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#75
by
Alcaid
on 24 Sep, 2014 07:44
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A fully loaded one with a kayak on the roof, that MPG is quite acceptable. It is an IDI after all and they will never be up to the fuel efficiency of a TDI
I have done 61.9MPG driving long distance with my '10 Passat wagon, 1.6TDI commonrail engine, no cat, no DPF and a custom tune
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#76
by
Gizmoman
on 24 Sep, 2014 08:04
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Just for reference, a vanagon getting 20 mpg is about the same as a jetta getting 30 mpg.
OK - I get that the mileage is not good - if this was your rig, where would you
start looking for issues?
I'd back off on the fuel screw a bit but go power would suffer greatly and as far as I know, there's no smoke.
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#77
by
libbydiesel
on 24 Sep, 2014 08:34
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International forum members should bear in mind that we use US gallons which are smaller than Imperial gallons. US gallon is 0.83 Imperial Gallon.
Your mileage isn't horrible, just a little less than I would expect even given the kayak on the roof. As I mentioned, my high top gets better than that while towing a loaded trailer. I averaged 25 mpg on a trip to Colorado towing a trailer loaded with a complete AAZ engine, a spare vanagon 5-speed, three high tops and the windows/vents to go with them. My high top is an AHU so that would account for a 15% (3 MPG) increase in fuel economy, but my experience has shown that the high top takes away some/most of that gain at highway speeds. Towing a trailer loaded in that manner would be similar to the kayak on the roof.
Low fuel economy is hard to track down as EVERYTHING affects fuel economy. There are three basic categories that affect fuel economy: aerodynamics, rolling resistance and drivetrain tune. Often too much focus is on the engine. There is also often a lot of time and expense required for small changes. I would personally take the approach of driving more, enjoying the van and tracking fuel economy. Depending on the results, go from there. For reference, your van moderately loaded cruising flat ground (round trip or no wind) at 65-70 mph with your AAZ engine and no kayak on the roof should average 27 mpg with everything is reasonable tune.
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#78
by
Alcaid
on 24 Sep, 2014 08:51
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International forum members should bear in mind that we use US gallons
My numbers where in miles per US gal. 3.8 liter / 100km to us Europeans
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#79
by
Gizmoman
on 24 Sep, 2014 08:52
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Thanks libby.
To be honest, I'm pretty happy with it as it is.
I wish I had nothing better to do than fiddle with it but I have a house renovation I have been putting off.
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#80
by
libbydiesel
on 24 Sep, 2014 11:05
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To be honest, I'm pretty happy with it as it is.
That sounds to me like the best approach.
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#81
by
745 turbogreasel
on 24 Sep, 2014 12:43
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The kayak and rack are probably - >2 MPG, killing the boundary layer over the entire surface of the roof.
Driving slower
perfect alignment and tire pressure.
Cruise RPM should be at peak torque, not sure where you are at.
My Xcab 4x4 is close to that if I can keep it under 70, so I'd think you have some room to improve.
Read this?
https://cumminsengines.com/uploads/docs/cummins_secrets_of_better_fuel_economy.pdf
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#82
by
libbydiesel
on 24 Sep, 2014 19:17
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A westy even without a kayak already has the boundary layer destroyed by the luggage rack. The cd of a westy is 14% worse than a tin top just because of the luggage rack. I'm not saying the kayak didn't also have a significant effect but probably not the full 5-7 mpg.
Stock AAZ peak torque is at 2,000 rpms. I'm sure it's a fair amount higher than that with the Holset. Regardless, gearing for highway cruising at peak torque for an AAZ in a vanagon may not be the best approach if your cruising speed is 70-75 MPH. To maintain those speeds on moderate grades with rpms at peak torque will likely require enough of an increase in torque that the transmission will not survive well. IMO, for a vanagon, it is much more cost effective in the long run to gear shorter, cruise with more power but less torque and replace the trans less often.
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#83
by
Blocksmith
on 24 Sep, 2014 19:33
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Don't want to rain on anyone's parade--I certainly understand the efficiency and thrift side of owning a vw (wouldn't daily drive one if not, eh?
), but for something like a vanagon that (I would imagine) gets used only for vacations etc., for myself I wouldn't get too worked up about 'lower than expected' fuel economy, especially for anything that isn't getting driven across the entire U.S. every summer like my family is used to. I mean, we're talking about spending x amount of money on a number of different things to go have a good time; is another 50 bucks (or less) for fuel per trip really worth a massive, potentially ongoing headache trying to track down what combination of things is causing an issue that may not even exist in the first place?
You've done a
fantastic job with the build--I guess I'm just saying that if I had just finished something like what you've accomplished here, it might be nice to just enjoy it for a while before pulling hair out trying to fix the ways that it doesn't fully live up to every expectation.
Whatever you end up doing, I'll be reading your updates with interest
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#84
by
theman53
on 25 Sep, 2014 06:31
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For mileage that bad you must be boosting all the time. Mine got a few 28mpg when I was taking that trip to SD, but the entire tank was 7-10psi, if I keep it under 5psi I get low 40s mpg.
I had 20-30mph head winds and was boosting hard to get that horrible tank. I also had 600lbs of gear with me. I know it wasn't good, but the wind was the killer. The Giles pump I have is set to really start giving fuel at 5 psi and the more boost you run the more fuel you get, to a point. 10psi for 5 hours straight is a ton of fuel. I think the areo/wind was 90% of the bad mileage. I was also doing 70mph most of the time. Pretty windy in Iowa, Mn, and SD for whatever reason. I think that is why they had all the wind farms along all the roads.
Gizmo, bottom line is if you like it that is all that matters.
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#85
by
Gizmoman
on 25 Sep, 2014 08:47
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I really appreciate all the comments. I'm not going to spend any more time or money on it at this point. The #1 goal was to build reliability into it. Goal 2 was to be able to do 65 mph on the local freeways, even when loaded. I was worried about the transmission when I left but it held up fine.
I passed the 200K mark on the odometer about 75 miles into the trip and it's 32 years old. One day we took a day trip North from our campsite and got trapped out by a fire that closed the 395. While we were sitting in a small town tavern sipping a cold brew, a local cowboy mentioned a dirt road around the closure and we went for it. 46 miles of corrugated single lane torture that climbed to 11,500 ft - 1st gear switch-backs and all.
Heres a shot of one of the smoother sections. . .
Everything survived save the crappy oil pressure sender. I had just replaced it before the trip relocating it off the engine using a 1/8" grease-gun hose. It was mounted hard to the engine bay but the corduroy road still beat it into producing silly numbers. I'll just let the next sender hang loose off the hose.
Other than the sender, both goals have been reached.
As I've said many times, without this forum and all the contributions from every one of you, this would have never happened.
Jim
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#86
by
Syncroincity
on 25 Sep, 2014 18:23
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Try doing a dyno run when you get the chance, that'll tell you a lot about the drivetrain drag as well as the engine output.
I'm at the same point as you, just tired of fuxing with it all the time.
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#87
by
Gizmoman
on 25 Sep, 2014 20:32
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Try doing a dyno run when you get the chance, that'll tell you a lot about the drivetrain drag as well as the engine output.
I'm at the same point as you, just tired of fuxing with it all the time.
Thanks, but a dyno run would just have me wrenching on it again and it purrs like a kitten - albeit a hungry one. I may change the oil after the 1576 mile trip and add the new pressure sender unit. Other than that, I'm just going to enjoy it.
Here's a foreshortened video of the trip if you have 10 minutes.
http://youtu.be/FB7h19Rs67Q
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#88
by
92EcoDiesel Jetta
on 26 Sep, 2014 07:27
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Nicely done video! After all the work you've done, you deserve to be rewarded with a beautiful and problem free trip.
What's the deal with the grease gun hose for the sender? Seems too stiff and to much mass for such application. Is it a electric sender?
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#89
by
Gizmoman
on 26 Sep, 2014 08:17
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Thanks, the video was a blast to make - time consuming though.
The sender is electric. The gauge set is from Glow-Shift - I like the look and it auto dims at night but it's a cheap gauge. Wish I had gone to something more robust.
Originally I had it mounted to the engine and the vibrations took it out. The grease gun hose is quite flexible - about 12" long. I figured hard mounting the sender to the engine bay would be fine but didn't count on going off road. As you can tell in the video, the road was pretty brutal as far as shaking things up. The 40+ miles took over three hours. The video doesn't show the grades I was climbing as there's no perspective, but I had to drop into 1st several times.