Most economical minivan?

[Gringo-Gaucho]

Ok, so back at the economical minivan ranch- a few weeks ago I said we were headed south to get a lite-ace, which we have now done. Van is a JDM 1996 toyota liteace 2.2l turbo diesel with true 4x4 (not AWD)manual hubs and manual transmission. All the things we need. Smaller than imagined, but still seats 8 total humans, plus gear space. So far, with 600kms traveled, we are seeing right at 29 mpg's. Not bad, but not as good as our hopes. I suspect this is because the toyota 3c-t diesel is being revved at 3100 rpms to maintain 100 km/hr (60 miles/hr) This is very high, and must reflect the different driving realities of Japan, where I have never been.
My first thought is to use a larger diameter tires/wheel setup, but even 2" diameter increase only equates to an 8% reduction in rpms(I think?) so around 2800 rpms at 60.
Second thought is to alter the gear ratios somehow, but I'm not sure how hard that is to do- but ALL the gears seem really really low to me. I don't need 1st gear from a stop unless on a steep hill, and I can use 5th gear by around 25-30 mph.
Ecomodders, what ideas for improving this van, and also ,what minivans can beat this mpg?

[freebeard]

I'd look critically at the present tires. Any excuse to go to a larger tire, or not?

The other half of the equation, from power delivered to the tires contact patch, is what it takes to punch a hole in the air. ....and close it again. How many feet of boat tail could you tolerate?

For comparison -- in the 1980s I put a fresh rebuild in my 1961 VW Type II panel van (1600, dual Solexes, 4 into 1 extractor exhaust) and drove 60 miles through the Coast Range at 55MPH. It took exactly 2 gallons, so suggesting 30 MPG. It cruised at 75 thereafter (gas pressurized shocks and quartz-halogen headlights).

Back in the last decade, I turned it into money to put into the Superbeetle.

[JSH]

Originally Posted by Gringo-Gaucho

Ok, so back at the economical minivan ranch- a few weeks ago I said we were headed south to get a lite-ace, which we have now done. Van is a JDM 1996 toyota liteace 2.2l turbo diesel with true 4x4 (not AWD)manual hubs and manual transmission. All the things we need. Smaller than imagined, but still seats 8 total humans, plus gear space. So far, with 600kms traveled, we are seeing right at 29 mpg's. Not bad, but not as good as our hopes. I suspect this is because the toyota 3c-t diesel is being revved at 3100 rpms to maintain 100 km/hr (60 miles/hr) This is very high, and must reflect the different driving realities of Japan, where I have never been.
My first thought is to use a larger diameter tires/wheel setup, but even 2" diameter increase only equates to an 8% reduction in rpms(I think?) so around 2800 rpms at 60.
Second thought is to alter the gear ratios somehow, but I'm not sure how hard that is to do- but ALL the gears seem really really low to me. I don't need 1st gear from a stop unless on a steep hill, and I can use 5th gear by around 25-30 mph.
Ecomodders, what ideas for improving this van, and also ,what minivans can beat this mpg?

The highest speed limit I saw during my visits to Japan was 80 kph (50 mph) on a raised freeway.

For 4 years my wife and I rented a campervan in Vegas for the week of Thanksgiving and toured the National Parks around the area. It was a Dodge Caravan converted with a kitchen, fridge, and fresh water / grey water tanks.
Even with the extra weight we averaged about 28 mpg (30 mpg on the trip computer)

That was driving mostly 2 lane highways at 55 - 60 mph.

[cRiPpLe_rOoStEr]

Originally Posted by Gringo-Gaucho

Smaller than imagined, but still seats 8 total humans, plus gear space.

Those JDM forward-control vans are a miracle when it comes to packaging...

Second thought is to alter the gear ratios somehow, but I'm not sure how hard that is to do- but ALL the gears seem really really low to me. I don't need 1st gear from a stop unless on a steep hill, and I can use 5th gear by around 25-30 mph.

Such a low gearing was quite usual to those vans, back in the day when they were seemingly underpowered. Not sure which wide-ratio transmission with a taller ratio could be interchangeable with its stock one, but it would be a good option.

[Gringo-Gaucho]

I'm suspicious that Isaac is on the right track pursuing a manual Previa, though I am impressed with the numbers on the above dodge caravan as well. especially considering the roof rack on top. It had to be the flower power netting it such an impressive average!
Another 450 miles yesterday for the liteace, and we tanked up at 31 mpg, but we are limited to around 60 miles an hour by the revs, which is a little dangerous here in the pacific northwest, as average traffic speeds are 70-80.
I suspect that with a diesel setup such as this I would see very modest gains from aero-mods, but substantial gains from less RPM.

[Piotrsko]

What are the differential gearing sets available? Or even the whole pumpkin options in different vehicles? I would think a gear swap that way would be possible and perhaps relatively easy. But in my experience, didn't do diddly. At one point I tried every stock ratio available in my surfer van and the results were oddly counter productive with a 4:11 set providing the greatest improvement over a 2:90

[Gringo-Gaucho]

well, I'm working on finding out what I could do to the differential(s) but if I understand it right, you should have been revving really high in that surfer van with the 4.11 gears and much lower at 2.90, so yes, counterintuitive.

[Piotrsko]

More probably: the 4:11 was in a more efficient portion of the torque curve, the 2.90 was only 2200 @ 55 the speed limit of the times.

[Isaac Zachary]

Well, trying to rent a van this summer looks like it's going to cost an arm and a leg plus more time. I was wanting to rent a 12 or 15 passenger van, but they stopped renting them up here. So I'd have to go the 226 miles to Denver and then the 226 miles back just to rent one, and they (Hertz, Avis, Budget, Enterprise) want me to bring it back to Denver afterwards.

So first thought is to get all drivers and vehicles together and split up those that can't drive and forget any other trips other than the most necessary.

The second is to rent two minivans or SUVs if I can get one other driver to help out.

The third would be to take the bus at $90 per person (there and back) and see if we can get a hotel with shuttle services.

[freebeard]

Fourth.... Buy one and flip it when the road trip is done.