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Intelligent Intercooler Water Spray, Part 2

The water spray hardware.

by Julian Edgar

Click on pics to view larger images


Hardware Options

The pumps, reservoirs and nozzles that are used can vary widely, depending on how heavy-duty you want the system to be and how much you are prepared to pay for it. Note that the electronic control system is happy operating with either of the following approaches.

1. Heavy Duty

Click for larger image

A high-pressure 12-volt pump like a Shurflow or Flojet can be used. These pumps are durable, develop pressures of up to 45 psi, and can be rebuilt if necessary. They're available from agricultural, caravan and boat suppliers. One commonly available pump is the Shurflow 2088-423-244 Multifixture Pressure Pump, that costs about A$110. This pump has a max pressure of 45 psi and an open-flow rate of 10.6 litres/minute. Most of these high-pressure pumps are of the diaphragm type, which makes them a little noisy unless they are rubber mounted. This means that you need to make sure that there is room for a good rubber mounting system (eg a gearbox mount) where you place the pump.

In addition to noise, another problem with these pumps is that many are designed with a built-in pressure switch. This is fitted so that the pump will automatically turn on and off when it is being used to supply a tap. The pump starts when the tap is opened and then stops when the tap is closed - imagine a sink tap in a boat and you get the idea. However, when the pump is used for an intercooler spray, this feature can cause problems, with the pump cycling on and off frequently. A pressure accumulator or pump bypass can be used to reduce this problem.

The intercooler spray water tank can comprise a boat plastic fuel cell - a container that comes with a fluid take-off, large filler facility and good tie-down provisions. A tank of around 10-15 litres is a good compromise of size and practicality for a heavy-duty system. A Scepter high density polyethylene 12 litre tank costs only A$45, with the tie-down strap and support brackets another A$12.

An intercooler water spray system using a diaphragm pump and boat fuel tank will result in a very heavy-duty intercooler water spray. It will also be expensive and relatively bulky. But if you have a high power application - eg race or rally - and the spray will be on very frequently, we suggest you use a diaphragm pump and a large tank of the type described above.

2. Light Duty

However, in most road car applications the heavy-duty type of system is expensive overkill - so we decided to look at a much cheaper solution. Supercharger kit manufacturer CAPA uses an ex-Holden windscreen washer pump and motor as part of the water injection systems in their kits. While in the past we have been very critical of taking this approach (over using a system that has better quality hardware), Tony Rullo of CAPA has assured me many times that his company has never had a pump fail in this application. As a result of this background, we decided to test one of these pumps for durability, flow and pressure. AutoSpeed asked CAPA to make available a pump/reservoir combination to be tested, which they duly did.

While the Holden (VDO, actually) pump could have been simply turned on and left running for a few days, this approach is not at all representative of actual intercooler water spray use. Instead, a sequence of tests was devised that roughly replicated different performance car uses. This on/off test sequence is shown in the table at the end of this article.

Click for larger image

The reservoir was filled, the pump connected to a brass Spraying Systems nozzle (more on the nozzle in a minute), which was directed back into the reservoir. Labtronics, partner in the development of the AutoSpeed electronic performance modules, then wrote a software program and developed the hardware to operate the pump in accordance with the test cycle.

To complete each test cycle took about 40 minutes, with 7.5 minutes of that being cycle time and 32 minutes being longer 'rest' times. As described last week, a road-driven forced aspiration car running boost more than 5 per cent of the time is rare - this test made the pump work hard for about 19 per cent of the time, with the worse possible control system being simulated (ie one that causes many on/off sequences). The test ran continuously for more than 350 hours. At the end of that time the pump was still operating without problems, though its current draw had increased marginally and it was a little noisier than at the beginning. However, the test showed that for normal light duty, road car use, this pump and reservoir are quite adequate for an intercooler spray.

The pump (Part No GM90058691) is available from Holden dealers, including a strainer grommet (Part No GMVS20344) on the pick-up. Suitable reservoirs were fitted to late model Commodores - some with short filler necks like the one shown and others with longer necks. The pump suits either. The pump and long neck version of the reservoir are now available in the AutoSpeed Shop. Be aware that this is a good pump - aftermarket cheapies will probably not develop the required pressure.

The Nozzle

Click for larger image

In either heavy or light duty systems we recommend that a high quality nozzle be used. While miniature plastic nozzles are available very cheaply from hardware stores, their durability (especially if exposed to engine heat) isn't very high. Instead, it's much better to go for good quality nozzles of the type that you'll find at agricultural supply shops. The US company Spraying Systems is one that has extensive catalogs listing different brass (and engineering plastic and ceramic) spray nozzles that are available - most agricultural spray shops have these catalogs.

A nozzle that is very suitable for intercooler use is the Spraying Systems TX-4 ConeJet spray tip. This nozzle develops a hollow cone, finely atomised spray, with a water flow of about 200 ml/min. Because all the Spraying Systems nozzles are part of a professional system, there are also some pretty good extras available for these nozzles. One useful addition is the 4193A combination filter/check valve, which prevents the nozzle from becoming blocked and also stops it dripping. Different mounting fittings for the nozzles are also available, including bulkhead fittings and adjustable angle swivel fittings.

Even if using a cheap pump, we strongly recommend that you use a good quality, brass nozzle. The effectiveness of the spray at reducing the temp of the intercooler will depend greatly on the size of the droplets produced by the nozzle - and the better the nozzle, the more consistent over its life it will be at producing fine droplet sprays.

Spraying System nozzles are available from larger agricultural supply shops. You will need to specify that you require: the Cone-Jet TX4 spray tip, a 4193A brass strainer check valve, a CP1325 cap, a CP1321T brass body, and a barbed hose fitting to suit 5mm ID hose. They are also available from the AutoSpeed Shop

Conclusion

The electronic controller will handle pretty well any 12-volt pump. For heavy-duty use we suggest a positive displacement diaphragm pump working with a large tank. For light-duty road car use, a VDO/Holden windscreen washer-based pump and small reservoir are adequate. Whichever approach you take, we strongly recommend the use of a quality Spraying Systems nozzle, though.

Intelligent Intercooler Water Spray - Part 1
Intelligent Intercooler Water Spray - Part 3
Intelligent Intercooler Water Spray - Part 4
Intelligent Intercooler Water Spray - Part 5


VDO Pump Test Cycle

Test Type

Pump Status

"Through The Gears Fang"

3 seconds on

1.5 seconds off

4 seconds on

1.5 seconds off

6 seconds on

1.5 seconds off

12 seconds on

1.5 seconds off

60 seconds on

500 seconds off

"Through the Hills Dash"

10 seconds on

5 seconds off

15 seconds on

3 seconds off

30 seconds on

8 seconds off

60 seconds on

10 seconds off

60 seconds on

500 seconds off

"Single Lap Racetrack Dash"

20 seconds on

5 seconds off

45 seconds on

5 seconds off

45 seconds on

5 seconds off

3 seconds on

3 seconds off

3 seconds on

25 seconds on

900 seconds off

Then back to starting point

Test ran for 350 hours non-stop.

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