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Old 04-24-2011, 10:55 PM   #1 (permalink)
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VW Beetle TDI Kammback

I just finished an experiment with my homemade Kammback. Made of cloroplast and packing tape, my design improved my fuel economy remarkably. Typically, my car averages around 38/39 city and 43ish Highway.

With the Kammback, I achieved 55.4 mpg.








Anything relevant is welcome. Please give me suggestions or comments.

Thanks!


Last edited by SwamiSalami; 04-24-2011 at 10:58 PM.. Reason: mistake on photos
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Old 04-24-2011, 11:00 PM   #2 (permalink)
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Nice! what was your testing procedure?
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Old 04-24-2011, 11:04 PM   #3 (permalink)
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That's amazing for such a simple set up.
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Old 04-24-2011, 11:15 PM   #4 (permalink)
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Well, I've been using fuelly.com for quite a while to track mpgs. (which is where I get previous #s)

For my experiment with the kammback, I drove around town with it for a few days. Then to test it on the highway, I fueled up, hit the highway and came back to the same station and refueled in EXACTLY the same manner, for a round trip of 57.6 miles @ 1.040 gallons.

Unfortunately, I don't have a scanguage at this time. I'd love to get one, though. I think that if I was able to get a "live" or "immediate" reading, it might even reveal more mpgs. I say this simply because I did have to enter/exit the freeway.

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Old 04-24-2011, 11:49 PM   #5 (permalink)
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Quote:
Originally Posted by dieselbeetle View Post
Well, I've been using fuelly.com for quite a while to track mpgs. (which is where I get previous #s)

For my experiment with the kammback, I drove around town with it for a few days. Then to test it on the highway, I fueled up, hit the highway and came back to the same station and refueled in EXACTLY the same manner, for a round trip of 57.6 miles @ 1.040 gallons.

Unfortunately, I don't have a scanguage at this time. I'd love to get one, though. I think that if I was able to get a "live" or "immediate" reading, it might even reveal more mpgs. I say this simply because I did have to enter/exit the freeway.
Sorry, not trying to rain on your parade, but a 33% gain from before is a bit much (considering MetroMPG only achieved a 15% gain from a full boat tail).

http://ecomodder.com/forum/showthrea...mpg-10691.html

Since you dont have a scanguage, i strongly suggest testing tankful-tankful, instead of relying on small fillups. Small fillups are very misleading because they don't average out any "miscellaneous" factors that could affect your mpg readings. Try to get as many tankful readings as possible to strengthen any mpg results you are achieving.

If you can only do short highway runs, at least try to use the cruise control to cancel out your "foot bias."

I highly recommend reading this thread
http://ecomodder.com/forum/showthrea...ery-11445.html
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Old 04-25-2011, 04:16 AM   #6 (permalink)
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Beware, it begins with only a test (mine was with cardboard) and a morning you find a chloroplast car in your driveway

You should consolidate the chloroplast as the gravity will make it bend.
This will be accentuated by fast speed for the top and side winds for the sides of your mod.
You should abuse strong tape and monitor it closely before the heat deteriorates it and so your mod flies away...

Does your mod always permits you to open your hatch ?
Please take a picture with the open hatch.

How much your mod reduces the rear view from the steering wheel ?
Please take a picture from inside.

Did you felt a difference under your right foot ?
I can definitively feel a difference with/without the rear wheel skirts, the car accelerates stronger and it's more difficult to keep it at a steady speed when the road isn't perfectly flat.

What about a rear wheel skirts test now ?

About the scangauge, I have 3 advices : buy it, buy it and buy it.

Have fun,

Denis.
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Old 04-25-2011, 05:35 AM   #7 (permalink)
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Quote:
Originally Posted by dieselbeetle View Post
I just finished an experiment with my homemade Kammback. Made of cloroplast and packing tape, my design improved my fuel economy remarkably. Typically, my car averages around 38/39 city and 43ish Highway.

With the Kammback, I achieved 55.4 mpg.
Like jedi_sol wrote, a 33% increase is huge for a mod like this, so expect this gain to be watered down in everyday driving over an entire tank.

Then again, the Beetle's rear end is notoriously bad in the aerodynamic department. Everything and anything will likely help it


What transmission is in the Beetle - I'd guess an automatic ?
50+ averages should be in there for the manual version, but the auto (even DSG) will only work really well on the motorway.


Didn't the Beetle come with an on-board computer showing the mileage ?

A ScanGauge will work on diesels, but it's not a miracle solution for them.
I've found they get calibrated to one's driving style rather than to your actual fuel consumption.
Keep the same driving style, and it'll become very accurate with calibration.
Change your driving style, and it will be off ... until it gets calibrated to your new habits.
But if the Beetle didn't come with any FE display, a SG (or the cheaper ultragauge) will help you getting better FE.
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Old 04-25-2011, 05:41 AM   #8 (permalink)
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There's something in that overall shape, I think.
See the Toyota Will Vi:

And this concept from Teijin:


These are 'closed' shapes so I wonder what the aero difference would be with a rear panel on yours?
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Old 04-25-2011, 10:55 AM   #9 (permalink)
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I'm a little confused. I thought the goal was to reach a high rate of efficiency?
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Old 04-25-2011, 11:12 AM   #10 (permalink)
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Quote:
Originally Posted by jedi_sol View Post
Sorry, not trying to rain on your parade, but a 33% gain from before is a bit much (considering MetroMPG only achieved a 15% gain from a full boat tail).

http://ecomodder.com/forum/showthrea...mpg-10691.html

Since you dont have a scanguage, i strongly suggest testing tankful-tankful, instead of relying on small fillups. Small fillups are very misleading because they don't average out any "miscellaneous" factors that could affect your mpg readings. Try to get as many tankful readings as possible to strengthen any mpg results you are achieving.

If you can only do short highway runs, at least try to use the cruise control to cancel out your "foot bias."

I highly recommend reading this thread
http://ecomodder.com/forum/showthrea...ery-11445.html
I agree with you, there are a lot of variables at play here. However, I wholeheartedly achieved 55.4 miles per gallon with my kammback. No ifs, ands, or buts about it.

It, of course, does make sense that a better "testing" would be conducted on longer trips or "tankfuls" at a time.

I did run into a problem concerning the theory of testing:

Without using a scanguage, theoretically, it is a must to drive the EXACT distance, terrain, speed and using the same accesories (a/c, vent, radio, etc.).

WITH a scanguage, I would assume that there would be a problem as well. While the scanguage is incredibly accurate from moment-to-moment, it doesn't account for terrain at any given moment (especially where the terrain is less obvious).

So I guess what I mean is...with a scanguage, how do you know the moment is right to take a readout?


Also, of course I used cruise control.

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aerodynamics, kammback, new beetle, tdi, volkswagen

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