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Multi-profile camshafts

chris@highpowermedia.com
The most widely used term in the 21st century automotive world is surely the verb ‘to optimise’. Meaning “to make the best or most effective use of a situation or resource”, in the modern world and with so many variables, engine design must surely be a case in point. But in ensuring that each cylinder flows an equal amount of air, the cam is only part of the equation. These days, with the advent of computer design technology, designs are much more sophisticated, and...

Fishy tales?

chris@highpowermedia.com
I was asked a question the other day that, for a moment, simply floored me. Strolling around an exhibition, my friend and I were talking about the stand we had just visited and the company’s claim that its camshafts were being ground to an accuracy of 3 microns (0.003 mm). “If they can grind camshafts to that level of accuracy,” said my friend, “why do I have to adjust the shims on the engine I am rebuilding?” A simple enough question for the uninformed, you...

Good vibrations

chris@highpowermedia.com
Readers may well be familiar with the concept of torsional vibration in an engine crankshaft. The situation where the intermittent torques fed into the crankshaft by the successive firing of the cylinders induces cyclical strain within the shaft – which, unchecked, can lead to component failure – is something most power unit engineers will have come across during their lifetimes. When the shaft is revolving at a speed such that the frequency of the repeated applied torques or one...

Friction

chris@highpowermedia.com
While the friction in the valvetrain may not be particularly high, is it not insignificant. And even assuming a suitable motored rig can be developed, understanding the output data can bring considerable challenges. Indeed, my own attempts to measure the power to turn a simple direct-acting camshaft, although giving reliable and repeatable results, only served to underline the highly dynamic nature of the forces involved and the sensitivity of the final result to the many parameters in the...

The camless engine (2)

chris@highpowermedia.com

The demise of the camshaft has been predicted for many years. Optimised over a narrow window of engine operating range, in one way the camshaft can be used to enhance engine performance, but in others it can also limit it. So when optimised at one particular condition in the real world, where engines are used at a much wider range of speeds and loads, overall the engine may become woefully inefficient. Cam phasers, to adjust intake or exhaust timing (or both) are one way to limit the...

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