Many people see the diesel engined 4×4 as a superior vehicle, not least because the diesel engine’s strengths appeal more to driving in an off road or expedition environment. Certainly, most Land Rovers are diesel as standard, but why? This article is a run down on main strengths of diesel engines on expedition and what that means in the real world.
Performance
Diesels have most of their power or torque at low revs, wheres petrol engines get more power at higher revs. This means that as you would think in a petrol car, the more you push the accelerator, the faster the car goes. However, in a diesel engine, the more revs you have, the more the power disappears so the use of gearing is more extensively needed to keep the engine in the optimum number of revs for more power.
Since this is the case, many diesel engines, and Land Rovers since the 80′s have Turbochargers fitted, to increase the power at higher revs to that effectively, less gears are needed. Although, acceleration still suffers as engine speed is needed to see the benefit of the turbo. Whilst it may seem that diesels are inferior engines, since they have more power at lower revs, they are better for moving heavy loads at lower speed, such as towing trailers and crawling over uneven terrain.
Having the strength at lower revs mean that the engine is more in control when traversing more tricky off road sections which will naturally be at a lower speed. This strength also has the benefit that they have better engine braking down hills, requiring the brake less and forgoing any skidding situations.
Reliability
Diesel engines are generally considered more reliable, as they are built more ruggedly to withstand higher compression ratios in the cylinders, and are seen to go over 250k miles.
Cost
Although the initial price of buying a diesel engine is more from the outset Litre for litre, they are considered to have better fuel consumption for a similar size petrol engine (although diesel fuel is currently more expensive in the UK).
No electronics
Petrol engines run by the pistons in the engine compressing a mixture of petrol and air in the cylinders. A spark is produced at the optimum time which explodes the piston downwards, creating the driving force. A diesel engine differs as it has no spark to ignite the fuel, with the fuel igniting due to immense pressure and heat inside the cylinders.
If a battery goes flat in a diesel, it’s not a deathknell of hopelessness. Diesels don’t require a spark to ignite their fuel, so no electronics are actually needed to run the engine. In a Land Rover, even a faint glimmer of amps from the battery is enough to open the fuel solenoid so that a good push, tow or roll downhill will get the engine going.
It’s also important to note than if wading in deep water is encountered, then the engine won’t cut out from having shorted electrics. The engine can essentially run underwater, as long as it can breathe through a raised air intake.
Fire risk
If you happen to be camping out in the bush, carrying diesel in jerry cans poses less of a fire hazard than petrol does.
Fuel Availability
Petrol comes in many guises of quality, with most petrol engines requiring a minimum octane level to work. For a diesel engine, diesel is diesel, and in some of the more backward places you may visit on expedition, diesel is more likely to be found and pumping in a tankful of the local stuff is not an issue. The only thing that may be required is a more frequent oil change for high sulphur diesel fuels.
Range
For a given amount of fuel, a diesel will go further, meaning that you can either take less jerry cans along for the ride, or can travel further afield without worrying about filling up.
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