Section through Core

INTERCOOLER Pictures and Information with K & J core and Custom endtanks © by Anthony Hyde, Australia 2003

Extruded Aluminium Alloy

 

Click images to enlarge  The following topics are discussed below: 1) CORE MODIFICATION 2) INLET ENDTANK CONSTRUCTION 3) OUTLET ENDTANK CONSTRUCTION 4) INSTALLATION 5) How does it PERFORM Suggested reading is a superb technical article on Intercoolers by ARE, Australia. Their web address link is at the bottom of this web article. K&J cores are supplied by PWR, Queensland, Australia.

A modern high efficiency K&J core was used as the basis for building up a custom air-to-air intercooler. Endtanks using optimal shapes were designed and made by the author. LAYOUT: Core tubes are extruded aluminium alloy lengths that are stacked together and fused. Length is simply cut to order. Within each core tube are 20 smaller tubes plus two additional end ribs or fins. The cooling core size I selected (height 300 mm) consists of 18 horizontal tubes, with a special shape and features shown in the drawing below. * The chances of a hot air molecule bouncing into a cooler surface and dissipating heat - is very high with this modern core design * Looking through the core end, daylight is clearly visible at the other end, a good design for flow. The above diagram shows design advances by comparing a modern K & J tube cross section and overall size, with a typical 20 year ago design, in this case 1984 Volvo core tube. Note: your Internet browser might distort actual size. CORE DIMENSIONS: If the complete intercooler core is in direct contact with in-coming air, the intercooler need not be oversized. The front mount core dimensions (as chosen) were width 460 mm or 18" x height 300 mm or 12". (Bell IC size equivalent #300120180). This gives a core cooling area of 0.14 sq metres or 1.5 sq feet. Chosen core thickness is a generous 73 mm or 2.875" and extruded tube height is 8 mm or 0.312". This core thickness should still allow adequate airflow through the core and into the engine radiator. Rigid 10 gauge (3.1 mm or 1/8") sheet is used by KJ on the four ends. The assembled core is heavy in weight at 7 kg or 15.4 lbs due to solid construction. This bodes well in ability to handle heat load without becoming too hot, too quick. Pressure drop across the core would be very low given the generous tube sizing of this extruded design. Internal airflow of this core size would be around 300 cfm. OWNERS INTENDED USE: circuit sprints & club hillclimbs, 13-16 psi, general road use. ENDTANK MATERIAL: Al.Alloy sheet, 14 gauge or 2 mm thick. TUBE BENDS: Thin Al.Alloy mandrel bends are hard to find, so the next best method is to purchase two lathe spun half rings and have them welded together to form a donut. These halfs are commercially available, are inexpensive, and come in different diameters. The hollow donut is strictly speaking a 'hollow torus'. Sawing the torus into 90 deg segments gives x4 quality short radius tube bends. OVERALL DIMENSIONS with endtanks: Width (Core 460+In110+Outlet196)= 766 mm or 30.125"; Height (Core 300+top pipe) = 380 mm or 15"; Width of core end flanges are 90.5 mm or 3.560". Air entry - Pipe elbow 'internal' diameter (at smallest point) are 62 mm or 2.445". This suits a Gates silicon hose 'internal' diameter of 66.8 mm or 2-5/8", a size above the usual 2-1/2" internal hose size. In retrospect, a smaller pipe dia feeding from the turbo to intercooler could have been used, with velocity IN being a point considered by a few informed people. Volume of core and attached endtanks is 5 litres, or a bit over 1 gallon.

INLET CONSTRUCTION: Aim is even flow distribution into core tubes - pre purchase advice mentioned uneven flow distribution if cores were to much higher than 300 mm (12"), so luckily this height suited my application. Construction took longer than expected as flow testing of the 1st shape revealed a few low-flow zones, thus requiring correction with dissection, re-shaping and re-welding fill into corners. Back and sides are folded from one piece of 14g Al.Alloy with all the real metalwork skill going into blending the transition sections from the 90 deg bend into the tank. Mock up: After working out / drawing a shape on the computer, a cardboard sheet plus tape and metal pipes made a suitable mock-up to test and verify flow direction characteristics. For airflow velocity, I used two fans - one pushing air into the rear of the other, then collected down into a large funnel. To check flow directions I simply bent a thin piece of wire 90 degrees, and on the end looped on a very small piece of thin plastic bag and as it flutters you can start testing your shape. Tools used: Cordless drill for burr bit, round flapper sanding discs 80,120 grit in a range of diameters 1" to 2" for internal finishing, scrappers ground with a large radius for smoothing internal welds. From a Volvo fitment perspective, the top of the inlet pipe sits level with the top of the radiator.

Click pics to enlarge

Ultimately a delightful shape, and quite a journey getting there. After 2D drawing on the computer to work out dimensions, the outlet tank shape was formed by hand. It consists of eight pieces of 14G Al.Alloy expertly tig welded together. Pipework added another three pieces. Forming the tank shape was aided by a crafted wood block of the desired shape. Individual Alloy pieces were softened by ANNEALING. To anneal Al Alloy, place white soap into a small dish of water to soften, wipe soap goo over material. Heat surface evenly till soap fat burns towards a black color. Leave to cool naturally. Repeat as required when working into shape. If only 14G soft alloy sheet was available in Australia the whole endtank forming task would have been far, far easier. After welding each section, each internal & external join was smoothed perfectly by filing, scrapping and many hours of sanding. The finish on the inside is the same standard as the outside. As seen in the pictures, cool air exiting the core is flowed into a non restricting 3" ID long radius 90 deg bend. The bend connects to a reducing taper (3" to 2-1/2") through a flexible hose and onto the throttle body.

4) INSTALLATION - Click images to enlarge Front On View

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First published Sept 2003. Recent wording refinement April 2005