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Cooler Construction

We take a look at APS's impressive intercooler manufacturing technique...

Words by Michael Knowling, Pix by Julian Edgar

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Ever wondered how an aftermarket intercooler is made? What separates quality intercooler construction from lesser jobs? We went along to APS (Air Power Systems) to see how Australia's largest aftermarket tuning house does it!

The APS Intercooler Manufacturing Process...

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This photo shows the core that is used in the APS DR 500 front-mount intercooler kit for GD-series Subaru WRXs/STis. The specifications of the core are nominated by APS - heat transfer area, fin dimensions and spacing, thermal conductivity and other variables are all considered in the selection of the core. Note that the same core specifications are rarely used in more than one application.

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With the intercooler core supplied from an outside manufacturer, the next step is to attach the end-tanks. APS uses a jig to ensure accuracy during this process. As seen here, the end-tanks are initially heated on a hot plate, which improves the welding.

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End-tanks are first tacked to each corner of the core before the seams are fully TIG welded. The intercooler mounting bracket and tabs are also welded on at this stage - APS use sturdy 10mm thick aluminium mounting tabs on the DR-series intercooler.

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Cast aluminium end-tanks are used in the majority of APS intercooler kits. These tanks are extremely lightweight and feature very smooth internals to ensure maximum charge-air flow. Note that the hose fitting incorporates an all-important raised bead around its outer perimeter - this reduces the chance of intercooler hoses blowing off at high boost pressure.

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One welded, the intercooler assembly is pressure-tested in a bath of water. One end-tank fitting is sealed with a rubber bung and the opposite end is connected to a regulated compressed air supply. Test pressure is generally around 10 psi. The pressurised intercooler is immersed in a tank of water and any leaks are identified as bubbles. If any bubbles are detected, the intercooler is returned to the welding bench for repair.

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After being pressure-tested, the intercooler is placed in a large cleaner/dryer machine. Inside, cleaning chemicals are sprayed onto the intercooler to remove the grease and grime and that inevitably builds up on the outside of the unit during storage and handling. Note that end-tank fittings are sealed to prevent chemicals puddling inside the core.

After cleaning, the machine then goes into a hot air drying cycle. In total, the process takes about 2 minutes.

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The main purpose of the cleaner/dryer machine is to prepare the surface of the intercooler for powder coating. At the time of writing, APS has powder coating done by an outside company - but this may soon change. Powder coating is essential to protect the aluminium core and end-tanks from corrosion - especially in areas where salt is used to clear snow-covered roads. The intercooler can be specified with either black or silver powder coating.

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Once powder coated, the intercooler is ready to be sent to its new owner. cardboard is taped around the precious intercooler core to protect it from damage during freighting. The 'cooler is then boxed and sent off with the rest of the hardware included in the intercooler kit.

The Rest of the APS Intercooler Kit...

The APS DR 500 WRX/STi kit comes with plumbing, clamps and absolutely every part required for the conversion.

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The main sections of plumbing are made from mandrel-bent aluminium pipe, which is ultra lightweight. The lengths of aluminium pipe are also as long as possible to avoid having a large number of hose connections.

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Hose sections are specially made to suit. In the DR 500 kit the hose that connects the post-intercooler pipe to the pipe that leads to the throttle is so complex that APS sourced it from Germany. This multi-layer hose gradually changes diameter while also passing through two bends.

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The rest of the hardware that is sent out in the parts box includes hose clamps, nuts and bolts, washers, cable ties, clips, blow-off valve adapter, replacement coolant hoses, parts list and comprehensive fitment instructions supported by professional diagrams.

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This replacement crossbar is also included in the DR-series 'cooler kit for Subarus. Why is it needed? Well, it's difficult to fit a large intercooler in the nose of a GD Impreza due to the space consumed by the standard front crossbar that ties together the two chassis rails. APS gets around this problem with this intricate replacement crossbar, which is said to maintain the full structural integrity of the vehicle. Note that the crossbar is presently being made from steel but, in the name of reduced weight, they may soon be aluminium.

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The APS DR 500 front-mount intercooler kit currently retails for US$1495 or AUD$2460 (including GST) - and note that an APS pod type air intake is also required to allow clearance for the intercooler piping.

Sure, there might be cheaper products on the market, but now you know the level of engineering and production know-how you're getting for your money; we haven't seen anything in the aftermarket that comes close...

Made for a Purpose

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APS configures its intercooler kits to suit not only the design of the vehicle, but also a specific power range. For example, its DR 500 front-mount kit for GD-series WRX/STis is suitable for up to 500hp while the DR 650 kit is recommended for 500 - 700hp. What is the difference between the intercoolers? Well, compared to the DR 500, the DR 650 core is almost twice as thick, but - interestingly - it is slightly narrower. The narrower core allows more space for larger end-tanks, which offer superior charge-air flow.

Not surprisingly given its higher power rating, the DR 650 intercooler offers greater overall charge-air flow and heat exchange performance.


Air Power Systems +61 3 9761 7244

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