JMortensen Posted November 28, 2006 Share Posted November 28, 2006 Again, we have other threads for lift and downforce so we should keep this one focused. The one thing I'll say is that pressure DIFFERENTIAL is what is important, and if there is high pressure on the bottom of the hood, that will cause lift. Low pressure on top, also lifts. Combination of both lifts more than either would independently. Quote Link to comment Share on other sites More sharing options...
Tony D Posted November 30, 2006 Share Posted November 30, 2006 the frontal area is 17.78 sq. ft. per acad and the chassis pic. i traced the outline of the car and went down as far as the lower valence. add a air dam and i estimate a total of 20.7 sq. ft. depending on the dam used. hope that helps jimbo I missed this one earlier, wasn't looking really, but stumbled upon it nonnetheless. There is some Nissan information that is published on the S30 stating the Frontal Area is 22 Ft^2, so I would tend to put the estimations toward the upper end of the range, and nowhere near the 7 sq ft initially estimated. The radiator opening, meaning the radiator opening in the frontal bulkhead, not inclusive of the bulkhead, is right at 12" X 24" for almost 2 sq ft there alone. As mentioned earlier, choice of tires will impact Frontal Area (sorry wide tire guys), as well as choice of spoilers front and even rear if it sticks up far enough (sorry rad ricer guys...LOL). Curiously, during the dropping of the Cd of the S30 from the mid .4's to the high .3's, it is interesting to note that the G-Nose cuts the available opening for the radiator to slightly LESS than the area available in the radiator bulkhead. When watching the factory G-Noses, and not knock-offs, the tapered ducting formed by the G-Nose really lends credence that they were using the aerodynamic theories surrounding duct design to use a radiator opening as small as possible and still feed maxiumum air to the radiator at speed. I know my car runs 15 degrees hotter when the plate is up on the G-Nose, than when it is removed... There seems to be a call for "published nissan figures" for their early wind tunnel tests, and I will direct you all to the Nissan Coffee-Table book "280ZX" that was presented to dealers and buyers of the new 1979 280ZX. In the section of this book relating to aerodynamics the numbers are all published, as a direct comparo between what the Old S30 chassis and the New S130 chassis were doing. This is my source for the 22 sq-ft number (if I'm recalling correctly) and just about most of the rest. They have nice photos in there on smoke and yarn testing of both chassis. If nobody has this book, I can see if I can dig my copy out of storage and scan the pages if required. They have a nice sidebar (in grey) with the profile of the S30 in various form of modification, Stock, G-Nosed, Spoilered, G-Nosed-Spoilered-Bellypanned. They post information on each permutation in the sidebar. Hope that give you something to go on, "In Print From Nissan". Quote Link to comment Share on other sites More sharing options...
rudypoochris Posted November 30, 2006 Author Share Posted November 30, 2006 Good info! It was never estimated that frontal area was around 7 sqft. That number was the CdA. Now it is seeming that it is nearer to 8-9. We shall see! Quote Link to comment Share on other sites More sharing options...
bjhines Posted November 30, 2006 Share Posted November 30, 2006 Tony D... You have some experience with body modifications for all out speed... What have your experiences told you about the various available parts for the S-30 cars...??? Quote Link to comment Share on other sites More sharing options...
Sven Posted December 1, 2006 Share Posted December 1, 2006 Tony, It just so happens that very book arrived today. It's awesome. I got a few of the relevant charts and pics for you. You can see the many improvements added to the basic S30 design, a tidying up of details. I haven't found any yarn testing yet, maybe you're thinking of another book... one that I'd really like to see. Excuse the pics, I didn't want to break the spine scanning the book. I've been reading up on ducting design also, it is surprising how small you can make the opening if it's designed correctly for the given HX size. Anyway, on to the pics: Quote Link to comment Share on other sites More sharing options...
Tony D Posted December 1, 2006 Share Posted December 1, 2006 The neat thing I didn't realize is how much more developed the Euro Turbo Cars were in underhood airflow management. The S130 Turbos in Europe got no A/C, and had a plastic duct from the front end that had a special spoiler,right to the bulkhead opening. No way for any stray air to hit the bulkhead, it ALL had to go THROUGH the radiator. But yeah, that's EXACTLY the page I was talking about! i must have the yarn testing in another book. I recall it shows "rollovers" and some water testing, mostly in B&W, if it's not in that book, then I'm going to have a heluva time finding THOSE since I was sure it was in there and hadn't catalogged it in my mind otherwise (oops!) Quote Link to comment Share on other sites More sharing options...
Tony D Posted December 1, 2006 Share Posted December 1, 2006 Tony D... You have some experience with body modifications for all out speed... What have your experiences told you about the various available parts for the S-30 cars...??? The small or large spoiler for the rear hatch cuts top speed. The small spoiler everyone likes cut 3 mph off our Bonneville car at El Mirage on the 1.3 mile course. We ran back to back runs, only difference being we took off the spoiler. Went 143mph, and on the previous run had only made 140. Back end was a little "light" without the downforce. I think there are better, more modern spoilers that can have better effect than the "Old School" BRE spoiler, which was designed to be used at speeds basically limited to below the 140 range... After removing the spoiler and having traction problems, adding 300# of concrete or lead shot in the spare tire well did the traction trick nicely. Adding that weight really helpde our acceleration (now how's that for a contraversial statement? LOL) The Xenon Urethane front spoiler will fold under at speed (around 125/130+mph) if left black, unpainted, in direct summer sunlight at 110F... When you run over your own spoiler and pick up speed, you begin to realize some of this stuff shouldn't be on a car... Doing a "shed the spoiler" routine on a rookie certification pass can be very embarrassing, both to you and the tech inspectors who let the thing on the track in the first place...LOL (Big hint for lovers of urethane front air dams: REINFORCE THE OUTER EDGE WITH A 1/4" ROD SKELETON!) Most of the stuff everybody wants to tack on to the car puts us out of the Production Class, so we haven't been able to play with much more. I have seen a lot of the front air dams on V-8 powered cars there. One guy glassed in the whole front of his car with a spoiler that made the front end look like a freakin' snowplow! He couldn't break 155, even with a 380 Chevy with dual quads on a tunnel ram... Our G-Nose and Bellypan does nicely, though I am looking forward to the chance to run the S130 chassis in years to come. Like the chart shows, that body starts where terminal "production" development of the S30 stops. We are hoping the S130 2+2 will let us bump the production speed record at Bonneville to at least 175, just above where our F/ALT record currently is (173.325), and in ALT trim with the S130 radiator blocked and full pan to break 180. And of course any development done on the N/A car will be used on the Turbo when we go F/PS. Lots of irons in the fire, just have to nail down some particulars and get the vehicles properly classified, and then go racing. After we kick that pesky Honda record out of the 2 Liter G/PRO Class! Quote Link to comment Share on other sites More sharing options...
Tony D Posted December 1, 2006 Share Posted December 1, 2006 On the ducting note Sven mentioned, in small experimental aircraft going speeds above 140knots, it's not uncommon to cool the engines by using two Chevy Impala Air Conditioning Cores! Their thicker core is inefficient at slow speeds, but when you have air pressure from 140 knots coming at you, and then realize you only need an opening of 2X3" to supply more than enough air you place them far back in the structure, and make a nice, long tapered duct. Imagine taking your 1X2 foot radiator opening, and run a 7 degree tapered line from all sides forward. Eventually they will meet, but the faster you go, the smaller you can make that opening and still get FULL COOLING from the core. Looking at the cutaways from the front end air-management ducting of the #83 Electromotive Car you can see they used thick cores with small frontal areas, and then tapered ducts for the smallest opening facing forward. Liberal use of NACA ducting as well... Oh, to be able to do these things legally at Bonneville! LOL Quote Link to comment Share on other sites More sharing options...
Gollum Posted December 1, 2006 Share Posted December 1, 2006 I know my opinion doesn't carry a ton of weight around here (as is fair considering the caliber of engineering here on HZ), but I just figured I'd add in my .00002 cents. My 280ZX drives great at 80mph, and I've talked to people who go scared out of their wits when they took their S30 over 80 (not car extremist granted). The main issue I seem to have in my car is how the car tracks at those speeds. In the bay area there isn't tons of places with long flat roads (that don't have pot holes), so in the turns the suspension gets quite unhappy thus getting into the 100mph range gets a bit hairy. But I don't think the limits are aero related. And aren't the main differences between the S30 and S130 in the front end? I think the windshields are at slightly different angles but that's not gonna make the difference. I know this thread is mostly about surface area, and I'm gonna get there. Trust me. The S130 is longer as we all know, but it's also quite a bit wider. The differnce is obvious just sitting the the car. The width of the roof is substantial too, wich adds yet more area for the wind to hit. Yet, the S130 SEEMS to have much better aero, but really the main differnce seems to be in air dam design. And I personally see heat as a big issue in this discussion. If you're running a turbo motor there's more to consider than getting JUST enough air through the dam to cool the radiator core. We also now most likely have an intercooler and a super hot turbo that's baking the engine bay. And the more times we turn the air to redirect it the more drag we're creating right? IMO there seems to be ALOT more to drag than just surface space of the front end/windshield (though I'm loving the thread chris). We also have to discuss how hard the air is turning inside the engine bay in order to get out. The new Ford GT lets large amounts of air out of the hood area after is passes by the radiator. Granted it's an MR car it's a cleaver idea witch should help create downforce correct? Another difference in the S30/S130 chassis is the wheel wells. I honestly have no TRUE idea as to why one would be better/worse than the other, but the S130 has quite a different shape to it (though i've never seen them side by side, only both at seperate times with no rims). But I generally think that the S30 has more potential than the S130 in the aerodynamics department, simply becuase you aren't going to make a S130 smaller any time soon. Though the S130 might be cheaper to get decent CDa ratings out of, I still think the S30 has the advantage of being a smaller platform that won't hit as much wind to begin with (though it's obviously hitting that wind a lot harder). I don't know how understandable this post is, but I hope that maybe it will get somebody thinking, becuase that's what we're all here to do. On the underhood pressure discussion, regarding the S130, my hood will lift up if not latched at around 30mph. I don't think it has as much to do with over hood pressure as much as it does under hood pressure. It's obviously the ratio of the two, but the underhood pressures can be modified with relative ease when compared to the overhood pressures. And I'm sure a Z with various setups could yeild VERY different results from cowl tests. If you lower the car, put on a Gnose, ect. The underhood pressure should drop dramatically since not as much air is getting under the car to begin with. I could see myself being very wrong though Closing comment - Take this all with a grain of salt, as my opinion is only worth .00002 cent as stated by ME! Quote Link to comment Share on other sites More sharing options...
Sven Posted December 1, 2006 Share Posted December 1, 2006 My 280ZX drives great at 80mph, and I've talked to people who go scared out of their wits when they took their S30 over 80 (not car extremist granted). The main issue I seem to have in my car is how the car tracks at those speeds. In the bay area there isn't tons of places with long flat roads (that don't have pot holes), so in the turns the suspension gets quite unhappy thus getting into the 100mph range gets a bit hairy. But I don't think the limits are aero related. Gollum, that really sounds like more of an alignment issue, particularly toe settings. You can have touch-feely alignment, smooth tracking at speed, or a compromise. Quote Link to comment Share on other sites More sharing options...
Gollum Posted December 1, 2006 Share Posted December 1, 2006 I've had alignment check, and it's fine (also has new tires). I think the issue is probably old bushings causing funky things to go on under load. It could a number of problems though. But I've owned and driven 2 S130 2 seaters and both felt identical. Quote Link to comment Share on other sites More sharing options...
bjhines Posted December 1, 2006 Share Posted December 1, 2006 The S130 nose is more or less like an S-30 with a Gnose... much lower hood line.... much less air goes into the S-130 nose Quote Link to comment Share on other sites More sharing options...
Guest Mike Posted December 1, 2006 Share Posted December 1, 2006 I know you guys are speaking of higher speeds but I've had my Alpha 1 to 100+ MPH with no stability issues. Mine has stock suspension except slightly lower/stiffer springs. Once I install taller gears and an OD transmission, I'll post how it handles at truly stoopid speeds. It's not that I ever travel this fast. I just want my Z to be CAPABLE of it. Quote Link to comment Share on other sites More sharing options...
OlderThanMe Posted December 1, 2006 Share Posted December 1, 2006 the level of drag is not so bad because most of us have the power to overcome the drag that a Z has. It is the dreaded lift that is not fun. With my old suspension I had the car way too fast at around 120 (guage said 140:-P) and the car was about to fly. 6500rpms in a 1:1 4th gear with a 3.54 rear end and 215/60r14 tires. It was scary. With all my illuminas, 225f/250r coilovers lowered 2", and 225/60r15 tires I have taken it to about 90 and it felt more stable than 45mph with the older setup Quote Link to comment Share on other sites More sharing options...
naviathan Posted December 1, 2006 Share Posted December 1, 2006 My 81ZX I had in high school would pick the front tires up off the ground at 135mph. That is really scarey. Quote Link to comment Share on other sites More sharing options...
JMortensen Posted December 1, 2006 Share Posted December 1, 2006 So you're saying your S130 had 1400 lbs of lift at the front end at 135 mph? Why am I doubting this? Quote Link to comment Share on other sites More sharing options...
OlderThanMe Posted December 1, 2006 Share Posted December 1, 2006 :lmao: Quote Link to comment Share on other sites More sharing options...
naviathan Posted December 1, 2006 Share Posted December 1, 2006 Don't ask me. At 135 you turn the steering wheel in either direction without the car moving. Now whether it was completely off the ground or not I don't know, but the front wasn't moving. The factory air dam was broken off on the car. Looked like the PO hit a curb with it. Quote Link to comment Share on other sites More sharing options...
Zmanco Posted December 1, 2006 Share Posted December 1, 2006 OTM, do you have anything up front besides the stock valence? I ask because I had the same kind of experience as you (albeit with less HP) until I added the BRE-style spook. Made a HUGE difference at freeway speeds, and was even noticable to a smaller degree at 40 mph. Last weekend I was on a track and saw 110+ on the straight before braking. I had no issues with wandering, front end lift, etc. I know the spook isn't everyone's favorite front end look, but I think putting SOMETHING up front to disrupt airflow under the car should be a requirement for anyone who even gets close to triple digit speed in an S30. Quote Link to comment Share on other sites More sharing options...
OlderThanMe Posted December 1, 2006 Share Posted December 1, 2006 Now with the home depot lip... With the engine on the car it has about 2" of clearance. I just need to reinforce it and seal off the top. The car has 26" tall tires so lowering the car is not that easy. It is about 1" lower than in the top pic right now. Quote Link to comment Share on other sites More sharing options...
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