Cool Runnings

DR TIM EXPLAINS HOW TO OPTIMISE YOUR CAR’S COOLING SYSTEM SO YOU DON’T GET HOT UNDER THE COLLAR

- Dr Tim

AS SUMMER approaches, it reminds us that a proper cooling system is critical to the life of your engine and the enjoyment of your street machine. Few things are more stressful than sitting in traffic watching your temp gauge rise. It’s the same as having bad brakes; you can’t relax because you don’t know what is going to happen next. We build cars to enjoy them, so we don’t need overheating.

A correctly running engine generates a certain amount of heat at idle, which increases depending on the engine load during faster driving and acceleration. This heat is a natural part of internal combustion and is removed from the engine as noise energy, exhaust heat, air transfer from the engine block and, most critically, water-to-air heat transfer from the radiator cooling system.

Every engine should be able to operate as a stationary engine where the cooling-system heat transfer is equal to or greater than the thermal energy created by the engine. This is the best test of any system. A car should not overheat after standing at a long traffic light or in a traffic jam. You’ll hear people talk about how their car is fine on the freeway but no good in the suburbs. This means that their cooling system does not have enough thermal capacity.

The three factors that determine the efficiency of a cooling system are the waterflow rate around the system, the airflow rate through the radiator, and the heat transfer surface area of the radiator.

The water-flow rate is rarely the problem, because the manufacturer’s water pump is designed to give the correct flow rate for ideal flow through the radiator for best efficiency. The flow rate should include the thermostat. Obviously a blocked radiator is a source of flow restriction that needs to be checked.