G3500 van 'aerodynamics'...improving them.

I've this '01 Chevy big van that will likely be in my paddock for at least a couple more years, and I've been thinking about how to improve the aerodynamics. I have plans and money in place for lowering the thing about 2.5-3 inches, and I'm wondering whether to extend the airdam on the front, or to try side skirts or maybe slicking up the bottom of the chassis. This would be in the spirit of trying to get through the air a little more cleanly, and using less fuel. Current consumption is running 12.5-13 mpg@ 70 mph, and tranny doesn't shift down on a short 6% hill (long hill yes, but that's a different matter)

The side mirrors would get smaller than they currently are, but still stay legal, and the front of the van...grillwork and such...would get smoothed out as much as possible without compromising cooling too much. The angle of attack will drop a bit, and tire profile will likely stay as it is, LT245/75x16, as those tires are new and I expect them to last about 45-50K miles. The last ones went 55K and were chancy, so 50K max for these...

So then: extend airdam, yes/no, and how much if yes. I'm thinking enough to give me about 3" ground clearance at the front, but that's just a guess at this point. And it will depend on how much drop I can get into the suspension and not kill the ride.

Side skirts, yes/no?

Smooth the chassis bottom, yes/no?

Moon-type wheel covers? I'm leaning toward yes for now.

And before anyone gets nuts about how much this thing weighs: yeah, I know. There will be as much weight as possible lost by removing unused seats and extra gear. The winter emergency stuff stays, though. This IS Montana after all, and we do get snow in June fairly regularly.

What say ye, me hearties?

Put a long teardrop shape on the back end that sticks out about 20'. I dont think you can go wrong with an airdam and side skirts.

Do as much as you can do to reduce the silhouette and smooth airflow around, over and under it. Air dam (I've heard old conveyor belt material works well on large vehicles) and side skirts, aero tabs in front of the tires if you can't get coverage otherwise, underbody trays (not just in the obvious places, but covering every void and projection possible), wheel covers, and general smoothing will all help your cause.

mw wrote: Put a long teardrop shape on the back end that sticks out about 20'. I dont think you can go wrong with an airdam and side skirts.

There was a good article a few months back on aerodynamics. I'd suggest referencing it. Air dam, side skirts, and a diffuser. Maybe add a lip at the rest roof line like a wing.

I bet this is what you had in mind:

any and all. smoothing of anything and blocking off grilles or front openings will help.

Needs more ground effects!

Sorry, I couldn't help myself.

Yes, lower the airdam. How much? You get snow in Montana? Can you afford to replace it after every snowbank event? Have you thought about replacing the 300 lb. front bumper with fiberglass? Same snowbank question though.

Mirrors from something like an 80s Monte Carlo would work, slightly aerodynamic, probably lighter. I wouldn't go crazy slicking up the bottom of the chassis, the aerodynamic gains at 70 mph don't justify the added weight.

Does it have air conditioning? Get rid of it, there's a quick 300 lbs. and a horsepower drain on the engine.

How is that engine anyway? Running like a Swiss watch, can you eat off it? New wires, plugs etc. could give you better mileage.

Lucas juice in the tranny.

Dan

I don't think smoothing the belly will pay off as much as you'd like. Stick with air dams and side skirts to reduce the amount of laminar flow under there and be done with it.

Do the windows in the back doors open? If so you might find that opening those windows along with the driver and passenger windows helps. In some sedans that can reduce MPG since its "scooping" air, but if you have an outlet for it at the back it can reduce the aerodynamic footprint. Instead of all the air having to go around and instantly collapse at the back, it can go straight through the van. There is basically a large low pressure area at the tail of the van. Opening the back windows and giving them a supply of air can greatly reduce that drag.

If you're concerned about climate control for the driver, maybe you could put air vents on the side of the van just in front of the wheel wells. That kills two birds with one stone. Usually there is a high pressure area just in front of the rear wheels. If you can reduce the pressure there and use it to increase the pressure at the tail, you're removing work resistance from two areas.

http://www.youtube.com/watch?v=xzlqNp8R90A They say you can retrofit a bus for $40, so you can probably fit the Van for ~$10 or so... 165mph in a Chevy Van. YESSIR!

Experiment with blocking off as much of the radiator as possible via the grill area and any redundant openings.

Weight. Drop some. In the van I mean.

I have a lot of van miles. Air dam and skirts will go a long way. As will lowering and finding some way to fill the hole in the air behind the van.

A rear spoiler will fool the air into thinking the van is longer than it really is. Think Volvo wagon spoiler.. something to extend the roofline maybe a foot will make the air think the van is much longer and smooth out the flow over the top.

I agree with deflectors around the wheels.. maybe use some of that plastic you are using for the air dam to create small underbody dams infront of the rear wheels

Full covers over the rims will not hurt in the least.

I would not go crazy with lowering. While it will help, you still need to deal with snow half the year. Make sure you can remove that front spoiler.. you do not want to be plowing snow in winter

why not find some conversion van ground effects used? at least for the sides it may help deflect air around the wheelwells.

when I had my 94 chevy, lund made some clip in pieces for the front grill, supposedly designed for running in the winter months but I ran them year round with no issues. Not sure if it helped aerodynamics at all I just liked the way they looked.

its called Lund Cold Front. its perforated with small holes so there is still airflow.

some sweet rear wheel skirts!

while most people on these sites are using the smallest vehicles they can find, the tips still mostly apply. there's some guys with trucks on there that could be helpful.

http://metrompg.com/posts/efficiency-mods.htm

http://ecomodder.com/

failboat wrote: why not find some conversion van ground effects used? at least for the sides it may help deflect air around the wheelwells. when I had my 94 chevy, lund made some clip in pieces for the front grill, supposedly designed for running in the winter months but I ran them year round with no issues. Not sure if it helped aerodynamics at all I just liked the way they looked. its called Lund Cold Front. its perforated with small holes so there is still airflow.

Those would probably work well.. most likely stops about a 1/3 of the airflow

I was looking for things to slick up my camaro for highway miles and these links might help you out. All I ended up doing was extending my air dam down and out to the sides of the car, picked up 2-3mpg.

http://grassrootsmotorsports.com/forum/grm/aero-mods/27845/page1/

http://www.timeattackforums.com/forums/aero-dynamics/2918-lots-aero-parts-built-my-garage.html

http://www.thirdgen.org/techboard/auto-detailing-appearance/530877-rear-air-diffuser.html

http://www.recumbents.com/car_aerodynamics/

http://ecomodder.com/forum/showthread.php/show-me-your-wheel-spats-13669.html

http://www.miataturbo.net/showthread.php?t=31227

there are a few good threads on aerodynamics over at www.protouring.com with a lot of really good ideas for cleaning up airflow.

i wonder if these vortex generators work, i've been meaning to try them myself.. http://www.pro-touring.com/showthread.php?61936-Aerodynamics-Vortex-Generators-Spoilers-etc.

Thanks to all who responded!

Based on the responses, it will get sideskirts and a little lower front dam, Moon wheel covers, and a first class tune-up...@100600 miles, it could probably use it...Is it REALLY this long? Doesn't seem it....time apparently DOES fly when you're having fun!

I hadn't considered the Lucas fluids...Thanks Dan! Or the potential impact of a snowdrift...yeah, we get them...sometimes even in Aprill and May .

I will forgo lowering it, since that may give me grief getting the suspension right again. Instead, that money and effort will go toward just rebuilding the suspension I have and getting it re-aligned. That way, if I keep it another 100K miles, I'll not have lost anything except old suspension pieces.

I AM having trouble visualizing a 20' extender on the rear, but the opened rear windows make sense. This, I can do right away and see what (if any) change happens in mileage. Thanks Curtis! The other suggestions on air flow will be looked at as well.

As much of the radiator will be blocked as practical. That will be a work in progress untill I've gone too far and have to undo some of it. Thanks Iceracer!

Wheel skirts? If I can figure out how to make them easily removable to change tires, yeah, you betcha! Thanks coll9947!

And Nitroracer and novaderrick, thanks for the links! Those will studied in some detail.

Again thanks to all who responded, and for keeping response (mostly) to the point.

{edit } for spelling

One thing about those Lucas fluids: they have a bit of a dubious reputation among the oil nerds over at BITOG. The whole site started with a test demonstrating how bad Lucas oil additives were, IIRC. You might be better off simply going to a high quality synthetic from one of the mainstream oil producers, or something like Redline or Amsoil, all of which seem reasonably well-regarded.