Michael Posted December 17, 2007 Share Posted December 17, 2007 Like all tools, CFD can be very useful in the right context, but otherwise becomes just another hammer. That context is a “tuned†setup where various configurations have been gridded and run through the code, with validation relative to experiment. Once such a setup is in place, it is straightforward and productive to make configuration changes (add spoilers, lower the ride height, block off the radiator grill) and so forth. The incremental effect of replacing air dam A with air dam B becomes believable. But until all that infrastructure is in place, all CFD answers will be clouded with doubt. The “ballpark†figure will probably be correct, but the increment between air dam A and air dam B will be smaller than the uncertainty in either of the answers. But as I’ve been mentioning elsewhere, car aerodynamics is actually harder than airplane aerodynamics. Much of the car aerodynamics business remains in the wind tunnels, while today perhaps the majority of airplane applied aerodynamics is done computationally. Computations are generally cheaper, so wherever the industry can get away with doing stuff on the computer, they will. There are many reasons for why the automotive world still largely relies on wind tunnels, but I think that the main reason is that numerical methods are so tough to “tune†to work for cars. So the bottom line is: CFD is not necessarily intractable for our Datsuns, but odds are that it will be easier, cheaper and more productive to stick with the wind tunnel. I still believe that we should consider option #3: testing scale models in a university wind tunnel. I don’t mean Franklin Mint 1:18 models, but 1:5 clay/wood models that we would custom-make ourselves. Here’s another thought: the Henry Ford Museum in Dearborn, Michigan has a beautiful display model of the 240Z, at around 1:5 scale. While that won’t work for a wind tunnel model, wouldn’t it be nice if we could make molds from that model? Quote Link to comment Share on other sites More sharing options...
Carl Beck Posted December 17, 2007 Share Posted December 17, 2007 I still believe that we should consider option #3: testing scale models in a university wind tunnel. I don’t mean Franklin Mint 1:18 models, but 1:5 clay/wood models that we would custom-make ourselves. Here’s another thought: the Henry Ford Museum in Dearborn, Michigan has a beautiful display model of the 240Z, at around 1:5 scale. While that won’t work for a wind tunnel model, wouldn’t it be nice if we could make molds from that model? Given the effectiveness we saw in the first wind tunnel tests, of blocking the air flow through the grill - and redirecting it elsewhere, we know that any 3D model would have to include a model of the engine bay so the air could flow virtually into and through it. (yes/no?). That is to say - we would need more than just the surface model of the exterior shape of the Z, if we wanted to compare results from the actual wind tunnel tests, to our virtual simulation or to a scale model in the physical world. With the Revell BRE Z Model Kit for example, you could build a fairly accurate engine bay, by scanning the individual component parts and merging them into the final 3D model. Building that model by hand in a 1:5 format of wood/clay, would be challenging at least. I would guess that an existing digital model could be easily scaled up to 1:5 then feed to a DNC and machined out of a block of relatively inexpensive plastic. That by itself wouldn't be cost prohibitive in todays world, once you have the 3D model. Lots of fairly accurate scale models of the Z's exist, and different component parts from those kits could also be scanned into a 3D digital format, then DNC'd and added to, or removed from, the 1:5 physical model. - the G-Nose itself exists in model kits - the Front and Rear Spooks and Spoilers are in Revells BRE 240-Z kit - the LeMans wheels/tires as well as the stock wheels/hubcaps With the above items scanned... you would have the 3D models for either CFD and/or DNC'd into the physical world - if you did both you would have at least a benchmark for validation of the results from either method. FWIW, Carl B. That desk top 3D scanner for $2,500.00 is looking better and better... Quote Link to comment Share on other sites More sharing options...
Mikelly Posted December 17, 2007 Author Share Posted December 17, 2007 I encourage all efforts and if someone, with the assistance of one of the HybridZ senior staff, would like to take on this effort, I'd be more than happy to sit on the sidelines. I'll be ther first to admit that I'm running thin on knowledge and time with many competing interests... I'll still plan for another windtunnel test come spring, and keep everyone posted on the donation drive... I WILL ask that someone else write the article. It was way to much of a strain on my time last time around. Mike Quote Link to comment Share on other sites More sharing options...
Daeron Posted December 18, 2007 Share Posted December 18, 2007 I have always had a feeling that a G-nose with a vertical wall going straight down from the front edge of the bumper would be a lot better than the standard G-nose that directs air to the underside of the nose. Just a thought... OTM My friend, you just described a porsche.... Quote Link to comment Share on other sites More sharing options...
Mikelly Posted December 18, 2007 Author Share Posted December 18, 2007 My friend, you just described a porsche.... It's kinda funny, because during the test I had the Porsche out in the parking lot, and Bob the windtunnel operator constantly referred to it when describing what we were trying to achieve. If I had all the money I've spent on Datsun over the years I could have bought a brand new 2007 Porsche GT2 and still had money left over for track days, and more time driving the car, and less wrenching it! Mike Quote Link to comment Share on other sites More sharing options...
OlderThanMe Posted December 18, 2007 Share Posted December 18, 2007 My friend, you just described a porsche.... Well if the monkey works... Let's do it... It's just reducing the amount of air we have to "push" in front of the car. In the mean time I've got to figure out what the problem is with our 944T P-car... It keeps getting MORE and MORE camber on the right front wheel!!!the Pcar's FR wheel has more camber than my Z's rear wheel when at full strut compression! I think the strut housing is bending below the cartridge. (car was once wrecked into a ditch...) Quote Link to comment Share on other sites More sharing options...
dimsum Posted December 21, 2007 Share Posted December 21, 2007 If I had all the money I've spent on Datsun over the years I could have bought a brand new 2007 Porsche GT2 and still had money left over for track days, and more time driving the car, and less wrenching it! Mike That idea is slightly depressing, especially for somebody who is just starting to dig myself into the pit. It doesn't help that I've always wanted a Porsche GT2. Quote Link to comment Share on other sites More sharing options...
tfreer85 Posted December 21, 2007 Share Posted December 21, 2007 I'm looking forward for the next test. Just let us know when and where and how much $$. Also would like more testing with the G-nose and non-standard G-nose front valance. Tyson Quote Link to comment Share on other sites More sharing options...
Daeron Posted December 21, 2007 Share Posted December 21, 2007 It's kinda funny, because during the test I had the Porsche out in the parking lot, and Bob the windtunnel operator constantly referred to it when describing what we were trying to achieve. If I had all the money I've spent on Datsun over the years I could have bought a brand new 2007 Porsche GT2 and still had money left over for track days, and more time driving the car, and less wrenching it! Mike BLASPHEMY! Not trying to offend anyone, but in my eyes NISSAN MADE THE Z-car to give us a car that we could pour our blood sweat tears and soul into specifically to BEAT those german pancake cars..... ..but, I must grudgingly admit, they *Have* been the perfect shape for aerodynamics for the past sixty years... so the comment from the tunnel operator isn't much of a surprise. MY REMark was intended to show that personally, I would rather retain the car's character than "perfect" the aero by making the changes mentioned. (as an aside, I am tickled PINK that the new skyline did so damn well in the nurburgring.... ) OTM: My advice on the 944: the crusher That idea is slightly depressing, especially for somebody who is just starting to dig myself into the pit. It doesn't help that I've always wanted a Porsche GT2. I wouldn't call it depressing at all.. In my eyes there are two kinds of race efforts. The "buy your car and take it to the track" mentality, or the "let's see how *this* works!!" mentality. It should be pretty easy to tell which camp I belong to... BUT, whatever camp you belong to, racing means bleeding out massive quantities of money. It's just like buying a boat.. B.O.A.T.== Break Out Another Thousand. /end offtopic discussion; if you wanna reply to me about my opinions about ferdinand's faster fuhrermobiles, please do it in PM.. Quote Link to comment Share on other sites More sharing options...
Carl Beck Posted December 21, 2007 Share Posted December 21, 2007 While there is certainly a lot to admire about Prosche in general, and in view of their wonderful history, I wouldn't envy a 2002+ Porsche GT2 when compared to a 70/73 Datsun 240-Z. I mean, lets say; here you are - "PORSCHE" - and you've dominated the race tracks and rally circuits of the world though-out the 60's with your wonderful 911... evolving it to ever higher levels of performance...hyping air cooled rear engined, boxer six's... German Engineering, nose to the grind stone, constantly sharping that perfect blending of form following function. You even come up with a mid-engined example, said to have even better balance.. the 914/6... Then a cheap little tin can from Japan, loaded with great looks and good design blows you off the road courses first year it's out of the box.. and beats you at the worlds most watched international rally in Africa the following year... Yea GADS.. what happened here!! Quickly you up your engine displacement in the 911.. and move out of the class those pesky 240-Z's compete in on America's tracks... so long C-Production...... Then 32 years later... you have a $180,000.00+ model that can beat the 240-Z on an auto-cross course.. WOW.. that is something isn't it !! I can certainly understand why "Porsche People" love their cars... matter of fact I was/am one of them... to this day I do admire much about the company and their cars. I sold my 67 911S about six months after I bought my first 240Z in 1970. On the other hand, there is just something so efficient about that 240-Z that greatly appeals to me to this day (solid design and engineering?)... and I'd personally feel like "the fool and his money being separated" ... if I had that 35 year old, $25K, 240-Z right on my tail at any auto-cross... Matter of fact, I'd be embarrassed to be placed in the same class... what does that tell you about the two designs? but that's just me... efficiency vs effectiveness... we can put a man on the moon or a rover on Mars - if you don't care what it costs... both were very effective... FWIW, Carl B. Quote Link to comment Share on other sites More sharing options...
username Posted December 21, 2007 Share Posted December 21, 2007 is there any chance of testing the removing of the drip rails from the a-pillar and roof line? i am considering doing this and was curious as the overall effect it would have on a car with a whale tail and kamari front airdam. thanks Quote Link to comment Share on other sites More sharing options...
Mikelly Posted December 22, 2007 Author Share Posted December 22, 2007 I actually think the drip rails might have aided in stabilizing the air. Bob Smith commented that removing them might not produce the desired result when considering the cost to do so... Carl, You make good points... We're comparing a current technology supercar that cost about $140K new vs. a 1970 $3400 car. There is no comparison. That said, an autocross is not where a Porsche Turbo or GT2 should compete. Using that as an analogy is a bit absurd. The only reason I brought up what the dyno operator said was because of the previous member's post about Porsche. "Let them eat cake!" Mike Quote Link to comment Share on other sites More sharing options...
Daeron Posted December 22, 2007 Share Posted December 22, 2007 The only reason I brought up what the dyno operator said was because of the previous member's post about Porsche. Mike Honestly... It was bordering upon foolish not to have noticed that and consciously set our goals on it sooner. Even an untrained eye can look at the porsche body style and tell that for the last 50 years theyve been on the cutting edge of aerodynamic design. Anyone who is truly after ultimate aerodynamic performance would do well to look at the vehicle, AND ALSO the design of the Subaru XT(6). A Breakthrough in Automotive Aerodynamics The extreme wedge body shape was possible due to the engine's flat horizontally opposed cylinder layout shared by all Subarus in 1985. Extensive wind tunnel testing was used to lower wind resistance and even "aircraft type" door handles were used that were totally flush with the outside of the door. You had to push a hinged panel out of the release mechanism's opening to open the door. Rubber spoilers before each wheel well opening doubled as "mud guards" but really acted to direct airflow smoothly past the tyres and wheels. The result was one of the most aerodynamic production car of its time with a coefficient of drag or Cd of "0.29". (all these are earlier cars; the first is a turbo' date=' hence the hood scoop.. The later, post 87.5 cars were smoother, but I couldnt find reasonably sized, decent quality images of the angles i wanted of any of the newer models.) So now, what conclusion could be drawn from this? Maybe we need to start swapping WRX engines and drivelines into our cars, shaving the hood bulge and the door handles, lowering it nearer to the ground, giving the front spoiler a smooth face to pass over yet still retain a proper duct opening to flow air where we want it, combining wheels, tires, and fender flares to make the wheel wells as seamless as possible.... oh, wait.... My friend, you just described a porsche.... Quote Link to comment Share on other sites More sharing options...
blackwidow Posted October 20, 2008 Share Posted October 20, 2008 I love whats happening here and as soon as my car is up and moving I will be doing some aero mods myself. But i like the lines and Cd of my other girl at the moment. .31 from the factory and easily into the 20s. I wish I was keeping it:biggrin: Quote Link to comment Share on other sites More sharing options...
fantagon Posted October 20, 2008 Share Posted October 20, 2008 I would also like to see a 2+2 in the windtunnel just to see the differences in aero between the 2 and 2+2. This would aid alot of the guys that race their 2+2's. Quote Link to comment Share on other sites More sharing options...
Rustyfriend Posted October 20, 2008 Share Posted October 20, 2008 I second that. It would be very nice to see some 2+2 data... Quote Link to comment Share on other sites More sharing options...
JMortensen Posted October 20, 2008 Share Posted October 20, 2008 I would also like to see a 2+2 in the windtunnel just to see the differences in aero between the 2 and 2+2. This would aid alot of the guys that race their 2+2's. How many guys are racing 2+2's really? In the US, they're not very common, and to race one is to immediately handicap oneself with a heavier car, so if given the choice the best move is to avoid the 2+2. I think the 2+2's are probably outnumbered 50:1 here by the coupes. With all that in mind, I can't see dedicating any time at all to them. It would be like Hybrid Z testing Z31's... Quote Link to comment Share on other sites More sharing options...
Tony D Posted October 21, 2008 Share Posted October 21, 2008 Many people get the horribly mistaken idea that the reason we run a 2+2 at Bonneville is because of some sort of 'aerodynamic advantage' produced by the longer roof and different hatch slope. Listen closely to the following statement carefully, all those who believe that, your world is about to be shattered: WE RUN IT BECAUSE WE HAVE TO FOR THE CLASSIFICATION (/PRO) IN THE RULEBOOK, NOTHING MORE That's the extent of the "2+2 Choice", we need to run a car with FOUR seating positions, and that is a 2+2. The Coupe runs in GT class, and goes just as fast as we do, but unfortunately since it's a coupe, it ultimately can only run in GT and MS classes. Whereas being a "Production Sedan or Coupe" allows us to run in up to 13 different configurations. It was purely a matter of 'most bang for the buck'...for $20K into the car (er....thereabouts, give or take...er, yeah...) we get the possibility of competing in 13 classes, as opposed to two. Two classes, I might add that car contested by guys like Bob Norwood in Ferraris, and crap like that. We went after a record set by a Z, and broke it with a Z. And then went to other classes. But there was absolutely no 'aerodynamic advantage' we sought by using a 2+2 over a Coupe. Does one exist? Doubtful. The speeds achieved by either car are identical according to SCTA BNI records. Personally, as curious as I might be about a 2+2's aerodynamics, and much as it would mutually benefit me to get data in that direction, I personally think it would be a terrible waste of resources to put a 2+2 in there and start fiddling on it at all. If you want a better aero package in the Z, or in a 2+2 Z, get an S130 which comes out of the box better and slipperier, and with less lift and drag than the S30 in it's best configuation! Just my .02 on the whole 2+2 thing. Quote Link to comment Share on other sites More sharing options...
Mikelly Posted October 21, 2008 Author Share Posted October 21, 2008 Thanks Tony for posting that. I feel your first hand, real world experience with your land speed efforts is extremely valuable to this thread, this category, and this subject. Mike Kelly Quote Link to comment Share on other sites More sharing options...
Tony D Posted October 21, 2008 Share Posted October 21, 2008 The whole focus of our effort was to break Nissans Record. We did so, and have been working on engine power ever since. Our eventual goal is to, after seeing that we have gotten as much speed out of the S30, to go with the S130 and then 'bump' the records using yet the next generation of Z Car. The numbers are startling, a F/GT in ZX form should easily be capable of the same speeds we have gone in F/GALT (173.325) simply due to the bone stock aero and lift figures being that much better. If someone has a coupe, go for it. That was kind of the reason for fighting so hard the last year over wether the G-Nose was a 'production option'...I had laid the groundwork years ago to try and keep the GS130 (2+2) classified as a 'Production Vehicle' like the GS30 currently is, so that this progression could occur. The Z31 is out. Period. It's already in the rules, they are classified as 'Jump Seats' and will run against a Porsche 911-Style Vehicle (GT or BGT Class). If they nix our bid out the gate as a Production Car in the GS130 Chassis...we will run a 2+2 simply because I have three of the damned things in my back yard that I've harvested over the years towards this eventual goal (Two Slicktops, and one Turbo...along with a spare slicktop roof for the Turbo). As much as I have a curiosity, I would rather the time be spent on knowledge gained on the front end of the car, that is where the gains will be made, and will be applicable to both models regardless. Frankly, anything more than rolling a bone-stock 2+2 in for a basic test to compare one to the other doesn't seem justified. And for the time it would take in the day to accomplish that...it's just not worth it IMO. Anybody wants to know about lift, we got wheelspin over 140mph at ElMirage after removing the small spoiler. We solved it by filling the spare tire well of the car with solid concrete and welding in a couple of pieces of rebar to make sure it didn't come out and start bouncing around. If you can figure out how much the concrete weighed, that was enough to counter our lift at 140+... How many guys in 2+2's are going 140+? Even more to the point, of the guys requesting information on 2+2's, how many are going 140+ to actually use any prospective information gained on rear lift should the data become available? And if (big IF)the numbers are large enough of a difference, who's going to make 2+2 specific modifications to maximize on this? It's diminishing returns in my book. Hey, if I won the lotto for $110 Million Lump Sum after taxes, we would set up a testing WEEK and have guys in to set up their personal cars as my 'thanks' to the site. Till that happens, wise utilisation of resources should dictate the testing regimen. Quote Link to comment Share on other sites More sharing options...
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