The question of valve material selection has been discussed before in the RET-Monitor. Much of the motivation for a given selection is provided by the operating conditions in which the valve must operate. Some materials are not suited for very high temperature use while others are too dense to be used in conjunction with very extreme valve lift profiles. In previous articles, we have looked mainly at the different classes of Read more…

There are few components in a race engine that, given a free hand in terms of design and development, we wouldn’t choose to make a little lighter. However, there can also be few components in the engine where the effect of lightening is potentially more potent than the reciprocating parts of the valvetrain. In particular, ‘clean sheet’ engine designs allow us to fully optimise around well designed valvetrain components. Read more…

In designing a new race engine, or developing an existing one, the management of heat in poppet valves - and the transfer of heat from them - is only one small aspect, but it has an effect on performance and reliability.

The subject of hollow poppet valves that are cooled internally through the use of sodium or a similar material has been discussed previously, both in Race Engine Technology magazine and in my RET-Monitor articles. Read more…

The matter of ensuring that valve-stem lubrication is sufficient has two main benefits. First, any friction between stem and guide creates energy that is necessarily subtracted from crankshaft output power and converted to heat. Minimising this is clearly a desirable aim. Second, if the lubrication is sufficient, we minimise the rate of wear of the valve guide and valve.

There are a number of surface treatments that aim to Read more…

In developing a race engine it is common to evolve valve-lift profiles constantly to improve the ‘breathing’ of the engine. The aim is to increase volumetric efficiency or, more precisely, to increased the trapped mass of fresh, unburned charge. In the case of race engines this often leads to the use of more ‘aggressive’ cam profiles. By ‘aggression’ in the case of valve-lift profiles, this means higher accelerations and the derivative of acceleration with respect to time called ‘jerk’ or ‘pulse’. Put simply, jerk quantifies the gradient of the Read more…

In the recent Race Engine Technology article on valves, there was some discussion of the merits of hollow valves, and indeed the subject has been covered by Anne Proffit and I in these Monitor articles in the past.

We should briefly restate here the reasons for hollow valves. The first and more obvious reason is mass reduction in cases where a reduction in stem axial stiffness does not compromise the proper action of the valve or present problems through lack of bending Read more…

With the dominance of four-stroke engines in racing, and the near-monopoly that poppet valves have in such engines, it is little surprise that these parts have become well developed. While most racing is still based on naturally aspirated engines, it is likely that a much greater proportion of race engines in future will be turbocharged, following the continuing trend in series production engines toward smaller boosted power units. There are compelling reasons for doing this; not only is engine efficiency improved, but a small, light engine

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When you visit a large motorsport trade show, as I recently did, there will be a number of engine component suppliers present, some of which will be selling high-quality valvetrain components. In the display cabinets ranged before you, among other things you are likely to see valves of all sizes, shapes and materials, there for you to examine and discuss with the various specialists manning the stands.

Among these exhibits, there is sometimes a single, Read more…

In the previous article on valves, I turned to the subject of reed valves and their use in the induction section of a two-stroke engine. In race series where two-stroke engines are still popular, reed valves are commonly used and, owing to their mechanical simplicity, are likely to remain so. They require no mechanical drive or other actuation, and depend only on pressure differentials to open and close.

There have been a number of uses of reed valves on Read more…

Most of the articles I’ve written about valves have looked at the design of, or materials in, conventional poppet valves as applied to many four-stroke engines. So I thought it would be good to take a brief diversion from this and look at something completely different.

Two-stroke engines have been used widely for grand prix motorcycle racing (although this era is soon to come to an end), motocross, snowmobiles, jet skis and so on, and are currently enjoying something of a resurgence for Read more…