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Old 09-09-2011, 12:09 PM   #101 (permalink)
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Originally Posted by Sven7 View Post
Wow, cool project. I'm tempted to put some belly pans on my own Twin I Beam now!

One question: what did you bolt the belly pans to?
If you go back through the thread there are 30 or 40 or so step by step photos of the process as it progressed. So far the belly pans have been the least productive of the mods, but to be fair about it, I've only tested them once and I still have to vent the front better and finish the differential and add some wheel fairings.

If you want to go for maximum results build a boat tail first, then the belly pans. The first test of the boat tail yielded a 33% increase in mileage! That was a one way slightly down hill run but the average for that trip was still over 25%. Not bad for 24 foot (OK it's 28 foot now) 7.3L diesel RV.

You also get the added benefit of having four more feet of storage space, and, you get to answer everyone's questions when you stop for fuel. That part is fun, especially when they walk up with the deer in the headlights look and say, 'What the hell is that?'.

If you'd like to see the build of the boat tail, go to page 7 (at the moment) of the 'Aerodynamics' page, and click on 'Aero RV', it's laid out like this thread with lots of step by step photos.

Sorry, now it's on page one, I forgot when you post something it moves the thread to the first page. I need to figure out how to do links on this site.


Last edited by orbywan; 09-09-2011 at 01:30 PM.. Reason: forgot something
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Old 09-09-2011, 01:46 PM   #102 (permalink)
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Originally Posted by Sven7 View Post
Wow, cool project. I'm tempted to put some belly pans on my own Twin I Beam now!

One question: what did you bolt the belly pans to?
The answer to that question is anything you can find or fabricate. The frame, sub-frames, the coach body at the underneath edges, cross-members, and mostly brackets that you fabricate along the way.

The most surprising part of the process is that 5/16 hex head self-tappers went through the frame and sub-frames faster and easier than any drill bit I tried, and I tried several, hardened, titanium, etc., all new. They don't exactly go through it like butter, but I was surprised at how well they did go through it. The sharpest and fastest to go through by far were made by L.H. Dottie company in Commerce California, someone left a whole assortment of them in my shop, but even the Hillman screws at the local ACE hardware did a good job.
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Old 09-13-2011, 07:13 PM   #103 (permalink)
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After reading this entire thread: I realize I am relatively a noob when it comes to aeromodding but here are My thoughts and suggestions to get a little more out of your project:

1) Change all lubricating fluids to 100% full synthetic such as Royal Purple or Amsoil (engine, tranny, differential, wheel bearing grease)

2) Extend your boat tail further instead of making it square in the back

3) Flat panels over the wheel openings

4) Air Bag suspension, lower cruise height on flat smoooth highway runs

5) Boat Tail Nose of vehicle

6) Replace Both Door Mirrors with Video Cameras (you're already setup for this)

7) Get Aftermarket Computer Chip - Retuned for better fuel economy (some kits have handle held controller with both economy and performance switch)

8) Add Overdrive Unit or change rear gear ratio.

9) Drive a little slower

I hope to see you break 25mpg soon... If anyone can do it, I believe you can do it after seeing your craftsmanship and work ethic.

Keep it up

Dave
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Old 09-13-2011, 09:04 PM   #104 (permalink)
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Quote:
Originally Posted by orbywan View Post
I can't do the pizza pans on the front Otto, they're dually type wheels where the center of the wheel sticks out at the hub. I'm reluctant to do that in the back because of brake overheating but I suppose I could take my infrared thermometer gun, make a run without them in the mountains pulling the boat, check the inside wheel temp, and do it again with the pizza pan and check it again.
Orbywan,

I was looking at the mooneye website and they had mooneye disks for chevy duallies. The centers were cut out, so if you wanted you could go to thier site and see if they have disks that would fit, or you could cut out the centers of your pizza pans. I think a little cover is better than none at all.
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Old 09-14-2011, 05:42 AM   #105 (permalink)
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I'm thinking what might work well for belly pans is to go from the front to just ahead of the bottom of the firewall, then on the next section curve it up to fit to the bottom of the firewall/floorpan area, cutting as needed to fit closely around stuff.

Then you'd have an outlet for engine compartment air through a slot that shapes and smooths the airflow, and as little as possible of that hot air getting between the floor and the rest of the belly pan.

Google semi trailer skirts for plenty of interesting reading. Just about every semi trailer now is running various types of angled skirts. They catch the air coming from under the tractor and in from the sides, smoothing it out and directing it out past the trailer wheels. Around 7% MPG improvement. Full skirts that resemble "ground effects" kits and also skirt the rear wheels do even better but cost more, are more difficult to install and have to be partially removed for wheel service. They'll also get trashed by tread coming off and blowouts. I suspect the extra cost and the annoyance/time/damage potential of full trailer skirts are why they're seldom if ever used.

IIRC the idea is a big isosceles triangle wedge with a 15 degree pointy end with the back ends right out to the edge of the trailer. The upward angled cut at the front also factored in, the angle works better than a simply straight bottom edge. Might be an experiment to try under your van.

One article I found when I looked this stuff up was a paper on the effect of various rear mud flap designs. A full width flap increased drag and reduced MPG but one with a gap in the middle increased MPG over no flap at all. Have to find the article to see what the numbers etc. are.

What's the average MPG for semi trucks these days? I recall not long before the flat front tractors died out, some company built one with every aero trick they could come up with and squeezed 10 MPG out of it, which was bleeping excellent for any semi.
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Old 09-14-2011, 06:03 AM   #106 (permalink)
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Here in Europe a bigger van than Ford E-150 like Ford Transit Jumbo, Iveco daily H2 3950, MB Sprinter, Renault Traffic, Fiat Ducato ... are getting 27-21 mpg on diesel. And I'm trying to reduce aero drag, lol
Because my van have a cd=0.365 iveco daily and cd = 0.355 Volkswagen LT
If i want 30 mpg i just turn on cruise control at 50 mph, 400 Nm of Torque and 177 bhp.
I will try with belly pans from engine to rear on my 24 feet vans.
I know better is a tail 6 feet width and 8 feed tall of flat rear its a big vacuum generator, but i think is very difficult because i need to open doors (270) loading/downloading goods.
Thanks for your post and lots of time.

Last edited by ausias; 09-14-2011 at 09:21 AM.. Reason: correction on units
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Old 09-14-2011, 12:48 PM   #107 (permalink)
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Quote:
Originally Posted by R0gue76 View Post
Orbywan,

I was looking at the mooneye website and they had mooneye disks for chevy duallies. The centers were cut out, so if you wanted you could go to thier site and see if they have disks that would fit, or you could cut out the centers of your pizza pans. I think a little cover is better than none at all.
I've been reading so much information on all this I need to get a notebook and start writing down web site locations, authors, etc. I don't remember where I found it, but I read a paper on undercarriage air flow that said that their experimentation showed that having the front wheels 'vented' and the rear wheels blocked (as in with a wheel cover) reduced drag on the wheels by 96%.

I'm impressed on one hand and wondering if they got their data screwed up on the other. My front wheels have the stainless steel covers on them that have fake lug nuts on them, or did. I took that smaller cover off and took all the fake lug nuts off and put a plate on instead to eliminate all the nuts hanging out in the breeze. There's a joke there but I'm going to leave it alone.

I attached a photo of the modified cover, don't have a before shot, my digital camera was dead at that point.

The rest of the cover has four small holes in it to let the disc brakes breathe a little. For now I'm going to leave the front alone and put the pie pans on the rear since they claim that had such a huge effect.

Who knows what is right with a lot of this stuff. If blocking off the rear duallies has a noticeable effect, I'll try them in the front as well. Thanks for the suggestions Rogue.

I just looked at the photo I posted. There's part of the problem. The tire and wheel are covered with disc brake pad dust, the other side is clean as can be. That means the driver's side disc brakes are hanging up. Time for servicing the disc brake calipers. Oh boy, I get to get greasy.
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Old 09-14-2011, 01:08 PM   #108 (permalink)
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Here in Europe a bigger van than Ford E-150 like Ford Transit Jumbo, Iveco daily H2 3950, MB Sprinter, Renault Traffic, Fiat Ducato ... are getting 27-21 mpg on diesel. And I'm trying to reduce aero drag, lol
Because my van have a cd=0.365 iveco daily and cd = 0.355 Volkswagen LT
If i want 30 mpg i just turn on cruise control at 50 mph, 400 Nm of Torque and 177 bhp.
I will try with belly pans from engine to rear on my 24 feet vans.
I know better is a tail 6 feet width and 8 feed tall of flat rear its a big vacuum generator, but i think is very difficult because i need to open doors (270) loading/downloading goods.
Thanks for your post and lots of time.
Thank you ausias. So let me see if I understand this right. You're getting 30 mpg gallon out of 24 foot van at 50mph, from a vehicle with 177 bhp? So that would make it about 3.0L, is that right? If you don't mind me asking, what are the dimensions of your box and how much does your rig weigh when you're doing this?

If my guesses about your vehicle are correct, I can only imagine what kind of gains you would get with a boat tail. If reducing the rear drag on my 7.3L boat anchor gives me 25 - 30% + improvement, so far, I can only imagine what your motor of half or less displacement would see. I realize you have to open your back doors. Could you make the tail in two halves that would swing away to allow access to the box doors?
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Old 09-14-2011, 04:41 PM   #109 (permalink)
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Quote:
Originally Posted by orbywan View Post
Thank you ausias. So let me see if I understand this right. You're getting 30 mpg gallon out of 24 foot van at 50mph, from a vehicle with 177 bhp?
Yes
So that would make it about 3.0L, is that right?
Yes, Iveco 4L F1C engine 3.0 HPT, with 380.000 milles, and 200 thousand more expected.
If you don't mind me asking, what are the dimensions of your box and how much does your rig weigh when you're doing this?
Wheelbase: 12.96 ft. 3950 mm
External=> Long: 23.01 ft. Height: 8.76 ft. Width: 6.55 ft.
Cargo Area=> Volume: 15.6 m3 (550.68 cu ft.) L: 14.96 ft. H: 6.23 ft. W: 5.91 ft.
3500 kg overall weight on average (legal maximum), 7716 lb.
Top speed: 112 mph (but I was a little afraid driving >100 mph on German Autobahn and I did not reach or exceeded that speed)


If my guesses about your vehicle are correct, I can only imagine what kind of gains you would get with a boat tail. If reducing the rear drag on my 7.3L boat anchor gives me 25 - 30% + improvement, so far, I can only imagine what your motor of half or less displacement would see. I realize you have to open your back doors. Could you make the tail in two halves that would swing away to allow access to the box doors?
The IVeco Daily with full Load consumption at cruise speed of 107 kph (66.5 mph) is 10.5 L/100 km or 22.4 us mpg.
In same condition Volkswagen LT 35 2.8 TDI 158 cv, 23.5 mpg@66.5 mph, 230.000 milles ODO.

My first attempt will be underbody drag.
I have a partner with the same Iveco Daily and 585.000 mi on the clock. and he have not plans on buying a new one yet.
Maybe first conversion in usa will be put a small eficient turbo-diesel engine,
I did some calculations and getting cd=0.32 on that van will reduce consumption in about 9 %, (sorry I think in I.S. units and not in milleage,) that is 11 % milleage improvement at full load.

Last edited by ausias; 09-14-2011 at 04:50 PM..
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Old 09-14-2011, 05:06 PM   #110 (permalink)
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The IVeco Daily with full Load consumption at cruise speed of 107 kph (66.5 mph) is 10.5 L/100 km or 22.4 us mpg.
In same condition Volkswagen LT 35 2.8 TDI 158 cv, 23.5 mpg@66.5 mph, 230.000 milles ODO.

My first attempt will be underbody drag.
I have a partner with the same Iveco Daily and 585.000 mi on the clock. and he have not plans on buying a new one yet.
Maybe first conversion in usa will be put a small eficient turbo-diesel engine,
I did some calculations and getting cd=0.32 on that van will reduce consumption in about 9 %, (sorry I think in I.S. units and not in milleage,) that is 11 % milleage improvement at full load.
Good information Ausias, thanks. 22.4mpg is pretty outstanding for a 7,700 pound load at 65mph. I need to get a gross weight on my RV. I found several photos of 'IVeco Daily' on the web, is yours like the one in the photo below?

I read something two days ago that said blocking off the rear wheels (like with a full moon hubcap type disc) would reduce the wheel drag by 96%. I seriously doubt that number is accurate but it does get my attention.

When you do your belly pan I hope you'll take photos of the process and post them on ecomodder. Your van is close enough to the MB Sprinter chassis many many owners here would love to see the process and see the results. Good luck. If I come up with something good for the wheel fairings I'll let you know. Crap, now I can't load the image of the IVeco for some reason. Basically it looks very similar to a MB Sprinter van right?

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