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I got the 3-piece boat tail built and installed. Installed the first two pieces on thursday and drove through the weekend with it. At 28F, the car coasted as well as it used to at 90F and at 50F it coasted much better than it did at 90F. The boat tail has caused the greatest improvement in coasting ability of any single aero mode that I have installed so far. With the 2 pieces installed, I can still use the back hatch. This monday I built and installed the 3rd part (tail cone) of the boat tail, but with all of the rain today it was impossible to tell if it made any difference. The boat tail is made of an auminum bar frame covered with coroplast (bottom) and clear vinyl (upper portion). The clear vinyl makes it possible for me to see out the back and so I didn't need to relocate the tail lights and license plate. I used the Questair Venture tail cone as a model for the shape of my boat tail and did a quick run with taped yarn to test the air flow over the parts that I can see through the rear window (attached air flow all of the way to the tip). Next project, front wheel skirts.
Lets see if I can get these pictures to work.

2 piece boat tail

http://img.photobucket.com/albums/v417/MikeMariettaSC/80MPG%20Honda%20Civic/CivicBoate.jpg

http://img.photobucket.com/albums/v417/MikeMariettaSC/80MPG%20Honda%20Civic/CivicBoatd.jpg

http://img.photobucket.com/albums/v417/MikeMariettaSC/80MPG%20Honda%20Civic/CivicBoatc.jpg

http://img.photobucket.com/albums/v417/MikeMariettaSC/80MPG%20Honda%20Civic/CivicBoatb.jpg

3 piece boat tail

http://img.photobucket.com/albums/v417/MikeMariettaSC/80MPG%20Honda%20Civic/CivicBoatbb.jpg

http://img.photobucket.com/albums/v417/MikeMariettaSC/80MPG%20Honda%20Civic/CivicBoataa.jpg

http://img.photobucket.com/albums/v417/MikeMariettaSC/80MPG%20Honda%20Civic/CivicBoatcc.jpg

Questair Venture
http://img.photobucket.com/albums/v417/MikeMariettaSC/80MPG%20Honda%20Civic/Venture_s_th.jpg
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Interesting. I'd like to see that car in person some time.

Can this make tailgaters back off? :D

YOU
ARE
THE
MAN!

that does look sick! (slang for good!)

basjoos ,
Rock on! You defintely have to bring this to Hybridfest (http://www.hybridfest.com)next year along with your data.
Thanks for sharing!

You know, I see stuff like this and just have to wonder... if everyday guys can dream up and make stuff like this in their own backyard, why the h#$ can't the fine folks in Detroit make this happen on the assembly line??

rhwinger. Mostly because of saftey laws, market demand, cost vs. benefit analysis. There are some strange laws on the books about what manufacturers can't do to production vehicles.

Usualy things like this that are radical departures from the norm are scorned by consumers. Sure there will be a bunch of people that will buy the car, but probably not enough to make it profitable for the company.

I remember when rounded corners on the first Tauris was considered cutting edge. Thats about as radical as you can get and attract consumers.

Another vote for Basjoos bringing his car to HybridFest 2007 :)

I would love to see someone with a Prius II get this extreme with aeromods.

basjoos ,
Rock on! You defintely have to bring this to Hybridfest (http://www.hybridfest.com)next year along with your data.
Thanks for sharing!

Why should I bring my car to Hybridfest? I thought that was a hybrids-only event. My car isn't a hybrid, even though its gets the mileage normally associated with them.

I'm doing all of these aero mods on my car because I got tired of waiting for the car companies to come out with an inexpensive high MPG car. And despite all of the automotive advertising, 40MPG is not "high MPG" in my book.

The tail end of a 2 mile long coast on my way home from work really drove home the overall improvements that the aero mods have made to my car's coasting ability. At the point on the road where my car's speed would normally have dropped down to 35mph in its pre-aero days, I am now doing 50mph and I can roll on for another quarter mile down the road before I have to start the engine.

The PriusII has a lot of room for aerodynamic improvement starting with SMOOTH underbody panelling that also covers the exhaust system, a grill block (possibly an active grill), boat tail, rear (and front) wheel well skirts, rear wheel spoilers, smooth hub caps, side skirts, rerouting the exhaust air from the radiator to reduce its contribution to underbody turbulence (I exhaust mine out through my front wheel wells and the rest out through the exhaust pipe underbody tunnel), video or smaller drag profile rear view mirrors.

Great modding, basjoos! I think the spirit of HybridFest isn't in the technology and the batteries, but in the hypermilers themselves. I speak for all of us when I say that you certainly qualify. It's the inventive mind that makes a difference.

Looking forward to seeing tank data on this new improvement! :D

basjoos,

The EV1 was at Hybridfest and it's not a hybrid.

Eric is the President of Hybridfest and if he endorses your car - go for it!

WOW! That is awesome basjoos! A 15 mph improvement is no small accomplishment. You've got me thinking about what I can do with my plastic body paneled Saturn. I may have to get my car up on jackstands and see what I can do with the under-body area.

Why should I bring my car to Hybridfest? I thought that was a hybrids-only event. My car isn't a hybrid, even though its gets the mileage normally associated with them.
The official tile is "Hybridfest: A Hybrid Electric Car Show and More! (http://www.hybridfest.com)"
Your car is definitely qualifies as part of the "..and More!"

Although the car couldn't be in the all hybrid car show, you certainly would be welcome to be a part of most other parts of the event, especially the camaraderie of other like minded people. Just like the ones here at CleanMPG. In fact the camaraderie is one of the best parts about Hybridfest. It was really great to be able to put faces with names and actually meet a lot of the hybrid community in person! What a concept!

At Hybridfest we don't say hybrids are the only answer. Hybridfest is simply to promote understanding about hybrids. For many people, it may turn out hybrids are not for them. No problem! We just hope to provide the facts and dispel some of the myths and misconceptions that are floating around about hybrids. And have a good time in the process!

In 2007 Hybridfest will be two and a half days of fun. (Friday afternoon through Sunday) Maybe we'll see you there!

I'll have to consider attending the next Hybridfest.

Got 68mpg from this tank dispite 120 miles of driving in the rain, which at these temps would normally have dropped the mileage into the low 60's. I should be able to improve the mileage as I adjust my driving to the car's new slipperier shape. I am finding myself using the brakes more than I should because I am entering into coasts with more velocity than I currently need.

It would be interesting to do the full aero treatment to an Insight. Although it probably wouldn't help much in a low speed hypermarathon such as the recent one in Oklahoma, at normal highway speeds it should allow the ICE to remain in lean burn at higher speeds than normal and improve overall mileage at those speeds.

Hi .First post.
I have a 1993 Civic DX Hatch automatic.
I have a high of just over 47 MPG, and just last year was averaging 42 MPG.
( Car is running at half that the last few months though :( )
I am shocked to see that you get the mileage you do, yet do not drive a VX.
What engine mods have you done ?

The main reason I have posted today is that I have been interested in doing just what you have already done to your Civic. I started to build an under tray to go undr the engine ( out of aluminum ) but I chickened out because I was unsure whether it would trap any leaking oil and start a fire.


I'd also like to build a partial boat-tail, but have it all legal - 12" past the bumper ... max.

I love the fact that you have done coast down test with your aero mods , and I'd really be interested in seeing a breakdown of how much of a gain each mod was worth.


Thanks for posting ! This is just what I have been searching for !

For an encore....

Why not cover the chassic underneath?

I hear so much about this being a source of drag.

This could be the best place to get drag reduction on some of the small hybrids...

The VX is a FE animal. Add to that hypermiling skills and you get results like his.

My car is a civic CX with a stock DX engine. I haven't done any mods to the engine. So far, I have installed complate underbody panelling, grill block, rear wheel well skirts, smooth hub caps, wheel spoiler on all 4 wheels, side skirts, gap sealing, and a complete boat tail. The next project is front wheel well skirts.

My Civic DX is only able to get 42 MPG because I drive slow enough to make my grandmother mad.
( I have actually had RVs pass me on the road. )

O.K. maybe a slight exaggeration, but I do drive very slowly. If the speed limit says 55, I find that 52 MPH is slow enough to not burn too much fuel, but fast enough to be polite to other drivers.
( I drive whatever the speed-limit says, or just under it. )
I also don't use my A/C unless someone else is in the car. ( Which is stupid really )
I roll down the drivers side window 2" or less to get some air circulation, but not screw up the aero too much.
I find that the vent on my Civic is absolutely useless when it comes to cooling the inside of the car.
Also my averages of 42 MPG were on a rural road that I used to get to work and back.
I never drove in stop and go traffic, and the route I took had only three stop lights.

So....as far from 'real world' driving as you can get.

Whatever secrets you have for getting that kind of mileage out of a stock DX .... please let us all know. I would love to get that kind of mileage.

Since I now take a different route to work, I drive in a small amount of traffic. I was seeing 35 - 38 MPG ...untill recently. Now something is screwwy with the car and I just used close to half a tank to go only 130 miles. I'm not sure if I'll be able to break 25 MPG this month.

Strange as it seems, I just had the car inspected yesterday, and my emissions are supposedly cleaner than four years ago when I was getting twice the mileage.
I'll post the results at this site to see if I am reading the figures right.
I don't think the guy tested it right.

One more thing ...do you fold back the drivers side mirror ? Honda did an excellent job of designing the mirrors, so that they could be folded back.
I did a tuft test on my car and found them very streamlined when folded back.
I have pictures of the test if you would like to see them.

It seems reasonable. Lots of times you can trade off emissions for mileage. We would prefer people not doing that, but many still do (you guys know who you are ;) )

IIRC, you said that you had an automatic transmission. That alone will cost you 10-15 MPG under mild hypermiling conditions vs. a 5 speed. Basjoos has a very tall 3.25 final drive transmission which also helps with FE. The automatics were around 4.25:1. I do fold back the drivers side mirror on the VX. There is no mirror on the passenger side.

Good luck!

Yes. Automatics are not as good as standards when it comes to fuel economy.
I was just stating how hard it is to get the mileage that I had gotten in the past ( 42 mpg )

BTW, I hope I didn't hijack this thread.

Back on topic : The boat tail idea.

Basjoos : I think it's really quite clever of you to use clear plastic around the tail lights . I had wondered how I would make that work myself.
I planned to use plexiglass around the glass, but the problem with plexiglass is that it scratches so easily.

Guys - please post more images of your work. Im already inspired by what I have seen here.

It seems reasonable. Lots of times you can trade off emissions for mileage. We would prefer people not doing that, but many still do (you guys know who you are ;) )



I'll have to create a new post concerning emissions testing so that I can keep this thread on topic.

I'm curious - how has the public reacted to the boat tail?

Installed front wheel well skirts. The skirt is a made of an aluminum bar frame covered with coroplast and hinged at the top with piano hinge. There is enough tire clearance inside the skirt for normal on-road turns (lane changes, curvy roads, etc), but when I have to make a sharper turn, the tire rolls against a low profile (1/2"x6") conveyer roller that pushes the skirt out while I am making the sharp turn. Two springs at the bottom pull the skirt back in when the tire straightens out.

http://img.photobucket.com/albums/v417/MikeMariettaSC/80MPG%20Honda%20Civic/CivicBa.jpg

Front wheel well skirt
http://img.photobucket.com/albums/v417/MikeMariettaSC/80MPG%20Honda%20Civic/CivicBb.jpg

Wheels in full left turn position.
http://img.photobucket.com/albums/v417/MikeMariettaSC/80MPG%20Honda%20Civic/CivicBc.jpg

View of inside showing conveyer rollers.
http://img.photobucket.com/albums/v417/MikeMariettaSC/80MPG%20Honda%20Civic/CivicBd.jpg

Very clever. Man I'd love to see your car go to a body shop and have everything cleaned up and painted. Maybe after you save enough from gas you can do that and make it into a show car.

Yes - very clever indeed !
Can we see a picture from the front of the car with the wheels straight on ?
I'd like to see how flush that the assembly is when viewed straight on.
( How far does it stick out from the fenders ?)

Have you tested it on the road yet ? I'm curious to see what effect wind and water will have on it.

One other thing - the rear view mirror ... I don't see one.
Have you rigged up cameras in place of the mirrors ? If so, where can I purchase them ?

I've always day-dreamed of doing stuff like this to my car, but haven't had the guts to carry through with it. It's interesting to see something like this become a reality.

Thanks for posting.

So far I have driven it 200 miles at speeds of up to 70mph through all off this rain we are currently getting on the east coast with no problems. It also didn't overheat, a possible concern since I am exhausting my radiator exhaust air out through my front wheel well openings.

There is no driver's side rear view mirror, I just retrained my reflexes to look over my shoulder when I need to check that quadrant instead of looking in the mirror and then looking over my shoulder as I used to do. There are plenty of automotive video camera/small screen LCD displays systems available (google automotive video lcd), but I haven't gotten around to buying one yet.

As I keep adding all of these aero mods to my car, it coasts better, my mileage keeps increasing, the noise levels inside the car goes down, and the engine runs more relaxed when driving at higher speeds.

This photo was taken at night while it was raining. When closed, the assembly sticks out 2.5 inches at the bottom and gets less as you go up to the hinge.
http://img.photobucket.com/albums/v417/MikeMariettaSC/80MPG%20Honda%20Civic/CivicBe.jpg

I didn't notice the spring that holds the piece flush to the body at first.

Again, very clever ! ( My first thought upon seeing it was that it might have a tendency to catch air and act a a parachute - but this was before I saw the spring )

I would be really interested in seeing a breakdown of the varius modifcations that you have performed and the resulting changes in MPG ( Also,this way I could get a better idea of what the .cd is currently at. )
Thanks for the front view picture.

So far, I have installed a boat tail, grill block, underbody panelling, front and rear wheel well skirts, smooth hub caps, wheel spoilers on all 4 wheels, side skirts, removed driver's side mirror, and sealed body gaps. These mods are listed in order of effectiveness. Since a number of other factors (temps, rain, etc.) changed from tank to tank as I was installing these mods, it is difficult to fully quantify the exact improvement that each one contributed to the overall improvement in mpg. You can check my gaslog over at Gassavers (http://www.gassavers.org/garage/viewgaslog/40?) where you can see my how my lower driving technique only mpg's started rising as began adding the series of aero mods. I noted in the comments section when each mod was added. My original mileage in this car back before I started using either driving techniques or mods to improve mileage was 50mpg in the summer and low 40's in the winter.

We have the exact same car except for the transmission. ( mines an automatic )

I got an average of 42 MPG in ideal conditions ( a 12 mile commute to work on level roads , minimul turns, and half of this being at 3:30 in the morning ( early morning shift )
so no stoplights , traffic etc. never used the A/C ( even in 90* Texas heat ... is this insanity ? ), I tested a grill block one time in summer and got about 2 MPG better FE, but soon took it off because I got tired of the jokes at work.
( By the way this was during high 90s to over 100* temperatures when I did this. ) I did notice that it seemed as though the inside of the car was hotter and my transmission shifter would get really hot ,... despite this, the guage said that the engine was running COOLER with the grill block.
( I had a hole about the size you have in your grill block . )
I drove at 52 MPH ( speed limit 55 on the road i traveled )
I would even shift into neutral and shut off the engine at times - this only worked at night when there was no traffic and it was of little help since I have no hills. I could only coast for about a quarter mile before going so slow that I had to shut the engine back on.
I soon stopped doing though since I wasn't sure if I was dammaging the transmission by doing it .
I would also fold back the driver side mirror ( none on passenger side )

I plan to switch to LRR tires and possibly some lightweight aluminum wheels.
Besides putting a boat tail on the car, what other less visible mods can I do to the car to improve the FE ?

( Besides a transmission swap )

Thanks

Edit : Checked your gaslog. Thanks for posting that !

WOW! That is awesome basjoos! A 15 mph improvement is no small accomplishment. You've got me thinking about what I can do with my plastic body paneled Saturn. I may have to get my car up on jackstands and see what I can do with the under-body area.


My parents have a 2002 Saturn SL1 ( I think that is what it is - the 4 door with the rounded back glass )
I crawled under it and looked at the underbelly. From the factory, the car is very clean and tucked in. The only area that I saw that needed some help was around the back bumper.
The back bumper is hollow on the inside and acts as a parachute - cover this flush, and the air will exit much more smoothly.
I did some tuft testing out of curiosity on the back glass to see how the airflow would react to a rounded back glass. There was a lot of seperation back there.
Overall though the car is really clean. Saturn usually prints the .Cd to the third figure. The .Cd on the SL1 was something like .315 if I remember correctly.

I'm curious to know if some of those trips that you took in your gaslog were from a single trip at an average steady speed with no ' cheats'.
I'd like to see what this thing could do on several different ( short ) trips - each at a different speed. ( And without using 'cheats " )
Have you found a 'sweetspot' when it comes to speed ?
For example without coasting and other cheats, what is your average mileage at a steady 45, 55 , 65 and so on Mph ?
You car is my benchmark.

My commute is 52 miles in I-26 in North Carolina (speed limits 55, 60, 65mph) combined with a steep climb up the mountain from South Carolina. My other commute is 74 miles through mostly rural roads (speed limit 35, 45, 55) in South Carolina in mostly rolling terrain.

Less visible mods include underbody paneling, wheel spoilers, gap sealing using a clear caulk, using clear tape to do the grill block, and running the tire pressure up to 50+psi.

Most of the trips in my gaslog were my normal commuting to work, shopping trips, occasional road trips, etc.. My car is too old for a Scangauge, so I use my gas fill ups to calculate mileage. I haven't had the time to cruise at a chosen steady speed for the 150-200 miles it would take to get a reasonably accurate steady state mileage based on gas fill ups.

Do you know the cars .Cd figure ?
I'm eager to know what it is at now.

Published figures for our car are .31 for the Civic hatch and .32 for the Civic coupe. ( Honda )

I went out and looked at the front wheel well on my Civic. I seem to remember the front wheel being more flush with the body. As I began to look more and more at your design, I have come to appreciate it more and more.
Well done !

Not having access to a wind tunnel, I have no idea what my car's current .Cd figure is except that it is significantly below its original value since the car coasts much better than it did before I started messing with it.

Since you are getting about 30% better fuel economy and a a 20 % .Cd drop is about equal to a 10% raise in fuel economy, you must be some where around .124 !

Is that even possible ?

If I remember correctly, 0.11 is the theoretical minimum for a ground based vehicle.

Also remember that aerodynamicist in the wind tunnel spend supposedly thousands of hours refining the shapes of their cars, and still have a hard time even getting a car to drop from .33 to a .30 Cd.
I have read of things as small as an extra 1/16 of an inch body gap throwing off a good .Cd figure.
I doubt whether the caulk is doing you much good either, since it insn't exactly flush.

I did the exact same thing on my car, but made sure it was nice and smooth by smudging it using my finger and a wet rag. I used black caulk on mine since I have a blue car. I didn't want it to stand out too much.

Also remember that aerodynamicist in the wind tunnel spend supposedly thousands of hours refining the shapes of their cars, and still have a hard time even getting a car to drop from .33 to a .30 Cd.


let me reword that.... many has spent time trying to smooth of the shape of their cars without making it being REJECTED BY THE GENERAL PUBLIC.

Truth is, people want sexy cars, not a boat... lol even though I'd take the boat ;)

Phil's right. Cars' exteriors aren't designed, they're styled. If aerodynamicists had freer reign, we'd be burning a lot less fuel.

The general public generally rejects aerodynamic design because it's a fundamentally rational thing - which is counter to the emotional & irrational approach the majority of the car-buying public uses in purchasing decisions. E.G: the SUV fad.

Aerodynamics is a fairly mature science. It's not at all true that it's hard to get a vehicle from Cd .33 to .30. Give me or basjoos some cardboard and duct tape and a typical .33 vehicle and we'd be under .30 in an hour!

(It is relatively hard, on the other hand, getting a car whose Cd is already low - say, low 20's - even lower. Only due to diminishing returns as you approach an ideal shape.)

No, the real challenge is educating people on the issue of style vs. design: do you want to play along with the marketing departments' need to have you choosing between different "styles" just to make some kind of personal "expression"? Or do you want an efficient car? (Of course the two aren't necessarily mutually exclusive, but you get my drift.)

My hat's off to basjoos for taking his aero mods to the extreme, not only because his car is more efficient for his effort, but because maybe it'll help open a few people's eyes to the question of style vs. design, and think about why people react negatively to effective (and even practical) aerodynamic elements in auto design.

Hmmm....yes and no. The Lexus LS 430 is the most aerodynamic car in mass production today. ( Yes - I know the Insight makes this claim too, but they are actually equal - both are at a .25 Cd. The main difference in the two cars aerodynamically speaking is that the Insight has a smaller frontal area ... so I guess you could call it the winner. )

If they can make that brick of a car ( the LS430 ) have a .25 Cd, then they should easily be able to produce some exciting designs that the public would accept !

MetroMPG : I recognize your car from Phil Knoxs' group. Looks like you installed the wheel covers. The car looks much better than the factory design now .
The car looks 'grounded' now. ( The Metro design always seemed to look as if it were jacked up in the back . ... but you fixed it .... and it actually looks better now ! It looks like a factory install too by the way. Well done !
What kind of mileage change are you seeing now with the covers ?

(Sorry for the delayed reply...)

Hmmm....yes and no. The Lexus LS 430 is the most aerodynamic car in mass production today. ( Yes - I know the Insight makes this claim too, but they are actually equal - both are at a .25 Cd. The main difference in the two cars aerodynamically speaking is that the Insight has a smaller frontal area ... so I guess you could call it the winner. )

Minor point: the Lexus 460 is currently in production with the same Cd as the older 430 (out of prod'n). And they only get the .25 rating with the optional air suspension - without it, both Lexus models are .26 (still nothing to sneeze at).

To your point: I'd also call the Insight the winner because it's much shorter, and from what I've read, it's more difficult to get a low Cd on a short car than a long one like the LS, where you have so much more length to shepherd airflow in desired directions. Thus I'm not as impressed with the Lexus relative to the Honda.

MetroMPG : I recognize your car from Phil Knoxs' group. Looks like you installed the wheel covers. The car looks much better than the factory design now .
The car looks 'grounded' now. ( The Metro design always seemed to look as if it were jacked up in the back . ... but you fixed it .... and it actually looks better now ! It looks like a factory install too by the way. Well done !
What kind of mileage change are you seeing now with the covers ?

Thanks for the compliment. I'm happy with the way the skirts turned out. :)

Results of my aero fiddling to date:

Adding grille block and rear wheel skirts (http://www.metrompg.com/posts/grille-blocking-part-2.htm), I saw about a 5% FE improvement at 95 km/h. A cardboard partial Kammback (http://www.metrompg.com/posts/boat-tail-prototype.htm) mockup improved FE by about 2% at 89 km/h. Deleting the passenger mirror and folding back the driver's (http://www.metrompg.com/posts/mirrors.htm) netted about +2% at 88 km/h, and a full undertray improved things by another 2% at 85 km/h (not yet documented online).

MetroMPG : I love what you have done with the car. You are doing everything I wanted to do to my Civic.
I'd really like to see what kind of results you would get if you refined that Kamm back idea !


Thank you for posting your results !
One thing I really like about your car is that the changes that you have made to the car look like 'aftermarket' add ons.

You take it to the next level.

I did a tuft test on my Civic ( and posted them over at the other forum. )
It is surprising to see what the air does back there at the back of the car.
I'm curious to see what kind of results you would see if you did a tuft test on the back of your Metro.
( Best to do something like this as far out in the wild as possible so as not to be seen.) :o

I had everyone slowing down to take a look when I did my tuft test.
They must have thought someone shot that confetti that comes in a can all over my car .

What I found when I did a partial Kamm Back test like you did, was that the air reaches the edge of the cardboard extention and then curls underneath the extention. Im wondering if adding a small 'trip' strip to the edges would give the air a clean break and keep it from swirling under the extention.
What do you think Basjoos ?

About the LS430 : I think what makes the .Cd so impressive is that the car has those huge open spoke wheels , open wheelwells, upright three box design, and huge (upright ) grille. The car doesn't LOOK streamlined at all.
The point I was making is that if stylist can make a car like that so sliperry, then it would seem as though they are tring to fool the public into thinking that a 'slippery' car must look BORING.

Hey Basjoos,

I used to see your avatar (it being small) and I thought it was a pic of an 80's era car, the Avion (I knew the Avion was red but it was intended on being duplicated) then.....I found this thread and thought......man that is the coolest, that's a Honda and he lives in SC and did this himself! I'm really impressed with the front fender wells and the ingenious way you have dealt with turning wheel contact.

.......This thread should be Archived or made sticky for aerodynamic reference.
Excellent job without tons of $$$ or corporate support. Can I come see this car? I live in Concord, NC - Dale

Well right now you might not want to see it today: http://www.cleanmpg.com/forums/showthread.php?t=17016