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Ford Escort ZX2 Aerodynamics
I'm starting a new thread here that will handle the aerodynamic aspects of my car exclusively :)
Here is some data on my car: Stock Cd - 0.33, Ford ZX2 Automatic (2000) Frontal area - 20.8 square feet, Ford ZX2 Automatic (2000) Stock CdA - 6.9 square feet, Ford ZX2 Automatic (2000) Stock Aerodynamic Resistance @ 62 m.p.h. - 15.8 kW/21.3 HPR, Ford ZX2 Automatic (2000) Pretty good numbers for a 1998 car, but not good enough for us! |
So far, I have added the following mods:
Wheel covers; the side skirts and air dam are no longer on. http://s26.postimg.org/ed3u7qn4p/1117142225a.jpg Foglight hole covers http://s26.postimg.org/gkd3b6yah/0125151800b.jpg http://s26.postimg.org/lkajj53x5/0125151800c.jpg Front belly pan http://s26.postimg.org/3rjfd6yzd/0415151306a.jpg Rear belly pan http://s26.postimg.org/ygw3sqc2h/0415151356.jpg Windshield wiper cover http://s26.postimg.org/kohox3lax/0415151357.jpg 85% grill block http://s26.postimg.org/hrlh5c0pl/0415151229.jpg Fender skirts http://s26.postimg.org/bfqjjymxl/0421151616.jpg I do plan on making new fender skirts that extend to the rear bumper, as some members have. The sharp edge will promote cleaner separation. |
I am planning on a kammback and eventually a boattail :)
Here is the template overlay - http://s26.postimg.org/sp208zixl/Aero_Template.jpg For the front :D http://s26.postimg.org/it5in32jd/Aer...late_Front.jpg I doubt that this is the proper way to go about a vehicle's front aerodynamics. I do want to improve the front aero, if possible. |
How is the wiper arm shield mounted?
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Below the wipers, it is a tight space so it was originally wedged in place. A day of brutal crosswinds made me rethink that lol ;) now it is held down with a few pieces of Gorilla tape.
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Aerodynamic & rolling resistance, power & MPG calculator - EcoModder.com
I have been doing some playing around with this calculator. If my efficiency numbers check out, then I may have dropped my Cd down to the 0.28-0.29 level! That is awesome to me! |
Is it fixed to the hood or the cowl?
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With more weight reduction, LRR tires, a Cd of 0.19, a drivetrain efficiency of .90 for a manual swap, and 77* air puts me at 70-80 mpg for my usual drive speeds of 45-50 mph (theoretically) :)
Aerodynamic & rolling resistance, power & MPG calculator - EcoModder.com |
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A picture may help to explain it better. I'll get you one tomorrow! |
reverse-template
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What we don't know,is if we can cheat on the windshield.If we can't,then the angles of the glass would make it impossible to see out of the car. 'Elliptical' bodies have the same drag as teardrop bodies,for the same fineness ratio,so I don't think you can hurt anything by extending the front.The pro's might say that you're creating undue additional skin friction. Testing would tell. |
45-50-mph
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GM did have tires with something like 60% less rolling drag than conventional steel radials of the day.I suspect that this gap has closed since 1991.:) |
Freebeard -
http://s26.postimg.org/5laq7vue1/0502152305a.jpg Here is a picture shoing how the deflector fits on my car. It is rigged pretty badly lol. I plan on having a more permanent one soon. |
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I have thought about doing a second windshield similar to what basjoos did on his aerocivic. He said in another thread that while he didn't have exact numbers, it did help improve his coasting distance. With a car as light and as aerodynamic as his, I am guessing randomly that his Cd key have dropped close to 0.15. http://s26.postimg.org/nqnolxtw9/aero0a.jpg What exactly do you mean by cheat the windshield? I do plan on extending the front. I need to lower the stagnation point so air can flow over the Top, rather than under my car. I probably won't extend it to match the template... If I did, LOL |
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That is great news, aerohead! So I could be looking at having a 100+ mpg car if I max the aero out. Just the motivation I need :D It is good to hear that my frontal area will not differ very much. I was concerned that it was already a penalty to overcome. What I do have planned to help lower FA is the give the ZX2 a Probe IV treatment. I plan on lowering just the front, and maybe lifting the rear 0.5-1" ONLY if it would help aero. I suspect the same as well. Sounds like they had RE92s haha. I plan on going with them as my next set of tires, unless there is another tire with lower LRR. |
I had not seen the windshield aerocivic added. It looks hard to see through. Here's my own attempt at kicking out a windshield:
http://ecomodder.com/forum/member-fr...how-sketch.jpg |
I find your attempt rather awesome freebeard! Was it just an "attempt" or did it have permanent merits?
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http://ecomodder.com/forum/member-fr...0-100-0632.jpg
I've gotten this much further. But the drawing and that picture don't show the boattail very well. http://ecomodder.com/forum/member-fr...7-100-0623.jpg The boattail is full length to the reverse camber, or could be truncated to a 45° angle at the solid bulkhead or the original vehicle length at the open bulkhead. The redwood strip version could be made with flexible sheets in simple curves. The sides flat but twisted and the center one bowed with curved edges. If I built the photoshopped front end instead of a bubble (as suggested by the highlight), there would be three flat pieces like the Shalaho or Grumman post office trucks, but the center piece would be a hexagon with the side triangles following a line that sort of folds over the edge. I should document that. Here is is before being 'hexagonized': http://ecomodder.com/forum/member-fr...windshield.jpg Can you see how the angles on the hexagon would be about where the quarter panel ends? With the bottom edge the width of the spare tire, it could fit on an unchopped front valance. The current plan is to leave the front as-is with a flat aluminum bar bridging across the two horns that are what's left of the quarterpanels, with headlights hanging from it. It will have a Superbeetle gas tank where the back seat used to be. I'm backing off from the electric motor conversion. The next round on the boattail will be in a material called Omega-Panel. The pontoon fenders are also further defined but not documented. |
Simply awesome, freebeard :thumbup: I can't wait to see what this thing looks like when finished!
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We talked about me again. I'm sorry. :(
So, '57 Mercury Turnpike Cruiser style rear skirts? Have you seen bubble skirts? https://www.google.com/search?q=bubble+fender+skirts What about the front? skirts or air curtain? https://www.google.com/search?q=bmw+air+curtain Edit: Just found this on http://ecomodder.com/forum/showthrea...rts-28821.html http://i855.photobucket.com/albums/a...1/P1010111.jpg |
cheat
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http://i1271.photobucket.com/albums/...Untitled13.jpg http://i1271.photobucket.com/albums/...Untitled12.jpg ------------------------------------------------------------------------- With respect to 'reversed' bodies,there is zero wind tunnel studies performed with 'mutilated' forebodies.So we don't have any knowledge about what happens if we disturb the contour of a reversed body to create a 'working' windshield. If it turns out that we can't,without raising drag,then Hucho would say 'fuggetaboutit', 'cause,the distortion of the radically-raked windshield would be too great to see through.:( This Citroen Karen would be impossible to see out of http://i1271.photobucket.com/albums/...titled15_3.jpg |
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I did not know bubble skirts even existed till you posted this. I don't know about them... wouldn't you want to fill the frnders till they were flush with the body, instead of "bubbling" them out? It seems like a recipe for slightly increased frontal area, along with being not as aerodynamic. I'll wait for you to prove me wrong :D Edit: I did some more reading and they appear to be pretty aero friendly. About the front skirts: You're link is extremely interesting! I did not know about air curtains. They may be too hard for the average lay person to do correctly, as you would almost need a wind tunnel to see the effect. I have a plan on solid front skirts, similar to basjoos's. In fact, his Aerocivic is my inspiration for continuing aero refinement. First thing I would have to do is obtain skinnier rims with a higher offset. I am wanting to run 14x4 spare wheels with my tires, which would set them in a good ways. I eventually will run 165/65r14 Potenzas. Then, I want to build an aluminum frame to match the body contours, and use coroplast for covering. This will be hinged at the top, and I will have rollers on the frame. Inside the fender well and on the frame, I want to place rare earth magnets so that there is no chance of a strong side wind pulling them out while driving. Quote:
This "optimized windshield" seems to have a steeper angle than my own. I wonder what penalties there are with a more layed back windshield like mine. Is there a certain way the windshield is shaped that is not shown in the drawing? It would make sense if the windshield pictured was pointed in the middle to redirect air to the sides. I agree that the Citroen would be hard to see out of, and its rear aerodynamics leaves much to be desired. I am curious to know what benefits there are with a working windshield. I have thought about building a platform, if you can imagine it, on top of my hood to relax the sharp angles from it to the windshield. I'll post a picture of what I mean to ease confusion :thumbup: |
Here is a quick mock-up of front skirts and a complete rear boattail. The length will be 20-21 feet overall, not counting the extended front end.
http://s26.postimg.org/71wt3mqvt/Aero_Template.jpg FOr the front, I had the idea of adding a nose on. The length is a bit much, but I wanted to relax the angle going to the hood. The black on top of the hood is the "platform" to shorten my windshield. I do think it may cause visibility problems if the height is too much. http://s26.postimg.org/scud7w909/Aer...late_Front.jpg Here is a link to a new sheet of MPG calculations using the Aero & RR tool. I have adjusted it to theoretical numbers that will come to pass... one day;) I put in numbers that would reflect having lost weight, having Potenza's, lowering, complete aero mods, lean burn, turbocharger and a manual transmission. I would be ecstatic if I could really break 125 mpg between my usual 45-50 mph :D Aerodynamic & rolling resistance, power & MPG calculator - EcoModder.com |
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http://ecomodder.com/forum/member-fr...70-imagesa.jpg You could get a low-tech peek at the performance on a freeway in the rain. I'm always watching other cars front wheelwells there, but I haven't seen one of these BMWs. Quote:
Magnet hold and then let go completely. Bungee cords will release and then increase tension. I propose a four-bar arrangement for the front skirt. Nobodies made one yet. http://ecomodder.com/forum/member-fr...2-11-13-05.png You have to imagine the pivots into place, until I make a better drawing. They could be done in 1/4" steel rod and follow the contour of the wheelwell. The two top bars are connected together so that any tendency to rock front to back is damped. Or it could be clamped in the center and be a torsion springs to hold it closed. You want the front skirts to be bubbles, so you can turn the wheels a bit without invoking the skirt. But it's there for sharp low-speed turns and parking. _________ Your side view looks reasonable. Extending the nose isn't really necessary unless you are going 250 mph and entering tunnels.Keep in mind the 3D view. Here's a VW Beetle in the aeroform: http://ecomodder.com/forum/member-fr...-aero-bug2.png There are thing that don't show up in side-view. |
working windshield
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http://i1271.photobucket.com/albums/...d2/Scan3-1.jpg http://i1271.photobucket.com/albums/...d2/Scan2-3.jpg Once the windshield header/A-pillar radius is 'enough' to get attached flow,no amount of further rounding will produce a drag reduction.It has reached 'saturation.' As to the angle,of course,the steeper the better up to the point where internal reflections interfere with outward vision. Your windshield should be okay as it is. ------------------------------------------------------------------------ I built blisters for the hoods of the Dodge and Toyota trucks.I don't know if they do anything to lower drag,but I don't think they increase drag.Since I couldn't lay the glass back at a steeper angle,the blisters helped to relax the angle of the flow coming at them.Here is the Toyota http://i1271.photobucket.com/albums/...HPIM1874-1.jpg It flowed very well in the wind tunnel although I intend to widen it out to the edge of the fenders in hopes of slowing the flow a bit which will impact the side-view mirrors. |
nose
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http://i1271.photobucket.com/albums/...titled-7-2.jpg http://i1271.photobucket.com/albums/...titled-6-2.jpg The upper 'ideal' nose had no lower drag than the lower 'optimized' nose.Again,once the rounding is enough,you're done. Consider these two cars with identical drag coefficients http://i1271.photobucket.com/albums/...titled10_1.jpg http://i1271.photobucket.com/albums/...titled16_4.jpg:p |
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I had to look up what exactly is the Coanda nozzle and the Coanda effect. From what I can glean, the air coming in would be trapped inside the wheelwell similar to a parachute. Having the narrow slot for the incoming air to escape would allow it to "reattach" smoothly to the body of the car, thereby decreasing drag. Correct? I will design the Coanda effect to work in conjunction with front skirts. Quote:
I wanted to use magnets because they were different. Springs and bungee cords would work better, and they have been proven. I personally think your 4-bar arrangement with a torsion spring is great! I will figure out someway to implement it onto my car. I wish I had access to your software, I only have Paint. I would like to avoid bubble skirts as much as possible. I will have them if the tire is not as inset as I am planning. Avoiding an increase in frontal area is a concern of mine. Quote:
Would having a shorter nose with a steeper angle encourage more air up and over the car? That is what I am after. Basjoos said that he added the nose so less air would flow underneath his car. Is he right, or no? |
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The nose did not help front aerodynamics, but did it change the final Cd by diverting air towards a less dirty part of the vehicle? If I am beating a dead horse with this nose business, then by all means tell me to stop! I have a problem with getting caught up on non-critical aspects at times ;) It is hard to believe those 2 cars have to same drag coefficient! The top photo's uncovered tires likely played a big roll in that. On your word, I'll leave the windshield alone. So the name of what I want to do with the hood is a blister... I would like to design on of those if possible. It can't hurt, like you said. |
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The bottom angle is 2.5*, and this gives the best angle for... I can't remember the name, but the angle is ideal :p I do remember from a post by Aerohead that the angle can go to 4-5* and still provide improvements. After that, there was a regression. Increasing the angle may be the only way to shorten this beast. |
One thing I have thought of is to build a containment system in order to keep the air from spilling over the sides of the car. You can see an example of this on the Bonneville Fusion:
http://image.motortrend.com/f/blogs/...21914.jpeg.jpg Notice how the side edges of the roof is raised slightly. Doing this from the front bumper to the boattail end should encourage air to flow straight over the car in an organized fashion. |
roof fences
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The fences may be required to longitudinal and upright to pass inspection.
For examples that follow the airflow better, the Bertone BATs: http://upload.wikimedia.org/wikipedi...px-BATcars.jpg http://en.wikipedia.org/wiki/Alfa_Romeo_BAT |
Another idea that bites the dust :) I don't mind being wrong. It is how you learn, and learning is what I am receiving!
Those cars made me sing out loud "Duh-nana-nana-na-nuna BATMAN!!!" Wait, Batman drives an eco-car?! :eek: |
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TBH, I kinda forgot about this thread LOL :)
I'm back to it though! It seems that my car has hit a "fuel economy ceiling" and will not break it. 48 mpg is as high as my tank average can get, and this is with heavy P&G EOnC. Is there any aero mods that I can refine? Do tire splats really help? Side panels will reduce drag, I have just got to figure out a way to attach them to the body! I really want to make a pair for each side, one flush along the outside edge of the car, and the other along the inside of the tires from front to back. For example, the inner ones would be similar to those found on the Bonneville Corvette you posted, freebeard. The outer ones would be the same as everyone else who has ever done them! |
What have you done at the rear of the car ?
I notice that the rear of a stock ZX2, such as yours, is very rounded. Before you go all out with a full boat-tail, have you considered some trip strips, or giving the rear of the car a sharper edge like new cars have ? http://touch.toyota.com/img/vehicles...or-405x225.jpg |
Cd - I have fender covers and a rear belly pan on the back. I have contemplated a kammback, but I have not gotten around to it yet.
I remember Darin made the rear of his Civic like that. I'm going to head outside and figure out how to do likewise! Btw, what are trip strips? |
trip strips
Technically,a trip strip is any device which acts like a turbulator to trip a laminar boundary layer into a forced transition to turbulent boundary layer,or energize a TBL over a 'fast' contour.
It can be sand glued on,a wire,a bright molding on a Landau roof,dimples,nubs,ribs,micro-vanes,vortex-generators. The sharp edge on the Prius is a fix to a design problem discovered in the wind tunnel.The original body created bistable flow,buffeting,and noise generation. The hard edge fixes the separation line to maintain a constant drag coefficient,rather than one which 'hunts.' Since they extend the elongation of attached flow and pressure recovery,they contribute to higher base pressure and lower pressure drag.All good. Don't expect any remarkable savings. |
I'm a big fan of rooftop tailfins. This could adapt to a Kamm-back for your notchback:
http://i.kinja-img.com/gawker-media/...0076062759.jpg http://jalopnik.com/meet-the-mitsubishi-pajero-evo-the-last-forgotten-homo-1704009601 |
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