39.5 MPG in a sedan!! (1999 Plymouth Breeze with custom Kammback)
 

My wife recently took my plymouth breeze out for a little 750mi jaunt to visit family. I had just finished a prototype "fastback" and this provided for a good way to test it on the highway. She got 39.5 mpg on the first leg of the trip, which was 370mi of highway/expressway 55/65 mph. Our best effort before ecomodding was 32mpg, so this was awesome. On the way home she averaged only 35mpg but this included driving around, Grand Rapids which could account for most of the loss. All in all I think she saved almost a full tank of gas!!
My other mods are: AC delete, Power steering delete, Wiper blades removed taped front wheel covers.

I got 39.74 this winter in my sedan. It is amazing what you can get in a full size car. I still need to fab a kamm back.

Have any pictures, bsch? That's pretty impressive, as a plymouth breeze doesn't have a very steep angle coming off the roof, so I wouldn't expect such an improvement. Great job!

I think actually that the AC and PS deletes also affected FE. I had been averaging around 31-33mpg an my mostly highway commute to work and back with just these. As for Pics, How do I go about posting them? I am much less adept with computers than with cars.

Click "POST REPLY" below, left.
Click the paperclip icon above the message text box.
Click "Browse..." and find the file on your comp
Click "Upload" once found
Close the "Manage Attachements" window and click "Submit Reply"

tried this, but the it seems that my connection is too slow. I will try again later at the library.

Photo is likely too large if it's not working via dial-up. There's a ~100 kb limit on attached images. Resizing down to approx 500 pixels wide will get it in the right neighbourhood.

That is a Awesome increase. Congratulations!

thanks, these pics are with the plexiglass window out, as I am preparing to turn it into a finished hatchback.

Very cool! Thanks for posting.

I don't suppose you did any tuft testing as well?

One question- With a kammback on a sedan, how would you get to the trunk?

Hmmm...

You could also hinge it at the upper rear window. Open & prop the kammback, then open the trunk.

I might try some tuft testing, but the winds in my area are fickle so I might need to borrow a ventilation fan from the Fire Dept

I plan to remove the trunk lid and rear window, permanently attach the kammback and make the window into a hatch. currently I get to the trunk via the rear doors, as I have removed the entire rear seat.:thumbup:

Check your local laws - you may need to install safety (tempered) glass into the window slot to comply with inspection standards. I don't believe so, though, considering that most 'verts have plastic/plexi windows in the back.

bschloop -

Wow! That looks great. I always liked the Plymouth Breeze. A hatchback Breeze would have been cool. The side view reminds me of a Mazda MX3.

CarloSW2

There are no annual inspections in MI, but I want it to be safe, so I checked, and plexi is ok for the rear.

wow, that looks pretty nice. I'm still amazed that it improved the highway mileage that much for a breeze. I really gotta do a fastback test on my car now. I've been wanting to for a long time...

The Cd on the newer metro sedan is better than that of the hatchback, I'm assuming due to the smoother airflow off the back due to the trunk, a fastback like this would benefit it even more. Plus it would have a better attachment point for the farther back portion than a cammback or boattail on a hatchback :) Getting into the trunk is what the folding rear seats are for lol. you could just do the whole thing out of plexi, and make a hinged edge type frame that attaches at the top of the rear window...

Bschloop, great accomplishment!! I would have guessed the slope is too steep to keep flow attached.
Is your Breeze a manual transmission or automatic?
2.0 or 2.4 engine?
Ray Mac

Can you still access the trunk? how are you going to go about putting a hatchback on it? Will be interested in seeing it mature.

I'm starting to hatch a plan on my Maxima. Looking at the pics of the breeze, I wonder if there is a very clear elastic plastic that is also durable. If so, I would attach the plastic like how he has it on the breeze and use the closing of the trunk to tension it and make it stiff enough to be useful. And still have the use of the trunk.

Did any of that make sense to anyone else?

Great results

I want to do exactly the same on my gen 1 Prius except all in plexi.

So, you want to stretch a straight sheet of plastic from the roof to the trailing edge of the trunk? Well, I bet it would reduce drag somewhat, and once you find suitable materials and fasteners, the rest will be trivial.

On the downside, the most aerodynamic shape is a gradually increasing curve. It will be hard to approximate that shape with something flexible.

If you follow the lead of convertibles with transverse stiffening rods, you'll probably end up with lots of drag (just like soft-top convertibles have).

On older sedans with large trunks, you might be able to get away with having a rigid, composite section attached to the trunk, another one attached to the roof, and a flexible section in between.