'99 Chevy Astro Van build thread ~ Goal 30 mpg

[oil pan 4]

What mods were you really thinking about doing?

[ChopStix]

I'm not sure yet. I wanna see what these get me in real world mpg:
Chin Spoiler, Spats, Side Ground Effects, Filled Bumper Pockets, Skirts

Then I'm going to install my pulleys and fan, which should be good for another roughly 3mpg. I'll start a another fuel log for this step as well.

If I get above 30mpg on the highway then I'll stop. Edit: who am I kidding! If I get above 30 I'll will be trying more stuff! Otherwise these are my list of possible mods to try:
Smaller Mirrors, Taller Tires, Filled Radiator Support Holes, Different Style Grill Block, Nose Pan, Belly Pan, Filled Panel Gaps, Kammback, 3 Inch Drop, Carbon Fiber Drive Shaft, Gear Vendors

Some of those obviously will make bigger changes than others. But the biggest gainers also cost the most. And its this fact why these little hobby projects like making ground effects from lawn edging are so interesting.

[MobilOne]

How about removing the mud guards at the back of your fender openings? They act as small sails.

[ChopStix]

Originally Posted by MobilOne

How about removing the mud guards at the back of your fender openings? They act as small sails.

I tried taking one off. But the fender does not extend below the panel. So removing it leaves an open pocket. (I don't have these on the rear, only the front.) I would have to find another pair to use as a frame to cut up and remake them in a more aero way. I like this idea but I need to explore it further before committing to do it.

[Big Dave]

Aero mods are always effective. there have been a number of folks on this forum working on van aero mods. My suggestion: You now see the big rigs with four-petal tail fairings. You could make something like these. Their fairings fold back when they go to the loading dock. You could manually fold them back for city driving.

If you are really serious about improving MPG, you simply have to slow the engine down for a given road speed. Your Astro probably has 3.55 gears. If you can retrofit 2.73 gears that would slow down your engine by 24%. That will result in a 55% reduction in engine frictional HP load. EFHP goes up with the cube of RPM. With my exotic drive train I have achieved a 34% reduction in engine RPM and a 70% reduction in EFHP.

Caution: Lower engine speeds are murder on automatic transmissions. If you go to the effort to re-gear the van, find a reputable transmission shop that rebuilds automatics for hot rods. Tell the guy you intend to run at 25% less RPM across the board all the time.

Most automatics use the torque converter to pump ATF to the cooler, but by slowing down the engine you reduce the ATF flow to the cooler and heat builds up. Good hot rod oriented shops can provide boost pumps to restore the ATF flow to the cooler.

Not an issue to me as I have a stick, but I've never seen an Astro with a stick.

[ChopStix]

I've been thinking about making a kam-back over doing the 4 fairings. It seems like one of those would not interfere with the rear doors as much. I envision flipping it up on the roof to get it out of the way while using the rear doors.

But immediately I'm in rust repair mode. As I can't put on the rest of the rear aero mods until I get these repairs completed.

I learned a lot about how rake angle affects my mpg today. When the rear is sagging, the mpg goes to crap. Not to mention driving with a rocker panel missing!

[SpikeDiesel]

ChopStix... would you be able to refresh the pics or PM them? I know this is thread is many years old, and am assuming the pics expired or were deleted on the hosting site (photobucket?). I'm looking at an Astro and would be really happy with mpg results you were seeing and would be glad for any pics of what you found that worked for you. Thanks-

[ChopStix]

Originally Posted by SpikeDiesel

ChopStix... would you be able to refresh the pics or PM them? I know this is thread is many years old, and am assuming the pics expired or were deleted on the hosting site (photobucket?). I'm looking at an Astro and would be really happy with mpg results you were seeing and would be glad for any pics of what you found that worked for you. Thanks-

I apologize I didn’t see your post. The vans been gone for years. I never could hit 30mpg that others had claimed to get in a 4.3 Astro van. But also there were mods that could have pushed me over 27mpg that I never got to do on it. I did consistently get 27mpg everyday on the highway above 60 degrees outside. Removing the roof rack was 1mpg in any temperature. The biggest mpg gain was skinny LRR tires with 15x7 steel ralley rims and smooth hub caps. The spats and chin spoiler and air deflectors on the rear bumper was also worth my time as was booster springs to give it a slight hotrod rake (raised backend). These listed mods with mindful driving techniques will surprise you with good mpg gains. Plus these mods were cheap cost for what I got back from them.

Side skirts never proved themselves worthwhile.