This is a basic method to help determine what size water jet to use. This is based on water....Alky injection demands a diff approach to calculating proper jet selection, and a better understanding of alky injection is necessary in order to do that = another thread will be made to address those needing info for alky injection.
Please review the "Turbo Chargers & Knock" paper for a detailed insight in to what's going on in the combustion chamber and why water injection if introduced in the right amount is wanted. You can send a request for it to
jackblalock@gmail.com
In short, the factory is dumping fuel for cooling and knock suppression in order to protect the engine. How much of the total fuel being dumped for this is typically between 10% - 15%. Ideally you want to replace this dumped fuel and instead use water because it does a much better then fuel for this purpose.
Once the things mentioned in the above link become understood the water injection user will realize that ideally he/she wants to introduce water in a ratio of water to fuel. The user also understands that just as with fuel, too much water inhibits or reduces performance. I want to quote one paragraph from the above linked document that IMO will cause the reader here to actually read that document:
"The relationship that you should seek to manage with water injection is the ratio of water to fuel. Metered to exacting proportions as little as 3% water to fuel can replace the amount of heat absorption that fuel previously provided when leaning from 10:1 to 12:1 AFR. There is no system that can meter water in that exacting a relationship with fuel that does not utilize a full fuel injector driver, port installed nozzle jets, high flow pump(s) and a rising rate pressure regulator. At this point you are talking about stand alone engine management like a Motec and a duplication of the fuel system but for water. That being the case the best solution is to use a system that will get you as close as you can to mirroring the fuel injector flow and run at least 10% water to fuel for margin."
Note: On cars that are highly modified or are used in an extreme racing environment more water can be used.
On to a basic method with which to use in determine what water jet to use on your system.
You would need to know before hand:
1) Capability of the fuel injectors your using (cc?s per minute)
2) Rated PSI of the water pump that you intend to use
Here's a link to a chart and thread about the fuel injector sizes most commonly used on the SRT-4:
SRT-4 Common Injector Flow - Math/Info/Chart!
So if for instance, the fuel injectors in your car are rated at 577cc/min and you had 4 of them, you would be injecting 2308cc/min of fuel (4 x 577 = 2308cc/min). Take this total and times by a percentage between 10% to 15% or maybe even 20 (highly modified)
Here?s some simple examples of how a stage II/III injector is broken down with regards to above
Stage II 100% duty cycle
S2 injectors rated at 682CC x 4 = 2728cc/min x 10% = 273.8cc/min
S2 injectors rated at 682CC x 4 = 2728cc/min x 11% = 300.1cc/min
S2 injectors rated at 682CC x 4 = 2728cc/min x 12% = 327.4cc/min
S2 injectors rated at 682CC x 4 = 2728cc/min x 13% = 354.6cc/min
S2 injectors rated at 682CC x 4 = 2728cc/min x 14% = 381.9cc/min
S2 injectors rated at 682CC x 4 = 2728cc/min x 15% = 409.2cc/min
S2 injectors rated at 682CC x 4 = 2728cc/min x 20% = 545.6cc/min
OK so now you get an idea, but injectors do not typically get maxed out at 100% duty cycle, more likely they are maxed out at 85% duty cycle. So take the total (using stage II/III again) 2728 and times that by .85 = 2318.8. This is a more realistic to real world operating conditions
Stage II 85% duty cycle
S2 injectors rated at 682CC x 4 = 2318.8cc/min x 10% = 231.9cc/min
S2 injectors rated at 682CC x 4 = 2318.8cc/min x 11% = 255.1cc/min
S2 injectors rated at 682CC x 4 = 2318.8cc/min x 12% = 278.3cc/min
S2 injectors rated at 682CC x 4 = 2318.8cc/min x 13% = 301.4cc/min
S2 injectors rated at 682CC x 4 = 2318.8cc/min x 14% = 324.7cc/min
S2 injectors rated at 682CC x 4 = 2318.8cc/min x 15% = 347.8cc/min
S2 injectors rated at 682CC x 4 = 2318.8cc/min x 20% = 463.7cc/min
Now you need to know the capability of the WI pump you are using. If you are using a pump rated at 100psi, such and such jet might flow 280cc/min but that same jet with a pump rated at 75psi might only inject 215cc/min.
Aquamist jets using Aquamist race pump
Aquamist jets using Aquamist/Shurflo 150 psi pump
NOTE: This is a very simple and not a scientific method but it allows the WI user to have a good starting point from which to begin with. Aquamist sells kits with 3 jets to allow the user to tune the WI system to their needs.
NOTE: Calculating S3 injectors requires that you take the increased 75 psi pressure on the S3 setup. I came up with a flow rate of 775cc @ 75psi.
Stage 3 owners need to adjust the math accordingly to reflect the increased flow capabilities of that system. But please check this as well
How S3 fuel system works?...is driving me f*#k@%g nuts!
QUESTION: If these calculations are for water, what happens when you add methanol? On some of the Aquamist literature, it says to add .1mm to the jet size for each 25% of methanol you add to your water. How would this convert into the nozzle sizing we use? (M-sizing)
If I'm using an M5 @ 100psi, can I switch to an M5 @ 150 psi with running a 50/50 mix?
ANSWER: All Aquamist flow recommendation are based on the cooling effect due to the latent heat values.
Latent heat table:
To convert 100% water to 100% methanol, you need to multiply the flow by a factor of approximately x2.5. (methanol's mass is x0.8 of water, so if injecting by volume you need to use the density correction). Most non-Aquamist systems use oil heater nozzles (or similar looking), all based on lb/hr of oil and not liter/hr of water.
NOTE: If you have the flow ratings for the nozzles that are typically supplied you can let me know and I will post up the info..........otherwise contact the place of purchase.
Help with water injection jet/nozzle selection
Linear Mode
