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World's Best Intercooler Water Spray, Part 2

Installing the brilliant water spray

by Julian Edgar

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At a glance...

  • Ultra high pressure 220+ psi pump
  • High quality professional brass water nozzle
  • Interchangeable tips for setting flow rate
  • Built-in strainer and check valve
  • Unique approach and relatively low cost
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This article was first published in 2005.

Last week in World's Best Intercooler Water Spray, Part 1 we covered the components that make up this fantastic intercooler water spray. They include the ultra-high pressure piston pump, the mains power inverter, high quality brass nozzle and industrial quality hose and fittings. Now it’s time to install the system in a car.

The Nozzle

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The nozzle should not be placed as is normally done with an intercooler spray. Conventionally, a spray nozzle is aimed at the intercooler, or in some cases, across the intercooler. However, the droplets produced by this high pressure system are so small that it’s best to simply add them to the airflow in font of the intercooler. The air that passes through the intercooler will then carry the droplets with it. To best achieve this outcome, there should be 150mm or so of clear air in front of the nozzle – if there is a surface closer than that, the drops with coalesce (ie join together) and the very small droplet size will be lost.

Of course, when adding tiny droplets to the airflow in this way, there is a potential problem if the frontal aero of the car is poor and lots of air does not pass through the intercooler. In that case, that’s just what many of the tiny water droplets will also do!

Another aspect to keep in mind is that the nozzle should be accessible so that it can periodically be unscrewed, the internal filter removed and cleaned and then reassembled.

Click for larger image

On the guinea pig car, the nozzle was placed in front of the centre of the intercooler and aimed forwards. When stationary, this created a cloud of drops in front of the car (as shown in the opening pic to this story) but testing showed that when moving, the distribution of the droplets over the intercooler was good. To see the effect of different nozzle positions, you can temporarily tie the nozzle in place with cable-ties before making a more permanent mount after the location has been shown to work well.

The Pump

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Last week we said that the pump was quiet, but we need to qualify that. When tested on the bench and supported by the hoses, the pump is very quiet. However, when hard-mounted to the car’s bodywork, it can be quite noisy! Because of its rapid piston movement, the pump generates a low frequency vibration which is easily picked up and transmitted by hard mounting. However, this is easily overcome by the use of a couple of rubber isolation mounts (arrowed). These can be bought new or the Mazda 121 (“bubble” model) uses them in the engine bay – they’re cheaply obtained from that car at a wrecker.

The pump doesn’t readily lend itself to mounting – there are no mounting holes, for example. In this installation, the pump was held in place by the use of two sections of aluminium angle that tightly sandwiched the pump metal parts. A sleeve of high density rubber (like thin wetsuit material) was first placed around the pump. A second bracket – also made from scrap aluminium – was used to support the two rubber isolation bushes which bolted to the pump bracket.

This made for a cheap, reliable and easy to fabricate mounting system.

The Reservoir

As mentioned last week, the reservoir used to supply water for the intercooler spray is the standard windscreen washer reservoir – in this car it’s a large 6 litres. But how do you tap into it for the intercooler spray supply? There are a few ways – the best depends on your application.

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Easiest is to simply put the new feed tube to the pump through a hole made in the reservoir cap. The Ulka pump will draw up the water and so the system will work fine – although it’s a bit ugly. Another way is to carefully drill a hole in the base of the reservoir (best in fact to drill a small hole and then enlarge it step by step with a tapered reamer) and then fit a tight rubber grommet. If the plastic water supply tube is an equally tight fit through the grommet, there won’t be any leaks. Finally, if the wall thickness of the container is sufficient, you can do as we did and drill a hole and then screw a brass fitting into place. If you carefully size the hole, the fitting will self-tap and the result will be leak-proof.

The Hose

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As covered last week, we had an industrial hose supplier make up a new high pressure hose to connect the pump and the nozzle. While you can use barbed fittings and hose clamps, multiple clamps will need to be used as the pressure is so high that single clamps will fail. The length of the fitted hose that you get made is important – it cannot easily be adjusted afterwards! In this application we also used a right-angled threaded fitting on the pump outlet which allowed things to be better squeezed into the small available space.

The Inverter

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The mains power inverter should be securely mounted and carefully wired into place. For a comprehensive coverage of how to do this, we strongly suggest you read Mains Power for Your Car!. About the only change in this application is that the 12V relay that is used to turn on and off the DC supply to the inverter is triggered to operate the water spray. That is, when the spray is off, so is the inverter. Note: the inverter must not be mounted under the bonnet or anywhere else where it is exposed to the elements.

Make sure that you use 240V mains rated cable between the inverter and the pump, and be absolutely certain this cable is well protected from having its insulation breached.

Triggering the Spray

The spray can be triggered by any method traditionally used to switch on an intercooler spray.

From worst to best, that includes a dumb boost pressure switch; the electronic Temperature Switch kit working with the Simple Voltage Switch kit (ie monitoring both intercooler temp and airflow meter output); or the Intelligent Intercooler Water Spray (see – Intelligent Intercooler Water Spray - Part 1). We’ve also covered the use of the Auto Timer to cycle an intercooler spray on and off, an approach that saves even more water – see Cycling the Squirt.


The first step is to make sure the distribution of the small droplets is good. This can be tested in a number of ways. One method is to have the car driven past you while you observe where the mist of droplets is going. However in some cases, for example a top-mount intercooler, the core will not be able to be seen when the car is moving. In that case, temporarily cover the intercooler with some sheets of paper towel and assess the spray distribution by looking at which parts of the paper get wet. It’s important to again note that in most applications, the spray nozzle will not be aimed at the intercooler core but instead will be positioned relative to the airflow reaching the core.

The next step is to do some temperature measurement. When measuring either intercooler core temperature or intake air temp after the intercooler, the on-boost temps should be lower with the spray working. If there is little change - and the intercooler is getting hot – look at the spray direction and also possibly the size of the nozzle.

In the guinea pig application – a turbocharged NHW10 Toyota Prius – there was a difficulty. Even without the spray, the intercooler works so well that after 45 or more seconds of full boost, the intake air temperature on a 19 degree C day rises to only 32 degrees C. That’s with a measured temp coming out of the turbo of 67 degrees C! On short doses of full boost – like 10 seconds – the intake air temp barely moves, rising by perhaps only 2-3 degrees C.

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This graph shows the temperature recorded when climbing a fast, steep country road hill. The hill flattens towards the top so the last half of the run is off-boost. The blue line shows that the measured intake air temp without the spray peaked at 32 degrees and then dropped to 22 degrees by the car-park at the top. The starting temp was 19 degrees.

The red line shows the temperature change with the spray running. Despite the starting temp being 4 degrees higher at 24 (it’s hard to get a starting point that is identical in temp), the peak temperature was 2 degrees lower and this lower temp was maintained to the car-park.

But in absolute terms, in this example spray dropped the peak temp by only 2 degrees C. As we said, when the temp rises just 13 degrees C after 45 seconds of full boost, the intercooler is already working very well!

Incidentally, for those who have followed the modification of the Prius closely, the excellent intercooler performance is probably aided by the presence of the front undertray, which helps draw air through the four radiators (intercooler, power converter heat exchanger, air con condenser, engine coolant radiator). This assumption is based on the fact that the measured intake air temp was lower after the bumper and undertray had been re-fitted to the car than when the front of the car was bare. A front undertray also substantially helped move air out of the engine bay in another car – see series starting at Undertrays, Spoilers & Bonnet Vents, Part 1.

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However, the importance of testing over lots of different road conditions was made obvious when driving at lower boost, but with a much slower road speed, resulted in higher measured intake air temps. With just 4-5 psi of boost and about 50 km/h road speed up a long hill, intake air temp on a 20 degree C day rose to 35 degrees C. The spray was effective at reducing the rate of increase and then once the boost event was over, dropping the intake air temp much more quickly than when the spray had not been running.

Interestingly, when running off boost at 100 km/h, by using the spray it was possible to drop the measured intake air temp to a little below ambient!

In cases where the intercooler core gets really hot in normal use, and especially when the ambient temp is high, the high pressure spray will make a substantial difference to intake air temps. In fact, we suggest that there’s no better intercooler water spray hardware available anywhere at sane costs.

The Parts



Ulka E5EX coffee machine pump

In Australia, Jumbo Coffee on 02 9666 6114

12 > 240V AC 150W inverter

Auto parts accessory shop

Spraying Systems Unijet ¼ inch TT male body spray nozzle holder, screen strainer, spray tip and a tip

In Australia, Spraying Systems on 03 93180511

Custom high pressure connecting hose

Industrial hose supplier eg EnZed


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