Know Your 4×4: Power Sources
A diesel engine uses a system known as compression ignition. It is a ‘closed’ system, making it marginally more waterproof than a petrol engine. Starting is by means of a glow plug which is much like an element for cold starting. Torque develops at lower revs making diesel 4x4s ideal for off-road use. They are more economical that their petrol counterparts but some have shorter service intervals and require the lower sulphur fuels that may not be readily available. Modern diesel engines are quieter, cruise well on road and are well suited for towing. Some turbocharged vehicles suffer from lag – delayed response to throttle at high altitude.
Known as a spark ignition engine – a spark ignites the fuel in the combustion chamber. Petrol engines deliver their torque at higher revs and have longer service intervals. They are not as forgiving as diesel derivatives when off-road and require unleaded fuel which is not available across Africa. They cruise easily at all speeds and tow well.
Biodiesel and Liquid Petroleum Gas (LPG)
Is very popular abroad, performance is similar to petrol and is cheaper as it is not taxed. Space is lost as you have to fit an extra tank. Biodiesel contains vegetable matter and performance is similar to diesel.
Engine performance can be improved by fitting a turbocharger, this utilises exhaust gas to force the air/fuel mixture into the cylinders under pressure thereby increasing power.
Cools intake gases from a turbocharger, cooler air is denser and richer in oxygen which improves ignition.
Many off-roaders mistakenly believe that a snorkel is a device fitted to the air intake that enables you to wade through incredibly deep, long stretches of water, if correctly fitted and sealed it can, however prolonged immersion in water may ultimately cause a relay or other electrical component to fail as they are not waterproof. A snorkel allows your vehicle to breathe cooler, cleaner compressed air which optimises engine performance.