OlderThanMe Posted February 25, 2008 Share Posted February 25, 2008 Well I thought that I'd post about my thoughts for an aerodynamic first gen Z car. The goal for this theoretical car: 1. Street legal (lights, signals, wipers, etc...) and feasibly driveable for around town use. 2. Provide ample downforce in the 70-140MPH range. 3. Reduce drag to a minimal amount to increase the effectiveness of horsepower when a car is being run in a category with limited engine work. 4. Still look like a Z car when finished (no radical roof, front end, or rear end changes that alter the personality of the car) 5. Be affordable for most people (body shaping under $4,000 for DIY in a garage) I believe that the G-nose is an excellent starting point for front end enhancements but not the end-all "fix" to the lift/drag problem. In fact a regular Gnose may even make the lift problem worse without an air dam by acting as a funnel to cram air under the car. Here is an initial sketch that I never finished because I changed my mind about some things. (never erase designs...they could be good to look back upon) Now I do have some alterations that I will make to this design. The front end seems very good for a top speed car but may not provide adequate cooling and venting for a track/street car. After watching NASCAR for several hours and looking at the high downforce/low drag/high cooling concepts I have a few new front end ideas. I will address issues such as underbody airflow, wheelwell problems, front end treatments, hatch work, and other treatments to the car that will improve aerodynamics but not go too heavily into $$$$. Note, I am a Mecanical Engineering student so I am still working my head around many of these subjects but I have put many hours into reading about aerodynamics just so I could apply this to my aspirations to be a good all-around engineer. OTM Quote Link to comment Share on other sites More sharing options...
gnosez Posted February 25, 2008 Share Posted February 25, 2008 As an owner of a 240 w/ an aftermarket g-nose I found that by simply closing the gap from the nose to the radiator support wall made a difference in how the car handled in the 100+mph range. I did this right after the seeing the results of the wind tunnel tests. My nose did not have the OEM style funnel shaped inner piece that directs air to the radiator. At speeds below 100, I couldn't really feel a difference. From 100 to 130 it was doable but still a bit flighty in the front end. Once I remove the nose next week to put on the headlight covers, I will build a completely enclosed box to funnel air to the radiator (similar to the ones in Alan's great pictures from the '70s). I also plan on making a removable FG lower chin spoiler shaped like a "C" with a small leading bottom edge. This will give me a bit more downforce in the front but still allow me to drive the car on the street. It will be in the mode of the C4 corvette front lips that were recessed under the nose of the 89-90 versions. Without the ZG flares and with the 225s on the front I realize I will not be able to lower the drag effects from the sides of the front tires but I have no desire to go that route style-wise. Quote Link to comment Share on other sites More sharing options...
OlderThanMe Posted February 25, 2008 Author Share Posted February 25, 2008 GnoseZ, If I recall correctly you had a BRE style rear spoiler back at Fontana Village in 07. Are you going to retain it? Are you going to make ducts to your brakes through the lower chin or through the main radiator duct? Quote Link to comment Share on other sites More sharing options...
Pete84 Posted February 25, 2008 Share Posted February 25, 2008 What material are you considering? Fiberglass, urethane, sheetmetal? What school are you majoring in ME at? Haven't had to make the decision on ME or ME Tech. Quote Link to comment Share on other sites More sharing options...
m4xwellmurd3r Posted February 25, 2008 Share Posted February 25, 2008 I found this when I was trying to find a picture describing what my idea was From the looks of it, that would correct the problem that you're talking about, would it not? or maybe something similar to the BRE front spoiler? Quote Link to comment Share on other sites More sharing options...
HS30-H Posted February 25, 2008 Share Posted February 25, 2008 The goal for this theoretical car: 3. Reduce drag to a minimal amount to increase the effectiveness of horsepower when a car is being run in a category with limited engine work. Question: You mention a race "category" above - but can I ask what kind of category, under what sanctioning body, you envision such a car could run in, and be competitive ( especially as you mention "limited engine work" in the same sentence )? Such radical unhomologated body modifications will usually bump an S30-series Z up into a category or class where it is going to be less competitive. It would be akin to putting a Middleweight boxer into the Super Heavyweight division. Alan T. Quote Link to comment Share on other sites More sharing options...
HS30-H Posted February 25, 2008 Share Posted February 25, 2008 ................. Quote Link to comment Share on other sites More sharing options...
frank280zx Posted February 25, 2008 Share Posted February 25, 2008 Question: You mention a race "category" above - but can I ask what kind of category, under what sanctioning body, you envision such a car could run in, and be competitive ( especially as you mention "limited engine work" in the same sentence )? Such radical unhomologated body modifications will usually bump an S30-series Z up into a category or class where it is going to be less competitive. It would be akin to putting a Middleweight boxer into the Super Heavyweight division. Alan T. Welcome to the class of super cars a z could only keep up when you would do massive and massive work to engine drive line suspension ... well leaving not much to call a z. however hill climbs time attacks and track days would be fine! Quote Link to comment Share on other sites More sharing options...
gnosez Posted February 25, 2008 Share Posted February 25, 2008 I will retain the rear "BRE" style spoiler for now but realize that as I increase the front down force I will be in turn increasing the rear up force. My plan is not to make a very deep (read that as low to the ground) chin since road conditions, speed bumps and the like would make it near impossible to keep it from getting cracked. The idea to to limit within street-usage reason the amount of air getting under the car. If this was a track only vehicle I would mount expendable rubber strips to the air dam and sides. As to brake ducting, I will have optional ports on each side of the radiator duct should the need arise. The chin itself will not have any openings. And unless something else comes up I will be at the Tail again this year. Quote Link to comment Share on other sites More sharing options...
JMortensen Posted February 25, 2008 Share Posted February 25, 2008 I agree with Alan here. You should at least figure out what class you're going to plan to run in and then build to suit that class. As stated, classes that allow radical aero mods are likely to be fairly unlimited. The Z can still be competitive if you find some oddball series like the Open Track Challenge that John Coffey ran his car in. In terms of aero design, what you have looks fairly slippery, but I wouldn't be worried about slippery much at all. My own objective would be to get the most downforce out of the front end that you can. Getting downforce to match in the rear is fairly easy; just keep adding bigger wings until the rear keeps up with the front. Getting downforce in the front is the hard part. Think splitters, front diffusers, etc. I don't see a radiator duct at all. I'd put in a radiator duct and then either duct the air out the fenders or up through vents in the hood. Quote Link to comment Share on other sites More sharing options...
Tony D Posted February 25, 2008 Share Posted February 25, 2008 My 73 has a big flat spoiler like that on the front, as well as the whale tail on the rear. It's stable at speed. The radiator opening is in the standard spot, but you have to be careful of obstructions---the pictured license plate placement would affect my cooling. Hell, putting ifberglass teeth on the bottom of the rear bumper affected cooling, I had to Appalachianize it and remove every other tooth to restore cooling to proper levels. The opening is right at 2 sq ft, so a duct is critical to proper radiator function. If you duct it, and lay the radiaiator down ALA Z31, you can lower the front of the hood, and make is a bottom-breather, keeping that front end aero-clean. Quote Link to comment Share on other sites More sharing options...
johnc Posted February 25, 2008 Share Posted February 25, 2008 I agree with Alan here. You should at least figure out what class you're going to plan to run in and then build to suit that class. As stated, classes that allow radical aero mods are likely to be fairly unlimited. The Z can still be competitive if you find some oddball series like the Open Track Challenge that John Coffey ran his car in. Even in an unlimited category, there are still limits. It took massive amounts of engine work to get 320hp out of a NA 3L L6. I could have gone Turbo but that would have bumped me up one class in the unlimited category where I would be running against Porsche 944 Turbos, Supercharged Honda S2Ks, World Challenge BMWs, etc. Although it appears that my old car was a completely unlimited build, it was actually limited in many ways by a couple different sanctioning bodies. Quote Link to comment Share on other sites More sharing options...
Tony D Posted February 25, 2008 Share Posted February 25, 2008 Yeah...class rules, er...rule... Quote Link to comment Share on other sites More sharing options...
260DET Posted March 4, 2008 Share Posted March 4, 2008 In Competition Car Aerodydamics some tests were done on the NASCAR type boot/trunk lid spoiler, as to the effect of spoiler height and angle. For heights up to 160mm, angle up to 60 degrees. Not surprisingly drag increased in relation to height and angle in all cases, interestingly so did downforce. I can't reproduce the graphs provided but for my purposes with an occasional road car that will see some racing I've decided on a dual spoiler. That is the usual S30 type bobtail spoiler with an attachable more agressive plate for circuit work. The bobtail will give some downforce with little or no drag while the plate will give a lot more downforce with more drag. So the car will still look traditional but will have some quite effective rear aero. Quote Link to comment Share on other sites More sharing options...
OneSickZ Posted March 4, 2008 Share Posted March 4, 2008 I wanna know if a dirty car is less aerodynamic than a freshly clean and waxed car. LOL Quote Link to comment Share on other sites More sharing options...
proxlamus© Posted March 5, 2008 Share Posted March 5, 2008 OneSickZ.. the answer is yes... Airplanes can build frost on the wings and control surfaces at colder temps, close dewpoint spread and visible moisture.. the frost acts like sandpaper on the wing surface and creates TONS of drag and reduces lift on the aircraft.. in addition to weight. Mud and dirt stuck on the surface of a car will increase skin friction and drag. Quote Link to comment Share on other sites More sharing options...
JMortensen Posted March 5, 2008 Share Posted March 5, 2008 Mud and dirt stuck on the surface of a car will increase skin friction and drag. I don't think that's true at the speeds most cars can reach. The one case I've seen where a windtunnel tested it resulted in no difference between waxed and non-waxed. Large clumps of dirt sure, but dirty vs waxed at car speeds apparently makes so little difference that it wasn't measureable. This is from the Hot Rod magazine from 3/2007. Quote Link to comment Share on other sites More sharing options...
gnosez Posted March 5, 2008 Share Posted March 5, 2008 Back many years ago when I mixed paint for a Ferrari dealership outside of NYC, we carried a wax that promised a 3% increase in speed. The VERY small print noted that you could do 206mph using the wax instead of 200mph without the wax. Of course the catch was you had to have a car capable of getting to 200mph in the first place. Quote Link to comment Share on other sites More sharing options...
JMortensen Posted March 5, 2008 Share Posted March 5, 2008 Now that I think about it the wind tunnel in question only blows at 80 mph and then extrapolates up to whatever speed you think you'll be going. Maybe it would show if the air actually went 140 or 150... Quote Link to comment Share on other sites More sharing options...
proxlamus© Posted March 6, 2008 Share Posted March 6, 2008 Interesting.. Thanks Jon! Quote Link to comment Share on other sites More sharing options...
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