I have to agree, looks pretty simple! Per the other thread in this forum section, I plan to build a simple setup in the next couple of months.
Figuring to run most of the time without, but a master switch to flip on, to use when needed. Also a Hobbs switch keyed to boost pressure, that W/M kicks in anytime I hit 10lbs or above boost, when the system is switched on.
I'd probably go with straight water most of the time, just to keep EGT's down in the mountains. Towing I'd toss in the go juice for more power plus more EGT cooling.
Looks like a guy can build a decent but simple system for about $200 or so, depending on what he has laying around the parts pile. I already have the Shurflo pumps so that saves me a few bucks.
I seem to recall reading a few post on DTR about home made set ups.
Heres one post: The pump Snow uses puts out 150 psi and is identical to the pumps used in many RVs (SHURflo) except for the high pressure. The pump must be high pressure in order to create a mist. I've checked out these pumps before and it seems that all you would need to do to jack up the pressure would be to change out the spring in the pump's pressure regulator. These pumps are under $50 at RV supply stores.
The electronics Snow uses to trigger the pump according to turbo boost would be the hard part to copy.
You need a high pressure pump to overcome the air pressure in the intake, post-turbo. While not having done this myself (only reading about it), I think you should be able to get away with a lower pressure pump if you tap an air line from the intake pipe to pressurize your water/alcohol resevoir--that way the pump doesnt have to work so hard. Just remember that the resevoir will have to handle the pressure that your turbo will put out
Fogger nozzles (ie. the garden mister variety) are fairly cheap on eBay; I bought a couple for like $10 for a biodiesel refinery that I'm building. I seem to recall that it was rated in terms of gallons per minute or gallons per hour or something--presumably at a standard garden hose water pressure (which is probably around 50-60 psi). If your pump pressure rating matches that, then you should get the flow rate on the nozzle label.
Another trick that might work (or might not): If you take your pressure tap from right after the turbo, and then put your nozzle after your intercooler just upstream from the intake manifold (leave yourself enough room for the water/methanol to mix into the airflow, though), the pressure drop across the intercooler might be enough to forego the need for the pump? It would depend on how big that pressure drop is; if its only 1 or 2 psi, then you might not work so well (dribbles might not be all that helpful), but the upshot would be that the water flow would be roughly proportional to the engine output and you wouldnt need a controller. Even if it didnt work, it'd be cheap to try. You could even go so far (thinking WAY outside the box here) as to induce a mild restrictor after the intercooler/upstream of the nozzle to increase that pressure differential to make it fog better (you'd want to increase the boost output accordingly)? That setup might lose some efficiency as the turbo has to work harder, but it might save you the cost of expensive plumbing (definately make sure that the restrictor is NOT something that would get sucked into the engine
A few other posts warn about mixing too much meth and having pre detonation wreaking havoc on engines.
From what I see lately the Shurflo pumps run from $60 to roughly $100++.
There are repair kits across a Shurflo model platform, so you can often upgrade a pump by changing out the parts to a higher pressure model. In addition these pumps are adjustable for pressure. Not sure how big the range is, like if you can adjust a 60 psi pump to 100 psi, have to check that.
I don't think you'd have much luck inducing injection pressure from turbo boost. You have that boost pressure in the intake tract already heading for valves, so if it's attempted to use it for injection of W/M you have a net zero pressure increase because of head pressure. Most say that you want at least 60 lbs. increase over boost for injection pressures, more is better.
Nothern Tools has some pumps for about $60 that would probably do the trick, check pressure output [but it's adjustable].
Depending on needs a fancy electronic controller isn't really required. A Hoobs presure switch actuating a solenoid valve will do the trick, with Hobbs switch set to desired boost pressure of beginning injection. A master switch to overide Hobbs is best.
Methanol is some pretty caustic stuff so all plumbing & container has to be methanol rated. It's also poisonous on contact or breathing, very poisonous.
Water injection is pretty common with guys running turbos on gas engines.
Most of the setups I have seen is the mist nozzle is installed directly infront of the turbo intake inlet. The idea is for the compressor to homogenize the air/water vapor mixture. The cooling effect isn't because the water vapor is "cool". It is the phase change when the water vapor flashes into steam. The phase change absorbs heat. There are other benefits also. The phase change very effectively cools the valves and cools the exhaust gases. The steam in the intake charge "steam cleans" the combustion chamber. Also another benefit is the expanding STEAM give a slight power boost. It turns your diesel engine into a quasi-steam engine.
My father in law built a rig on his 1950 model Chevy that injected a water mist at cruise. He found when he got the ratio just right he got a boost in gas mileage.
The "sweet spot" was very narrow and hard to maintain through out the RPM band. He found this was because he could not achieve a homogeneous mixture of air/ water vapor. He needed a turbocharger or supercharger but these were very hard come by back then.
From all that i have read on the subject it can be extreamly detrimental to your turbo to spray before its compressor inlet. Although i did read somewere that some turbos can take it but am unsure wich ones. Best to err on side of caution and put nozzels just before intake manifold.
On the subject of building your own unit I live in australia and have just taken delivery of a basic two nozzel, two pressure switch uint from BE COOLING in Steevensville MI (49127-9569) and it was only around $350 US. it has everything but the tank witch im building myself so for the price why would you spend several hours sorting and sorceing the parts, I just have to fit it.
I built mine out of parts from a used snow kit. I ended up drilling out the nozzles a little at a time until they sprayed a desired amount. I used fittings for ice water line from home depot and useed an adjustable hobbs pressure switch from napa. I would definitely recommend some sort of boost switch. When mine was just toggle, my brother drove my truck and tried out the w/m, left it on and I ended up with water in my oil. It didn't hurt anything, its just easier to have the boost switch for extra safety.
The W/M systems on my trucks both went through several evolutionary changes. I eventually settled on setups using more smaller nozzles mounted in the intake plenum (as opposed to the horn). I have 3 200s on the 1st Gen and 4 200s on the commonrail. The 1st Gen seems to get better effect from it, both in terms of lowering EGT and power boost. I suspect that is mostly due to the commonrail's better overall breathing efficiency with 24 valves and a much better turbo. I also believe progressive controllers will give the best overall results for anything other that strictly racing or sled pulling. An on/off switch is fine if you are just using it for competition, but that would be the only way I'd use anything other than a progressive controller to run it. I initially ran just a switch on the commonrail and it was difficult to find a the starting boost point below 25psi that didn't cause quench at anything less than full throttle.