Making a minivan more aerodynamic.

[Frank Lee]

On that little van I'd first see to it there is no luggage rack sticking out. Then, no mudflaps.

Ride should be slightly nose down. If it's level or nose up, lower the front a bit.

Grille block for sure. A full one probably is too much tho'.

Air dam or belly pan? One or the other, maybe both. Should help some. The wife wouldn't see any belly pan.

Maybe a cowl panel over the wipers would help.

Skirts? Meh. Do it if you feel like it, but I wouldn't expect too much from them

Other than that, just adjust the nut behind the wheel. Since the frontal area and Cd isn't too awful bad I would expect higher fe from that thing. Keep it at 55 mph or less.

[lunarhighway]

Would the "custom spoiler with side fairings" be very effective? (As shown in the little blue Corsa pictured above.)

i'm not sure how effective the fairing is on the corsa, it's more to show that potential aero stuff can blend with the existing bodywork.

the reason why i think i relative short add on might work is that the back of the vehicle has these rounded edges that where widely used in the 90's. potentially these edges might cause the air to separate at the wrong angle adding a small lip spoiler at the top (as is very common on a lot of current hatch designs), and at the sides you might be able to control the separation angle.

[ShadeTreeMech]

I've noticed that a lot of the newer aerodynamic cars have sharper edges on the rear, which I read in here somewhere helps to reduce turbulence, as lunar mentioned. I've wondered whether adding a border around the rear perimeter to create a sharp edge might not look cool, as well as reducing the turbulence. If I were to make it out of Plexiglas, the tail lamps would still be visible as intended. And I'm thinking a Plexi part kammack would look good also.

I'm going to include some pics soon as I can upload them to the internet.

[Concrete]

Shade Tree,
hate to derail an aero thread but Frank is right
at .35 Cd - and mixed driving - aero is not your first concern
(if you were long hauling at 75mph - that would be different)
look for a draggy break set up or mechanical issue
air up the tires and coast a bit - drive mello

then come back to aerodynamics - but don't expect much
aero is finesse and many mods with many small gains
better just to sllooowwww down
I would bet 40mph is your sweet spot - based on CAFE standards
instrumentation (scan gauge etc.) is very helpful

and way easier than a driving backwards

[ShadeTreeMech]

From what I'm reading, .35 is very low for such a large vehicle. I'm wondering if the weight of the vehicle (nearly 2 tons) isn't partly to blame. The engine is a fairly old design (it still has a distributor and 2 valves/cyl.) and it revs fairly high in overdrive. It spins about 2400 rpms at 65 mph. But the engine size is quite small @ only 3 liters. I might have some tuning issues, and there is a dragging brake caliper, but I'm averaging 22 mpg, in mixed driving, which is close to the EPA est for highway driving. I'm thinking maybe some of those new iridium spark plugs might help. They sure did wonderful things for my friend's truck. A warm air intake would be fairly simple to pull off, but my van tends to octane knock awful easy as it is.

My wife and I only accelerate heavy when necessary, otherwise we keep the rpms under 2800 or so. I'm trying to remember if advancing or retarding the timing helps low end torque....

Either way, we live in the Ozarks, which is quite hilly. There are a few places we can put the car in neutral and coast at speed from gravity.

Before I drop the aero ideas, would a belly pan help much, or should I just shackle up the rear a bit?

[QuickLTD]

Advance the timing in 2deg increments. If you check it it might be lower than factory spec anyway. When I had my Mustang 5.0s we would dial in 14deg initial instead of the factorys 10deg. On an 87-95 5.0L 36 degress total was what we were going for. Not sure if its the same on a Nissan motor. I know if you go to far you will need premium fuel to stop the knocking. Wich would take away from what you are trying to do. I always ran regular at 14deg with no issues. It has be claimed to give better mileage and a better burn. My right foot was too far in it 90% of the time to notice any savings lol

On that motor I would go with the Denso brand Iridium plugs for sure.

Dean

[ShadeTreeMech]

now to buy a timing light. Haven't needed one since '03 as all my vehicles had coil packs

[QuickLTD]

Yeah seriously.. I know the feeling.. When I threw mine out I felt like I lost my puppy LOL

[MetroMPG]

Originally Posted by ShadeTreeMech

From what I'm reading, .35 is very low for such a large vehicle.

FYI, drag coefficient (Cd) is independent of size (design constraints notwithstanding). The better minivans have drag coefficients of .30, eg: the original Pontiac Trans Sport / Chevy Lumina vans, Toyota Sienna.

But total drag is Cd times frontal area, and yours is smaller, so you may still be ahead.

Have you seen this thread?
http://ecomodder.com/forum/showthrea...-6-a-6069.html

I know you started this thread to talk about aero, but I'd have to say before I spent a moment or a penny on mods, I'd get instrumentation. The easiest & fastest gains will come by modding your driving style, and you need feedback to do that best. Your garage entry doesn't show any fuel economy instrumentation.

[ShadeTreeMech]

Fuel economy instrumentation? I do have one very important one, espacially for a vehicle with an automatic tranny that loves to downshift-a tachometer. according to revised epa estimates for my van, I should be getting 17 mpg mixed driving, while I'm getting 21-22 mpg fairly regularly; a 25% increase. My wife and I not too long ago were getting 19 mpg out of a 91 ford explorer, so driving economically is not foreign to us.

While a mpg meter would be nice, I've had one before, and I know get into top gear and staying there is the key, as well as gentle application of the throttle and keeping the revs as low as possible nets the best fuel economy. And letting the van coast in neutral on the downhills brings up economy. I know this because I idle @800 rpms while I coast at much higher rpms.

Remember, I live in hilly country, so the 2 tons of steel come into play more than in flatter country.

I think part of the reason I'm pressing on the aero issue is that the average speed limit for this van's regular route is around 50 mph. That may not be 70, but that is a consistent amount of higher speed, and from experience I know the van struggles to maintain speed while staying in overdrive when even the slightest hill is introduced. That and some of the factory plastic "belly pan" under the radiator has since been misplaced on the highway somewhere, leaving a flat brick right in the way for the wind to hit. So I suppose I'm wanting to restore the original aerodynamics and maybe improve upon it a bit.

I know this may be an aero thread, but I appreciate other comments. I plan on getting a ScanGauge when finances permit, and I'm planning a 4400 mile trip in the future, so anything I can do beforehand to save me a buck is money in the bank. I know the earliest version of the villager had a partially blocked grille, because it had a light bar in place of the wide open grille I have now. As much as finding that older version of the grille is desireable for maintaining a stock look, a mod of my current grille is likely to be cheaper. I like basjoos's philosophy: I won't do it unless I can earn the money back fairly soon in gas savings. And unfortunately, even the open source mpg meter mentioned on this site is around $60 to buy, and right now that is 2 weeks worth of gas.