with using them is that I'm guessing that mounting them would have to be done fairly high in the back to get a decent amount of airflow to be effective, then again I might be completely wrong, the whaletales are effective if a bit unsightly and cumbersome. Quote Link to comment Share on other sites More sharing options...
260DET Posted November 15, 2002 Share Posted November 15, 2002 kalium99, call me on 3354 3204 if you want to have a look at the Zed. It is up on stands with the wheels off at present. Quote Link to comment Share on other sites More sharing options...
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