LDV Lorry Engines: Truck, Convoy engine, Pilot, Maxus
The LDV Convoy also called DAF 400 Series and offered air suspension and a 2.5-litre Peugeot-sourced diesel engine. The LDV Pilot it’s power came from a 1.9 litre Peugeot Diesel car engine. The LDV Cub production was from 1996 – 2001. The LDV Maxus 120PS 2499cc diesel engine. At Engines and Gear Boxes they are offered as used, reconditioned or secondhand.
The diesel engine is an internal combustion engine that uses compression ignition, in which fuel ignites as it is injected into air in the combustion chamber that has been copressed to temperatures high enough to cause ignition.
Compressing a gas raises its temperature, the method by which fuel is ignited in diesel engines. Air is drawn into the cylinders and is compressed by pistons at compression ratios as high as 25:1, higher than used for a spark-ignition engines. At the end of the compression stroke, at the start of the power stroke, diesel fuel is injected continuously into the combustion chamber through an atomizer, igniting from contact the compressed air whose temperature is initially about 700–900 °C (1300–1650 °F). Combustion further heats the air in the chamber, increasing its pressure to move the piston downward. A connecting rod transmits this motion to a crankshaft to convert linear to rotary motion and delivers power to an output shaft. Scavenging (pushing products of combustion from the cylinder and drawing in a fresh air) the engine is done either by ports or valves. To increase power, a diesel engine may by mechanical supercharger or by an exhaust turbine, have a turbocharger to to increase intake air volume. Use of an aftercooler/intercooler to cool intake air after compression by a supercharger improves efficiency.
In cold weather, diesel engines can be difficult to start because the cold metal of the cylinder block and head draw out the heat created in the cylinder during the compression stroke, thus preventing ignition. Most Diesel engines use small electric heaters called glow plugs inside the cylinder help ignite fuel when starting. Some even use resistive grid heaters in the intake manifold to warm the inlet air until the engine reaches operating temperature. Engine block heaters (electric resistive heaters in the engine block) connected to the utility grid are often used when an engine is turned off for extended periods (more than an hour) in cold weather to reduce startup time and engine wear. Diesel fuel is also prone to ‘waxing’ in cold weather, a term for the solidification of diesel oil into a crystalline state. The crystals build up in the fuel (especially in fuel filters), eventually starving the engine of fuel. Low-output electric heaters in fuel tanks and around fuel lines are used to solve this problem. Also, most engines have a ‘spill return’ system, by which any excess fuel from the injector pump and injectors is returned to the fuel tank. Once the engine has warmed, returning warm fuel prevents waxing in the tank. Fuel technology has improved recently so that with special additives waxing no longer occurs in all but the coldest climates.
A vital component of older diesel engine systems is the governor, which limits the speed of the engine by controlling the rate of fuel delivery. Unlike in petrol (gasoline) engines, incoming air is not throttled and an engine without a governor can overspeed. Older injection systems were driven by a gear system from the engine and thus supplied fuel in proportion with engine speed. Modern, electronically controlled engines apply controls similar to those of petrol engines and limit the maximum RPM through an electronic control module (ECM) or electronic control unit (ECU)—the engine-mounted computer. The ECM/ECU receives an engine speed signal from a sensor and controls the amount of fuel and (start of injection) timing through electric or hydraulic actuators.
Controlling the timing of the start of injection of fuel into the cylinder is a key to minimizing emissions, and maximizing fuel economy (efficiency), of the engine. The timing is usually measured in units of crank angle of the piston before Top Dead Center (TDC). For example, if the ECM/ECU initiates fuel injection when the piston is 10 degrees before TDC, the start of injection, or timing, is said to be 10 deg BTDC. Optimal timing will depend on the engine design as well as its speed and load.
Advancing the start of injection (injecting before the piston reaches TDC) results in higher in-cylinder pressure and temperature, and higher efficiency, but also results in higher emissions of oxides of nitrogen (NOx) through higher temperatures. At the other extreme, delayed start of injection causes incomplete combustion and emits visible smoke made of particulate matter (PM) and unburned hydrocarbon (HC).
Modern diesel facts fuel passes through the injector jets at speeds of nearly 1500 miles per hour (2400 km/h). Fuel is injected into the combustion chamber in less than 1.5 ms – about as long as a camera flashes. The smallest quantity of fuel injected is one cubic millimetre – about the same volume as the head of a pin. The largest injection quantity at the moment for automobile diesel engines is around 70 cubic millimetres. If the crankshaft of a six-cylinder engine is turning at 4500 rpm, the injection system has to control and deliver 225 injection cycles per second.