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 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.
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.
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.
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.
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.
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
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
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
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
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.
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.
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.
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