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#1
24-07-2005, 07:47 PM
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Fuel Injectors as Water/Meth Injectors
Hi,
I'm looking to design a water injection kit using a high pressure fuel pump, some top feed fuel injectors with an rx7 lower fuel rail. My only question is how much flow do i need. I see some people using nozzles rated at 6 - 8 lbs per min for their injection systems. But about the smallest injectors i have lying around are 19 lbs. Will this be too much? If so I will need a way to adjust injector duty cycle...which i think is very doable. BTW I am building this system for a turbocharged 4g63 2.0 liter running 20-23psi of boost on pump gas and would like to run 50/50 water meth. TIA!
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90 Galant GSX 92 Laser RS AWD 
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#2
25-07-2005, 02:56 AM
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I had the very same idea, and I don't think it would be a problem if you had a method to control the injection. My plan was to use the staged injector setup of Megasquirt to control it as extra fuel. With the ability to control injector duty cycles, there shouldn't be a problem with injector sizing as long as it's reasonable.
The problem, however, with using them for a meth system is corrosion. As far as I know, the whole system that you use for the meth injection has to be designed for alcohol (ie, you can't just use normal injectors, you'd have to get injectors designed for alcohol). Otherwise you'd probably encounter problems with corrosion.
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#3
25-07-2005, 05:39 PM
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Re: Fuel Injectors as Water/Meth Injectors
Quote:
What makes you think that fuel pumps or injectors are happy pushing water? :?:
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#4
26-07-2005, 02:02 AM
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Re: Fuel Injectors as Water/Meth Injectors
Quote:
so i should stick to fuel oil burner injectors? lol - what i'm confused with is how large to size them 2.0 turbo ~300-350 crank hp
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90 Galant GSX 92 Laser RS AWD
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#5
26-07-2005, 02:17 AM
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You can buy corrosion inhibitor for radiators cheaply. I'm planning on trying a similar setup with a little corrosion inhibitor added to the water. The parts I need for my prototype should arrive by the end of the week.
If it works, it will be a nice, cheap system with full mapping capability.
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#7
29-07-2005, 01:15 PM
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Quote:
One thing to keep in mind is that the specific gravity of fuel is less than that of water. So a an amount injected at certain flow rate at a certain pressure for fuel will be less than the amount injected if the fluid is water.
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#8
30-07-2005, 09:58 AM
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Measuring the delivery rate is easy - just have it squirting for a minute in a calibrated container.
It would be interesting to see if corrosion inhibitors do help a fuel pump and injectors push water. Hadn't thought of that 
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#9
31-07-2005, 11:49 PM
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Got the control curcuit built up last night, the FPR should arrive this afternoon, hopefully, I'll have it in prototype state by next weekend..
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#10
01-08-2005, 11:19 PM
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Here is the build of the control curcuit, it all came from a local electronics shop in kit form www.jaycar.com.au
I'm using a Pulse Width Adjuster to control the duty cycle of my injectors. Here is the initial board build up:  I've also built a duty cycle counter/generator just to make it easier to bench test it all. For a quick demo of the adjustability, I took these two pics: In this one, the engine is at 41% duty (LED display), and the adjustment for this duty cycle range is set to +16 units, which results in an injector duty cycle of 54.8% (multimeter).  By changing the settings on the adjuster to -28 units, I've altered the output of the device to 20.2%.  This give me a lot more adjustability than I really need, and it's fairly cheap and simple (but, you have to build it yourself).... I could probably use a megasquirt for the same functionality, but, I really like the way this is indexed to the fuel injector duty cycle, this way I just need to work out the percentages, then whatever tuning changes are made to the engine, the water follows.
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