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Old 06-24-2010, 06:02 PM   #1 (permalink)
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Eggy - '99 Saturn SL2
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Talking Pics of my aero mods - opinions welcome

Here are pictures of my aero mods. Please share opinions because I'm trying to break 45 mpg, currently at 38. Is there any way that I can improve on the "nose" of the car (see pic) that won't appear to "abnormal".



Links to aero mods pics. Ignore the HAI pics, those are old.



Below is a quick list.

Already installed did the following
Passenger side mirror delete
Sealed hood to bump gap
Grill block
Smooth hub caps
Full belly pan
Hood gap sealed


Others that I plan to do are
Rear wheel skirts
Divert air away from front and rear wheels
Turbulator tape (need to find the zig zag scissors)
Smaller driver side mirror or make current mirror more aerodynamic

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Old 06-24-2010, 06:06 PM   #2 (permalink)
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I spray painted the wood panels black so they wouldn't be so obvious while driving. Also, still working on the belly pan, you can see the temporary duct tape panels.
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Old 06-24-2010, 06:15 PM   #3 (permalink)
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Eggy - '99 Saturn SL2
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Also, the wooden belly pan dropped by clearance to a minimum of 4" around the mid section of the car. The front and rear sections are angled so I have a bit more clearance.
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Old 06-24-2010, 07:30 PM   #4 (permalink)
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Ev-1

Quote:
Originally Posted by sl2eggplant View Post
Here are pictures of my aero mods. Please share opinions because I'm trying to break 45 mpg, currently at 38. Is there any way that I can improve on the "nose" of the car (see pic) that won't appear to "abnormal".



Links to aero mods pics. Ignore the HAI pics, those are old.



Below is a quick list.

Already installed did the following
Passenger side mirror delete
Sealed hood to bump gap
Grill block
Smooth hub caps
Full belly pan
Hood gap sealed


Others that I plan to do are
Rear wheel skirts
Divert air away from front and rear wheels
Turbulator tape (need to find the zig zag scissors)
Smaller driver side mirror or make current mirror more aerodynamic
sl2,I was playing with some simple numbers.If you're at 38 and going for 45,that's roughly a 18% improvement.To get that you'd need a 36% drag reduction.
For the sake of simplicity,if you were sitting at Cd 0.30 right now,then you'd have to get to Cd 0.19 to get 45 mpg hwy.
So we're talking about an EV-1 body on the SL2 platform.
GM did it with one of the best windshields ever on U.S.roads,and the backlight was pretty sweet too! And you may also be aware,that the EV-1 body began a teardrop plan taper at the center of the doors.
Short of a $3,000 GTP windshield,complete remodelling of the Saturns roof,with a mid-1990s Camaro/Firebird backlight,you're looking at significant extension to the rear to get the drag down.
Maybe think of a top quality bicycle rack which would non-destructively attach to the trunklid,to which you could attach various prototype structures for testing.
You can go the 'other' direction,but I think you're looking at active suspension at a minimum and completely sealing the front of the car while moving the cooling system and air conditioning to the back,as Ford did with PROBE-IV and V concept cars.( really low front ( bordering on illegal ) while at hwy speed ).
If the powertrain is low-time and you plan to marry yourself to the project and devote mass quantities of energy you can get there.And you'll work for every bit of it.
P.S. And all this is predicated on the BSFC of the engine not changing,saving a gear change as well.

Last edited by aerohead; 06-24-2010 at 07:33 PM.. Reason: P.S.
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Old 06-24-2010, 08:11 PM   #5 (permalink)
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Eggy - '99 Saturn SL2
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Thanks Aerohead. I think my 45 mpg SUMMER TIME goal for a 64 mile daily drive (58 highway, 6 city) is doable. A few Saturn SL2 (SOHC, allbeit manuals can get as high as 50+). Before all mods, I was running 40 mpg for an ideal 100% highway road trip.

There are few inefficiencies that are keeping me down, most unrelated to aerodynamics
- My own personal driving habits need to change (currently driving 65-75 mph to keep with traffic)
- Tires probably are on the higher end of the rolling resistance curve, maybe the set of OEM firestone tires sitting in the basement will help.
- My drum brakes are dragging a bit because I am trying to break in the brake shoes
- Future weight reduction include removing all AC parts and carpeting, depending on my mpg performance
- Still have to improve the "nose" (front bumper and headlight area) for the Saturn, its very drafty. Thinking of extending the nose out some 3" to make it pointier
- I would be willing to do a mini boat tail by extend the bumper out about some 3". I was thinking of laying a PVC pipe parallel the rear bumper and taping it so the bumper is extended out as far as the diameter of the pipe
- Planning to switch to synthetic oil once I reach 200k miles in 2 weeks
- Planning a second drain and fill on the tranny to effectively remove 92% of the old fluid and replacing with Valvoline Maxlife (meets the Dexron 6 spec)
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Old 06-24-2010, 08:24 PM   #6 (permalink)
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For kicks, I would consider adding a removable kamback so it makes the overall shape of the Saturn changes to a hatchback like shape (Prius anyone??). I don't plan on selling the car so it doesn't matter what I do. The prototype items that I would use is wood, plexiglass, rubber trimming, various bolts and paint. The extra space won't using like AeroCivic, but it would achieve at least 60% of the benefit.
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Old 06-24-2010, 09:25 PM   #7 (permalink)
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sl2eggplant -

I'm just flat out impressed. Very Mad Max!





Quote:
Also, the wooden belly pan dropped by clearance to a minimum of 4" around the mid section of the car. The front and rear sections are angled so I have a bit more clearance.
Ok, does that mean that the bottom of the side skirts are the height of the belly pan? :



If yes, then this is interesting. On one hand you are adding to frontal area and "compressing" the volume of air that travels under the car. On the other hand you are smoothing the flow out. I would guess that if you want to have a pan that low, you need to stop the air at the lower-front of the car, aka a frontal air dam at the same height as the belly pan like so :



But I'm just specumalatin'. Let's wait to see what the experts have to say.

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Old 06-24-2010, 11:37 PM   #8 (permalink)
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Thanks CFG. My goal was to create a flat area to cover up everything. I was trying to effectively lower the car while allowing the assembly to sustain high temps, hence I chose wood over coroplast. Hopefully it will pay off ... knock on wood!! What I did was bolt on a 2x4x7 stud to each of the two protruding beam-like things under the car The studs go from the engine to the back where the suspension cuts it off. Next, I laid up some wooden boards. The belly pan follows the layout of the "belly" except it is about 2 inches lower.

To answer your question (I think). Yes, the bottom of the side skirt (when they get installed) will the bottom of the belly pan. This was my attempt to achieve two things ... (1) force the air to follow along the side of the car and (2) reduce the effect of cross winds. I could have put an angle on the sides so the cross winds can flow gently under the car, but it wouldn't mesh well with my side skirts when they get installed.

I don't think I am compressing the air significantly anymore that it was already getting compressed by the stock belly. The angles on the front and rear bumper are the stock angles. I just laid the wood boards to cover them up.


You can see that some parts are not even ... those are will get fixed when I find a few hinges to connect various boards that do not meet at the same level.


Also, attached are my planned side skirts for both front and rear wheels, and a better picture of the front showing the belly pan.
Attached Thumbnails
Click image for larger version

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ID:	6239   Click image for larger version

Name:	Front view 2.JPG
Views:	72
Size:	117.9 KB
ID:	6240  
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Old 06-25-2010, 10:00 AM   #9 (permalink)
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Those mods look awwwful familar!

Definitely go for the wheel skirts for full batmobile effect. Nice work on the belly pan, but I feel like you're adding quite a bit of weight by going with wood. If wintertime in Detroit is anything like it is here (it is) then you're probably going to want that pan to be easily removed, as snow will find its way on top of the pan and just sit there, eventually rotting the wood. See if you can find a sign shop to give you some scrap coroplast and make the pan out of that instead.

Very nice work!
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Old 06-25-2010, 10:59 AM   #10 (permalink)
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Quote:
Originally Posted by sl2eggplant View Post
- Future weight reduction include removing all AC parts and carpeting, depending on my mpg performance
If you want to increase your MPG, replace that 300 lbs of wood under the car with aluminum.

Not to mention the first time it rains, that plywood is going to swell up and gain about another 50 lbs, then the ply's are going to start separating.

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