Postby chickenwafer » Sat Dec 19, 2009 9:14
Yeah, you only inject when in boost, and all quality kits on the market are progressive. Meaning you set a Start Spray setting for say 6psi and and End Spray setting for your max boost of 17psi or whatever. So the controller progressively ramps up voltage to the pump which can start spraying at 60psi all the way up to 220psi at max voltage on some kits.
I run a lot of water/meth, I start spraying pretty early around 4psi and hit my max spray at around 13psi. I've hooked the pump up to test it spraying outside the intake track and at full voltage it will empty a gallon quickly. The nozzle which atomizes the droplets slows your volume down significantly, as well, and this is how you can fine-tune how much water/meth you inject.
I don't drive my car that often to really track my water/meth usage, but doing about 30-40 WOT dyno pulls when I was self-tuning I used maybe 2-quarts, but I was spraying too much and drowning out my AFRs.
The benefits of water/meth injection are so great I would run it on any forced induction vehicle I would own, daily-driven or not, and I'm even debating putting one on my truck. It increases reliablitly, effectively allows you to run race gas timing/fueling schemes and boost on premium pump gas, and literally steam cleans your engine from the inside.
When the water/meth mixture is injected into the air stream under high pressure, the nozzle atomizes it into tiny droplets that are suspended in the moving air stream. Since your intake charge is so hot, the water goes through a chemical change to a gas state (steam). Water absorbs 4 times it's weight in heat, so the conversion of the water to steam is what drops your intake air temperature so drastically.
The steam also acts a buffer during the combustion process which is what effectively raises your knock resistance. The methanol has an effective octane rating of 114, so it's available for the combustion process as a fuel.
The steam charge also cleans the inside of your engine by removing carbon deposits. If you run water/meth on a rotary you need to be careful as the steam can wash away the oil on the exposed seals on the rotors, so usually you should premix more and/or ramp up your OMP oil volume if you're running water/meth.
Also when selecting a water/meth kit, be sure to know what kind of fluids the kit can handle. The internal seals in some pumps don't like pure meth or alcohol. I know my Snow kit can't run higher than 49% by volume meth or alcohol. AEM kits, on the other hand, can handle 100% of the stuff. For a street car that's pretty aggressive (and expensive), though.
Some kits can also actually improve your MPG by injecting small amounts of your water/meth mixture and pulling fuel injector pulse widths. Kits like the Snow Stage 3 MPG Max interface your fuel injectors to dial back fuel and inject water/meth when you're cruising at a high vacuum pull. Then when you go into boost the kit acts like a normal water/meth system and injects a progressively variable ratio of water/meth.
