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Intercooling Plan of Attack - Part Two

A thoroughly considered plan of attack for intercooling your streeter...

By Michael Knowling

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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.

Let's go!

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 of bends.

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Begin 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.

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If 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 treat.

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 for details.

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.

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In 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...

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An 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.

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An 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 in that.

Okay, now that we've handed you a detailed intercooler plan of attack, let's see you put it into action!

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