Water injection for the Uno Turbo.
The first part of this article dealt with the theoretical aspects. We will now turn our attention to the practical means of installing a water injection system.
Water reservoir.
You will need a sealed bottle or other container which can hold about 1 to 2 litres of water. In the prototype system a thick-walled windscreen washer bottle was used, a radiator water reservoir container would be a better choice. The container chosen must be able to withstand a pressure of at least 1 bar without excessively expanding or distorting. It must also be capable of being totally sealed with a filler cap for initial filling.
The metered spraybar.
Dimensions are mostly quoted in imperial sizes, as these are not universally used the nearest metric size is also quoted.
This item has to be fabricated to fit into the air-flow metering unit. Those familiar with model diesel or glow-plug engines will immediately see the principle. It consists of a tubular centre portion approx. 8mm diametre (5/16") with nuts and lock nuts screwed onto each end. The spraybar fits into the air-flow metering unit on the outlet side.
(It cannot be fitted to the inlet side as the water mist will upset the operation of the hot-wire temperature sensor). To fit it is necessary to remove the air-flow metering unit and carefully drill 2 holes in-line with each other in the portion of the unit just before the hose attachment piece. These should be positioned so that the spraybar is vertical. (Ensure no bits of swarf are left in the metering unit).The spraybar has a needle valve which is the means to adjust the water rate. This is made from stainless steel for preference and has a point which is conical with an angle of 90 degrees.
For the body you need a piece of round brass or bronze bar of 8mm (5/16") diametre with a length of approx 5" (125mm). The bore for the body is made by drilling through the round bar with a small drill of about 2mm. This will have to be done in a lathe and started with a small centre drill (BS1). The bar is held in the 3 jaw chuck and the end faced. After making a small centre drill hole the 2mm drill is fed in as far as it will go.
(Run the lathe slowly, apply plenty of coolant/oil and withdraw the drill often to prevent it jamming with swarf, especially if the body is made from bronze). Remove the bar and chuck it the other way round. Repeat the facing and centre drill operation and drill with the 2mm drill as before. The 2mm hole should now extend through the round bar. Use a long series 2.5mm drill and pass this through the bar to clean up the hole.Thread the outside of each end with a suitable die (8mm metric or 5/16") for about 25mm and make suitable half-nuts from 12mm hexagonal bar to suit (2 per end). From one end drill into the bar exactly halfway with a 3mm drill. This hole is now opened out to a diametre of about 3/16" (4mm) for the full depth less about 3mm and tapped with a fine thread - preferably 1/4" x 24 tpi. The threads only need to be for about half the depth. The 3mm hole is now formed into a conical seating with a BS1 centre drill fitted with an extension rod to cut the seating. Try and obtain a good finish on this or the needle valve will not seat properly.
On the other end turn down about 10mm length to a diametre of 6 mm to take the water inlet tube.
(This tube connects to a fitting on the side of the reservoir bottle about 1/2" from the bottom. This fitting can be turned up from brass and fitted with fibre washers to make it water-tight. You will need 3 of these fittings, one for the outlet, and two for the inlets. The fitting can also be made from a 1/4" hexagonal brass bolt about 25mm long with the threads machined away on the end furthest from the head. Drill right through the full length with a 2.5mm drill. Use standard nuts to secure to the container).
The needle valve is made from 1/4" (6mm) stainless steel round bar. Turn down one end for a length of about 1/2" (12mm) to a diametre of just under 3mm and form a pointed chamfer on the end of 90 degrees. This should have a highly polished finish, use a fine slip-stone to achieve the necessary finish if the lathe tool does not cut cleanly.
(Ensure the angle is 90 degrees by testing it into a hole drilled in a scrap piece of metal with a BS1 centre drill. Adjust the angle if the end of the needle valve does not fit exactly).Thread the bar 1/4" x 24 tpi with the die set to give a tight-ish thread
(open the die slightly to cut over size). The length of thread needs to be about 2" (50mm). Assemble the needle valve into the body and screw it fully in. It should be stiff to screw in and seat firmly. Allow about 25mm extra on the stainless steel rod and cut it off and face the end. Make a small knob from 12mm or so diametre brass or aluminium rod with a knurled finish and press this onto the end of the needle valve stem to form a means of adjusting.Measure the spraybar depth from the threaded internal side and ascertain the depth to the end of the thread. Mark this on the outside and then drill a 1mm diametre hole straight across. Rotate the body 90 degrees and drill a second hole straight across. Clear out any bits of swarf left from the drilling operation and run the tap through to clear out any swarf. You should now be able to test the needle valve operation. Screw the needle valve fully in and blow into the other end. As you open the valve the air should exit via the 4 small spray holes and the amount of air is controlled by the needle valve, it should be possible to completely shut off the air by screwing the needle valve down tight.
Assembly into Metering unit.
Screw a nut onto the body on both ends and a fibre washer. Remove the needle valve from the spraybar and insert the body into the air-flow meter so that the end for the needle valve is on top. Screw another nut onto the body on both ends with a fibre washer and tighten the nuts so that the spray holes are central.
(Do not over tighten nuts or you may distort the aluminium casting of the air-flow unit).Re-assemble the air-flow unit into the vehicle and ensure everything is connected up correctly.
(Mount the water container in a suitable place under the bonnet, in front of the battery is a convenient place).Disconnect the small diametre rubber hose from the turbo outlet which goes to the waste-gate piston. Fit a Tee-piece between the waste-gate tube and another length of the same tubing to re-connect to the turbo outlet. Connect a second piece of tube to one of the top fittings of the water container. Fill the container about 3/4 full with clean water and screw on the cap tightly.
(Garden centres sell lots of useful plastic fittings for garden irrigation systems and fish tanks, the Tee-piece fits 6mm bore tubing and costs a few cents).The water replenishment system.
The outlet pipe from the water container is a 6mm bore rubber tube which connects to the spraybar. As the bottle is pressurised by the boost the bottle will eventually become empty. To replenish the bottle the second inlet is connected to a windscreen washer pump via a non-return valve.
(This valve is the little black plastic "goodie" connected to the rear windscreen washer pipe, found on the left-hand side under the bonnet near the windscreen, and is used for the rear windscreen washer on the Uno to prevent the water draining back to the reservoir. They may be obtained from your local agent, the pump can be found in most scrap-yards from almost any vehicle. You will also need a large water container which can be mounted anywhere convenient. The pump draws water from this to replenish the turbo reservoir bottle).
The water container has 2 extra holes drilled in the side, these are for the water level sensors. The top sensor should be positioned at about 3/4 of the way up the side and the bottom sensor about 1/2" from the bottom. The electronics are a bit difficult to describe without pictures. Essentially it works like this:
The top sensor is a 1/4" brass hexagonal bolt with its head inside the container. Fibre washers on the inside and outside prevent leakage. The bottom sensors is exactly the same. Water is a conductor of electricity and when the water level reaches the top sensor the pump is switched off via an electronic sensing circuit using an operational amplifier (op-amp). The bottom sensor is connected to 12V from the battery and the top sensor connects to the op-amp. The op-amp provides a high degree of amplification to the small current flowing through the water and drives a relay to switch the pump.
Setting up the water metering.
Start with the needle valve about 10% unscrewed. Drive normally and observe the performance.
(It is useful to bring the water pipe from the outlet of the water container into the cabin and fit a section of clear plastic tubing so that you can see the water flow). Increase the flow gradually as you drive with full boost. At some point the flow will become excessive and the power will drop off, adjust the needle valve to just slightly closed from this point.A quicker way to set up the water flow is on a rolling road, where the power output can be measured and the flow adjusted for maximum power.
7/11/98