Water Injection - What does it do?

I remember years ago people were putting water injection kits on their
engines. I beleive it was a water tank with a hose running into
either the air intake near the carb or maybe directly into the intake
manifold. A small oriface metered the amount of water that was sucked
in.

What did it do for the engine? Any affect on gas mileage?

Larry

 

I believe that was covered in the 'Popular Mechanics' article that debunked
all of the 'fuel saving' devices tested. Much of this stuff is still being
advertised even though it had only a possible application in carbureted
engines.

Water injection came as an extra measure of high power and ping reduction in
piston engine military airplanes. The throttle (I'm doing this from
memory... it's been a long time) went from idle to cruise to maximum - then
there was a button interlocked further position marked 'WEP' which stood for
War Emergency Power. You used that one only when you were in peril of having
your ass shot off! What it did was open the throttle all the way, increase
the supercharger/ turbo boost and dump about 50 gallons of water into the
intake over the next 3 minutes. The water mist did a couple of things. It
flashed to steam and added an extra measure of compression. It also absorbed
some heat energy in the process of turning to steam which reduced peak
cylinder temperature and reduced pinging.

Neat idea but absolutely has no place in a modern automobile street engine.
Can cause more problems than it could ever hope to fix. Aside from possible
water lock and corrosion, there is also the aspect of how to winterize the
water reservoir. You could add alcohol to it and then it further tips the
cost - benefit scale in the wrong direction.

Just as a point of interest, google for "war emergency power" or 'engine
"water injection"'

Oppie

 

Dunno much about it. I dont think a stock engine would take much if any
advantage from it. The cons would be greater I think.

Pro's:
Cooler Cumbustion
Carbon Remover

Con's:
Rust
Moisture in Oil
Set up cost

Unknowns:
Fuel Mileage
HP

If it would give better gas mileage I think the automakers would jump
right on it.

 

Neat idea but absolutely has no place in a modern automobile street
engine.

Well, that depends. On your car as it came from the factory, I would tend
to agree.

But on a very high compression or forced induction motor - that's a
different story.

First paragraph on this page does a good job describing the use:
http://www.volvospeed.com/Reviews/aquamist.htm

Lane [ lane (at) evilplastic.com ]

 

It was covered in PM TV show last week as a debunked gadget along with the
tornado, etc. and they expressed concern over potential damage if not hooked
up correctly. It was used in WWII to extend gas mileage in fighter planes. I
first learned about this in the '80s when an old friend garage built such a
device as designed by his father, a WWII pilot/mech. for his , lol, K-car.
He claimed it worked but never proved it.

marx404

 

Wasn't there an olds motor in the 50's that had something like this?

 

You need to get up to speed on water injection. Especially when used on
diesel engines.

 

Would you care to point me to some information please? I may be wrong at
times but never wishy-washy <g>.
Oppie

 

In many respects, Water injection works like EGR does in modern street
engines. It lowers the peak combustion temperature under high power and
controls ping. Water inj does have the result of aditional expansion (ie
power) but this is not a fuel saver as you have to supply additional energy
to vaporize the water. Bottom line is that it may improve power but not fuel
economy.

 

The WW-II use of water (usually combined with alcohol) injection was
strictly for detonation suppression at high power settings. It cooled
the charge in the cylinders while the alcohol raised the effective
octane rating of the fuel/air mixture. It certainly did NOT improve fuel
economy and was good only for short duration (full military power).

Note that those aircraft used either superchargers or turbo
superchargers to boost the intake manifold pressure to 60 or more inches
of mercury (15 in is sea level ambient).

Detonation susceptibility increases with charge pressure and temperature
and decreases as octane increases.

Forget about it for improving fuel economy!

 

I saw a 1940's airplane engine on display at the Intrepid Sea and Space
Museum in New York City. Don't recall what it was from but it had a 2-stage
induction system; first stage was a turbocharger and second stage was a
supercharger. As you said, that could easily get 60 psi at a cruise
altitude.

 

For improved economy have any of you tried fuel preheating. Saw an
article on it and built a heater with good luck on 2 cars: 74 Mercury
Capri (had Ford Pinto engine) and a 78 VW Dasher Wagon (standard VW
water-cooled 4). It used radiator fluid to raise the temperature of
incoming fuel a bit. There was about 1 foot of jacket so it probably
didn't heat it too much.

As the engine (and radiator fluid) came up to temperature the idle
speed increased. Gas mileage was up about 20% as I recall. It was
all downstream from the fuel pump to avoid vapor lock. Never had a
problem other than the increased idle speed.

Didn't have the guts to try it with a fuel injected Rabbit given the
high pressure fuel system. And the funky fittings for the lines. If
it works why don't companies work it into their fuel systems?

And last, how about heating incoming air a bit more? That should
help, too.

Jim

 

I never considered fuel pre-heat on a modern engine since the fuel is always
flowing in a loop (pump from the tank, take off what you need for the
injectors, fuel pressure regulator and dump back into tank). Too much
pre-heat and you heat up the fuel in the tank excessively (which just might
be a problem).

Heated air induction is a far safer way to get the same effect.
Oppie

 

That's probably your answer right there.... it doesn't work. And a 20%
improvement sounds very improbable.

And as for heating air, seems to me you need enough to vaporize fuel, but
beyond that it's counterproductive because air becomes less dense and you
don't want that. That's why turbochargers have intercoolers, to lower intake
temperature.