Inexpensive MPG Modding

[basjoos] modded [via] the body of his ’92 Honda Civic – and managed to improve his fuel efficiency from 50-60MPG up to 95MPG for about $400. Even more interesting is the SuperMID (Translated) that he added to the car to monitor his fuel efficiency. It’s based on an ATMega8 that reads the CAN bus and displays realtime MPG information an a character LCD. The SuperMID is popular for Prius modders because the on-board display maxes out at a paultry 99MPG. If micro-controller’s aren’t your thing, [Atilla] put together his own CAN bus decoder and ported his code to a Zaurus SL-C700. He even added voice feedback notification for certain data events.

70 thoughts on “Inexpensive MPG Modding

  1. Ewwwwww…

    Great idea; disgusting implementation.

    If he just paid a body shop $1-2k to do it right he would have probably seen a 0.1CD. Someone should introduce this man to Bondo and Paint.

  2. thats the madest thing i’ve seen in a while, i proper love it!
    never really realsied how aerodynamics can effect mpg so much.
    it would be wicked to see more cars like this (and more people beening inventive with being “green” in mind) ….*drifts off into post apocalyptic hacking fantasy*

  3. the uber green hack that somebody should do is make a solar powered hydrogen distiller (or whatever you call the device that splits water apart). Then use that to fill up the cells in your hydrogen car.

    i think ill wait for someone else to do it first, given that i dont want to blow up… anytime soon…

  4. 95mpg? I don’t believe that for a minute.

    Then there’s this gem:

    “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.”

    I won’t believe that simply having your goddamn headlignts on will cost you anywhere near that much.

    Also, I wouldn’t want to be in that car in any kind of crosswind or behind any kind of large vehicle.

    1. I think you don’t know much on Hypermiling, 95 MPG is totally achievable on this aeromodded car. Plus, it have an 1.5 L VX engine. 95 MPG is at very low speed like 45MPH on the HWY. Come make a turn on, you will discover wonders.

  5. josh: headlights/wipers/heated windscreen/fans and other accessories use 6.6% of the total useful energy output of a gasoline engine, and headlights are a large percentage of that. (the 6.6% figure is from my own calculations and some approximations – if someone could find a better figure it would be great).

    Looking at it another way, of the ~10kw out of the engine, an extra 100w (or 1%) could go to the headlights.

    Having said that mpg will be lower at night due to using the brakes more because the driver sees obstacles/bends/hills later.

  6. He should look into metal halide lamps, rather than dimmers or cutting out one light, for his headlights.

    It’s pretty recently that they’ve been able to make polycrystalline alumina transparent enough for that application, but some prototypes should be available if he contacts the manufacturer.

    Also, he may want to consider giving over control of his alternator’s field coil current to a microcontroller: it’ll allow regenerative braking and perhaps some other tricks, especially if he switches to a system with more windings.

  7. @5: I doubt there are any body shops that could do it for $2000. The corner of my Crown Vic got hit and they quoted me over $2k to fix it — more than half of that was just for paint. I bet to get this kind of thing done at a professional shop would be at least $5k.

    @11: I’m not too sure about his figures either. 50 mpg sounds high for a Civic — my ’94 Civic Si topped out at 40 mpg if it was gently driven. But as long as his measurement methods are consistent, it’s still a 53% improvement no matter what the actual numbers are.

    2-3 mpg for the headlights suggests the headlight load is around 2% of his engine output. That sounds high; he’d have to be cruising on only 5 horsepower or so. Later I think I’ll run the numbers and see if I can approximate how much horsepower he’s actually consuming…

  8. I think this is fantastic. I just wish others had some more positive comments. I mean, look at the work this guy has put into this. I doubt if any of the armchair critics have attempted anything similar.

    I wonder if it would help at all to completely remove the belt from the alternator and have one that uses ram air to spin the alternator with a propeller, similar to some ordnance on NAVY jets. Would that offset anything or just cause more drag and make it a useless mod? Just wondering. If he’s commuting at mostly highway speeds it might be an option.

  9. OK, running the numbers for 95 mpg at 60 mph, I figure that amount of fuel would produce about 8.5 horsepower at the rear wheels. Assumptions I used to get there:
    – 30% overall efficiency for the engine and drivetrain (a guess, but a typical number for most cars)
    – 114,100 BTU/gallon of gasoline

    I don’t know enough to figure out whether this is reasonable given the C/d and frontal area of his car, though.

  10. @18: I don’t think it would help; the energy has to come from somewhere. Reducing the load on the alternator is the way to go, and it sounds like he’s on the right track there.

  11. It seems like some of you guys are only just hearing about hypermiling. Check out or google wayne gerdes. The forums over at gassavers has crazy amounts of info on engine accessory load vs. mpg, electrical load increases vs. decreases in mpg, etc. Not certain, but I think this guy posts over there as well.

  12. Soooooo – I don’t buy any of his cited MPG. It’s known that air resistance increases as a square of velocity:
    resistance = velocity^2

    He gives us:

    95mpg at 30 to 65mph
    85mpg at 70mph (change -10mpg)
    65mpg at 80mph (change -20mpg)
    50mpg at 90mph (change -15mpg)

    Since the mpg should decrease substantially as speed increases, EVEN WITH “IMPROVED” AERODYNAMICS. We know that the air resistance can be accurately approximated as:
    AR = -A*v^b
    where A and b are related to the car geometry (fixed)
    and air viscosity (also fixed)

    Then his MPG should decrease greatly as speed increases and continue to reduce more and more as speed increases, so his numbers a baloney.

    You also do not want a tear drop shaped rear end, you want a VERY steep drop on the back, straight down would be ideal as this will decrease the drag due to the air moving along the increased surface of the car since you are tripping into turbulent flow at the back end. This is the same reasoning that caused mythbusters to show that you are better off leaving your tailgate up, not down, as you’ll have less resistance.

    There is also no mention of the added weight of all of this paneling, which is not weight free. He may as well left the whole thing alone and spent money regearing the transmission to some ridiculously high gearing, concentrate on covering/eliminating any holes in the front of the car (bumper/gaps around any lights), and finally make the back of the car more sheer than long and drawn out like that.

    . . . and it’s really ugly

    1. CM… If that is true then why aren’t planes rear ends ever flat in the rear? They have a pointed rear end because there would be too much drag and wouldn’t fly. This is an amazing feet especially for the cost. And to the people that say why haven’t the auto manufacturers done this I ask why is an old 1992 Honda civic the fifth rated gas mileage car of all time? People with money who buy cars don’t really care about mileage as apposed to style or image. Also this car has 92 HP stock with 97 fp of torque which is the highest power of the top ten gas mileage cars of all time so it moves. Weight to power ratio is great in this car stock.

  13. Seems a bit far fetched. One would think the added weight of the “body kit” would decrease MPG. Plus the 1992 Civic has fairly good aerodynamics to begin with. How about going to a higher temperature thermostat and advancing the the static timing as far as possible. Install a vacuum gauge and change your driving habits according to the vacuum gauge. You will see a very serious MPG improvement for about $75 for parts and a small time expenditure.

  14. To all the people calling bullshit, go ahead and try it yourself and bask in the wonderful empirical basis of science. The addition of at most 150 lbs is not going to decrease fuel efficiency by much, however if that 150 lbs goes towards lowering drag coefficient from something like .30 to .15 you are going to see some serious improvements in efficiency.

    This kind of modding is not new, but as pointed out by some of the other less mature commenters it can mess with the aesthetics of the car, so you don’t see many production vehicles incorporating these elements. I agree that much of his work looks far less than professional, but from what I gather from the forum topic it’s a work in progress and most of the fairings etc are just prototypes to test performance.

    To see what you get if you design a car around aerodynamics check out the Aptera Type-1. A production level hybrid car offered by Aptera that gets 300 mpg, costs 30,000 (they started taking deposits in September)

  15. #26, i have to agree and disagree with you.

    first i’ll disagree. I’ve taken enough ME classes that deal with more types of dynamics than i care to remember, and i can not see that modification doing that well by itself. In fact i can not see his fab skills making anywhere near that large of a difference. yes the less drag will help, but those mods also added a ton more drag and the creation of eddies. Simulating his work in a PC would be nearly impossible because modeling that workmanship would be nearly impossible.

    on to better things however. I do believe 95 mpg in that car if done correctly would be possible. However it would require gutting it. switches for nearly every pully and electrical item in the car. and possibly even a replacement transmission.

    modification discussion could go on forever about this and it would go nowhere really. I would actually like confirmation on the 95 before i believe it.

  16. @27 As stated in the original write-up along with the forum post, he’s using a supermid to monitor instantaneous fuel consumption. there’s nothing that needs to be confirmed, it’s all there.

  17. josh: and we have never seen mods here that stretch the truth at all either. sorry but one person saying something is completely different than verification of that as well. anyway good for him for driving that, but i’m a skeptic, kinda like that water engine thing we have been told about since we could walk :P

  18. I think reducing the strain by the alternator would be better by reducing the load on the electrical system, switching to HID headlights at 35w each would be a start from the 55w fillimant lamps, and also converting the rest of the light bulbs to LEDs would give an improvement.

    Great work, even if it is as ugly as ****! lol. But nice to see someone put efficiency before looks. brave guy.

  19. I am skeptical about MPG at higher than 50MPH. his design is so thrown together that the seams and caulking mess will start to cause more drag at those speeds ( and the wheel skirts should flap like wings, then rip off and take out another car’s windshield.)

    Now, build a wooden buck, lay some glass and make a REAL body mod that is smooth and has laminar air flow instead of what he has and I’ll take a closer look. But, legality start’s to hit, I guarentee that any cop that wants to can impound his current car as unsafe. He really needs to refine it and make it look less like a rolling white turd and more like a “what the hell is that?”

    On the bright side, I love how he is proving that hybrids are nothing but a boatload of BS. a regualr civic getting 50-60mpg SAME mileage as a hybrid.. Proof that hybrids are a buttload of BS and regular cars can do what they can without the complicated crud.

  20. 98mpg, Yeah I can see that.
    The thing to remember is at highway speeds you need very little power to continue to coast, the majority of the power you are using however is to overcome Aerodynamic drag.
    In traffic or at low speeds This would probably decrease mpg (more effort required from the engine to move itself)
    Ive the “Areo” style Crown Victoria and on the highway 70+mph it does get very good economy

  21. @38: Steep drop? WTF are you on mate. Aerodynamics has told us forever that you want the air flow to come back together smoothly behind the vehicle to avoid the creation of a dragalicious low-pressure zone behind the vehicle. Dumbass.

    On the topic of the precise MPG numbers, well instantaneous readings are as good as shit on pie, though I’d say his kit still has some significant improvements.

  22. @35: Steep drop? WTF are you on mate. Aerodynamics has told us forever that you want the air flow to come back together smoothly behind the vehicle to avoid the creation of a dragalicious low-pressure zone behind the vehicle. Dumbass.

    On the topic of the precise MPG numbers, well instantaneous readings are as good as shit on pie, though I’d say his kit still has some significant improvements.

  23. if we are going to get anyone to believe the stated MPG we will need some proof. can someone tell this person to go on a road trip? ideally he should also go through some large city and find out the MPG. if this does all turn out to be true then i will think about doing this to my car, and maybe we could move the experiments up a bit and try this on a coach. yes it will look ridiculous but if you can get a better MPG than a hybrid car then we can send this information to some group or a car program and we can all have a good laugh at the morons that design cars to sound good, “this car is a hybrid so it uses even less petrol (or gas, the watered down american version) and is even better for the environment” “yeah, it uses more petrol than a coach!”

  24. Not sure if I believe the mpg either, but nice work. My only fear is that this guy is going to start thinking of himself as some vigilante Michael Knight type character and start cruising the street looking for crime. He’s already got the car talking. Isn’t there a danger of that rear fairing taking out a pedestrian on the sidewalk when you make sharp turns?

  25. Haha, really great idea. That guy is hardcore.

    I also like how people misuse formulae in an attempt to show their “mad skillz”. 95 mpg is not an unreasonable number, and he’s measuring it directly in real-time…I don’t think there is a need for a “road trip” since he knows the fuel economy where ever he is.

  26. Most of you seem to have never heard of aeromodding at all in your life, please go ahead and google it, *it is nothing new*.

    Thousands have people have done similiar mods to this, front and rear wheel skirts, wiper windscreen, boat tail, belly panel, front air dam, and relocating the side-view mirrors inside.

    All of this significantly reduces air drag. Most cars have a Cd of around .3 or so. Reducing this to .15-.18 with mods is relatively simple. Cars designed around reducing Cd can reach as low as around .07. It’s nothing new.

    To the people suggesting mods to the electrical systems/alternator yes that can help some, but you won’t see nearly the increase in efficiency as you would from aero-mods, low rolling resistance tires, and supermiling driving techniques. Which do you think is more important, saving 100-200 W in electrical load or lowering that (approximately) 15000 newton force pushing backwards on your car.

    @35 you’re an idiot. a teardrop is one of the most aerodynamic shapes, this why fluids in free fall assume this shape. they want to assume a minimum energy configuration like all things in nature (this is rain in case you haven’t figured it out). Also you might want to go study up some more on fluid dynamics rather than regurgitating simplified dormulas that you learn in high-school physics, trust me it’s not that simple.

    SO in closing to all the people calling bullshit look at the hundreds of examples and hard data out there by tons of modders. Which do you think is more plausible: a giant conspiracy contrived to fool people you can increase fuel economy by 50% or DIY hackers who understand how to apply aerodynamics. Time for a shave with occam’s razor.

  27. @45
    > @35 you’re an idiot. a teardrop is one of the most aerodynamic shapes, this why fluids in free fall assume this shape.

    except that they don’t, they make shapes very similar to spheres

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