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Old 04-04-2011, 08:25 PM   #1
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Default How to caculate what size and how many jets/nozzles you need

Here is a link to a nice little write up on how to determine what size and how many jets/nozzles you need for your water injection setup.

http://howertonengineering.com/tech-...ating-jetting/

I also printed the page to .pdf and attached it to this post in case the webpage goes bye bye.
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File Type: pdf Calculating Jetting _ Howerton Engineering.pdf (246.0 KB, 309 views)
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Old 09-18-2011, 02:50 PM   #2
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Assuming you haven't dyno tuned, a good way to quickly check if you're spraying to much or too little water is to take a look at your water consumption per tank.

Per the article above, if you're spraying a 50/50 mix, you want to be consuming 15-20% mixture for your fueling. The 15-20% number is what you should be spraying under boost. That means that if you have a 12 gallon tank of gas and are driving around normally on the street (not at WOT all the time), you shouldn't be using up more than 1 gallon of mixture per gas tank fill-up.

Again, this is just a real quick ballpark check to see if you're spraying too much or too little. I had issues with spraying too much so hopefully you can use this info to avoid doing the same.
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Old 09-18-2011, 07:11 PM   #3
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is it just me or does that not take into account how much fuel you're ACTUALLY injecting into the engine?

If I have 1000cc injectors for the lulz, but my engine will have all its fueling needs serviced by 500cc injectors, and I do my calculations off my injector size, the calculations for the 500cc will be spot on, and the 1000cc calculations will not. I thereby call shenanigans.
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Old 09-18-2011, 09:06 PM   #4
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Quote:
Originally Posted by tasty danish View Post
is it just me or does that not take into account how much fuel you're ACTUALLY injecting into the engine?

If I have 1000cc injectors for the lulz, but my engine will have all its fueling needs serviced by 500cc injectors, and I do my calculations off my injector size, the calculations for the 500cc will be spot on, and the 1000cc calculations will not. I thereby call shenanigans.
Right, if you want to be precise you should be going by the fuel consumed by your average injector duty cycle while in boost, while the water injection is flowing.
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Old 09-18-2011, 09:07 PM   #5
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Another way to figure it out is to look at your dyno chart, view your hp, and work backwards via BSFC, fuel pressure, to find out CCs of fuel consumed...
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