Life is a compromise. As engineers we are all familiar with the principle of ‘give and take’, and once the problem is identified, until now we have always managed to come up with a workable solution which, if not altogether perfect, suits most of the people most of the time. Rather like engine plain bearings. A plain white metal, bi- or tri-metal engine main or big-end bearing has to cope with a range of conflicting requirements. First, it has to be strong enough to support the...
As used in automotive applications the internal combustion engine is woefully inefficient. Many gasoline race engines can claim up to 35% thermal efficiency at specific speeds and loads, but a figure of 25% – even as low as 20% overall – may be more realistic on the track. The fact is that the opening of the intake and exhaust valves by mechanical methods is rarely anywhere near that for optimum performance, largely because of transient conditions and the use of the throttle to...
The widespread phenomenon of fretting is a form of wear found between pairs of components that are normally designed to have no relative movement or at least very limited amounts. We often find evidence of fretting on splines, where the degree of axial movement is small, and in race engines we also find evidence of it on mating faces between large structural components. Race engines are commonly constructed using aluminium for the structural components, and where both components are of the...
Many of us will be aware that the con rod bolt is very often the most highly stressed fastener in any race engine. Not only is it highly stressed but if a rod bolt fails then the consequences can be catastrophic for the whole engine. I have seen engines where there has been a rod bolt failure, and very little of any real value could be used again. Thankfully though, by using careful tightening procedures and the correct bolt for the application, rod bolt failures are relatively rare. The...
It is an inescapable fact that pressure charging the intake air of an internal combustion engine invariably increases the temperature of that charge. The degree to which the temperature increases is essentially a function of the type of compression that takes place (adiabatic, isothermal) and therefore the efficiency of the compressor. The turbocharger, with its centrifugal compressor, accelerates the charge very quickly and then diffuses it slightly slower to convert the velocity energy...