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Aryana
Samba Member
Joined: November 09, 2015
Posts: 568
Location: Southern CA
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 Posted: Mon Jul 26, 2021 6:51 pm Post subject: Re: What is the actual OPTIMAL speed for MPG in a Vanagon? |
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| Igeo wrote: |
| Aryana wrote: |
| szegedin7 wrote: |
I wouldn't want to be running my engine over 4000rpm all day long, but you have a more modern engine.  |
A stock WBX that's maintained well has no problems whatsoever sustaining 4000+ rpm for hours on end.
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Ok I'll bite. You are driving a Vanagon 80 mpg with the slider open and a motorcycle hanging out in the breeze. Are you bragging or complaining? Hope I never encounter you on the road! |
Deal with it. Forget seeing each other on the road, I hope I never encounter you period. You must be a blast at parties. 
You do you and I'll do me. I've been driving this Vanagon for about half my life going back to the last century, so just remember: SLOWER TRAFFIC KEEP RIGHT
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Igeo
Samba Member
Joined: September 25, 2018
Posts: 888
Location: Oakland, CA
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| Posted: Mon Jul 26, 2021 7:22 pm Post subject: Re: What is the actual OPTIMAL speed for MPG in a Vanagon? |
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"You do you..." Spare me. How is that bike secured and what does it weigh? With that, your gear and (probably) only you, you're already pretty close to max GVW. Go ahead and ridicule me. You are irresponsible and dangerous.
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1987 Westfalia 2.1 WBX Manual |
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RolandD
Samba Member
Joined: January 15, 2017
Posts: 247
Location: Menomonee Falls, Wis
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| Posted: Mon Jul 26, 2021 7:44 pm Post subject: Re: What is the actual OPTIMAL speed for MPG in a Vanagon? |
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I believe the first step to determining the best RPM for the engine to run is to find the BSFC curve It shows fuel used per horsepower. For a rabbit diesel engine, that valley is at about 2700 RPM. I then changed tires and gear ratios to cruse at that speed. I consistently, for the last 20+ years, have gotten 32-34 MPG in a 82 Westy.
Roland |
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jimf909 
Samba Member
Joined: April 03, 2014
Posts: 7466
Location: WA/ID
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| Posted: Mon Jul 26, 2021 7:57 pm Post subject: Re: What is the actual OPTIMAL speed for MPG in a Vanagon? |
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[quote="khughes"]
| LachlanMcLean wrote: |
And the Westy is more like 0.51 - without the crap in the luggage rack, top carriers, solar panels, several inches of lift, and a Beverly Hillbillies' load of stuff hanging off of the rear...
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Hey! I resemble that remark...
15 mpg on a good day crossing WA state at 70 mph, which happens to be the optimal speed for minimizing mpg (the motorcycle doesn't fit in the van even with the slider open).
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- Jim
| Abscate wrote: |
Do not get killed, do not kill others.
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Current: 1990 Westy Camper - Bostig RG4, 2wd, manual trans w/Peloquin, NAHT high-top, 280 ah LFP battery, 160 watts solar, Flash Silver, seam rust, bondo, etc., etc.
Past: 1985 Westy Camper - 1.9 wbx, 2wd, manual trans, Merian Brown, (sold after 17 years to Northwesty who converted it to a Syncro). |
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dabaron
Samba Member
Joined: June 21, 2018
Posts: 2559
Location: Philly, mang
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| Posted: Tue Jul 27, 2021 5:24 am Post subject: Re: What is the actual OPTIMAL speed for MPG in a Vanagon? |
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| vegpedlr wrote: |
So turtling along at 45-55 listening to something groovy, I’m happy, the bus is happy, the people behind me, not so much. |
i like the cut of your jib. i've been starting to eschew the highways for the by-ways. sure it's a bit longer but it's hella nicer scenery and i've stumbled upon some fun roadside diversions.
the one thing i forgot to account for in my tests was the added load on the alt to charge the LiFePo system. in all instances for some period the system was recharging. how that translates into a decrease in MPG i'm not sure.
_________________
1991 Vanagon GL Camper
i had no idea i wanted to be a mechanic
"burnin oil and cookin coils" -- Destructo
BiWerks Design, LLC |
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Steve M.
Samba Member
Joined: July 30, 2013
Posts: 6829
Location: Fort Lauderdale, Fl.
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| Posted: Tue Jul 27, 2021 5:56 am Post subject: Re: What is the actual OPTIMAL speed for MPG in a Vanagon? |
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| dabaron wrote: |
| vegpedlr wrote: |
So turtling along at 45-55 listening to something groovy, I’m happy, the bus is happy, the people behind me, not so much. |
i like the cut of your jib. i've been starting to eschew the highways for the by-ways. sure it's a bit longer but it's hella nicer scenery and i've stumbled upon some fun roadside diversions.
the one thing i forgot to account for in my tests was the added load on the alt to charge the LiFePo system. in all instances for some period the system was recharging. how that translates into a decrease in MPG i'm not sure. |
It can translate into the alternator creates electricity by breaking a magnetic field in the coils.
The more it would have to generate the more resistance to spinning the armature. If it takes more energy to spin the armature the power to do it is coming from the engine.
How strong is that magnetic field?
I have seen 6 cylinder diesel generators with broken crankshafts because the generators where not syncronized when trying to connect them in "parallel". The magnetic field in the coils was strong enough to stop the engine doing 1800 rpm from rotating instantly when the switch was thrown. It was like putting a pipe into the spokes on a motorcycle wheel at 100 mph.
Now trying to measure that drag on the WBX it is probably not anywhere near the drag caused by the ac compressor which uses about 10 hp. to spin it, but it is taking energy to spin it under load.
Add some 100 watt headlight bulbs, ac fan, transaxle oil pump and cooling fan plus your kick ass music system and you are creating more load on a 90 amp alternator.
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This free advice is worth exactly what you paid for it.
There are seven days in a week. Someday is not one of them. |
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szegedin7
Samba Member
Joined: April 03, 2017
Posts: 117
Location: Southern California
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| Posted: Tue Jul 27, 2021 7:25 am Post subject: Re: What is the actual OPTIMAL speed for MPG in a Vanagon? |
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| vegpedlr wrote: |
So turtling along at 45-55 listening to something groovy, I’m happy, the bus is happy, the people behind me, not so much. |
Same here. I just did a very enjoyable ride up the east coast avoiding main highways most of the way. This country still has a lot of beautiful natural scenery when you get off the interstate. The van LOVES turtling at 45. At least in the South, people just pass you if you're going too slow for their liking. Round about Maryland, people start riding your rear end and getting ornery.
| RolandD wrote: |
I believe the first step to determining the best RPM for the engine to run is to find the BSFC curve It shows fuel used per horsepower. For a rabbit diesel engine, that valley is at about 2700 RPM. I then changed tires and gear ratios to cruse at that speed. I consistently, for the last 20+ years, have gotten 32-34 MPG in a 82 Westy.
Roland |
Interesting and great numbers. I might think about doing the diesel conversion if my van doesn't rust too much by the time it needs a rebuild.
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1990 Vanagon 2.1 |
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DuncanS
Samba Member
Joined: October 17, 2013
Posts: 4583
Location: New Hampshire
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| Posted: Tue Jul 27, 2021 11:44 am Post subject: Re: What is the actual OPTIMAL speed for MPG in a Vanagon? |
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Roland--Do you have those curves for the Vanagon? Seems the best thing would be to keep all four gears stock and have a fifth which would allow the engine to spin at the optimum RPM's while having a road speed of 65/70. When I took roadies with my brother, he would always ask when we got to 65 if I had another gear.
Duncan
P.S. looked at the Subie conversion. Would you guess it would be the same for an automatic? My original question was related more to the fore and aft position you would need for the engine to have the axles at the original Vanagon location Would the engine stick out the back or does the sloping firewall need moving forward? |
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RolandD
Samba Member
Joined: January 15, 2017
Posts: 247
Location: Menomonee Falls, Wis
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| Posted: Wed Jul 28, 2021 6:45 pm Post subject: Re: What is the actual OPTIMAL speed for MPG in a Vanagon? |
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I can probably put my hands on the curve. It was in some Industrial VW literature from the 80's.
I did change my final drive from a diesel to an air cooled, a ratio of 41/32, and put in a higher 4th. My third gear is roughly where 4th used to be, when tire size is included.
Roland |
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Abscate
Samba Member
Joined: October 05, 2014
Posts: 22644
Location: NYC/Upstate/ROW
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| Posted: Wed Jul 28, 2021 7:44 pm Post subject: Re: What is the actual OPTIMAL speed for MPG in a Vanagon? |
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60 amps at 12 volts from an alternator is 720 watts or about 1 HP. Give up 10-20% for alternator efficiency but it’s a lot less than an AC compressor
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