Exhaust valve seat recession
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Introduction

   Anabex^® 92 is a safe and effective valve seat protection additive which is designed for use in engines which require the protection of lead. Tetraethyl lead was originally designed as an octane enhancer, but it was soon discovered that the metallic oxides which result from combustion form a protective coating on valves which prevent microwelding of the valve seat to the valve face under high temperature operation. This welding of the two hot pieces of metal causes the removal of the softer seat metal and subsequent recession of the valve into the cylinder head. Wear debris then contributes to valve stem and valve guide wear. Valve recession causes poor sealing of the compression gases, which means loss of power and fuel economy, poor idle and driveability, and the eventual need for cylinder head replacement.

   The trend towards lead-free gasoline is well established throughout the world. Several countries have banned leaded regular gasoline and replaced it with lead-free premium or regular gasoline. Tax incentives are being used to encourage the use of lead-free gasoline for a healthier environment.

   On the other hand it is not possible to use lead-free gasoline in automobiles of different manufacture, especially those produced before 1985, because their valve seats are made of soft materials that are easily damaged when subjected to use with lead-free gasoline (see Fig.1).

   In 1987 the total number of cars and light-duty vehicles on the road which required lead-containing fuel to protect against abnormal valve seat wear, was estimated to be up to 70 million. In the United Kingdom the figure was approximately 7 million. There are some additives on the market claiming to cope with this problem. None of these additives can provide satisfactory protection for engines with very soft valve seats (see Fig 2).

Anabex^® 92 gasoline additive

	is a new type of additive, developed and produced by Slovnaft VURUP, a. s.
	provides a perfect protection for the exhaust valve seats when lead-free gasoline is used.
	does not worsen any properties of the gasoline and is also compatible with catalyst equipped vehicles.
	is the only additive on the world market that is effective against very soft valve seats recession in cars using lead-free gasoline.
	also provides a corrosion control and deposit control to the intake system of the engine.
	was extensively tested in co-operation with the health institutions during its development and is neither toxic nor mutagenic.

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