Superchargers and turbo chargers do to engines, what bellows do to a fire. Valve overlap changes help even more, using the compressed air to scavenge the cylinders of burnt fuel. It’s all good!
There are draw backs though; Compressing air creates heat. It’s still got the same heat energy, but now it’s all squished into one space. The higher the boost, the more heat there is in the ‘charge’. For even better performance it needs to be removed. This makes the air less viscous and means more expansion in the cylinders.
The down side of cooling is greater air volume between the compressor and engine. The higher the volume, the slower the boost pressure is to rise. This can mean annoying turbo-lag, which is why some racing disciplines remove the intercooler completely and link turbo and inlet manifold with a short pipe. Others fit huge intercoolers and never let off the throttle. But there is a third way!
The charge cooler is a little used item with many advantages. It’s not for major car manufacturers, who buy intercoolers for £20 each, but it might be for you! The construction is simple enough, being an intercooler that’s cooled by water instead of air. Water can store a lot more heat energy than air, so the equivalent charge cooler can be much smaller. This reduced package size means it can be placed closer to the turbo charger or inlet manifold and can even be built into the inlet manifold. This gives a two fold advantage to turbo lag, in that the air volume is less in a charge cooler, and there is less hose work required to plumb it in.
As the circulating water is cooled at another location, there can be twin coolers either side of the engine rad, so main engine cooling doesn’t suffer from a large intercooler stuck on the front.
What’s Required for a Charge Cooler?
Here are the basic bits without pump and hoses. There’s a simple header tank with pressure cap, a pre-rad, and the charge cooler itself.In this case the pre-rad is a centre mounted type, but a pair of intercal units do the job, and are good value for money. They are best plumbed in series with each other.The charge cooler itself is shown with 76mm ports at either end, though the unit can be made with the ports on the same end. Position is only really dependant on the engine and turbo installation and the ideal piping route.Although the charge cooler size plays a part in the temperature of the compressed air, the pre-cooler size and position is also important, as is the volume of water in the system. The proportion of these components depends on the duty cycle of the engine. If short use at full power is required, or short bursts of power, the ability of the water to suck up the heat is more important. The pre-rad can loose that heat at its leisure. So water volume is more critical. Maybe you only need a bucket of ice to feed the charge-cooler? But on constant high engine power the system will soon become saturated with heat, so a good sized pre-rad and pump are required. And the water volume need only be big enough to fill all the parts.It’s also worth noting that the nearer you want to get the charge temperature to the ambient air temperature of the day, the bigger the coolers. Getting close to the ambient gets harder and harder, so really it’s a balance between ‘Perfect ideal solution’ and practical installation.
For further information on the range of charge coolers available, please contact our motorsport team on: +44 (0) 1889 574880 . Alternatively e-mail our motorsports team on: firstname.lastname@example.org.