Water Injection -

[Bort62]

I know this has been covered here before, and I went and read a few of the threads...

I am wondering if anyone on this board is actually using it. My setup isn't even close to tuned yet, but I am getting some detonation above 7psi and I plan to use water injection instead of an intercooler to control it.

I have read the DIY water injection website, and it looks fairly straitforward. I just wanted to see if anyone here had any experience.

Thanks.

 

[Anlushac11]

8)

I used to run it on my 79 Capri carb turbo and my dad ran it on his 75 Pinto runabout.

There are several sites that tell you how to build your own and you can mount a Hobbs switch on the intake to make it kick in with boost.

One way of doing it was a windshield washer tank with the pump wired to the Hobbs switch and the nozzle ideally blowing in just under the carb base.

Also you can mix water/methanol. Just use non detergent windshield washing fluid.

 

[Bort62]

I understand the principles, it's actually right in my area of professional expertise.

However, I wanted to know how well it works in practice, and it is practical for a basically street car.

I've got a buddy who is telling me that I shouldnt WI, but run an IC instead... he says WI is not reliable enough for the street.

Id like to know how much water people are going through, etc.

 

[TCIC 300ci superbeast]

what does WI really do for u? im guessing it not just spraying water in the motor

 

[Bort62]

Well,

I don't have any experience with it on cars, so I can't speak from that standpoint. However, from a thermodynamics standpoint it does a lot.

First, when you spray water into the intake air stream, the temperature of the water and air are going to equalize. Because water has a very high specific heat (ability to absorb energy) it will raise in temperature just a little bit. Air has a very low specific heat, and as such it will lower in temperature a lot. This cools the intake charge which helps with detonation as well as increasing the density of the incoming air - hence making more power.

Also, when your intake charge combusts in the chamber, the water that is suspended in it flashes to steam. This creats more pressure than the combustion would alone. It's the same way a steam piston works.

So as the water heats from the combustion process, it boils to steam and increases the pressure in the cylinder, forcing the piston down. That makes more power.

It allows you to gather more of the combustion energy than you would otherwise - energy that is w/o the water being wasted as heat out the exhaust pipe.

Remember that internal combustion engines are only about 30% efficient at capturing all of the energy released by the combustion of gasoline and air. The other 70% is waste as heat, noise, and friction losses within the engine. Using water injection allows you to bump that % up a little.

It also keep's your top-end clean, too.

 

[TCIC 300ci superbeast]

ok thanks.
but what about the fact ur puting water in the intake? or is it just a small amount?

 

[addo]

It's a tiny amount, and basically is sprayed in as fine droplets.

Some people say "long term" usage may harm an engine, but others seem to have used it for years with no hassles.

 

[rickwrench]

Long term use, if anything will keep the chamber and pistons spotlessly clean. There won't be a speck of carbon -anywhere- to be seen.
Bort, a lot of folks use the blower to pressurize the water tank, making it a boost referenced system.
Rick(wrench)

 

[hasa68mustang]

Long term use, if anything will keep the chamber and pistons spotlessly clean. There won't be a speck of carbon -anywhere- to be seen.
Bort, a lot of folks use the blower to pressurize the water tank, making it a boost referenced system.
Rick(wrench)

which would also change the pressure, more boost=more water... but that isnt very much pressure is it?

 

[Bort62]

Well, boost referencing the water tank would just keep the deltaP across the injection nozzle constant.

So more boost = the same amount of water, instead of less.

Good idea Rick...

My engine is going to look like it's covered in spaghetti by the time all of this is done

 

[Anlushac11]

8)

Im not sure what your friend is talking about it not being very reliable for a street car? On a turbo car its like checking your oil.

Yes intercooling is better but if you dont have a intercooler or running a system like draw through that does not lend itself to intercooling then water injection is a good alternative.

People have been running it on vehicles for years. In WW2 German fighters like the Bf109 carried the MW50 water methanol system to allow short term power boosts.

From what I understand when water is sprayed into a pressurized inlet like a turbocharged intake the water gets atomized by the turbulence. As Bort62 said this will help lower the inlet charge temperature.

When compression occurs the water changes from a liquid to a gas by means of a phase change. The physical act of performing a phase change takes alot of energy to do and this energy is in the intake charge in the form of heat.

The result is a great deal of the the energy aka heat is used to perform the phase change thus cooling the chamber allowing you to run higher than normal boost.

On a draw through turbo system you dont want to spray the water in too close to the turbine as people have reported the water droplets hitting the impeller going at thousands of rpm's has caused wear and pitting on the leading edge of the turbine blades. If it gets too bad this can cause a inbalance problem and catastrophe.

I dont off hand remember how much water/windshield washer solvent I used. I want to say I had to fill it up about once a week or top off on Friday and top off again on Sunday if I was out playing on the weekend.

On my Capri it was setup to only come on with boost, so I didnt use that much. My dads pinto was normally aspirated but had a big solid lifter cam, ported and polished head, 11.6:1CR and a 500cfm Holley 2bbl. His was on all the time to allow that high compression. He had a smaller bottle, maybe 1-1.5qts?, and had to refill it every couple of days. He always complained about needing a larger bottle but I dont remember him ever changing it.

 

[sabre694]

I have some experience with water injection but not on forced induction. It seems to me that you guys are looking for the cooling effect and as water is very dense compared to air It can hold more heat and send it out the exhaust. I was using it to compensate for High altitude. The droplets flashing into steam will actually increase compression ratio at altitude (above 7000 feet) bear in mind The tiny amount of time that this process has to work. My best rigs were over 90 psi with very small orifices, Try to make the finest mist you possibly can. my best source for parts was air conditioning repair parts supply house. small pieces of brass tubing inserted thru an adapter plate under the carb then drilled with orifice drills. (tiny hair sized bits used for gas or ac ) use multiple tubes and valves for a throttle effect. for reliability over achieve your psi and use a relief valve and return line to the reservoir. set the releif valve to your desired operating psi. My experience was there was no noticeable horsepower gain below 7000 ft. but the cooling effect worked at all altitudes and I would switch it on when towing up hills at low altitude etc. Hope this helps