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Ok, I did my diffuser, I am attaching a link here to another 3RD Gen page instead of bombarding this thread with my stuff. The side winglets are next, then a splitter.
Dennis https://www.thirdgen.org/forums/fabr...ml#post5831417
Why not this?
http://www.ebay.com/itm/Universal-Rear-Diffuser-Kit-Under-body-spoiler-Increased-down-force-reduce-drag-/290660214214?pt=Motors_Car_Truck_Parts_Accessories&hash=item43acb2e5c6&vxp=mtr
Being the first one, there was some trial and error.
I had a sheet metal one made for patterns for $250, installed it drove it around, saw where it rubbed, modded it, then made a winglet template.
My biggest cost was 4mm carbon fiber sheet @$350.
I bought the tools to do this, and afetr i figured how to cut and trim the material, I saw a universal splitter on Craigslist someone was trying to unload for $150 OBO.
If there is a next time, I will buy even a used splitter and cut it up...LOL
I paid $60 to powder coat the pan and the angle pieces.
So lets add it up....
Template $250
Fiber sheet $350
Tools, blades, sanding block $75, the belt disc sander was a huge here.
Powder coat $60
Aluminum round stock $25
machine stand offs $30
$800 total, I have some stand off material left and a whole sheet of carbon fiber which i will work on the winglets and the side plates for a wing.
Could it be done cheaper, yes, after the learning curve.
the 30 x 45 piece fit so nice it was the nicest fitment i've ever had.
If you buy the 30 x 45 outright, and bought an old splitter this can be done pretty cheap, I'm buying up splitters in LA now, the material is a tenth of the price, it's your labor to make the fins, that's where all the work is.
I drove it this weekend, between the wing and the diffuser, the high speed uneasiness is gone, I'm going to try a 5 to 8 inch spoiler in the rear and try that out versus the wing, news at eleven... It's fun.
Dennis
Last edited by dennisschreuer; 10-20-2014 at 12:32 PM.
Reason: mis spell
Well since the OP is ME and you could easily ask him on his OWN TOPIC, I'll tell you I could notice differences around 45mph or higher. Just felt smoother, more stable.
I'll have one built, I'll have some pics, just be patient. I FINALLY have my third gen back, a 92 Z28. Looks like crap, and is crap, but it's perfect for this type of thing. I see what Dennis did and it's very nice and professional. Very impressive. Mine was nowhere near as polished, but what do you expect out of barn materials.
Here is the only pic I have. You can see some little fins between the exhaust pipes. Wreck was caused by a bent tie rod, not the diffuser, my mods. I'd offer a better pic, but this is all I have. So there. Pic. It happened. Blah. Leave it to you guys to take something and turn it into something bad.
Oh, and one more thing, if the car hadn't been slowed down by side to side drag, it would have killed me. So there, drag is a good thing if done correctly.
In September you said you had a new chassis and were going to have a mock up soon... and now you post with the same old crap you've been saying for a year and a half now.... I want results!!! Pics or GTFO!
I will, but you said you wanted proof I had ever made anything, and there it is. Don't know what you expect. Maybe you want one for Christmas or something? Figured I would wait until after the holidays to start working. I have the parts, pieces, the chassis, everything I need. I'm really just lacking solid motivation, and you're not really helping.
Nothing is 100% aerodynamic. Controlling drag is the whole point, yes it's "bad", but it's not ever going to be 100% gone anyway so reducing and controlling what drag there is can have an impact on handling characteristics, that's all I'm saying.
I AGREE,i thought you viewed drag as a necessary evil.if you could have zero drag(which is impossible) it would be ideal.
this guy blew the 300 mph barrier away IN 1999!!!
DETROIT (August 31, 1999) - At this year's Bonneville Nationals Land Speed Trials on the fabled salt flats race course in western Utah, the Kugel & LeFevers Pontiac Firebird entry driven by Joe Kugel became the first stock-bodied passenger vehicle to exceed the 300 mph land-speed barrier. "This is probably one of the last great land speed record barriers at Bonneville to fall," Joe Kugel said. "There's not much left after this. Since the mid-1980s, the big thing has been to exceed 300 mph in a stock-bodied car. There have been some Roadsters in the 290 mph range, some Ford Thunderbirds that have attempted it as well, and also a number of Pontiac Firebirds, but no one had been successful until we were able to do it last week. This is just a tremendous accomplishment for everyone who had a role in making it happen." Kugel Komponents is a family-owned business started by Jerry Kugel in the late 1960s. The company builds street rods which fits in nicely with their passion for racing at the Bonneville Salt Flats. "It's a great sport for us to be involved in," said Jerry Kugel, "because it's only once or twice a year and it's a lot of fun to do. It's also fun to be a part of a sport that showcases some of the products that we manufacture and market as well." The Bonneville Salt Flats are a natural formation that provide a smooth unobstructed course for high acceleration automobiles. The Land Speed Trials take place during the third full week of August under the auspices of the Southern California Timing Association, the official sanctioning body of the Bonneville Nationals The trials are conducted on a five-mile track with the actual speed averages computed beginning with the second mile. Speed averages are calculated from the two-mile marker to the three-mile marker, three-mile marker to the four-mile marker, and from the four-mile marker to the five marker. The average speed, and not the top speed is the performance number used in determining new records. Jerry Kugel first began racing at Bonneville back in the early 1960s after an initial visit that got him hooked. After watching the Mickey Thompson four-engine Challenger scream by at 400 mph, Kugel knew that this was something he wanted to try as well. The next year, he returned to the salt flats with a 33-coupe and he's returned almost every year since, primarily running Roadsters that he began building in the late 1960s. His sons Joe, 29, and Jeff, 27, started going to Bonneville with their dad in the mid-1980s. In 1987, in order to get a feel for driving on the course, they began racing a Model-A Roadster on a 32-frame rail with a small block Chevrolet engine. Between 1990 and 1995, the two brothers began running that same Roadster with a twin-turbo engine that is very similar to the one used in their record-breaking Pontiac Firebird, and were successful in eclipsing the 200 mph barrier. During the Land Speed Trials on August 18, the Kugel & LeFevers 1992 Pontiac Firebird ran an average speed of 301.709 mph in the fifth mile of the race course with an exit speed topping out at 307.468 mph. In order to secure the new record, the Kugel & LeFevers team would have to return the following day and run an average speed great enough in the fifth mile of the course so that their two averages would give them a mean number above the 300 mph barrier. "What makes it so tough to do at Bonneville is the fact that anything can happen from one day to the next," said Jerry Kugel. "We ran great on the first day, but who was to say that conditions wouldn't change to where we would lose a decent shot at the record. The weather could be different, there could be a strong head wind, or the course could change, you just never know." On Thursday, August 19, the weather and track-surface conditions at Bonneville cooperated. The Kugel-Lefevers entry ran an average speed of 299.866 mph for a two-day combined average of 300.788 mph, making their 1992 Pontiac Firebird the first production-based stock automobile to break the 300 mph speed barrier. It was an emotional triumph for the LaHabra, Calif., Kugel family and their partner Mike LeFevers. "The key to keeping the car on the ground at those kind of speeds is its weight," explained Jeff Kugel. "Downforce works up until a certain speed, but then the car starts going so fast through the air that the aerodynamics have it almost flying. What keeps it on the ground is its weight. You're okay until about 280 or 290 mph, but when you hit 300 mph the wind tunnel tests on this car say it should be air borne. But the car is heavy enough that it stays glued to the surface. Even at 307 mph, the Firebird was showing absolutely no signs of getting light on the front. "We also run the stock rear spoiler from a 1990 Pontiac Firebird on our 1992 car because we feel that is the best spoiler that Pontiac has. It's not an aftermarket spoiler, it's an actual stock rear spoiler and it's the one that starts on the glass itself and goes all the way around the deck lid." In addition to the C(368 cubic-inch engine)/Blown Gas Altered record they now hold, the Kugel & Lefevers team holds the C(368 cubic-inch engine)/Blown Gas Coupe category record which is also a production class. The speed record in that category is 295.859 mph. "If you're going to go 300 mph in a stock-bodied production car at Bonneville, the car of choice is a Pontiac Firebird," said Joe Kugel. "Out of all the production cars, it probably has the lowest drag as far as aerodynamics are concerned, and at 300 mph, this Firebird has to be the most stable vehicle that's ever been built. "When you move up in power, and get into that 8000 rpm range you are literally nailed to the back of your seat. That's when you know that you're going very, very fast and everything is happening very, very quickly. You'll be watching the tachometer, feeling the engine at about 6000 rpm, and all of a sudden it shoots to 8000 and you think the engine is just going to explode. When the turbochargers kick in, it only takes a split second for everything to happen, so you really have to hang on." The Kugel & LeFevers Pontiac used in breaking the 300 mph speed barrier is a 1992 Firebird purchased from fellow Bonneville competitor Dave MacDonald. It utilizes a Mike LeFevers, Mi-Tech small-block gasoline-powered 368 cubic-inch Chevrolet engine with Hillborn electronic fuel-injected manifold, and Turbo-Garrett turbochargers. "When Dave owned the car he had an exit speed of 295 mph," Joe Kugel said. "He felt that the car picked up in the front, felt light and the situation got somewhat hairy. Knowing that information and finding out everything about the car enabled us to make the necessary changes to get the record. We made it heavier in the front and we stiffened the suspension in the back considerably. We put much stronger springs in the back with shocks that are more stiff. Sometimes with the heavier weight on the back, these cars have a tendency to 'squat' at high speed and that's something we've been able to avoid. "This Firebird made six runs during the week with three of them over 300 mph and we didn't have to replace a spark plug. That just shows the great work that Mike (LeFevers) does on these Mi-Tech engines. Dave MacDonald and Lionel Pitts sold us the car and we want to give them a lot of thanks as well. We not only got the car but we got years of research and development that they insisted we take along with it. That information told us how the car behaved and reacted under certain conditions and we couldn't have done it without them."
Reading through this thread is amusing. There are a lot of factors that come into play with aerodynamics... half of them were not even mentioned and frankly it’s to detailed to attempt to explain on here .. I have built a few in my life for a hang full of cars, most of which are American iron series cars. The one on my 3g starts at the rear axle and extends past the bumper by 2 inches, it’s also as wide at the body , and it’s blown
Hey, Looks very nice! Thanks for adding to the conversation, bringing this back up has got me thinking about some other ideas I had back when i was into making stuff like that. My original stance on the issue hasn't changed. Maybe somebody didn't understand what I was trying to say, but I don't think that the sum of aerodynamic theory can be boiled down to simply eliminating drag.
1. I'm not talking about only drag racing where straight line coefficients are the only things that come into play.
2. The car is not a razor blade and will have drag no matter what you do.
3. We must consider all the directions air will hit the car in a typical* driving scenario
4. We must consider how we want the coefficients to change as the direction of air changes.
In marrow's car and in my old one 2 purposes were served, baffle effect caused by the rear bumper and the empty spaces in the muffler / fuel tank / rear diff area were streamlined and eliminated (eliminating the hated drag), and the air expanding as it exits the bottom rear of the car was channeled through the fins also eliminating a source of turbulence.
To simplify an already simple concept, consider you're not simply driving in a straight line, as you cut a corner air impacts the side of those fins and creates drag that resists side to side motion, like if you were spinning out of control, the extra drag created there would slow your spin ( do the math to figure out how much). The shape and position of the fins or whatever ground fx determines the amount of resistance at whatever direction air is hitting it. So for example bigger fins would increase the amount of resistance to side to side motion and in theory help increase straight line stability or the ability of the car to correct itself. Too much and air could be bouncing off the sides and in between and cause undesirable effects. There's a lot that goes into it, air is a fluid, it behaves in odd ways sometimes if you're not careful, so above all else, control is the primary goal right?
Flame away! You can complain all you want but I know my science.
Edited to add this:
It's sad that when I started this thread quite a few people were interested in buying one, morrow's was made of cardboard and paper at the time, and the world was so full of possibilities. It brings a little tear to my hardened, forum surviving eyeballs. Yet, I'm still here, and my goal hasn't changed. I've always considered setting up some molds so I could make a few of these. It really was the first real fabrication project I ever did and it just surprised me how much of a difference it made. Even a normal everyday street car could benefit from these, the area is covers is just so large and cavernous. Much time has passed, but I've grown wiser, and taller, and longer too. Anyone who is dedicated like I am would still want one today as much as back then, so what difference does it really make? Can you blame a man for defending his work, especially when nobody had even seen it! I got a little laugh reading through from the beginning, but the ideas and concepts and contributions from others drowned out whatever else was on there. I'm no expert, I would prolly get people killed to be honest, that's what's so great about money orders. Mexico isn't that far either.
But hey now years later I've got a fairly capable little shop in my parent's basement, a mill, a lathe, mig, stick, tig, wig, big, lig. If I was going to make them to sell it would be one solid piece, probably some kind of fiberglass or carbon fiber. If I could I would make them out of ABS, but maybe there's an alternative there I'm not aware of. I thought the weight of mine may have been too much.
So I'm accepting money orders and check on delivery, you can place your orders in my PM. Units priced per 10, see price in checkout. Not available in Alaska or Hawaii. Certain restrictions apply. This is a paid advertisement. Do not stop taking until you have spoken with your doctor. May cause cancer. This product contains compounds known to the state of California to cause cancer. Do no take this product if you are pregnant or may become pregnant. Contains carbon monoxide. Diffuse responsibly.
i think even black delrin/plastic for the lower fins,a sheet of powder coated,clear coated(or even painted)aluminum to bolt to the car bottom,possibly aluminum angle to hold the delrin wings so they can be mounted,
moved,replaced easily.im also a machinist and have a pretty snappy imagination and come up with quick solutions on the fly.i think i may attempt one once i get my umi adjustable pan-hard,umi adjustable torque
arm,umi sub frame connectors and new exhaust on my car.i could probably come up with all the materials i would use for free from work and even build it there(metal brake,cnc mills ,lathes,mig ,tig etc)
mine whas designed for over a years, i studdied aerodynaics for 2 years befor that. my diffuser literaly covers the entire rear portion of the car to the axle... entirely
that does look cool,i wonder what effects tapering the outside(left and right)fins to match the body cladding would have aerodynamically?
those of us with non-100% track cars are a little more concerned about esthetic things . it would look insane if it didn't stick out so far outside the
profile of the rear bumper cladding on the left and right side.maybe even six fins instead of 8 might have little to no effect because the extreme
outside left and right fins are directly behind the path of the rear wheels anyway,but what do i know.im just thinking of a usable thing that fits the
profile of the car as well combining form,fit,function AND esthetics.it looks sick regardless and im not criticizing,just thinking out-loud.
Last edited by 1986BANDIT; 10-08-2018 at 05:48 PM.
looks like a great start,i always liked the clean look without the body package like the formula and your car as well
to answer your question about tapering the side flaps in wards.. it would create a high pressure zone behind your rear wheels resulting in lift .. causing you to loose traction and downforce.. technically the should be tapers our ward starting at a Serrano width and getting wider towards the rear. Also each (fin) or flap... should never be straight.. they should always have a slight curve out ward with the but never more radical that the next. It should be progressive and a little more radical then the last . Now this goes for the assumption the it’s made from flat surfaces... this changes if your using (fins) that consist of an air foil... then you can use straits but it is still more efficient to curve them.. the reason it needs a curve is because air has a hard time attaching to flat surfaces. If it can’t attach to the surface of the (fins) then it becomes turbulent witch is the opposite of what your trying to achieve... turbulent air creates a high pressure zone under the car (bad) . By curving the surface it slows air to attach itself and by doing this it speeds up creating a low pressure zone... resulting in downforce... if you have a high pressure zone on top of the car.. and a low pressure zone below the car... you have just created downforce... 🤙🏻 THE ONLY USE OR JOB THAT THE FINS HAVE... are to hold more air( control or direct more air) THATS ALL... THERE NOT FOR HELPING STAY STRAIT LINE A TAIL ON AN AIRPLANE.. the surface area is not large enough to control a 3,000 pound car. HOWEVER!!! The faster and cleaner the air can travel, the more downforce you have which will result in more mechanical grip as well as a more stable car
thanks,i never really dug that deeply into it.i just got back into the third gen game after 10 years of being toy free and the more i learn,the more i like.
your car is undoubtedly cool and looks fast sitting still,i love the carbon fiber front lip,im guessing you made that as well?
good call,if i had a decent road course/track close by i would probably gut and cage my car and go all out.i really like the louvers you have,i want to actually incorporate the stock gta vents into my fiberglass cowl hood or maybe something like the new camaro/vettes have.
We could characterize the comments in the thread in a lot of different ways. The most important thing is that it all remains civil, and reasonably respectful of others' opinions whether they are substantiated or not. As long as that continues, opinions are free.
So, as long as opinions are still allowed...
The "proper" and "accepted method" for this kind of work would require wind tunnel testing with inertial data collected at numerous points, computational fluid dynamics exercises, and numerous man-hours of analysis of the resulting data. However, consider that Lilienthal, Curtiss, Bleriot, Langley, and the Wright bothers did not have wind tunnels, did not have CFD software (nor even the base calculations to perform by hand), and did not even have instruments to check density, pressure, flow, and velocity. They DID have an understanding of the concepts, and if they had not experimented we might just now be playing around with biplanes and dreaming about enclosed fuselages.
That's no different than the wing I installed on my race car. No wind tunnel testing but it's built using known dynamics of a rear wing. Is it too long, too short, is the wickerbill too high or too low? Are the side plates doing anything at all? Don't know, but the idea of providing increased downforce at the top end of the track is all I was looking for plus the wing looks really nice on my car. Lots of fast cars out there without a wing.
That front diffuser looks nice but I'd rip it off going on and off my trailer. I think one speed bump, pothole or raised manhole cover would do the same thing. Track only car, sure. Driving on the street with that? I don't think it would last very long.
10-17-2014, 05:25 PM
It's fun.
