Installing the Aquamist 1S water injection system

by Mark Edgar

Firstly, I ought to say that the instructions with the Aquamist 1S kit are a little sparse - if you want to know a bit more about what you’re doing, then you need to download the pdf from their web site, which gives more useful info.

In writing this up I’m going to assume that readers will be reasonably car DIY savvy so will try to avoid stating too much of the obvious…

I decided to use (as recommended) the washer bottle as the reservoir for the system, particularly because it already has a low fluid warning built in. That’s the good news. The bad news is that to get at it you’re going to have to put the car up on axle stands…

To access the washer bottle, you don’t need to remove the wheel arch liner, but just the front offside quarter undertray. Once this is off, you will see the underside of the bottle. There are two pump motors that
you will see. The higher one is for the rear was/wipe, and the lower one (nearest the wheel) is for the front windscreen/headlight wash. You can identify this by the T piece situated close to the motor. This is the line I chose to use. By feeding the Aquamist post the pump, you also ensure it is primed every time you use the windscreen washer.

The location chosen for the pump was at the front nearside corner of the engine compartment (see pic). I routed the supplied hose along the front of the car across the member in front of the radiator. Unfortunately it doesn’t quite reach the bottle. I found that standard 6mm OD washer tubing has just the right internal diameter for the 4mm OD Aquamist hose to fit snugly inside, so used that for the last section. (The filter fittings are made for the Aquamist hose).

I mounted the pressure sensor on the removable bulkhead by drilling through and securing it with machine screws. The chosen location is just the right distance for the supplied cable loom. The relay was mounted adjacent to the pump on a stud, power was taken directly from the terminal block adjacent to the battery. I connected vacuum
tubing to the spare nozzle on the inlet manifold.

Mounting the injector takes a little bit of thought. The kit (conveniently!) supplies a tap for the thread on the nozzle, but you have to decide where to put it. Anywhere after the intercooler is suitable, although I decided to go post dump valve to avoid staining the engine bay and also to minimise water use. Being further away from the throttle body helps because of mixing, and you definitely want it before the temperature sensor. That doesn’t actually leave a lot of room on the pipe, and I opted for the curved section (see pic). The problem is, however, that the wall of the pipe is too thin to get adequate thread depth. To get round this (and the curved face of the pipe) I opted to fit a small flat piece of aluminium to it. In an ideal world, I’d have found an aluminium welder etc. etc… but instead I used one of the proprietary “metal” epoxy compounds. This needs to set overnight before working on it, so your car is going to be out of action for the best part of 24 hours. The pilot hole for the M8 tap is 7mm. I removed the pipe from the car for ease of working and also to make sure that any swarf could be safely removed.

Now comes the hard part… getting cables through to the passenger compartment. Although you could quite easily find an ignition switched live feed within the engine compartment, in my view you at least need to run the LED extension wires through- not necessarily for an LED but to give you an “off” switch if you run dry (I chose not to automatically switch it off from the low fluid sensor).

The pressure switch stays closed until a preset pressure is reached. At that point, it opens and the pump runs. There’s enough voltage across the terminals at this point to drive an LED. By wiring a manual switch in parallel with the LED/ pressure switch, you can use it to “fool” the unit into thinking that the pressure has not been reached.

For cable access, I chose the removable rubber bung section that sits approximately below the brake fluid reservoir. If you remove the glovebox, you can see it at the back. Pull the bung out, make a hole in it, feed the cable through and replace. (Sounds MUCH easier that it actually is). To make access in the engine bay easier, move the ABS
relay box to one side and release the brake/clutch reservoir. To feed cable through, I recommend poking it through taped to a long screwdriver from the passenger compartment. A friend can be useful here.

As supplied, the ignition sense plus 12V & ground wires are together in a sleeve. I removed the 12V & ground as they had such short runs and instead put a small 2 core wire in for the LED/switch. I connected it to the pressure switch wires at the pump end of the harness.

I removed the cable trunk cover adjacent to the battery and fed both wires up there. The sleeving for the pressure sensor can be forced into the boot with a bit of persuasion to keep things watertight there.

Regarding cable jointing, I do not recommend the use of the so-called “scotchblock” IDC blocks. Proper crimp terminals (used with the correct tool) or wrap together and solder are preferred methods for reliable connections.

Other than that, just follow the manufacturers’ recommendations!

As for how long, well difficult to say really, because I undertook other work at the same time, but I would estimate 3-4 hours assuming no hitches, and excluding the drying time for the epoxy.