KAMM-BACK Festiva! WHAT?

[Darlo]

Oh man, I am getting so many looks! Havent gotten pulled over yet though!

I think I will have to wait for a couple fills before getting any meaningful results, as I have been doing a lot of stop and go driving with this tank, and the Kamm only really is effective at hwy speeds........I will know more when I fill for the first time if I get REALLY good mpg, or even near my best, as with all the city driving I should get around 45-48mpg (summer average), and not 50-51mpg (my best).

[Festiva Time]

I think you need to flatten the "roof" part (to match the Festiva roof) in order to make it look right. Just my opinion.

[Darlo]

I think you need to flatten the "roof" part (to match the Festiva roof) in order to make it look right. Just my opinion.

That would defeat the entire purpose! I am attempting to reduce the area of the turbulence at the back of the car, and keep that turbulence as far away from the car as possible. If I make the angle higher, it would mean more total area, and thus be less effective...... I dont care about looks at all!

[Darlo]

I installed the Kamm at the wrong time, as I have only driven 2 tanks of gas in the last 2 months (Broke my foot). Also, my studded winters are on now, and the weather is rainy and it is cold etc.....Gas mileage is decreasing, lol....... I will be back to driving 600 miles a week in January - April, so I hope to compare those numbers to my mpg last year at that time........

Also. I did indeed flatten it out a bit, and changed the shape a little since the pics, but it is mainly the same......

[litesong]

I am attempting to reduce the area of the turbulence at the back of the car.......

I believe a 'spoiler' designed to 'fill' the generated vacuum at the back of Festiva is a better idea. Not a spoiler like so many manufacturers place on their vehicles. A thin downward curving metal spoiler that isn't attached to the top rear of Festiva, except at the right & left sides of the car, that is designed to skim off the 'boundary layer' of air flowing over the top of Festiva & direct it downward over the back of Festiva, would help fill the vacuum that is trying to suck Festiva backward & reduce its mpg. The 'spoiler' is like those 1960 metal attachments to large station wagons that were designed to keep the back window clean.

Of course, such spoilers are not made for Festivas to drive fast, since they could add a bit of lift at the back of Festiva. At velocity, Festiva could be loose at its rear & even lift a bit on its rear shocks.

[FestYboy]

the type of spoiler you describe won't "fill" the void as you would want it to. it WILL infact create a larger vaccum bubble by giving a lifting motion to the roof's boundary layer and starting the bubble sooner. what you REALLy wnat to so is gradually allow the roof air to join the side and most importantly, under car air at a gradual rate to keep boundary air from detaching and causing surface turbulance.

[Darlo]

the type of spoiler you describe won't "fill" the void as you would want it to. it WILL infact create a larger vaccum bubble by giving a lifting motion to the roof's boundary layer and starting the bubble sooner. what you REALLy wnat to so is gradually allow the roof air to join the side and most importantly, under car air at a gradual rate to keep boundary air from detaching and causing surface turbulance.

+1 on that point FestYboy!

The optimal is a boat tail, like the one on this Honda Civic ---> http://www.aerocivic.com/

[Advancedynamix]

I believe a 'spoiler' designed to 'fill' the generated vacuum at the back of Festiva is a better idea. Not a spoiler like so many manufacturers place on their vehicles. A thin downward curving metal spoiler that isn't attached to the top rear of Festiva, except at the right & left sides of the car, that is designed to skim off the 'boundary layer' of air flowing over the top of Festiva & direct it downward over the back of Festiva, would help fill the vacuum that is trying to suck Festiva backward & reduce its mpg. The 'spoiler' is like those 1960 metal attachments to large station wagons that were designed to keep the back window clean.

Of course, such spoilers are not made for Festivas to drive fast, since they could add a bit of lift at the back of Festiva. At velocity, Festiva could be loose at its rear & even lift a bit on its rear shocks.

Like the ones that they put on chevy blazers. They also keep the rear window a lot cleaner.

[mattman]

there was a IMSA body kit for the mid 70's honda cvcc hatch that had a large rear spoiler that came of the roof had an opening an then a wing it extended past the back about a foot or almost two an from things i had heard was a great additon for handling an all for the hatch been thinking of trying to make somthing like that for the festy once i get all the other stuff taken care of i will try to find some pics if i can

[kayweb]

imsatial.JPG
imsakit.JPG
reviving an ancient thread but this is the monster you speak of, yes?

[mikeyjd]

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reviving an ancient thread but this is the monster you speak of, yes?

ha that is cool! not that it would have much positive impact on coefficient drag reduction

edit: Darlo your kamm-back angle is about 1.5x as many degrees as it should be for attached air flow (22 degrees maximum) and about 3x as many as you'd want for maximum drag reduction (12 degrees)^

[Darlo]

I also should have made it about 1.5 times longer! But I was doing the best I could with tape and coroplast, lol.....I did see a 3% increase in fuel economy though!

[jawbraeka]

this would be interesting if you decided to sell these as a kit.. clearly this needs refinement, but, with the right look, i think this would take off.

as long as it was either bolt-on or clip-on, i think this would be a winner.

the rear wheels look interesting too.

ever thought of doing what the expensive performance cars do and have a "sealed" bottom so there's less wind drag and resistance?

[mikeyjd]

I also should have made it about 1.5 times longer! But I was doing the best I could with tape and coroplast, lol.....I did see a 3% increase in fuel economy though!

length would have helped. but the angle is more important. there is a template on ecomodder that can be used to overlay a side picture to show you where your line should fall. for maximum efficiency gains 12 degrees is what you are aiming for.

[mikeyjd]

this would be interesting if you decided to sell these as a kit.. clearly this needs refinement, but, with the right look, i think this would take off.

as long as it was either bolt-on or clip-on, i think this would be a winner.

the rear wheels look interesting too.

ever thought of doing what the expensive performance cars do and have a "sealed" bottom so there's less wind drag and resistance?

like this? http://www.fordfestiva.com/forums/sh...202#post598202