| Just a little place holder page as I only started this new life today. The picture at the right is the head of the Mitsubishi designed 2.2 L engine in my 1986 Dodge Omni. Yes, I bought it new, only new car I've ever owned. As far as I'm concerned, this is pretty much the height of internal combustion engine design, a power plant that generated countless speeding tickets while limiting pollution and fuel consumption to a minimum - 40 mpg on the highway with a nice little 5 speed manual transaxle. Since I doubt they expected anybody to keep one on the road for 20 years, I can forgive them that the head gasket started leaking antifreeze around 200,000 miles. |
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I actually own the shop manuals for the car, but this is one of those rare instances where I decided to ignore them entirely. Why fool around with removing the exhaust manifold, a pain in the neck which usually results in at least one snapped bolt or stud, when I figured there's enough room to get at the gasket by just braking the exhaust at the gooseneck and lifting the head a few inches. That's what I did and it worked like a charm, including the little "string up the timing belt trick" illustrated at the left. Wouldn't you know the timing belt snapped on the highway just two years later, first time I ever had to get the Omni towed home. I'd actually replaced the timing belt once before as a preventative measure, around 90,000 miles if I recall, annoying job since an engine mount goes right through it. |
The figure that sticks in my head for the efficiency of car engines and drive trains back in my teens (the 1970's) was 12%. In other words, 12% of the energy in the gasoline burned was transformed into useful tire-spinning work. Most of the efficiency losses occur right in the engine, thermodynamic rules (you can't win), friction and imperfect cylinder losses, incompletely burned fuel and valve timing losses, but there's also good old friction loss through the whole drive train right down to the wheel bearings. While I have no intention of building anything with an internal combustion engine, it wouldn't hurt to chase down the current efficiency ratings just for comparison. If we end up with an electrical power plant, the fuel (ie, battery) to useful work efficiency will be much higher, but if you're doing an environmental energy balance, it's important to take note of how that battery got charged in the first place. Speaking of batteries, it always bothered me seeing the big car companies talking about minimum mileage between charges to make a car practical. Practical for who? For my mom, 10 miles between charges would be more than sufficient, and I could easily make due with 50 miles. Add that to the both of us rarely driving more than once or twice a week, and we'd be perfect candidates for alternative energy trickle chargers. Not the standard driving pattern? Maybe not, but telling me that a practical car has to go 250 or 400 miles between charges is like telling everybody living in an apartment building they should all buy rider mowers to do their square foot of the lawn.
One of the first exercises I want to go through is looking at battery capacity vs sustainable horse power for electric motors. It's a pretty basic idea, so it wouldn't surprise me if it isn't available anywhere in a nice table yet. I'm really more interested in practical experimentation than theory here, and manufacturer ratings are just another form of regulated advertising, but it makes sense to create some sort of baseline to allow for quick comparisons. While it's obvious that a 5 horse power motor can move a car about (just picture 5 inefficient horses harnassed to a car), it will obviously be pretty limited in terms of performance, too much so to be road worthy in most cases. If experimentation shows that you can get by in town with a 10 hp motor driving one wheel, it would be nice to have a quick check as to how many minutes of life you can go per fully charged battery. So, I've got to brush off the old physics book and getting all of those work/power conversion factors back into the front of my brain.