Most of the oil we import goes to moving us about in personal vehicles, cars, trucks, and urban assault vehicles. Recently, we’ve seen the introduction of hybrid gas-electric vehicles that get significantly better fuel economy than their non-hybrid equivalents.

Still, I think there is a tremendous amount of room for improvement. A hybrid vehicle costs several thousand dollars more than it’s simpler non-hybrid equal and gets perhaps 50% again as many miles from a gallon of gasoline.

There is a technology, it doesn’t get much public attention, that can get about as much improvement in efficiency at about one-tenth the cost. That technology is water injection. I put this on a 1968 Rambler, and with some other tweaks that it made possible, improved mileage from 16/22 to 22-25/30 city/highway. The variability in city driving being a function of how I drove. I could stretch it to 25 in the city but averaged around 23 under “normal” driving.

To get this type of mileage you have some things you need to do besides just adding the water injection, specifically you need to advance timing and and lean out the fuel. Additionally, I believe that even more efficiency could have been obtained by also raising the compression ratio.

The kits that you can buy assume about a 10:1 fuel:water ratio but I found best results were obtainable with 1:1. The kit I had also had no filter, which caused the injector to get clogged frequently. To be successful commercially, water injection will need to have a water tank as large as the fuel tank. Because it’s possible to increase fuel economy to such a large degree, an increase in total tank volume will be minimal because more than half of the necessary water volume will simply displace an equivalent amount of fuel tank volume.

Water injection does a number of positive things, some of them are easily understood, some area not. Water injection reduces peak cylinder temperatures to a large degree. This allows more advanced timing, leaner mixtures, and higher compression ratios.

Water injection turns into steam during combustion increasing the gas volume and pressure on the piston while at the same time holding temperatures down. Less heat escapes through cylinder walls, more heat is transformed into mechanical energy.

Another thing water injection did is drastically reduce emissions, hydrocarbons and carbon monoxide was almost unmeasurable. The mechanism behind that is not known to me. I suspect nitrous oxides were also down since peak cylinder temperatures were down but I had no means of measuring these.

Why not combine water injection with a hybrid technology? Hybrids improve efficiency by recovering breaking energy, providing torque at low RPM ranges where a gasoline engine can not do so efficiently, provide a method of peaking power so that the engine can be sized smaller, and by allowing the engine to operate at optimal power and RPM ranges when it must operate. Combine that with a power plant that is considerably more efficient to start with and you’ve got some major fuel savings potential.

Then why not add plug-in hybrid technology to that? And maybe some solar panels to top off the batteries while the car sits in a parking lot all day?