Economy modding my Chevrolet Astro work van (diesel 5-speed conversion)

[Big Dave]

I wish you luck on the bigger tires. Most of the people I know of have lost MPG by putting rubber either taller or lower than stock. Selecting tires for MPG is something the factory boys and girls do fairly well.

Your van is a 4x2, is it not? If the 235s don't fit the front wheel wells why not just go with 205s on the front and 235s on the rears. I run 225-75x16 on the front and 235-85x16 on the rear of my F-350

[2007 ion2]

fairing the rear wheels can lead to issues if the vehicle is driven in the winter, as snow and ice will build up. taller (and yes, they are wider) tires are heavier, and changes the drive ratio. this will likely lower your economy. my car starts out almost as aerodynamic as a prius, but a rear underpan is the only aerodynamic mod that in and of itself made a noticeable difference. everything else was a minor cumulative effect.

235 (width in mm) 75 (sidewall height as a percentage of the tread width) R (radial) 15 (rim diameter in inches).

this is a cool mod, looking forward to seeing the efficiency numbers with the more practical engine. American vehicles just aren't built as light and aerodynamic as the euro vans are. they also have a lot smaller tires and shorter gearing to keep rolling mass down and make more out of the power. bringing the aerodynamics up to snuff is a great next step given the small engine you have. filling body gaps with sticky foam weatherstripping, silling door handle recesses to the point where you can just get your hand under the handle, fairing windshield wipers (be careful, you'll still need to be able to get in there to clean snow out), cleaning up the front end, fairing chumky window frames with shaped sticky foam weatherstripping, and under pans will all yield better efficiency, and make your engine effectively more powerful. I'm a fan of coroplast, it's cheap, easy to work with, and looks decent.

[spdfrk]

You would have done much better to put a v8 in and use the torque you need especially if you tow. The L05 350 is very efficient on the low end and even better on the highway with the lean highway ecm hack. I've gotten over 30 us mpg @ 60 mph with my 1/2 ton Silverado.

Check silverado30mpg

[slowmover]

spfrk, you might first account for differences not so much in truck spec but climate (similar enough), terrain (differences) and "driver" (which is use). Likely the difference comes in total engine time per day over distance covered. Average mph. There'll be good differene in an area with high population density versus one which is low.

IOW, that approach could work well for both you and me even given climate differences.

.

[Giovanni LiCalsi]

The Sprinter van (8,500lbs.) gets around 30mpg.
Your van should achieve at least that if not 35mpg.

[2007 ion2]

the sprinter is also far more aerodynamic, and has smaller tires and rims for a much lower rotating mass and rolling resistance.

[Giovanni LiCalsi]

It has a much larger frontal area.

[cRiPpLe_rOoStEr]

Originally Posted by 2007 ion2

American vehicles just aren't built as light and aerodynamic as the euro vans are.

The Astro is actually not any bigger than, let's say, a Volkswagen T4 Eurovan or an early Fiat Ducato. OK, these ones have the "advantage" of a transverse engine and front-wheel drive to improve efficiency due to the smaller transmission weight and lesser friction losses...

[2007 ion2]

frontal area has little to do with it when the engine is so much better, the whole driveline is so much more efficient, and the front and bottom of the vehicle is as aerodynamic as possible. it's not surprising they get better mileage, and manufacturers are one by one bringing these euro vans over to the states.

on the astro (not a bad van), the aerodynamics is going to be a huge improvement on efficiency. the engine the OP has already taken care of, but the aerodynamics are terrible.

need more proof? take the saturn ion and saturn sky. it's the perfect comparison. the ion has bigger frontal area, efficient front wheel drive, more reasonably sized wheels and tires, roughly equatable weight, and same available engine. the sky has crap aerodynamics, take the two cars side by side, same engine, and the ion will get better gas mileage every time.

spdfrk, the GM engines are definitely underrated, and not given nearly enough credit for their efficiency potential. my venture got 32MPG in the winter hauling stuff in the back on relatively hilly terrain on my last road trip, and it's relatively unmodified.

[JB3]

Originally Posted by spdfrk

You would have done much better to put a v8 in and use the torque you need especially if you tow. The L05 350 is very efficient on the low end and even better on the highway with the lean highway ecm hack. I've gotten over 30 us mpg @ 60 mph with my 1/2 ton Silverado.

Check silverado30mpg

I can't run the L05 350 on canola oil like I can these old mechanical diesels.

seriously though, thats impressive mileage. The 89 4.3 I pulled out of this van barely broke 20mpg regularly. Much more likely to get 18mpg or less. 2 more cylinders and 10mpg better is excellent results