This article was first published in 2003.
In the first of this two-part series we looked at the costs involved in
fitting an intercooler, we looked at selecting the appropriate intercooler,
and we compared mounting locations. For the second part, we'll now explore the
intercooler plumbing, charge-air cooling enhancements and more - all the stuff
you need to finish your intercooling plan of attack.
Intercooler Plumbing - How to Approach It?
Intercooler plumbing is fundamentally very simple - it merely describes the pipes that
route charge-air from the turbo to the intercooler and then to the engine. Don't
be fooled, though - the plumbing job can be quite complex and it's all too easy
to end up with a less than satisfactory end result...
As mentioned in Part One, the intercooler plumbing is relatively short and
simple in the case of top-mounted intercoolers. When you mount the intercooler
in the nosecone or front guard, however, the path for the piping can be very
long and intricate. To some extent this cannot be avoided, but to ensure a
decent result you must follow some rules.
To ensure optimal throttle response and charge-air flow you must pay
particular attention to the plumbing diameter, along with the number and radius
the plumbing with a diameter no smaller than the turbo compressor discharge
nozzle and progressively enlarge the plumbing diameter to match the fittings on
the intercooler. On the route from the intercooler to the engine, it's a good
idea to progressively enlarge the plumbing diameter to match the throttle. Be
sure to increase the plumbing diameter gradually - a sudden increase in diameter
will result in massive in-pipe turbulence.
Try to keep the number of plumbing bends to a minimum. This will aid throttle
response and charge-air flow. The radius of the plumbing bends should also be as
gentle as possible - this will further aid response and charge-air flow.
you're doing the plumbing job at home, we suggest using pre-fabricated mandrel
bends and a collection of second-hand intercooler plumbing and hoses from a wrecker. Using this combination, you can configure all the plumbing for
less than AUD$150. Hit the metal pipes with a can of black paint and it comes up a
Note that the intercooler plumbing must offer flexibility between the turbo and the intercooler, and the
intercooler and the engine. Flexible sections (which are typically lengths of rubber hose more than about
10cm long) prevent damage to the turbo, intercooler and engine when the engine
moves under load.
If you're concerned about under-bonnet heat warming the plumbing between the
intercooler and engine, we have recently covered a novel solution - oven mitts to
insulate the return pipe - see Insulating the Return
Ways to Improve Charge-Air Cooling
Regardless of where you decide to mount the intercooler, you can improve its
charge-air cooling performance in several ways.
Many people fail to recognise the importance of sealing the incoming ambient
airflow to the intercooler core. Without a seal, the ambient air will take the easiest path - which is invariably around the intercooler.
a top-mount configuration you should have the intercooler sealed against the
bonnet scoop, using rubber or foam strip. In the case of a guard-mounted
intercooler, you may need to cut a hole in the bumper to allow adequate ambient
airflow through to the core. Some cars have fog light cutouts that you can take
advantage of. Next, you should seal the forward-facing opening to the
intercooler using plastic or alloy sheet with rubber or foam strips to butt
against the core.
And what about forcing the cooling air through an
intercooler mounted in front of the radiator? Well, many factory intercooler
installations in this location have no form of airflow sealing against the core.
However, to ensure peak performance, we suggest fitting plastic or alloy panels
to direct air through the core.
And now we look at electric cooling fans and water sprays...
electric cooling fan should be considered essential for any top-mount
intercooler configuration; we suggest mounting the intercooler elsewhere if you
want a top-mount intercooler without teaming it with an electric fan. Electric
radiator fans and air-conditioning condenser fans are perfect for maintaining
ambient airflow through an intercooler when stationary or driving at low speed.
See DIY Budget Intercooler Fitment
for an article that covers the fitment of an electric cooling fan to the
underside of a side-mount intercooler.
Note that guard-mounted intercoolers
can also benefit from an electric cooling fan, but it's not an essential fitment
like it is in a top-mount or side-mount configurations.
intercooler water spray can be fitted to an intercooler that's mounted in any
position. An important point to remember is that the spray should be used only
when there is ambient airflow through the core - it doesn't matter if it's
derived from movement of the vehicle or from an electric cooling fan. The water
that's sprayed onto the intercooler core should also be very fine in droplet size. Maximum
charge-air cooling occurs when the water droplets are rapidly evaporated on the
core surface. For more information on installing a budget water spray set-up, see
Installing an Intercooler Water Spray
How Much Work Will I Need To Do?
To custom fit an intercooler properly it will take the average backyarder a
solid weekend of work - and that's assuming you've got all the hardware and
tools at hand. The exact length of time will depend on the complexity of the installation,
but don't underestimate the time it takes to fabricate mounting brackets, ducts,
etc. The intercooler plumbing can be particularly difficult to arrange in
confined engine bays - many people elect to farm this out and there's no shame
Okay, now that we've handed you a detailed intercooler plan of attack,
let's see you put it into action!