Aerocivic - how to drop your Cd from 0.31 to 0.17
 

New... Aerocivic has a web site: www.aerocivic.com

I started this project after the Katrina-insired gas price runup since I have a long commute. I first learned to drive during the 1970's oil embargo and have been perfecting my hypermiling tenchniques ever since. My car is a 92 Civic CX, which I bought new, and was giving me low 60's to low 50's before I started aero modding it.
Side view
http://ecomodder.com/imgs/aerocivic/BoatRebuild15.jpg
Side view with open hatch
http://ecomodder.com/imgs/aerocivic/BoatRebuild11.jpg
Rear view of boattail
http://ecomodder.com/imgs/aerocivic/BoatRebuild12.jpg
Cargo area inside boatail, extending the interior of the car into the boattail added 20cu ft to the interior space. Also there is a hidden compartment under the new load floor in the boattail.
http://ecomodder.com/imgs/aerocivic/BoatRebuild13.jpg
Radiator inlet slot (coroplast has since been replaced with aluminum sheet)
http://ecomodder.com/imgs/aerocivic/GrillSlot.jpg



The end result is a car with such low drag that the results of coastdown testing is linear out to 90mph (it coasts almost as well at 80mph as it does at 50mph). I have to get it over 90mph before I start to feel the wind load from high-speed driving. OEM max speed was 95mph. I have had it up to 100mph with plenty of power remaining at that speed (estimated top speed of about 140mph). Wind noise is much reduced from stock. Approximate mileage on a flat road at 85F, 95mpg at 30 to 65mph, 85mpg at 70mph, 65mpg at 80mph, 50mpg at 90mph.

Additional mods planned, include replacing the current one-size-fits-all radiator inlet slot with a driver-adjustible radiator door. Eventually I plan to automate the door by using a Basic Stamp or similar process controller to monitor the coolant temps and adjust the opening to the actual cooling needs.

Most of my driving is at night, especially in the winter, and night driving is costing me 2 to 3 mpg in additional electrical load from the lights. About half of this loss is from the parking lights, the remainder is from the headlights. I want to replace the parking and dome lights with LED's. Since retrofit LED headlight kits are still several years off, I want to investigate installing a switch to kill one of my headlights and/or a dimmer control to reduce the headlight's intensity and power drain for situations where I don't need the full intensity of the headlights for visibility.

More pics:
Side view of nose, front wheel spoiler, and front wheel well skirt (nose and skirt are now aluminum sheet, spoiler is still coroplast)
http://ecomodder.com/imgs/aerocivic/aero15.jpg
Front view of front wheel spoiler
http://ecomodder.com/imgs/aerocivic/aero12.jpg
Side skirts made of coroplast (there are 2 side skirts on each side, one even with the inner edge of the tires, the other even with the outer edge of the tires).
http://ecomodder.com/imgs/aerocivic/aero14.jpg
Rear wheel spoiler (coroplast)
http://ecomodder.com/imgs/aerocivic/CivicCaS.jpg
Underbody panelling (coroplast and aluminum flashing, I plan to replace it with alumunum sheet whenever I next need to remove the panelling for service).
http://ecomodder.com/imgs/aerocivic/aero7.jpg

More pics:
Conveyer roller inside of front skirt
http://ecomodder.com/imgs/aerocivic/CivicBd.jpg
Front skirt slightly open with wheels cuts all of the way to the left.
http://ecomodder.com/imgs/aerocivic/CivicBc.jpg
Windshield wiper windscreen
http://ecomodder.com/imgs/aerocivic/...Shieldside.jpg
Fairing behind muffler
http://ecomodder.com/imgs/aerocivic/MufflerFairing.jpg
Interior side rear view mirror (replaces deleted exterior side rear view mirrors)
http://ecomodder.com/imgs/aerocivic/Mirror.jpg
Low-tech hand throttle
http://ecomodder.com/imgs/aerocivic/Handthrottle.jpg
SuperMID
http://ecomodder.com/imgs/aerocivic/SuperMID.jpg
Another view of the car
http://ecomodder.com/imgs/aerocivic/CivicView.jpg

Very Nice.:turtle::turtle:
Basjoos how many hours do you think you have in it to get it to this point?

Probably about 250 hours and a materials cost of about $400 spread out over the past 2 years. It has paid for itself in fuel savings several times over.

Basjoos. I haven't seen pictures of your car for a while. I see the boat tail has been improved in looks and function.

What did you use for the rear window?

I have to give credit to you. Areo moding a civic to the max is not an easy undertaking.

The rear glazing is Lexan. Once I conclusively proved the FE benefits of the boattail on my car, I rebuilt it with more durable materials (aluminum sheet and Lexan) than the original prototype was built of (coroplast and clear vinyl) as well as utilizing the additional space enclosed by the boattail..

Is there anything to note when working with Lexan? I have clear vinyl on mine, but maybe I'd replace it.

Hey basjoos -

LOTS of visitors coming in from other sites right now - check the hitcount on this thread relative to some others.

If your car draws anywhere near this much attention in real traffic, you must have to be VERY careful around the rubberneckers!

I used 1/8" Lexan, which can be drilled, sawed, and bent into a curve as needed.

I sometimes have a problem with rubberneckers piling up and backing up traffic alongside my car. But the worst are the few who can't drive in a straight line while they are staring at something alongside them and start curving into my lane.

After you swap out to LED park lights if you want to reduce the headlight load you can wire up some relays to switch them to series load instead of parallel. That will make them dimmer but not really dark. It will cut the load in half though :)

The other thing would be using some relays to switch them out you can add several silicon diodes in line. You get a .7V drop across a diode so add 5 of them in series will drop you 3.5V. Just make sure to pick big enough diodes to handle the load.

I've heard of an instance where a university team solar car was forced off the road due to rubbernecking. Ended up catching a culvert and flipping the solar car. Fortunately nobody was hurt.

EDIT: the comparison of your Civic to a solar car (in terms of aero optimization) isn't that much of a stretch either either.

Whatever happened to your additional 'wind screen' :confused::

Attachment 40

Rain?

Mmm. I don't think so. Not according to this previous post by basjoos:

Coyote X, good idea about using series connecting the headlights and also using doides to customize the voltage drop.

The aero benefits of the "second windshield" (by eliminating the "A" pillar vortex and smoothing the airflow over the front of the car) were undeniable, but I had some operational problems with it when operating in cold rainy weather. I'm in the process of replacing the clear vinyl on the "windscreen" with Lexan. The vinyl was clear enough when looked at straight through (90 degrees), but was hazy when viewed through at an angle (30 degrees) as it is near the bottom of the windscreen. It also had a tendancy to overwealm the Fog-X and fog up on the inner surface when driving in cold, wet conditions. The Lexan should take care of the low angle visibility problem and I need to get a good watertight seal along the front and sides of the "windshield" so water can't find its way onto the hot hood and end up condensing on the cold inner surfaces of the "windshield". Also considering adding a windshield wiper to the "windshield" to placate any cops that might freak out at a car driving in the rain without wipers, even if I don't really need them.

Basjoos, you might want to stick a sock full of crystalline kitty litter (it's silica gel, the cheapest source you can find) somewhere in that space to get rid of any lingering moisture that finds its way in there.

I read this and was so impressed I had to write about it on my blog.

You can read my thoughts at http://www.energyrefuge.com/blog/caf...-be-that-hard/

Nice.

I was recently thinking about wheel spoilers and I thought of something I think is relevant.

Your front wheel spoiler mostly pushes air down, where it will end up hitting the tire (or ground) still anyway. I believe that won't help you any, and that it would be more efficient to just push the air directly to both sides of the wheel. Possibly more to the outside of the car than under the car due to the rest of your aerodynamics. So you would have a wedge where the leading edge is a vertical line.

And I would expect you to benefit from putting another set of spoilers behind the rear wheels (working well with your dual layer side skirts).

Of course I have no idea if these would give you enough benefit to be worth you doing.

That's a good observation for behind the rear tires. But do you mean to add a "boat tail" rather than "spoiler"?

You'll see wheels/tires effectively boat tailed on this car:
http://www.design-classic-cars.de/auto-union/stuck1.jpg

Yes. Same thing, other end.

Hey basjoos -

I'm a reporter at Wired News, and I'd love to talk you more about the car. I've already blogged about it and sent you a PM with my contact info. I hope to talk with you soon.

frickin' awesome.

guess this whole conservation thing might really catch on after all.

Nice! :thumbup:

basjoos, I have two questions about your design,

1:Fairing behind muffler - Any worries of Carbon Monoxide getting inside the cabin, or a fire started from the heat off the muffler?

2: Hand Accelorator - I'm new to the group, so I don't know if it helps or is it just a personal preference?

Hi rifraf -

1) I'll let basjoos comment on the exhaust routing.

2) The lever for the hand throttle is to provide very fine throttle control when cruising. It's a mod that enables a more efficient driving technique.

When you get fuel consumption instrumentation in your car, one of the very first things you notice is the relatively BIG jumps in fuel consumption from incremental changes to the accelerator position. Changes that are literally imperceptible to the butt-o-meter will show up on an instant fuel consumption display.

The hand control permits much finer adjustment of the throttle once up to cruising speed. It may also be more comfortable to use than feathering the throttle by foot for long periods.

Ahh thanks for the tidbit Metro! :D I take it though that there are electronic Accelerators out on the market? Something like a steering wheel paddle attached electronically to the throttle? Also it seems that basjoos' homebrew throttle could be a bit dangerous if not setup/maintained properly

Great job Basjoos, but why didn't you start with a civic VX instead of a CX ? It was the high mileage model. Feather light aluminum wheels. Wider ratio transmission with a higher final drive ratio (2000 rpm at 60 mph). Variable valve timing with a twist. In this engine only one intake valve opens below 2500 rpm. Since there is only one intake valve open more of the pressure drop between the atmosphere and the cylinder is across the valve rather than the throttle plate. This gives a more turbulent fuel air mixture which allows a leaner fuel/air charge, greater torque at low engine speed, and no predetonation . The use of a very sensitive oxygen sensor (unique to the VX) allows more precise control of the FA mixture making a very low idle possible. On a warm day mine idles at about 500 rpm. The practical effect of these engine tweaks is high torque at low RPM sort of like a diesel. As I'm sure you guys know, the great weakness of the Otto cycle (the spark igniton gasoline engine is an Otto cycle engine) are the large pumping losses at part load caused by sucking the FA charge past the throttle plate. The ability of this engine to deliver good torque at low RPM (and thus lower pumping losses) is the secret to the high fuel economy this car delivers. The CX and the VX share the same body, but the CX is listed at EPA 42/46 and the VX at 47/56. The VX also offers higher power since the engine has the same displacement, but four valves per cylinder (92 vs 70). I bought mine new in 1992, have put 208 thousand miles on it and still average 45 mpg to work and around town. When the car was new 52 or 53 mpg was not unusual on a long road trip. The fact Honda could do this with the technology of 15 years ago shows what a bunch of liars the auto companies are when they squeal about a 35 mpg average fuel economy rule.

as to the car model, a diesel, for example a VW golf TDI, will raise your mpg by 20-40%... hopefully the clean TDI's make it to the US ASAP...!

and i think smoother material surfaces should also help improve drag...

The exhaust exits straight through a hole on the back side of the fairing, so there is no trapping of exhaust gasses inside the fairing. Also the aluminum sheet making up the fairing is mounted on the underside of the aluminum sheet making the underside of the boattail, so there is no air connection between the air space inside the fairing and the air space inside the boattail. There is a 1" air gap between the back of the muffler and the front of the fairing to allow for movements of the exhaust system, which allow for cooling and also aluminum isn't known for its great flammability.

MetroMPG answered much of my reasoning for the hand accelerator (fine tuning of the throttle position, particularly useful for good FE at the lower speeds when your throttle position is just running just slightly above idle). Also, unlike normal cruise controllers, the hand throttle is a DWL (driving with load) cruise controller, not a constant speed cruise controller.

The hand accelerator is set up the same as the one on my John Deere tractor (the hand control sets a lower throttle position that can be overidden by pressing on the foot accelerator. The hand throttle only goes from zero to slightly above half throttle and I have trained my reflexes to automatically pull back on the hand throttle whenever I push down the clutch pedal. On the rare occasions when I do forget to pull back on the hand throttle when I push down the clutch, the engine just revs up and reminds me I need to pull back on the hand throttle.

I started with a CX (which I had bought new in 92) rather than a VX because that was the car I was driving at the time I decided to start aero modding my car. The CX and VX share the same transmission. The main differences being the in engine,, lighter wheels, some additional interior features in the VX (the CX is the bare bones Civic model) and some underbody aero to slightly reduce the Cd of the VX. The VX and CX have the same weight. When new, my CX typically gave me 51mpg on the highway in the summer (44mpg highway in the winter) and 38mpg was the worst I ever got with it (in snow driving and winter tires). Interestingly, when I installed a DX engine at 245,000 miles (but kept the same transmission), the mileage remained the same, but my 0 to 60 times dropped to 10 sec.

Exhaust / Coolant / Air intake
 

You were talking about changing the intake for the coolant to vary with need of cooling, have you thought of a heat exchanger for the intake air for combustion or for that matter from you exhaust, routing the cool air through the rad, then to an exhaust heat exchanger then to the engine, in effect reclaiming the heat that would have been waisted... there is an interesting article in Popular Science about using the heat to produce steam in the engine...

http://www.popsci.com/popsci/technol...cbccdrcrd.html

I figure my intake air gets warm enough just from the tightly cowled engine compartment (its completely underpanelled, with a mostly blocked grill and the hot radiator air exhausted out through the front wheel wells). They've had some discussions of warm air intake temps at Gassavers and concluded that although warm intake air improves mileage (at the expense of power, you are in effect driving a less powerful engine with a more open throttle plate with reduced pumping losses), but if the intake air gets too hot, it has detrimental effects on mileage (perhaps because the engine ECU isn't programmed to handle intake temps that are way above what its programmers thought it might ever experience).

70 years ago... the aero Model T
 

FYI - for those interested in the subject of radical aero mods, you might want to check the thread about Harry Stevinson, my friend's dad. He was bitten by the same bug that got basjoos ... 70 years ago:

All of this recent activity used up all of this month's bandwidth on my free Photobucket account. Next month's bandwidth allotment will become available on Jan 2.

If you want to send me the pictures I can host them on the ecomodder server for you. :)

The images can also be seen at this site: http://www.cleanmpg.com/photos/showg...=500&ppuser=18

I've posted the images on the Ecomodder server - they're all visible now. No more Photobucket bandwidth problems.

If we get the aftermarket body mod industry to start thinking ecomodding, changes like the ones Basjoos has made might be accomplished in a weekend. See: http://www.bodykits.com/store/home.php?cat=1281 as an example.

I do believe newton has had that thought (of making aero body kits for ecomodders), and I definately think it's worth a go. If I knew anything about molding and all that jazz I might play with it myself...

If someone made a boattail for a prius I'm sure that would get the business going.