Jeep Cherokee "Aeromatics" (Kammback / partial boat tail)

[JeepNmpg2]

Ok, I'll admit that I'm grinning from ear to ear, I got a lot finished today:

I spliced together a lot of 24x20 inch cloroplast signs that were donated to me by the local fort here, to make a "undershell" in the place of ribs to give the plastic skin some structure.



I liked it so much, I finally finished it all of with my heatgun and here is the cleaned up results:



Then I took a trip down to a friends house in Olympia, just off of the freeway (about 25 miles each way), stopped and picked up a couple of things, and left ten minutes later to come back home. No drafting or other stranage driving (except honking at a few rubberneckers so they wouldn't wreck), but my Jeep can now NC (Neutral Coast) and not lose any speed while going down two hills on the freeway, where it would lose a considerable amount before. And even better: Normally I drive at 60-62mph with the TPS reading 16 the whole time, now I hold it at 13-14 for the same sustained speed! So, "the proof is in the pudding" as they would say, and the whole trip averaged 26.6 mpg. EPA average for my vehicle is only 14 in town and 18 on the highway. Thats just shy of 50% better than highway!

Side note: Does anyone know how to interpret the IGN number on the scangauge? the highest I've been able to see is 40, but it's been everything below that.

Ok, enough tooting my own horn (even though it is my build thread). I make another trip out to the peninsula in the next two weeks, so I'll make another comparison to that old tried and true run. Oh, and here's a picture from tonight showing the fully funtional rear hatch as promised:



I suppose next for me is figuring out a better solution for the top mounts of the JeepKamm rather than the ratchet strap currently being employed. Then it's on to doing something about my ridicoulous front end. 30 mpg is in sight baby!

[ChazInMT]

Dang Dude, You work fast.

I like what you've done but my hunch is it could be improved. The length seems a tad long, you could build it shorter I think and get similar results. It looks like it may be cumbersome in the long run and foul weather, and I wonder about legalities with the covered rear lights and length.

I know Aerohed put a 3 foot (+ or-) flow collector on back of an old 67 (+ or-) VW Transporter van and improved its performance a bunch.

The shape seems to initially drop too quickly. The transition should be more subtle.

Here is my take on it.



The sides should curve in equally as well since a bunch of air is moving there too.

Also, if you're not using the roof rack, figure out a way to lose that, it can't be helping you.

Great Job!!

[Phantom]

You might want to get a 3rd brake light for the kammback, you could hang it from the back or glue a magnet to it and stick it just above the plate or on the back skid.

Now that I relooked at your pics you should be able to wire the lights on the skid to your 3rd light.

[ChazInMT]

Hey Jeep, ran across this today, great stuff that shows a bit more what I was trying to say. Check it out, it's right in the sweet spot of what your doing.

Cheers.

http://ecomodder.com/forum/showthrea...info-2072.html

[JeepNmpg2]

Originally Posted by Phantom

You might want to get a 3rd brake light for the kammback, you could hang it from the back or glue a magnet to it and stick it just above the plate or on the back skid.

Now that I relooked at your pics you should be able to wire the lights on the skid to your 3rd light.

By skid I'll assume that you mean the hitch carrier, I've already got plans to install lights on the kamm so I don't have to use the hitch carrier to stay legal. I definitely agree that a third brake light is needed asap.

The next problem ive found is to use the hatch with the kamm installed is a giant pain so I need to fashion some kind of clip-on cable system that essentially extends the handle to the rear or side of the kamm.

Thanks for the suggestions guys and gals. I thought this thing would be a weekend project but it has taken on a life all to itself.

[JeepNmpg2]

Originally Posted by ChazInMT

Dang Dude, You work fast.

I like what you've done but my hunch is it could be improved. The length seems a tad long, you could build it shorter I think and get similar results. It looks like it may be cumbersome in the long run and foul weather, and I wonder about legalities with the covered rear lights and length.

I know Aerohed put a 3 foot (+ or-) flow collector on back of an old 67 (+ or-) VW Transporter van and improved its performance a bunch.

The shape seems to initially drop too quickly. The transition should be more subtle.

Here is my take on it.



The sides should curve in equally as well since a bunch of air is moving there too.

Also, if you're not using the roof rack, figure out a way to lose that, it can't be helping you.

Great Job!!

Thanks man. I agree that in the pictures it looks like it has a really abrupt droppoff at the end of the roofline, but I can assure you, it's not as bad a transition as the photo's make it out to be. The sides are tapered in quite a bit and the whole backend turns into a half circle shape instead of keeping the square geometry that the vehicle has (Thanks to MetroMPG for that inspiration). I'm attaching a photo of the kamm sitting vehicle side down on the ground to illustrate the side profile tapering.

As far as length goes, it's exactly 48 inches further out than my bumper. I parked next to a extended cab Ford F-150 today and my rig with kamm was two inches longer. I'm also used to pulling a trailer with the Jeep, so having a little extra on the arse isn't out there for me.

Again, thank you for the well intentioned comments, and please keep them coming.

[RobertSmalls]

Originally Posted by JeepNmpg2

See, roof racks can be good for mpg.

You'll probably want to tuft test it eventually to find out where you have attached flow and where your angles are too steep / abrupt. I think you'll have flow detachment at the sudden transition from square to angled, especially near the top corners. But if you're seeing an mpg improvement, it's obviously better than stock.

[brucey]

Dude that's awesome! I hope you have better luck with yours than I did with mine.

[cons]

I love using bungee cords too. Its funny to hear bungee cord and rigidity in the same sentence though.

[JeepNmpg2]

Hey guys and gals, I just found a great spot for A-B-A testing really close to me! It's a nearly four mile stretch of "tree-tunnel" so winds should be minor, and on the weekend and at night, there is very little traffic. I don't have cruise control, but I'm used to holding my right foot steady while watching the TPS on my Scanguage. So if you are following this thread and waiting for proof, I should have some definative results posted by this weekend.