Week and a half to go before the 3,000 mile trip to Florida. I've done more work on the Great White Whale in the past month and a half than I've done on cars for the past 10-15 years and frankly (you don't mind if I call you Frank?) it's running pretty sweet for 12 year old minivan. I've got a catalytic converter on its way and hopefully I can get it in and not have the engine light staring at me for 15 straight hours. Each way.
I want to put a belly pan under it. You crawl under the Whale (which I've done a lot lately) and you see what looks for all the world like a sled. The bottom of the van is flat with some longitudinal hat sections and some cross reinforcing between two walls that almost enclose everything underneath. Like a 20 gallon gas tank. And the muffler and resonator. And a five foot axle with springs and sway braces and brake plumbing. And a full sized spare tire. And the trailer hitch receiver...Oh my!
Now the signs of desperation are starting to show. There is just enough stuff hanging down to prevent stretching rigid panels from side to side. (That would simply have been too easy) So I bought two 4 x 6 foot tarps. (< $5 at Harbor Freight) I'm going to try and stretch them underneath.
The requirements are:
1. It has to be removable on the road without having to go underneath. All secured points have to be reachable from the side and back.
2. It can't trap hot air from the engine or exhaust pipes under the floor (and slowly cook us).
3. It can't flap or drum.
4. I have to be able to get the spare tire out.
The plan is:
1. Start at the bottom of the firewall and angle back to the front of the gas tank (the first major obstruction underneath). That should provide a shallowish entry angle.
2. Cut an opening around the exhaust pipe to; a) keep the tarp from melting; b) let some air into the enclosure to keep the temperature down. Note that the catalytic converter is between the engine and firewall and not under the car.
3. Run it continuously underneath the rear axle securing it to the hitch receiver (eliminating that as a drag source). Chafing gear under the rough rusty axle should keep it from abrading.
There are a plethora of attach points on the sides to secure ropes to. Attachments behind the axle will have to be shock cords to keep the tarp taut while the axle moves. I don't think it will touch the exhaust pipe or mufflers because the axle will hold the tarp down.
I was not going to do anything under the engine. Between the oil pan, transmission pan and the cross beam between the tires, it's surprisingly flat down there as it is. I was going to attempt to fair over the bullseye grill for further streamlining (time permitting), which is going to increase temperatures in the engine compartment. It will be August and the air conditioner WILL be running.
I've seen under 'em and as far as a quick and easy approach to all that mess... I'd put on an airdam.
I remember The RoadWarrior..To understand who he was, you have to go back to another time..the world was powered by the black fuel & the desert sprouted great cities..Gone now, swept away..two mighty warrior tribes went to war & touched off a blaze which engulfed them all. Without fuel, they were nothing..thundering machines sputtered & stopped..Only those mobile enough to scavenge, brutal enough to pillage would survive. The gangs took over the highways, ready to wage war for a tank of juice
I looked at the bottom and I think it may be more amenable to a solid bottom than I first thought. The tank, exhaust, muffler are all so close to being flush with the bottom of the side moldings that a solid panel could be stretched across them. But the exhaust really needs to be segregated to avoid heating up the floor too much. That's not going to happen in the next week.
Replacing the factory air dam probably qualifies as an aeromod on Moby because it had been without for so long. One of the things I noticed as I was reinstalling it was that not only does it serve the aero purpose of controlling airflow under the car, but it is also seals the radiator inlet. I was going to put on the upper grill fairing (it could still happen!), depending on the lower air inlets to feed the radiator while running down the highway. However, with the air dam gone, there is no closure between the bottom of the radiator and the bottom of the bumper. It was wide open. Oops.
I did the quick cheesy air dam treatment. (Wife went to opera with daughter and friends. This'll teach her to leave her car behind) I used rubber kickboard and fastened it to the existing air dam with drywall expansion bolts. This reduced the clearance under the dam from something over 6" to something under 4". The crossbeam under the engine, which is the lowest point under the car, is between 5 and 6 inches.
Problem #1: The rubber kickboard material is too soft. I liked soft because this air dam will hit stuff. But I think this will collapse at 70 mph. I'm going to have to rig some reinforcing angle brackets to help it keep its shape. And it needs some shaping. It kind of has that potato chip thing going right now.
The factory air dam tapers at the ends. I've kept the full 4" thickness to provide some cover for the front tires. It doesn't come close to covering them. But I'm hoping it will generate a bow wave that will increase it's effectiveness. The ends in particular will need bracing to keep the corners from blowing in.
Problem #2: The oil pressure sender is busted in two and leaking my expensive Mobil 1. That would be why I was seeing oil under the beast while working on the rear end earlier. I'll get that tomorrow. (That'll be my excuse for fiddling with the car. "Honey, if I hadn't been destroying your car, I wouldn't have found this life threatening problem." )
Redid air dam. Now it looks less horrible and got some reinforcing to keep it from buckling. It adds about 2 1/2 inches to the original dam and actually covers almost 2/3rds of the width of the front tires. We'll see how this works. And if it's too ugly in daylight, it only has to last through the trip to FL.
Oil sender diagnosis was right and wrong. It was the wrong sensor. The knock sensor is what broke. Auto parts store wanted $67 for one. I went to the Pick-n-Pull and got one for $2. How did I get along without the junkyard all these years? But the oil sender IS leaking. I'll get that later this week.
I got pics. You know how pictures add 20 lbs? They also highlight every pit, ding and blemish. Moby needs a bath...and a paint job. And once again, in the light of day, I find it's not level. It's higher in the middle than the sides. Looks bucktooth. <sigh> Not sure if the wife going to let me have a third try at it. May have to send her to the opera again (which costs more than the modifications themselves).
My messterpeice. My only defense is that I've done better. But this is the third and last attempt. The stock airdam that it attaches to is not even (I blame Chrysler ) It only has to last two weeks until we get back from Florida. Of course the first thing my wife did was try to bulldoze a hillside with it because she parks it nosed up to an embankment.
The dam shadows about half the width of the tire. The sweep angle should help even more.
The stock air dam is far enough under the nose to be almost invisible. Only the corners of it really show. Which is good because its pretty unsightly. This makes it hard to get a good picture (especially at night) because the camera only picks up the strobe off the white body.
I had an idea today to address the difficulty of putting belly pans on big vehicles like minivans. Treat individual components separately. Some of the components under the van actually have two drag contributions. Body drag due to its shape and interference drag due to its location between the ground, floor and other components. Some of the treatments include:
Streamling the rear axle. The air dam will have limited effect in reducing airflow around the rear axle because of the long space between the front and rear tires where air can come in. The rear axle is a straight round pipe about four feet between the springs and 4+ inches in diameter. Unlike on a car, it is not shadowed by the floor pan of the cabin. It sits out all by its lonesome several inches under the floor. Putting a streamlined fairing on the rear axle could reduce it's drag contribution to almost nothing.
Place fairings in front of blunt shapes like the gas tank and spare tire.
Clamp sheet metal cones around the exhaust pipe in front of the muffler and resonator.
Anything, essentially to break up forward facing blunt surfaces without having to install 50 square feet of coroplast (or equivalent) and having to deal with the enclosed exhaust pipes under the floor. Alas, I probably can't act on this idea. We are five days from shipping out on the Big Trip and I'm 800 miles from home tonight on a business trip. $%&@#