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Discussion Starter · #1 ·
This is my first post, so I'm not sure if it is taboo to ask about other Honda models other than the Insight.
A lot of the other Honda forums out there are just devoted to racing, and I felt that you all might be more knowlegeable concerning a technical question I was wondering about :

I have a 1993 Civic Hatchback, and I would love to find any aerodynamic data that Honda did on these cars.

Does Honda guard their wind tunnel studies as a trade secret, or can the data be purchased ?

I noticed that on this site, Honda claims that " a civic hatchback has roughly the same frontal area as the Insight, but that the .cd is .36 for the hatchback.
What year hatchback are they refering to ?

Road & Track published a figure of .31 for a hatchback and .32 for a sedan on a 1992 - 1995 model

Was this figure accurate ?

Thanks for any help
 

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I've never seen any wind tunnel data other than the drag coefficient, which is .25. The other more aerodynamic car produced was the General Motors EV1 at .19, but they were never sold, only leased and they're now mostly all crushed. Making the Insight the most aerodynamic car you could buy.

This is the most data on the Insight's aerodynamics I know of:
http://www.insightcentral.net/encyclopedia/enaero.html
 

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Some other aerodynamic coefficients (taken from here):

0.14 1986 Ford Probe V Concept car
0.19 1996 GM EV1 Electric car
0.25 1999 Honda Insight Hybrid car
0.25 2000 Lexus LS430
0.25 2000 Audi A2 "3-litre"
0.26 1989 Opel Calibra 2.0i base model
0.26 2000 Mercedes C180
0.27 1996 Mercedes E230
0.27 1997 VW Passat
0.27 1997 Lexus LS400
0.27 1998 BMW 318i
0.27 2000 Mercedes C-class C200 up to C320


Sorry, couldn't find 1993 civic anywhere!
 

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Sean said:
This is my first post, so I'm not sure if it is taboo to ask about other Honda models other than the Insight.
A lot of the other Honda forums out there are just devoted to racing, and I felt that you all might be more knowlegeable concerning a technical question I was wondering about :
Not exactly "taboo" but we _are_ an Insight forum. Since your question is limited, specific and "related" enough its not off-topic enough to lock. And it is a question related to some posted data on this site. :)


Sean said:
Does Honda guard their wind tunnel studies as a trade secret, or can the data be purchased ?
With the CD information the calculation(s) needed for anything aerodynamic load related are possible. AFAIK no other data is available or for sale. Most "other" information related to aerodynamics is more textbook related and is an exercise in translating the book to reality. Other than the education you'll need a wind tunnel for the application side of the work. Some can be reasonably home built (small but "usable") I'd search the web if this is what your looking for.

Sean said:
I noticed that on this site, Honda claims that " a civic hatchback has roughly the same frontal area as the Insight, but that the .cd is .36 for the hatchback.
What year hatchback are they refering to ?
Hmmm. AFAI remember there was no 96-00 hatchback model offered so it must be the 88-91 model or older. [edit, Oops, there was. But it is a rare beast :!: ;) ]

Looks like clett posted some other CD data for you too :!:

HTH! :)
 

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Discussion Starter · #5 ·
Rick said:
I've never seen any wind tunnel data other than the drag coefficient, which is .25. The other more aerodynamic car produced was the General Motors EV1 at .19, but they were never sold, only leased and they're now mostly all crushed. Making the Insight the most aerodynamic car you could buy.

This is the most data on the Insight's aerodynamics I know of:
http://www.insightcentral.net/encyclopedia/enaero.html
Actually, the above link that you provided has the published figure of .36 for a Civic hatchback that I was refering to. ( Its at the bottom of that first paragraph. )
My guess would be that the figure is refering to the 1996 - 1999 (? ) body style since the roofline had a shorter overall length and the hood had the additional opening above the grille.
Unfortunately, I don't own an Insight ... but I do own the Civic hatchback that they are refering to.

I have an old article from Road and Track that has a published figure of .31 for my car ( a 1992 - 1995 model )

I intend to imitate the body style of the Insight as much as possible with my car. I intend to add wheel covers to the back, partial covers to the front, a full belly pan ..etc.
What's the old saying - imitation is the sincerest form of flattery ?
I just hate the fact that I can't clean up the cars emissions as much as I'd like to, since this is really what I'd like to do more than anything.

So how did Honda arrive at the .cd figures for their cars ? Surely some wind tunnel testing was done on these cars.
So what ever happened to that data ?

Thanks in advance !
 

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Discussion Starter · #6 ·
Since this is not really an appropriate forum, can anyone recommend a forum that might be more appropriate ?
Thanks !

BTW, have any of you replaced the mirrors on your cars with mini-cameras, or plugged up the grille for better mileage ?
 

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Sean said:
BTW, have any of you replaced the mirrors on your cars with mini-cameras, or plugged up the grille for better mileage ?
Re the camera mirrors, you could try to catch up with this guy who has already done this with his Insight. But good luck finding him because a whole lot of people on here want to find out how he managed to hook up a wind turbine to the stock battery! :?

If you want to plug up the front grille, you'd better convert to EV first! (like this guy). Otherwise best to cover up only a quarter to a half in the winter (like the truckers do).

I think given your project, you should aim for the lowest hanging fruit first - ie aim for the best mpg returns on the lowest amount of cash/time investment first. Here's a (not too exhaustive) list of what I think may help increase the mpgs of a stock vehicle considerably. Hopefully some of the others on here will be able to add to the list!

1) Increase the tyre pressures to their maximum rating - usually good for about 5% - 10% mpg improvement.

2) Learn to drive like a "hypermiler" - plenty of tips from the folks here elsewhere in this forum (eg accelerate gently, anticipate all lights and stops, no unneccessary braking etc).

3) Leave the air conditioning off until you really need it!

4) Keep the windows up - when open can detract 5-10% from cruising mpgs. Roof-racks are even worse - unless you've got to move a ladder...

5) Remove all unneccessary weight from the car. Tool boxes and other things in the back all add up to extra gasoline.

6) Make sure the car is tuned up nicely and serviced properly (oil, filters and plugs past their best can make for pants mpgs).

7) Switch to lower rolling resistance tyres. The most expensive approach in this list, but good for maybe another 5-8%.

Good luck! Any more tips out there? :)
 

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clett said:
Re the camera mirrors, you could try to catch up with this guy who has already done this with his Insight. But good luck finding him because a whole lot of people on here want to find out how he managed to hook up a wind turbine to the stock battery! :?
Thought we reasonably disproved the reality of the wind turbine in a thread way back when...

Sean said:
So how did Honda arrive at the .cd figures for their cars ? Surely some wind tunnel testing was done on these cars.
So what ever happened to that data ?

Thanks in advance !
DATA :?: the bottom line in any wind tunnel testing is CD. And its usually published somewhere in relation to the car. Data as to the wheel skirts, underbody cover and camera mirrors they didn't use :?: Doubt it ever existed since such aero friendly attributes apparently were never considered for production on that vehicle. There are general rules of thumb that can be applied to such mods and the resulting CD improvement factor. Don't have them though, sorry. Searched the web :?: Some university sites may have what your looking for.

Again clett has posted the best economical approach to better MPG. Custom modding of your Civic to equal the Insight's CD will be a long time in paying for themselves in MPG savings. And AFAI remember back in the last oil "crisis" there was a Datsun model that tweaked its CD by a several hundredth's of a point by adding a rear spoiler. The only problem was that if more than 20 lbs. were added to the trunk the resulting squat of the rear suspension made the CD even _worse_ with the mod than without :!:

Have you read :?: :

F.A.Q.: IMA and Insight Design Concepts White Paper
http://www.insightcentral.net/forum/vie ... php?t=3174

It should help you better understand how the Insight's MPG ability was achieved. There's not one individual thing that makes it happen. So simply modding a 95 Civic for better aero will have a correspondingly limited to none MPG improvement.

HTH! :)
 

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I have just discovered a very interesting book, although it is not directly related to the Insight. It's "The Leading Edge--Aerodynamic Design of Ultra-streamlined Land Vehicles" by Goro Tamai. The author was involved in the MIT solar car program, and the book is a terrific compilation of photographs, technical data, and analysis of low drag cars. About 99% of it is directly related to solar cars, but much of the material applies indirectly to the Insight. There's nothing in here about bicycles, which is good because bicycles are so different from cars. There is a moderate amount of math (which can be skipped over) that is a useful expansion on the text. Just the collection of pictures is probably worth the price; the ultra-high tech (and expensive) 1996 Honda Dream is featured several times.

The only shortcoming of the book is that it was published in 1999, so it doesn't cover the most recent solar car events. But for a general discussion of low-drag car aerodynamics, it's the best I know of.
 

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Another good book on this topic is "Race Car Aerodynamics--Designing for Speed" by Joseph Katz. It's got a similar mix of text, photos, and math as the previous one, and is also pretty interesting. The only real problem with this one is that it's targeted at the racing community, and drag reduction is not quite as important as lift/downforce management. As a result, the stuff they talk about is not quite as applicable to the Insight.
 

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Might as well also mention "The Anatomy and Development of the Sports Prototype Racing Car" by Ian Bamsey. This one is not really related to the Insight hardly at all, except for a few comments right at the beginning. It's a comprehensive history of the development of modern Le Mans type sports cars, starting in the 1930s when drag was first considered, and then moving on to the high downforce cars that emerged in the 1980s.

The one thing that does make it relevant to the Insight is that the designers of these cars, like the Porsche 917 for example, usually had two models, one used on the "regular" tracks and then a special version for use at Le Mans. That's because Le Mans has the Mulsanne Straight, a 3.5 section of track that is straight except for a kink about halfway through. So you need to have lower drag at Le Mans than at other tracks, and you have to be able to keep the car on the road at 200+ MPH (check out the movie "Le Mans" for some great photography showing how tough this is), and you have to be able to negotiate the kink without slowing down. (Some of this is a bit dated now that they've put in a chicane at the kink...)

My main complaint about this book is that it was published in 1991, just before Mazda won at Le Mans, the only Japanese company to do so--despite a long, big-money program by Nissan in the 1980s and 1990s.
 
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