Once again, I heard part of something interesting on late-night radio.

One of the big problems of driving during or after volcanic ashfall is that the ash is sucked into the air intake of your car until the filter is packed, then the car overheats. Or it sucks it in and the filter doesn't catch all of it. Whichever or both, the ash is bad for your engine.

The radio guy was saying that someone around Mt. St. Helens (I think, since it was the anniversary of the Big Blast) came up with an idea to circumvent the problem of keeping a car running through ash fall.

It seems that this guy removed his car air filter (and maybe the dish thing that it sits in), and attached one end of that expandable aluminum hosing (used to duct hot, damp air to the outdoors from clothes dryers) to the air intake place (probably with one of those pipe clamps with a screw), then stretched the tubing out and put the other end into the car through a window. It was said that he was driving emergency people around.

I guess the idea was that the inside of the car is cleaner than the outside air.

I am assuming that he blocked the rest of the opening of the window with something like wood or sheet insulation and taped it into place.

Do you think this would really work? I know that most cars aren't air-tight, so the air being sucked out would be replaced, right?

Would there be much of an advantage to covering the end of the hose that is inside the car with some kind of filter material? If I were driving, I would be wearing a mask and goggles, because I know the inside of the car still wouldn't contain 'pure' air, just less chunky than what is outside.

Any thoughts on this would be greatly appreciated, as I live within 80 miles of a slumbering volcano, and the people downwind of Katla might also find it useful.

Also, this looks like a useful source of info in dealing with ash loads on roofs, in agriculture, etc: Volcanic Ash Mitigation

Sue

Hey
When I was looking at snorkels for my truck, I came across some folks that ran the hose through their floorboard into their passenger seat foot-well. Same idea, but they were using it for driving through water. of course, a car isn't that waterproof...

But, I suppose the idea is the same. He just had a ghetto way of doing it.

I would be tempted to add a bit of hose/pipe to the existing intake before the filter and to route this to a simple box with one end cut out and a rough filter cloth, pantyhose?, covering the opening.

The box could be rough cut from plywood and nailed together, caulked and/or sealed with foil tape. But a simple cardboard box might get it for a time. The box shouldn't be under any great stress in use. I would sit the box on blocks on my hood, and tape down the assembly with duct tape.

One of the benefits of driving a beater is that you can modify and tape stuff to it without ruining the look.

I would arrange the box so the filter end was down so falling ash doesn't rest on the filter. Given the large area of rough filter the air flow would be quite slow through the filter even at high throttle. So the ash would tend to fall off the filter face and get swept away by the slipstream instead of clogging the filter. If it did get clogged it would be easy enough to stop the truck, get out, and give the box a few whacks so the ash falls off.

I am very suspicious of this late night theory. First, I believe that if a filter gets clogged, your engine won't overheat, it will just die.

As for sucking the air through the passenger compartment, I suppose it could work but all you will be doing is sucking air into the engine though the car's ventilation system and the air will still have a lot dust. Car engines use a tremendous amount of air and moving this through the passenger cabin won't be comfortable at best. Consider a 4 stroke engine with 3.0L of displacement running at 4000 RPM. That basically means some 6000 liters of air has to move through your passenger compartment every minute (4000/2 x 3L). That is 100 Liters of air or around 25 gallons every second.

wet-dry vac filter and clever use of some sort of hose?.
i would have a look at a real military truck unit and see if i could copy some part of it with hardware store parts,but the first idea would work in a pinch for long enough to drive out of the dust.dust??--what sort of extra filters do the folks in places that have more than normal dust levels use?--if any..

IMO Art is on the right path with this one. Leave the existing filter in place and rig some sort of rudimentary pre-filter; the larger the better.

Like Yuccca said, a lack of air is going to cause the car to start running richer and richer until (eventually) there isn't enough oxygen present to ignite the air/fuel mixture at all. If cars were overheating maybe ash was caking up in the radiator fins and not allowing sufficent cooling.

A lot of heavy equipment that is used in extremely dusty environments uses a combination of oil bath and conventional dry filtration. Oil bath filters were very common until the 60's or so when dry filters were improved to the point that they were not needed under most conditions. I can remember when virtually all lawn mowers used a very simple oil bath filter and they worked well.

Growing up on a farm, our tractors had a cyclonic pre-filter. This was a plexiglass bowl with a cone inside it. As the air was drawn in at an angle, it forced to swirl around the bowl, dropping a substantial amount of the dust out of it. Such a thing would be pretty easy to improvise.

Several of my older small engines have a two-stage filter. The paper filter is the final stage, but this is covered with a thin foam sleeve that is lightly oiled. It's amazing how much the foam pre-filter catches -- and how long the paper filters last as a result.

Cyclonic pre-filter is an excellent idea but probably wouldn't be off-the-shelf ready to install the same day.

The standard during Mt. St. Helens time was to add an extra foam filter around the car's standard paper filter. Amsoil makes them. Then you have to clean and re-oil the foam regularly.
Looks like the ShopVac arrangement.

Drawing air from the car's interior only means that you'll use the car's interior as your dust filter for the engine. Might be kind of hard to see out.

Modern vehicles will run on the correct mixture until there's not enough air to run because they use oxygen sensors in the exhaust to adjust mixture. Carburetors in the pre-computer age would run richer and richer as the air filter clogged.

The more filtration the better because volcanic ash is even worse than beach sand for the engine to breathe because the ash has very sharp edges while sand has been worn down.
You really, really don't want to drive in this stuff if you want your car to last more than a trip or two.

You also want to remove the ash immediately as it tends to set like cement when it gets wet.

Okay, some good ideas there.

Thirty years ago when Mt. Helens blew, cars were a little bit different than the ones these days: fewer computer parts, mostly still carburators rather than fuel injection, I think, etc.

A man I talked with was caught on the east side of the Cascades when the mountain gave its big blast, and he said when the ash started falling, he had to stop very frequently (every 2 minutes or every 2 miles, I forget which), take the cover off the air filter, remove the filter and beat it mostly free of ash. So, no matter what the eventual results were to the engine, the first and biggest problem was the air filter.

The falling ash was only half the problem; the ash that did fall was so light that any motion (walking or driving) would stir it up and mix it into the fresh falling ash, so the ash was coming from all directions. The air was so thick with it that while you could see headlights when they were relatively close, you still couldn't see the vehicle they were in. I've seen the photos of that, glowing orbs of light in very thick, heavy, dark fog.

Art, a couple of questions regarding what appears to be your very good idea...

Is there enough air actually moving through the engine compartment to clean the boxy pre-filter?

Would it be any better to have more than one side of the box open (covered with the filter material)? Even a wire frame instead of a box, covered with a filter? Would a fiber air conditioner filter work, wrapped around the box or frame? I wonder how many layers of pantyhose* could be used before it interfered with air volume?

Yuccahead's figures on air requirements for an engine would indicate that any filter material would have to allow enough air, fast enough, or the effects of a thick filter would have about the same results as a filter choked with ash.

Any more thoughts, keep 'em coming!

*Pantyhose, almost as many uses as duct tape!

Sue

Depends on your vehicle's design, you can simply get a cylindrical shaped filter and duct tape that onto your intake opening (although most passenger cars are too cramped in engine compartment to do this).

Or you can just put a sock on it, offroaders do this after their filter gets waterlogged and must be removed.

I was thinking of a fairly large box, too big to stuff into any engine compartment I'm familiar with. I'm thinking a standard medium mover's box (18x18x16) And cutting off the 18x18 side so you have 2.25 square feet of open area. More cross-section area equates to less air flow per unit area and less chance the caked ash will be held onto the filter by the air flow.

The intake on my truck is a rubber hose that is tucked in front of the wheel well. The when well is plastic so cutting a hole to allow a hose to pass should be an issue. The hose would come out the top of the wheel well and up onto the hood where the large box filter would be mounted on blocks filter side down. Duct tape and cargo straps should hold it down well enough.

Made out of plywood and with a little streamlining the box should ride at any reasonable speed. A cardboard box would be more delicate and might require you to drive slower. Then again with ash limiting visibility driving slow might be wise.

Filterwise I'm thinking pantyhose material might be better than a furnace filter. Furnace filters are 'depth' filters and tend to trap the crud they filter out. That's good for a house where you simply replace them but in this roll you want something that will drop the ash if you give it a whack.

I would try two layers of pantyhose material and drop to one if it seemed too tight.

I would think that doubling the filter area would have no other effect than doubling that time / distance - every 4th mile or 4th mile. No doubt a big improvement, but perhaps not the one you were hoping for.


I can try to poke around and see if I can hunt down some Icelanders and ask them. They're off season right now, but let's see who I can find.

In Operation Desert Storm, I see to remember that the fine sand was clogging tank/vehicle air filters and that the field expedient remedy was to stretch panty hose over the air filters.

> I guess the idea was that the inside of the car is cleaner than the outside air.

I'll say this isn't so.

Louise and I camp at Burning Man every year, and the playa surface is a very fine powder. Maybe finer than volcanic ash, maybe not. A sample video:
http://www.flickr.com/photos/civex/2831873456/
The worst dust storm we've been in was when the visibility was four feet; when visibility is four feet, you can't see the ground you're standing on.

The interiors of every vehicle at Burning Man is covered in dust. Worse, all the air intakes are full. When you start your car/truck/whatever, you get a huge blast of powder out the A/C vents that lasts a long time, further coating all the front seats in another layer of dust.

The seals on the doors don't protect against intrusion of the powder, the filters (if any there be) on your A/C intakes don't protect. I would not expect the interior of any vehicles in a Mt. St. Helens type eruption to be any cleaner than the outside air, _especially_ if you have a window cracked open and "sealed" against air.

Last week I turned on the air conditioner on our van for the first time this season, and I got a whiff of playa powder out the vents. shrug - fortunately it's a reminder of great adventures, so it's not a problem. The van was on the playa last American Labor Day.

I would suggest you're better off changing the air filter frequently. I'm not sure how long one would expect ash-falls to continue, but clogging the air filter is likely to take some time. I'd start with some research on that answer before doing anything else. If heavy ash were a concern for me, I'd have a couple of air filters in the trunk.

I'd say put a higher capacity filter in if you're that worried about it, but basically just follow the advice of cleaning the filter. Ultimately, I'd much rather damage my engine than have it suck air from inside the passenger compartment - if the interior air is any cleaner than the exterior air I just assume I breath that clean air and let my engine die a little quicker.

You can also wrap a new flannel shirt around your air filter and run til it clogs up w/ash. Then shake out the flannel cloth (downwind of your car), rewrap your filter and continue til it clogs, and repeat til you clear the ash cloud.

Youy want a new piece of flannel in order the catch the most particles and save your filter to the maximum distance/mileage.

I'm hoping that I never have to deal with it. The people who have done so said it's really nasty.

Thank you for all the input.

Sue