If the turbocharger can be described as the heart of the system, then the intercooler must surely be the "lungs"!!
APS has designed and manufactured a custom configured, vertical flow high efficiency intercooler utilizing custom designed light weight cast aluminium end tanks. Extremely high flow rates and massive charge air temperature reduction - a level of performance that other manufacturers can only aspire to achieve.
With a huge 600mm x 235mm x 100mm (24” x 9.25” x 4”) drag race specification bar and plate core, at 675 kW (900 hp) flywheel, the pressure drop is less than 1 psi. At the same turbocharger flow conditions, under full engine load the intercooler outlet temperature is less than 15°F higher than ambient, at any vehicle speed over 100 kph (60 mph). Truly outstanding results at such a huge horsepower level. So just like the APS turbochargers and twin cold air intakes, the APS intercooler system has massive additional headroom available for even higher power levels.
Vertical flow inside the APS intercooler is by far the optimum configuration given the space considerations that must be accounted for in the front of the vehicle. This solves the huge air flow restriction problems that horizontal flow cores experience particularly at high power levels.
The horizontal flow configuration shown above forces the charge air to flow through very few internal intercooler passages. In addition, each internal passage is very long, causing further restriction to charge air flow - resulting in a high pressure drop.
The vertical flow configuration as specified by APS spreads the charge air flow evenly over a far greater number of internal passages and results in significantly less restriction. The path length of each internal passage is also shorter, further improving air flow over a horizontal design. The net effect is massive charge air reduction but with improved air flow and less restriction over a cheap horizontal core configuration intercooler.
Another important aspect of intercooler design for the G8 is the number of times the charge air must change direction in order to enter and exit the intercooler. Since air flow is momentum based, each time the charge air must change direction, it consumes energy - which results in high pressure drop and reduced engine power.
With a horizontal flow core, the velocity vector turns 90 degrees twice on entry and again twice on exit. In addition, both turns must take place inside the hight of the end tank.
With the APS vertical flow intercooler, the velocity vectors turn only once over a very wide distance on entry (up to half the width of the core = 24/2 = 12 inches) on entry. This allows the air to turn very gradually a good thing. Air flow is momentum based and the end tanks on the APS intercooler are designed so that an equal mass of air reaches each internal passage. On exit, a similar situation exists however this time, the air velocity vector turns 90 degrees over a smaller distance (essentially the height of the exit end tank. This is one reason why the exit end tank is taller than the entry tanks.
Importantly, the APS intercooler uses the latest in Bar and Plate core technology, not low cost off the shelf tube and fin. Other than the fact that the APS intercooler core boasts the highest flow and greatest temperature reduction, the bar and plate construction results in an inherently strong intercooler core of high thermal inertia. The advantage here for the performance street car and drag race enthusiast is that with the core's high thermal inertia, massive reserves of cooling capacity are available in situations where ambient air flow over the core is low. So, after a power run to heat tyres prior to staging for a quarter mile pass, there is plenty of intercooler capacity to launch with full power at your disposal - rather than forsaking power with a tube and fin construction core that becomes heat soaked during the initial burst.
Another aspect worthy of consideration is the internal air passage cross sectional area and fin arrangement of the APS Bar and Plate construction in relation to tube and fin. The tube and fin core has a 5mm edge boundary so for say a 4” thick core, you lose half an inch in internal thickness which impacts on passage cross sectional area. In addition, the fins are extruded so they are essential in a straight line and parallel to flow. This means that the internal surface area presented to the charge air is nowhere near as great as that on a traditional bar and plate which has an alternating offset internal fin arrangement. The result is the bar and plate core used in the APS intercooler (which is actually an enormous 6" thick) flows better and removes far more temperature than the traditional horizontal flow tube and fin. These are just some of the reasons for APS specifying this vertical flow bar and plate core on the G8.
That said, for other vehicles, other configurations may be applicable, which is why taking a general purpose core from one vehicle and using it in another different type of vehicle is often fraught with problems even though the cores may be of similar size.
The true dual entry design of the APS intercooler system allows for the ultimate in true equal length balanced ducting from each turbocharger to the intercooler. This ensures the optimum utilisation of the intercooler core by spreading the charge air from each turbocharger evenly across the entire intercooler core - This is efficiency at its best!
Intercooler ducting length is critical on the G8 in order to achieve balanced induction and excellent driveability. By designing the turbocharger to intercooler ducting specifically to be of equal length, each turbocharger experiences the identical effective air path to the intercooler which results in totally balanced turbocharger performance (it's like having two separate intercooled turbo systems - one for each bank of cylinders). Other systems that are designed with unequal length, experience boost pressure and air movement issues where under certain conditions, one turbocharger pushes air back through the intercooler and into the other turbocharger ducting. As air movement is momentum based, this is simply wasted energy that should be better put towards producing higher horsepower, not restriction.
The advanced APS dual entry intercooler not only solves this problem but allows APS to utilize true equal length ducting - the most efficient intercooler system routing for the intercooled twin turbo G8!
The APS intercooler core is of internally and externally finned construction and offers significantly enhanced flow and heat exchange performance, particularly at high charge air mass flow rates (High boost pressure and high engine power levels). Also, unlike other manufacturers of intercoolers who reduce cost by using low cost off the shelf tube and fin cores, the APS drag race specification bar and plate intercooler is designed with the optimum ratio of intercooler core surface area (222 inches2) to intercooler volume (888 cubic inches) - unlike inferior quality intercooler cores that are very shallow (the APS core is 4 inches deep!). The result is an intercooler system with outstanding flow and cooling performance, particularly at high engine power levels of up to 820 kW (1,100 hp).
However, there is more to intercooling than size alone. Fully engineered light weight, cast aluminium end tanks ensure optimum charge air distribution throughout the entire intercooler core for maximum charge air cooling and minimum pressure drop. After all, everything about intercooling is achieving the maximum charge air temperature drop with the lowest possible pressure drop across the entire intercooler system.