Lead Replacement Petrol
Encyclopedia
Lead Replacement Petrol (LRP) is a fuel developed to provide an alternative to petrol (gasoline) containing a substance known as tetraethyl lead (TEL), a compound of lead in liquid form originally added to petrol to increase its octane rating
. A side effect of adding TEL is that a layer of lead compounds forms on the valve faces of the engine, retarding wear.
Lead is very toxic and lead compounds in exhaust gases escape into the atmosphere causing pollution. Impacts on human health are widely documented. This led to the introduction of lead-free petrol.
With normal lead-free petrol an adjustment to the engine's ignition timing solved pre-detonation problems (pinking or pinging) caused by the lower octane rating, but this did nothing to prevent accelerated valve wear. The use of lead in petrol had allowed the machining of valve seats directly in the cast iron or aluminium cylinder heads (or block of side-valve engines). Over time these seats would heat up, erode and even micro-weld the valve to the seat causing rapid damage.
LRP (Lead Replacement Petrol) was introduced containing other metal salts (such as potassium or manganese) to address the issue of valve wear.
Octane rating
Octane rating or octane number is a standard measure of the anti-knock properties of a motor or aviation fuel. The higher the octane number, the more compression the fuel can withstand before detonating...
. A side effect of adding TEL is that a layer of lead compounds forms on the valve faces of the engine, retarding wear.
Lead is very toxic and lead compounds in exhaust gases escape into the atmosphere causing pollution. Impacts on human health are widely documented. This led to the introduction of lead-free petrol.
With normal lead-free petrol an adjustment to the engine's ignition timing solved pre-detonation problems (pinking or pinging) caused by the lower octane rating, but this did nothing to prevent accelerated valve wear. The use of lead in petrol had allowed the machining of valve seats directly in the cast iron or aluminium cylinder heads (or block of side-valve engines). Over time these seats would heat up, erode and even micro-weld the valve to the seat causing rapid damage.
LRP (Lead Replacement Petrol) was introduced containing other metal salts (such as potassium or manganese) to address the issue of valve wear.