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Old 11-28-2018, 11:48 AM   #1
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Body pans?

What do the undersides of buses look like? Do they look like cars, with all kinds of stuff exposed - wiring, drive shaft, etc? Has anyone enclosed the underbody of a bus so that it is aerodynamically smooth - I think this is called a body pan? and if so, what was the effect on mpg?
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Old 11-28-2018, 12:52 PM   #2
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Everything is exposed. Enclosing it would create potential cooling issues (experience from armor on a Jeep in the transmission and transfer case). So any enclosures would need ventilation engineered to prevent overheating. Enclosing it would also make it more difficult to maintain and inspect parts.

My guess is that any potential savings in MPG would be mitigated by the additional hassle and potential failure for the reasons above.
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Old 11-30-2018, 02:58 PM   #3
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I honestly don't have a clue but there are some pretty sharp folks talking about it over on https://ecomodder.com
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Old 11-30-2018, 03:14 PM   #4
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I think enclosing it can help possibly minor-league with aerodynamics.. but ultiomately you are in a square box.. i think more can be done by buying a bus that has a more aerodynamic shape like a Safe-T-liner C2.. im told those get pretty good mileage esp with the mercedes engines in them..



with already aerodynamic vehicles, botoom smoothing does help.. racers and rally-ers have been doing it for year.. however you look at the fact they are going at 100 MPH plus therefore the % of return is likely higher than on a bus at 65 MPH..



also the newer busses.. even though hated by many on this board.. are more efficient and get better mileage than their older counter-parts.. better engines. transmissions, and proper gearing go a long way to increasing efficiency..



Speed takes energy.. driving fast kills MPG... its a known fact.. drive my red bus at 60 I can get a solid 13.. drive it at 65. and its 11-14 however much closer to the 11-11.5 unless i have a nice tail wind.. then i go up to 14.. thats 15-20% on average..



busses are notorious for springing fluid leaks at some point during their lifetime... the last thing I want is to blow a trans cooler or fuel line and have flammable fluid fill up a body pan till it runs into the hot exhaust... not to mention working on or diagnosing trouble.. having to remove the panning on the bottom..
-Christopher
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Old 11-30-2018, 03:17 PM   #5
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Originally Posted by cadillackid View Post
I think enclosing it can help possibly minor-league with aerodynamics.. but ultiomately you are in a square box.. i think more can be done by buying a bus that has a more aerodynamic shape like a Safe-T-liner C2.. im told those get pretty good mileage esp with the mercedes engines in them..



with already aerodynamic vehicles, botoom smoothing does help.. racers and rally-ers have been doing it for year.. however you look at the fact they are going at 100 MPH plus therefore the % of return is likely higher than on a bus at 65 MPH..



also the newer busses.. even though hated by many on this board.. are more efficient and get better mileage than their older counter-parts.. better engines. transmissions, and proper gearing go a long way to increasing efficiency..



Speed takes energy.. driving fast kills MPG... its a known fact.. drive my red bus at 60 I can get a solid 13.. drive it at 65. and its 11-14 however much closer to the 11-11.5 unless i have a nice tail wind.. then i go up to 14.. thats 15-20% on average..



busses are notorious for springing fluid leaks at some point during their lifetime... the last thing I want is to blow a trans cooler or fuel line and have flammable fluid fill up a body pan till it runs into the hot exhaust... not to mention working on or diagnosing trouble.. having to remove the panning on the bottom..
-Christopher
I wouldn't call late model engines "better". Maybe better at mpg's but not better for fixing, not better for longevity. I mean better is totally subjective but unless you own a service center newer engines are rarely considered better by most folks running diesels.
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Old 11-30-2018, 06:14 PM   #6
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we were talking aboiut MPGs in this discussion so I used Better in that context... we werent talking aboiut reliability or break-fix.. one cannot argue that many of the newer engines and transmissions are more efficient.. obviously some of the emission controls do cause issues with efficiency as Regen cycles definitely cut into MPGs.. but some of the mileages that are being achieved by brand new busses is impressive... now granted brand new busses are obviously much pricier to repair than their 15-20 year old counterparts.. but this disacussion is about smoothing the body and increasing MPGs...
-Christopher
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Old 11-30-2018, 07:15 PM   #7
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Originally Posted by pengyou View Post
What do the undersides of buses look like? Do they look like cars, with all kinds of stuff exposed - wiring, drive shaft, etc? Has anyone enclosed the underbody of a bus so that it is aerodynamically smooth - I think this is called a body pan? and if so, what was the effect on mpg?
Easier than that and aerodynamically more effective would be air dams and skirting. Basically you seal the front and sides with respect to the ground. Take a lock at the modern long-haul 18 wheeler rigs

If you make these fairings from a flexible material and movable you can improve long distance highway mpg and then raise the fairings out of the way for boondocking.
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Old 11-30-2018, 08:09 PM   #8
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under body smoothing - undertrays

When you enclose the under body there are many many things to think about, some of which has been touched upon, like fluid colllection, cooling of parts like transmissions.

I see aerodynamics come into play at about 35 mph. .I bought a bullet butt bus because of aero dynamics. looks cool too. but the trailing side is usually more significant than the front. I will be putting under tray in the engine area, but I have to allow air from the radiator opening to flow around the turbocharger, and exhaust... I will be using temperature sensitive paints and stickers to thermal map the engine bay. air has to be managed around the exhaust, transmission and rear end. There will be a number of openings to allow air out of the under area, I also have to manage temperature around batteries, and skirt mounted condensor coils, and webasto coolant heater.

fenders over the rear tires it is important to keep the fender as tight as possible. smoothing the trailing side of the rear end and suspension. and the trailing side of the front axle / suspension. soothie hub caps on the rear duallies would help some too, look at what is happening on some of the big rigs. tractors and trailers.

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