Kammback doesn't work on my sedan

[ChazInMT]

Hey Barna,

I'm a goofy wonk for the Draw feature in Microsoft Word. It is quite a powerful little drawing tool once you get the hang of it all. I mostly use the "Autoshapes/Lines/Freestyle" to make a very rough shape, then I right click the feature, select "Edit Points" then right click the points to change them into corner points, then you can make any sort of curve you want out of the lines by manipulating the "guide wings". I can trace a car almost perfectly in like 5 minutes to copy its rough shape. And working with the "Format Autoshape" you can manipulate and measure angles to 1°. (Make the degree "°" by holding ALT and type "0176" (zero one seven six) when you release ALT, Whuuups there it is....) I “Insert Image” to get the picture into the Word Doc that I want to work with. When I’m done, I then convert the Word Doc to a PDF using Adobe, then Save that as a JPG. And Voila, I have a handy modified picture. I crop & resize the JPEG pic using Microsoft Office Picture Manager…..I hope I’ve told you all this and you have a PC not Mac…..Oh well, others may dig this. I keep meaning to sit down and do an extensive “How To” on using the tools I’ve mentioned, maybe in December.

Also, I'm toying with the idea of making a “Prius Back” for my Honda Civic, look for a junkyard trunk lid, then you can get medieval on the junkyard lid mounting whatever you want to it, however you want, and you still have your OEM lid to put back on to normalize your car if you need to. Heck, you could get one that's in awful condition (as long as it seals the trunk area) so you may get a good deal on it. You could easily come up with a quick release and/or hinge system for the Mod to be able to open the trunk if needed.

Charlie

[cfg83]

3dplane -

I did (what I hope is) a closer analysis. When I shift the center-of-camber forward, I get a 7.7 degree slope from the edge of the roof to the vertical line denoted by "30" :



When I look at the profile of the Protege, I *think* I see a roof that is taller in the back than other cars, most probably for the sake of rear seat headroom. Therefore I think that your stated slope of 12 degrees is too steep.

My Protege image is from tirerack.com, so it is decent but also subject to error. I had to rotate it 1 degree clockwise to make the tires line up.

CarloSW2

[d0sitmatr]

if you wanted to do a full cover cam back, would it be possible to make it sectional (3 or more pieces) almost in an accordion style ?
each piece from the roof would overlap the next piece in line as to avoid any parachuting.
this way, you could get the advantages of a full camback and still have the use of your trunk.
see weak mockup below



Im curious about your results.
plus, what sort of mpg are you seeing with no mods vs with ?
I have a 94 protege, 5 spd, no AC (from the factory) that Im going to be doing some aero mods to as well.

[cfg83]

d0sitmatr -

That's really interesting. Conceptually it works, but I suspect the devil is in the implementation details. Would there be a single "hinge point" for all the pieces or multiple hinge points or ?!?!?!?!?

CarloSW2

[AeroModder]

One thing that's crossed my mind is kammbacking sedans without boattailing them increases the size of the rear area, thus increasing the size of the wake. Hatchbacks can get away with it because their rear ends are already large, and the kamm reduces it. Since airflow still reattaches on the trunk, the "suction cup" isn't as large, even if the air is perfectly clean.

After removing my partial kamm, I couldn't tell if it was even doing much good.

[d0sitmatr]

thats a good point, sort of along the lines of how adding a full camper top to a truck takes away from your mileage by creating a larger suction at the tail end.

I went out and looked at my protege real good after my post, and all in all, the sectional kamm wouldnt really be feasible, not with keeping the lines clean and sloping in towards the middle point.

I did think of another method, which would be a quick detachable kamm, if its made out of light weight materials, it wouldnt be too much of a hassle. the only problem I can really see is how to attach it at the roof line and still give you the benefits.

what Id really like to do with mine would be an extreme mod to the rear end, both the window and trunk, which would be to make it into a hatchback such as the 94 escort 5 door HB had. but if I was to go that route, Id just buy an escort 5dr HB

[dkunitz]

Would it make sense to extend the trunk surface? I've seen sedan-shaped drag cars with enormous extensions that continue the line of the trunk. I think the vortex created under the extension might be more beneficial on sedans where you want to maintain easy access to the trunk.

[3dplane]

@d0sitmatr! Hey! Before any mods,absolute factory I could hit 53.5 as best MPG and had several tanks of 52+ (summer).
After these mods: Larger wheels (6% GPS confirmed ), holes in wheels blocked off, airdam ,upper grill block, seal gaps at hood,between frt bumper and grill,lights, removed A/C / Power steering belt,..I can't think of any more.
Now I was able to hit...53.75 MPG as a new personal record. A whopping 0.25 MPG increase.
I got to admit that this maybe helped me stay above 53 MPG for 5 tanks in a row as I was trying for a new personal record, but the numbers sure make me look like I was just wasting my time with the mods.

This is also proof to me that the single biggest mod by far is adjusting the nut behind the wheel!
As boxy as the car looks I think we underestimate the aero of it!

Barna

[d0sitmatr]

Hey Barno, thanks for the information !

now I know something is wrong with my protege (or the wheel nut is bad...)
there is no way Im coming close to that mileage, and Ive been driving very conservatively in the past 2 weeks.

I'll have to do some looking to see if I can find something.

~Mike

[3dplane]

Mine has the 1.8 L single cam engine and I believe this manual trans comes with the tallest ratio,so if you got a different engine in yours,you might also have a "revvier" trans gear ratio so that could waste some fuel for you.

I also live in Florida so that helps a lot!
And obviously I hypermile the crap out of it but I do move along with traffic except my engine spends about 2/3 of the time in the off state,however other commuters can't tell.

(For some reason in the green fuel signature thingy it shows up as a 2000 but it is indeed a 94)

Barna