Thursday, May 29, 2008
Tales From the Used Car Lot
I was making some adjustments to my wife's mountain bike when an old gray Lincoln Mk VII pulled up at the stop sign in front of my house. Two teenagers got out and started looking under the hood. I walked over to see if I could help out. Turns out the brakes had frozen up. A.J., the owner, said the previous owner told him he'd put new brakes on it.
So after a few false starts (it seems it made a funny noise under the hood about the same time, but that probably wasn't related), I went and got a jack and lifted the rear off the ground. Sure enough, the left rear wheel wouldn't turn. So A.J. grabbed a tire iron and we took off the back tire.
This is where things got weird. It clearly had the original brake caliper. And there was something funny about the wear pattern on the rotor. It was all shiny on the inside, but the outer edge was rusty. Not just surface rust - it looked like it had spent a year at the bottom of the ocean.
Since they needed to get this car out of the street and lived less than a quarter mile away, I figured it would be safe to just pop the old caliper off and let it hang. Not exactly safe but it was better than a car that couldn't move at all. So I got to work unbolting it. Had to bang on a crescent wrench with a dead blow hammer to get one of the bolts off, like it had been on there for years.
Eventually the caliper came off. I couldn't believe what I saw: One of the brake pads was gone.
I don't mean the friction material had worn off and it wore down to the backing plate. I mean the pad was gone.
The inner brake pad simply wasn't there. The caliper piston was wearing directly against the rotor instead of pushing a pad against it. A.J. said he'd driven the car for about a month and it hadn't given him too much trouble, although the ABS light was on.
I've bought a few cars with lousy jury rigged repairs, and heard tales of countless others, but that's the first time I've seen an Evil Previous Owner try a brake job with only half the number of brake pads needed.
Labels: Automotive Awefulness
Friday, May 23, 2008
The plug-in hydrogen hybrid, part 2
Now I'm going to consider the electrical requirements of this thing. You're making 0.93 kg of hydrogen in an hour. Remember when I noted hydrogen's energy density is 142 megajoules per kilogram? You'll need to feed this thing 132 megajoules of energy in an hour if it were 100% efficient. Since power is energy per unit time, this works out to needing 36.7 kilowatts to drive the generator. Converting that to horsepower, by the way, indicates it would take 49 horsepower to drive this hydrogen generator. See why this thing isn't driven off the alternator? You'd be wasting a lot of the engine's power, need a much larger alternator, and probably have to replace your serpentine belt with a chain drive to boot. If this thing were running off 12 volt batteries, you'd need to supply it with 2500 amps. Far more current than a starter draws.
It's obvious this design is starting to get into trouble. In further posts, I'll size up a battery pack for this thing (it's going to be huge) and see if there are, in fact, ways this hydrogen hybrid idea might be salvagable.
Wednesday, May 21, 2008
The plug-in hydrogen hybrid, Part 1
But what if you powered it with a battery you'd charged from your home and recharged every night? Let's run a few calculations and spec out a system for a car. First, let's define what we want this system to accomplish. Suppose we are starting with a big SUV that gets 20 miles to the gallon when driven at a steady 60 miles per hour. And let's suppose we want it to get 50% better mileage, to 30 miles to the gallon of gas. Running a little bit of math shows that it would originally be burning 3 gallons per hour, and the improved version would be burning 2 gallons per hour. So this makes the math a bit easier to follow, at least up until this part. And let's add that this car will see 1 hour of use on a single battery charge.
The first question is, "How much hydrogen do we need?" Well, we'll need to supply the equivalent of 1 gallon of gasoline in hydrogen, per hour. Now the math gets hard: We need to figure out how much hydrogen that is. And we'll also figure out the device's water consumption. We'll start with a couple key numbers pulled from around the Web.
Energy density of hydrogen: 142 MJ/kg (most optimistic value from this source)
Energy density of gasoline: 46.9 MJ/kg (from Wikipedia)
Ratio of hydrogen to gasoline energy by weight: Hydrogen has 3.03 time the energy of gas.
Fraction of water that is hydrogen, by weight: 1/9
Ratio of gasoline's density to that of water: 0.739 (source)
Using these ratios, we find that you'd have to break down 2.2 gallons of water to get enough hydrogen to replace one gallon of gas. The calculations for this are pretty long, so I'm taking a break now. Next up, we'll see how much energy is needed to do this, how much power this thing is going to consumer, and what you'd spend on batteries. And why you shouldn't call it an HHO generator...
Monday, May 19, 2008
Well, I haven't reached the "waiting for my book to come out" stage. I have a book under contract, but my co-author Jerry Hoffman and I still need to complete the book. But hey, it's not too late to think about what I might do for a sequel. I have a couple other books in various stages of completion on my hard drive, including a fantasy novel and a sort of introductory text about car mods for the absolute beginner. But what if I wrote the next book on one of the topics that I blog about? After all, the book I have under contract is about electronic fuel injection, and I blog about that pretty often.
I could write about how to build a turbocharged slant six powered Dodge Dart, but that's a bit of a narrow subject, don't you think? And there's plenty of good books on turbos. I suppose I could see if Doug Dutra would be interested in a colaborative project for a book on slant sixes, but that still probably wouldn't have the appeal of a book on Chevy V8s.
One of my favorite things to write about has been gas mileage scams. But a book on gas mileage scams has its own problems. Who would buy it? Somebody looking to avoid getting scammed? Usually, the Internet is a pretty good tool for checking if an alleged gas saver is a scam, as you can often find people criticizing questionable gadgets. (Unless, of course, the scammers just haven't fleeced enough people for debunkers to notice them.) Unfortunately, I wouldn't be able to write very much about real ways to improve your gas mileage that a normal do-it-yourselfer could do at home to a modern car, as it's hard to out-engineer the factory designers without spending more than you could save on gas. The number of bad gas mileage devices out there vastly outnumbers the ones that work, and curiously, the things out there that could save a tiny amount of gas usually aren't marketed as such. (For example, you don't usually see carbon fiber body panels advertised as fuel economy aids.) For some reason, it's harder to sell debunking than flim-flam.
I guess some topics are better suited to blogs and the Internet, when you get down to it. Odd niche material can reach a wider audience. I can expose scams without having to worry about a magazine's ad dollars or bookstore sales. But really big topics still belong in books.
Next up is L. M. Ashton.
Also, check out the other blogs in the chain:
Life in Scribbletown
Polyamory From the Inside Out
For the First Time
Family On Bikes
Writes in the City
Elf Killing and Other Hobbies
Spittin' (Out Words) Like a Llama
As Yet Untitled
Labels: Blog Chain
Sunday, May 18, 2008
Interesting gas mileage scam link
Labels: Gas Mileage
Saturday, May 10, 2008
Happy Mother's Day! Here's another dubious gas mileage gadget!
The premise on this site is one I've seen before. So has Tony, the engineer behind Tony's Guide to Fuel Saving. The device takes electricity from the car's electrical system and uses it to generate a mixture of hydrogen and oxygen (which they, and a lot of promoters, call "Brown's gas," after Yull Brown, a somewhat shady huckster), which is then fed into the engine and burned. There's an obvious problem with this: You're spending more energy to make the hydrogen than you are getting back when you burn it. If you could take waste energy, like from regenerative braking or the exhaust heat, and use that to generate hydrogen, then you might have something worthwhile. A waste energy system would probably need a good way to store the hydrogen, since the best times for generating the hydrogen are not necessarily the best times to burn it.
Their system, however, is one that rules out being able to store the hydrogen for later use. They mix the hydrogen and oxygen to make "Brown's Gas." This very interesting page on Brown's Gas gives a very good description of the trouble with storing a hydrogen and oxygen mixture:
Since Brown's Gas is an explosive mixture it would be hazardous to store any quantity of it at atmospheric pressure. To compress it for storage would be criminally stupid.
A standard cylinder used for storing hydrogen contains just over a cubic foot of gas under about 150 atmospheres pressure. At that pressure it would contain the equivalent of about 5380 liters of Brown's Gas. That is 2880 grams or 160 moles. At 242000 joules per mole a cylinder contains almost 39 million joules or 36700 btu. There are two ways of looking at this. One is that the cylinder is a poor storage device since, for all its size and weight, it contains about as much energy as two pints of gasoline. The other is that each cylinder is the equivalent of 21 pounds of TNT in a steel tube. This is not something I'd want to have around!
Another interesting tidbit about that site is the very small amount of water the device actually consumes. This claim on their website is an interesting one to examine, and not just for the excessive use of bold print and the poor capitalization:
Water can be used to fuel a car when used as a supplement to gasoline. In fact, very little water is needed! only one quart of water provides over 1800 gallons of HHO gas which can literally last for months and significantly increase your vehicle's fuel efficiently, improve emissions quality, and save you money.The low water consumption claim would indicate that it doesn't inject very much hydrogen at all. They claim a quart of water lasts "months" in their system. A quart of water weighs 2 pounds, and 1/9th of the weight of the water is hydrogen. If a quart of water lasts two months, each month you'd get 1/9 of a pound of hydrogen into the engine. Suppose you used 30 gallons of gasoline in that same month. That's around 175 pounds of gasoline! The idea that such a tiny fraction of hydrogen in the system could improve mileage by 40% staggers the mind.
Thursday, May 01, 2008
Some cool junkyard EFI parts
1. Turbo cars often have pretty large fuel injectors. My Dart has injectors from a 3rd generation Toyota Supra Turbo; they're 440 cc/min, or 42 lb/hr. Turbo Eclipses have similarly large injectors. The trouble with both is that they use weird mounting hardware and connectors; they won't drop right onto a Chevy TPI.
2. Ford 2 valve 4.6's not only come with good-sized (65 mm) throttle bodies, they put them on an elbow that makes adapting them to a carbed manifold easier. The Mustangs have little short elbows that are really good for this. Crown Vic elbows are taller and you'd probably need to cut one down and weld it to make it work for most applications. That was the case on my Dart's slant six turbo project, which uses a Crown Vic throttle body and originally used the CV elbow too.
3. Late '80s / early '90s Ford full sized trucks have an external high pressure fuel pump that's good for moderate EFI applications.
4. Chrysler distributorless coils from the late '90s are pretty hot, meeting almost exactly the same specs as Ford's EDIS coils. In fact, Ford of Australia used Mopar coils on their EDIS setups. Only the towers on Ma Mopar's coils accept plug wires with HEI boots, making them much easier to get plug wires for. LSx and '90s DSM coils are also pretty hot distributorless coil setups.
Labels: Junkyard Scavenging