Page 4 of 5
By Julian Edgar
Sourcing the Core
There are a number of ways of getting together a very good air/air intercooler. Those companies specialising in the production of intercoolers (Spearco in the US is one of the largest) have a huge variety of cores and end-tanks available. However, as an aluminium item of fairly intricate construction, they are not cheap. For a really big air/air intercooler complete with end tanks, expect to pay about as much as you would for a turbo.
An alternative in Australia are the Japanese importing wreckers. While few factory turbo cars have really large intercoolers (and even less factory supercharged cars have them!), there are at least a couple of large ones available. As mentioned previously, the Nissan Skyline GT-R and Mitsubishi Evolution model Lancers all have very good intercoolers. The Nissan Pulsar GTiR also has a large intercooler (pictured), while the Mazda RX7 single turbo Series 4 has an engine-mounted intercooler that has a good flow, despite its appearance. Welding two of the RX7 intercoolers in series has also been shown to work very well.
You can also produce your own intercooler by modifying heat exchanger cores designed for other duties. However, having personally done so, I can advise that it is a great deal of work! One source of efficient heat exchangers are old airconditioners. Domestic and industrial refrigerative airconditioners use copper tube and aluminium fin heat exchangers for both their evaporators and condensers. When the airconditioner is discarded (perhaps because of a faulty compressor) these components are sold off at scrap value - less than the price of a few spark plugs! If you are patient and handy, you can cut off each end of the core and make plates that fit over the multiple copper tubes. Making end tanks that attach to these baseplates is then straightforward. The resulting copper-cored air/air intercooler is efficient and very, very cheap.
Another alternative it is to visit truck wreckers. Diesel turbo truck intercoolers are absolutely huge. They can also often be picked up very cheaply from insurance repair jobs, where the core has been twisted slightly, or one end tank damaged perhaps. If you chose with an eye to modification, the core will be able to be shortened without new end tanks being required - which substantially reduces the amount of work! This way you need only make new blanking plates for the ends of the shortened tanks. However, be aware that reducing the number of tubes of a truck intercooler in this manner can also reduce its flow by an unacceptable amount.