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:
4) 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 (sold by PWR) 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.

The K&J production core is very well made with generous material thickness. The technical drawings (below) illustrate work done by the author to optimise airflow into the tube INLET by removing inlet tube overhang. Each individual INLET side tube and fin (1,440 fins in total top & bottom) were hand filed with a lead-in chamfer, and although a time intensive process, is simply ' attention to detail '. The purpose is to reduce turbulant air flow as it enters the Core. Pressure conditions are always changing between atmospheric and boost. Tube OUTLET end overhang was NOT modified.

The above drawing replaces digital photos lost when a memory card was mistakenly wiped. The Al.Alloy core material is very soft I presume due to the heat treatment process for overall assembly, so care was req'd when sawing, straightening and smooth filing tube fins. The needle file(s) required constant cleaning to remove soft alloy from grooves, apparently chalk can help.

2) INLET ENDTANK CONSTRUCTION (suits Volvo 240 Turbo engine bay) Click pics to enlarge

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) HOW DOES IT PERFORM - Considering the amount of effort put into endtank design and construction, plus the impressive K&J core design, an improvement all round was expected.
IMPRESSED I am - at any boost point the engine breathes far easier and this continues right through the rev range. Most noticeable
free breathing point is where the boost builds up rapidly around 3 to 3,500 rpm, even with light throttle and low boost the engine revs freely.
Over the years one flow performance improvement indicator of mine is whether I notice the
engine cam characteristics becoming stronger. Well the intercooler upgrade has made the most significant improvement to cam performance through the rev range I have yet experienced, and this is on top of items like electronic boost control, ported manifolds, 3" exhaust etc.
Even after boost runs, the IC outlet side is still cold to touch, but hot on the inlet endtank. Temp probes bungs are fitted, but as the IC runs so cold there is little point recording temps anymore, its so efficient.
I noticed my air / fuel ratio was richer after fittment, so off-boost fuel was trimmed back. Ignition timing can also be run more advanced without pinging, all welcome improvements.

© Anthony Hyde, 2003
Links: Aluminium Radiators & Engineering, Australia - Best technical evaluation of intercooler cores with pictures in the world.
PWR Performance Products - K&J core manufacturer
PWR Performance Products
USA - Moreno Valley
Bell Intercoolers, USA - Good FAQs
VOLVO Factory Intercooler - by Anthony Hyde

Return to Anthony's Volvo Turbo World

First published Sept 2003. Recent wording refinement April 2005