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targis58 Samba Member
Joined: July 11, 2006 Posts: 539 Location: sunnyvale,ca
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Posted: Sun Feb 08, 2009 1:19 pm Post subject: roof cargo box vs. MPG |
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So.. I have been carrying the box for a few month and I was wondering how much it affects the MPG on the van...
Has anyone actully calculated/tested the MPG difference? _________________ 90 westy 2wd w/ TBD |
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PDXWesty Samba Member
Joined: April 11, 2006 Posts: 6235 Location: Portland OR
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Posted: Sun Feb 08, 2009 1:25 pm Post subject: |
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I have not calculated the mileage difference myself, but I only get 15-16 mpg both around town and on the highway. When others report 18-21 mpg, I don't know how they do it. I have a very good running tuned 2.1, but my cargo box is always full and I carry a lot of weight on board all the time. I have a feeling all this extra weight and the aerodynamics of the box and rack contribute to the lower mileage.
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mmdingman Samba Member
Joined: July 18, 2007 Posts: 49 Location: Metro Detroit
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Posted: Sun Feb 08, 2009 1:31 pm Post subject: aero |
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my experience is that the vanagon is such an aerodynamic brick to begin with, I cannot detect a difference w/ and without (could also have something to do with the accuracy of my fuel gauge). I have some objective equations concerning MPG w/ and w/o a ski box in an aerodynamics book... will dig up. _________________ 85 Wesfalia Wolfsburg (2009ish - present)
87 Syncro Hardtop (1997 -2010ish) |
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Crughy Samba Member
Joined: July 12, 2004 Posts: 576 Location: Montreal, Qc
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Posted: Sun Feb 08, 2009 3:01 pm Post subject: |
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Like all drags, it gets exponentially worse with speed.
Might not make such a diff a 60 but at 70 and over, it might hack more than a couple of mpg.
JP |
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levi Samba Member
Joined: February 11, 2005 Posts: 5522 Location: Las Vegas
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Posted: Sun Feb 08, 2009 3:28 pm Post subject: |
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Here's two vans for you to compare:
It's informative and not at the same time, as you'll soon discover.
The engine is identical, since I installed it in one, then removed the engine and installed it in another van.
First was an 86 pop-top with overhead rack almost identical to targis58.
However this had an auto tranny.
Pulled that engine and put it in an 85 westy/AWagen. 4 speed.
The 86 never returned better than 17-18 city, 14-16 hiway.
The 85 never gets worse than 21-22 city, 21-25 hiway.
All numbers from GPS.
Notable difference is tires.
The 86 auto had wide, soft compound Nokians, and I suspected they may have been out of alignment, since the outside 1-1/2" of the fronts wore considerably faster than the rest of the tire. However I did take it to a shop for alignment and they said it was okay.
The 85 has skinny hard compound tires. _________________ One of these days I'm gonna settle down,
but till I do I won't be hangin round.
Going down that long lonesome highway,
gonna see life my way
https://youtu.be/cSrL0BXsO40 |
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jackbombay Samba Member
Joined: October 19, 2007 Posts: 2723 Location: Eastern Idaho
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Posted: Sun Feb 08, 2009 3:40 pm Post subject: |
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I'm sure some of you feel the same way as I do about ODOs, that is unless the ODO is know to be accurate, I assume it is inaccurate.
Of the 6 cars I have owned in my life only one had an ODO that was within %1, that was a 1978 chevy motorhome.
I typically only trust GPS speed and mileage numbers, unless the ODO is regularly compared to 50+ miles of highway mile markers which I do often, I have plenty of time while road tripping so why not?
As far as the box/MPGs go, the front bin on westy's RUINs the aero so the box probably won't affect MPGs much, IMO. _________________
Gas struts to pop your top easily!
Pop Top strut kits now available for late Bay window Westies
Samba ad here.
DIY artificial rain gutters (ARGs) |
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WestyBob Samba Member
Joined: June 11, 2004 Posts: 2346 Location: Portland, Oregon
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Posted: Sun Feb 08, 2009 5:21 pm Post subject: Re: roof cargo box vs. MPG |
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[quote="targis58] I have been carrying the box for a few month and I was wondering how much it affects the MPG on the van...
[/quote]
I think the culprets have been identified: speed, tires, engine health, brick body.
Around town the carrier affect should be negligable since the engine isn't straining to move air out of the way for it. |
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targis58 Samba Member
Joined: July 11, 2006 Posts: 539 Location: sunnyvale,ca
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Posted: Sun Feb 08, 2009 6:50 pm Post subject: |
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jackbombay wrote: |
As far as the box/MPGs go, the front bin on westy's RUINs the aero so the box probably won't affect MPGs much, IMO. |
Anyone found the solution for this? any wind deflector for the front bin? _________________ 90 westy 2wd w/ TBD |
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MrPolak Samba Member
Joined: June 20, 2004 Posts: 1336 Location: AG ,atnaltA
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Posted: Sun Feb 08, 2009 7:23 pm Post subject: |
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Speaking of aerodynamics:
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tds3pete Samba Member
Joined: April 04, 2004 Posts: 914 Location: Seattle, WA
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Posted: Sun Feb 08, 2009 8:09 pm Post subject: |
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Years ago we had a small corporate fleet of VW Dasher diesel wagons. They were all identical, except some had the factory roof racks. The ones with the roof racks got around 2 mpg less on the highway.
We were surprised to see that much difference for just the bars running front to back.
Not a scientific test by any means, but a measurable difference. _________________ '58 Westy camper-come and gone
'73 Westy-bought new in Holland,now gone
'86 Syncro weekender-come and gone
'79 Westy...Oscar
'95 Eurovan Camper/5 spd...Marsha Mellow |
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dixoncj Samba Member
Joined: June 17, 2004 Posts: 1083 Location: Charleston, SC
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Posted: Sun Feb 08, 2009 8:40 pm Post subject: |
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We have an '02 1.8t Passat Wagon. With regular surf racks on it, it gets about 5mpg less at highway speed. W/our big aerodynamic Yakima box, it gets about 8-9 miles less. Big damn difference. You can really tell what a diff aero's make on a car that's the shape of a dart vs a brick. I take both off when we go on a long trip unless they're really necessary. |
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?Waldo? Samba Member
Joined: February 22, 2006 Posts: 9752 Location: Where?
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Posted: Sun Feb 08, 2009 8:46 pm Post subject: |
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I've been curious how much of a difference mud flaps make.
Andrew |
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madspaniard Samba Member
Joined: August 18, 2008 Posts: 3795 Location: Alameda, CA
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Posted: Sun Feb 08, 2009 8:50 pm Post subject: |
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Andrew A. Libby wrote: |
I've been curious how much of a difference mud flaps make.
Andrew |
south african or german? |
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jackbombay Samba Member
Joined: October 19, 2007 Posts: 2723 Location: Eastern Idaho
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Posted: Sun Feb 08, 2009 8:55 pm Post subject: |
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tds3pete wrote: |
Years ago we had a small corporate fleet of VW Dasher diesel wagons. They were all identical, except some had the factory roof racks. The ones with the roof racks got around 2 mpg less on the highway.
We were surprised to see that much difference for just the bars running front to back.
Not a scientific test by any means, but a measurable difference. |
TDI Jetta sedans have no roof racks and were EPA rated at 49 MPG, the Jetta TDI wagons have factory roof racks and are rated at 50 MPG, fwiw. _________________
Gas struts to pop your top easily!
Pop Top strut kits now available for late Bay window Westies
Samba ad here.
DIY artificial rain gutters (ARGs) |
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dixoncj Samba Member
Joined: June 17, 2004 Posts: 1083 Location: Charleston, SC
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Posted: Sun Feb 08, 2009 9:02 pm Post subject: |
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Jack - the roof racks on the jetta wagon just like the passat - runs front to back only out of the factory. You put a pair of crossbars on that sucker - with surfboard pads or other stuff - and mileage is going to drop. |
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jackbombay Samba Member
Joined: October 19, 2007 Posts: 2723 Location: Eastern Idaho
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Posted: Sun Feb 08, 2009 9:08 pm Post subject: |
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targis58 wrote: |
jackbombay wrote: |
As far as the box/MPGs go, the front bin on westy's RUINs the aero so the box probably won't affect MPGs much, IMO. |
Anyone found the solution for this? any wind deflector for the front bin? |
Cut it out, build a masonite "form", and fiberglass it over. Thats what I did, less wind noise on the highway too. I changed wheel/tire size at the same time so its hard to say how much of a difference the bin elimination alone made, but I picked up 2-3 MPGs on the highway.
Last trip loaded to 5200 pounds I got 34 MPG at 67MPH (speed and distance GPS verified) and it is really hard for me to ever drop below 30 MPG on the highway under normal conditions.
I get 31 MPG in city driving never getting above 35 MPH, I do have an E-TDI. I've never read any 1st hand MPG numbers as good as mine, fwiw. My best tank was 37 MPG. This spring I'm going for a 40 MPG tank, at 55 it should happen.
That \/ is what I was referring to when I said the bin ruins aerodynamics.
MrPolak wrote: |
Speaking of aerodynamics:
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_________________
Gas struts to pop your top easily!
Pop Top strut kits now available for late Bay window Westies
Samba ad here.
DIY artificial rain gutters (ARGs) |
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jackbombay Samba Member
Joined: October 19, 2007 Posts: 2723 Location: Eastern Idaho
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Posted: Sun Feb 08, 2009 9:12 pm Post subject: |
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dixoncj wrote: |
Jack - the roof racks on the jetta wagon just like the passat - runs front to back only out of the factory. You put a pair of crossbars on that sucker - with surfboard pads or other stuff - and mileage is going to drop. |
But the dasher racks are the same as the jetta racks IIRC, front to back, right? _________________
Gas struts to pop your top easily!
Pop Top strut kits now available for late Bay window Westies
Samba ad here.
DIY artificial rain gutters (ARGs) |
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targis58 Samba Member
Joined: July 11, 2006 Posts: 539 Location: sunnyvale,ca
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Posted: Mon Feb 09, 2009 7:07 pm Post subject: |
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dixoncj wrote: |
We have an '02 1.8t Passat Wagon. With regular surf racks on it, it gets about 5mpg less at highway speed. W/our big aerodynamic Yakima box, it gets about 8-9 miles less. Big damn difference. You can really tell what a diff aero's make on a car that's the shape of a dart vs a brick. I take both off when we go on a long trip unless they're really necessary. |
Wow it's amazing how just racks without box can cause 5mpg difference!!
Was that WITH or WITHOUT a wind fairing? _________________ 90 westy 2wd w/ TBD |
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dixoncj Samba Member
Joined: June 17, 2004 Posts: 1083 Location: Charleston, SC
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Posted: Mon Feb 09, 2009 7:10 pm Post subject: |
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Without - it's brutal. Blow's my mind. Just shows how big a diff aero's make at 70+mph. |
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reluctantartist Samba Member
Joined: August 13, 2006 Posts: 1927 Location: Bloomington, IN
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Posted: Mon Feb 09, 2009 8:04 pm Post subject: |
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Jack when you say "Cut it out, build a masonite "form", and fiberglass it over." Did you just build a cover to cover the indentation or did you remove the rack all together? _________________ 1982 Westy, 1974 412 Variant... Yes, Aircooled's are great! Oh and I do have modern computer controlled vehicles too, but I just don't care about them. |
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