Water Injection Wizardry

A water injection system can improve your gas mileage 20 to 50 percent.

| September/October 1979

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    The water injection system uses the feeder hose attached to the air filter cover to squirt water directly into the carburetor.
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    A jury-rigged gauge wired to the dashboard tracks the vehicle's fuel economy.

  • 059 water injection 01.jpg
  • 059 water injection 02.jpg

During the second World War, fighter pilots could push a button and inject a stream of water into the turbochargers of their monstrous powerplants to get extra thrust on takeoff. Some time later, Chrysler (among other auto manufacturers) installed water injection on a number of its large displacement engines, again for a performance increase. Indeed, water injection—used to produce power increases—is nothing new.

But using "Adam's ale" to save gasoline sure is a change of pace! You see, until recently there just hasn't been any way to effectively control the volume and atomization of the tiny amount of fluid needed to adapt H20 injection to a small, economical engine. And typically enough, while big technology has failed to figure out how such regulation could be handled, a small back-lot entrepreneur (with a wealth of experience and ingenuity, but a paucity of dollars and degrees) has succeeded.

Pat Goodman installed his first water injection system (on a Porsche racing car) in 1964, and the racing organization responded by banning his device—it made the vehicle too fast! Undaunted, Pat decided that even if the racing establishment wasn't interested in "improving the breed," he was.

Today, several near-bankruptcies later, the innovative mechanic owns a vehicle that only the government could argue with: a 1978 Ford Fiesta that gets 50 MPG in normal around-town driving. (This impressive figure has been verified by a MOTHER EARTH NEWS staffer, who accompanied Goodman on a 48-mile jaunt around Winchester, Virginia. During the drive—which Pat accomplished with, if anything, more speed than normal—the small four-cylinder sipped only 0.95 gallon of unleaded gas.)

Back to Basics

Like most good ideas, the Goodman water injection design is an amazingly simple approach to a frighteningly complex problem. In fact, the production system is much less complicated than the prototype model. It consists only of an atomization nozzle, plus two one-way valves from squirt guns, some hose (to supply water to the "sprayer" and draw pressure from the emission system), and a one-gallon water tank.

The nozzle is screwed into the top of the air cleaner housing and sprays minute droplets of water into the carburetor throat in response to orders from the engine's stock smog-control devices.

Despite his occasional criticisms of the government's regulatory bureaucracies, Pat is graciously thankful for all the time and money they've spent developing his system's volume-control device: the smog pump. This air injection mechanism carefully monitors engine speed and load, and provides the pressure to activate the Goodman unit's water nozzle!

By restricting air pressure from the pump (either with a valve or by crimping the hose) to about 2 1/2 PSI at around 3,000 RPM (measured with a fuel-pressure gauge), the proper ratio of 5% water to 95% gasoline is assured. And at 5%—if the motor burns a gallon of gas every 45 miles, for example—the gallon of water will last about 900 miles.

How Does It Work?

So—you may be wondering—just how does water improve gasoline mileage? After all, plain old H20 won't burn. However, because water doesn't burn, the fluid does (in effect) raise the octane of the fuel!

This higher "flash point" produces three specific benefits (as well as some offshoots). First, because the water cools the gas-air mixture, there is greater potential for expansion (since pressure is directly proportional to temperature). Second, combustion turns the water droplets to vapor, which also helps create a pressure bonus (much as the same substance drives a steam engine).

Finally—and most significantly—the conversion of water to steam consumes heat (at a rate of about 1,100 calories per gram of the liquid) at a very critical instant. This absorption of heat prevents the temperature of combustion from rushing to a sharp peak (as it does in a standard engine) and then dropping rapidly off. Instead, the car's heat increases more slowly, reaches a lower peak, and descends much more gradually. (In addition, the longer overall combustion duration creates more pressure than does a standard engine's cycle.)

Thus water injection alone can make your engine more efficient (and gas-thrifty), but a good mechanic can easily improve upon such benefits! Goodman, for instance, runs his Fiesta at a 12.7:1 compression ratio. He can do this because the reduced temperature of combustion prevents the normal problems of pre-ignition and nitrous oxide emissions (which are produced in a high heat environment): In fact, Pat's little Ford recently loped through the EPA's rigorous (and—at $3,000—expensive) nitrous oxide test with only half the maximum legal emissions.

A high compression ratio can have many benefits, but for the most part such "pluses" involve increased power. Most folks assume—or have been led to believe—that more power means more gasoline consumption. Not so! A compression-ratio hike does not change either displacement or fuel flow, but only makes better use of the fuel that's available. In the Goodman Fiesta, more power means that less throttle can be used to travel at the same speed. That efficient gasoline use translates to better mileage ... as well as a boost in performance. (By the way, the pistons Pat used to raise the compression in his little Ford are obtainable from his auto parts store.)

If you're reluctant to tackle piston replacement, you can still enjoy an approximately 20% MPG improvement by installing a water injection system on your stock engine. Since Pat plans to sell an installation kit—including nozzle, one-way valves, water tank, related hardware, and detailed instruction book—which will be available (by the time you read this) for under $50, a water injection system should pay for itself (at the rate of about a penny per mile) just 5,000 miles down the road.

In addition, the system is so simple to install that it can be ready to run in less than two hours, and the only recommended maintenance is a nozzle-cleaning (with vinegar) every 20,000 miles.

However, the future of the Pat Goodman water injection system is still undecided. Amidst negotiations for distribution with a large New York firm, Pat received word about the possibility of pending EPA action against people who manufacture automobile engine accessories.

While MOTHER EARTH NEWS can fully understand why devices that make noise, spit out smog, or gulp gasoline should be controlled, allowances must be made for small manufacturers who can genuinely help us all. Today Pat is not allowed to install his nozzles (nor is any professional mechanic, without that $3,000 nitrous oxide test) despite their seeming benefits. Tomorrow he might not be allowed to make them at all.

12/24/2010 10:11:41 AM

http://en.wikipedia.org/wiki/Water_injection_(engines) -----and links gives the good low down on h20 inject---funny they dont make much of the fuel savings that could be possible though around 25% looks obvious from the reading and the h20 inject dosent need(you dont want it to) to start til around 3 or 4k rpm or so which should help with metering//// generally speaking lean the carby and bump up the timing a few degrees----will try to give a more specific example later-- am going to experiment with a 86 350 chev engine in a 1 ton van getting around 10 mpg now i have already unrestricted the carby cover(stock was bad restricted and caused the motor to run alot hotter) and that added about 50-75% more power i didnt measure fuel use before but i'm sure it added 2-3 mpg( I forget the % but quite a bit of fuel on pre computer controlled ignition autos goes for knock prevention ---combustion cooling...thats why you get the big improvement in mpg on the newer setup--it runs leaner--- but when you get the newer repair bill that doesn't/ may not mean money saved --funny how that works--or is it----hmmmm sez da hillbilly

12/20/2010 4:14:53 AM

What happens if you add more h2o than the 95% gasoline to 5% h2o ratio??? Seems adding light oil or diesel to the gas tank might be a good idea----which i do anyway If i recall correctly i read somewhere it is good to have the h2o close to boiling when it is injected---any thoughts there?..Also cause of the h2o cooling effect i should be able to lean the carby some. What would happen if you did this on a diesel motor---blow it up maybe??? Truckers add 4-5% gasoline to race'in diesels fuel..Got a gas guzzler 350 stock chey engine on a 1986 motor home - anybody know the compression ratio off hand? any mileage or tips appreciated. Tks---I plan to add a trailer w a couple of wood gasifiers also and have a duel fuel sos i can actually travel some. Tks Race'inTom

Brian Rich
12/8/2010 6:05:32 PM

I have a 1977 ford thunderbird with a 351w. 11:1 compression ratio. I run a holly 600 and my own water injection kit. My kit I purchased from the aquarium section at my local dept store. useing clear tubing, air stone, airline regulator. I was able to increase my mileage with 93 octane fuel @19 mpg.. With h20 I down graded to 87 octane and increased my mileage to 26 mpg. Thats great for a 4400 lb car.


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