| Part 1 in FAQ Please Vote part 2 to VAQ :) Some updates on how the system works. Overall the system was working pretty well. The one thing I did change was how the water injection pump was regulating pressure. You have two choices
1) Use the set screw in the pump housing.
2) Use the pump control box by adjusting your “high boost setting” higher than your actual boost. When I was using method 1 the pump would pulse on/off creating some tuning issues with wild variations in water pressure. Adjusting the high boost setting higher than your actual boost will in effect limit the voltage to the pump allowing you to fine tune how much water you want to use. The nozzles I am using are a little big so I turned up the snow controller to 25psi and run the car at around 19-20psi of boost. I am leaving the safe injection module at full sensitivity. The safe injection is connected to a red led mounted near the boost gauge. Every time the water injection pump starts the safe injection will turn on just for an instant while the pump is generating sufficient flow to the nozzles. Keeping that setting allows me to verify that the safe injection system is working every time I boost. After making some calculations on how much water it will consume I would not have enough for a 20-30 minute track secession. I would need almost double what the front tank can hold (about 1 gallon). To maintain a high boost setting during the whole run I needed to mount a second tank somewhere in the car to increase the water capacity. I used a reservoir tank from an older Z that are located in the trunk area. I connected both rear pumps to a single line that moves the water to the front tank when the low level indicator activates. To prevent overfilling the front tank I used an adjustable delay timer that runs the pumps for a specific period of time. When I first started to use this setup there was one problem. Since the rear tank was slightly higher than the front there was a little siphon effect going on. Sometimes fluid would come out of the front filler neck. When I was on the track braking really hard the front cap would pop off. To isolate the two tanks I added a normally closed direct acting solenoid near the timer and relay circuits. I used the spare contact on the timer for the solenoid. Two more LEDs were mounted in the A pillar so I know when the rear pumps turn on and when the rear tank is empty. Whatever time you set the pumps to run just make sure it is long enough to turn off the front tank level switch before the timer runs out. If that level switch is not turned off the timer will not reset and will not activate. Worse case is you need to cut the power to the timer to reset the circuit. List of the parts I used:
1 normally open relay
1 normally closed relay (87a)
1 Omron Timer (model H3CR) pn# H3CR-A AC24-48/DC12-48
1 Omron Relay mounting bracket pn# Y92F-30
1 Omron Relay Socket pn# P3GA-11
SPST Switch with led to control power to circuit
Some aluminum plate to mount everything to One tool that helped me a lot is a good ratcheting style crimp tool for 1/4” terminals. pdf link for the timer On to the pics: Here is the test setup to verify that the pumps are in good order and to collect data on how much current the pumps use to make sure the contacts will not be pushed beyond their recommended ratings.
As you can see current draw is under the 5 amp recommended limit
Close-up of the Crimp tool
To make the connections a little more idiot proof I used both male and female terminals
One thing that made me very nervous was cutting the hole for the rear filler neck. I used a stepped drill bit to keep the hole round and with no flaws on the edges. I used another Z that already has the rear tank as a template to transfer the measurements with some reasonable accuracy
 
After the hole is drilled make sure you file all the metal flash using a round file and a little patience
After the hole is absolutely smooth and free of burrs prime and paint the bare metal edge
Filler neck installed
Here I am testing the logic of the timer circuit. One switch simulates the normally open relay that uses the front tank signal and the other simulates the normally closed relay that uses the rear tank signal to essentially shut off power to the timer and prevent dry cycling the pump.
The wiring was a little complicated so I made a couple of drawings to help. This drawing shows how the water injection system is wired up with the safe injection, LEDs etc
Brief overview of how the tanks are connected
 Wiring diagram of the rear pumps, timer, and switch
 To make wiring other accessories easier I installed a small fuse panel next to the ECU. The wires are a little messy when I was installing, will zip tie it later.
View of the pre-wired aluminum plate that will be mounted where the headlight aiming tool was located
View of the plate mounted
Installing the small manifold on the rear tank. Using 1/4 ID tubing (3/8” OD). I first tried 1/8" ID line, not big enough. There is so much pressure loss due to the long tube run the pumps would not be able to keep up with the snow pump which is a bad thing:)
The front tank tap location for the tubing (1/4” NPT tap)
Connection that routes water to the Water Injection pump
Tubing route through the vehicle
Putting all the stereo stuff back P.I.T.A.
Next I need to route some of the wires to the a pillar. Two things that help speed things up. I use a three conductor wire for both LEDs which cleans things up a little when I route the wire up through the dash. To help routing the wire or any wire in your car I use a piece of polyethylene tubing. It can give and bend a little but still have enough stiffness to go around obstructions and has enough lubricity to rub up against rubber, plastic, etc with ease.
LEDs from Radio Shack. If I were to do it again I would find the smaller diameter ones.
Finished A pillar with all LEDs mounted
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Water Injection Part 2 - 
