Automotive Design Interview
Valve controls – infinite possibilities
Imagine a valve control system that is infinitely variable irrespective of engine speed and load. Impossible? Not according to Camcon Automotive’s technical director Roger Stone, as Ian Adcock discovers
A
valve control system that operates in real time, adjusting individual valves according to the demands of each
cylinder and power stroke, seems like a dream come true for engine designers. It’s a step-change in engine design
and development that is probably even more important in the long run than the switch from points ignition to engine management systems or the move from carburettors to fuel injection. Such a significant move forward,
says Roger Stone, Camcon Automotive’s technical director, unlocks an Aladdin’s cave of possibilities. As he puts it, in terms reminiscent of former US Defence
Camcon’s second generation test rig
Secretary Donald Rumsfeld’s ‘there are also unknown unknowns’: “One of the things I keep saying about intelligent valve actuation (IVA) is ‘There are things we will be able to do with it, that we don’t know we want to do yet’.”
Unlocking the obstacles Equally applicable to petrol and diesel, IVA, Stone believes, could, amongst other things, unlock the difficulties that homogenous charge compression ignition (HCCI) is currently presenting to manufacturers, such as Mercedes-Benz, trying to develop it. “Potentially it’s an enabler for HCCI. For example, at lower speeds we are fast enough to get more than one valve cycle in during a 720° period, so we could have the normal exhaust event, if you like,
followed by an additional smaller event during the inlet stroke to give us the amount of exhaust radicals that we need.” Meanwhile, he is equally
convinced that, because the link between the valves and the crank is broken, it would be possible to open the valves every stroke between 2,000 and 3,000rpm to run the engine as a two-stroke for short periods of time. “Even the ability to run for short periods as a two-stroke is thrown in for free, although you get the breathing compromises that are inherent in a two-stroke.” He talks enthusiastically about the
ability to run Miller Cycle where the intake valve is left open longer than it would be in an Otto cycle engine and of sophisticated cylinder deactivation on demand, which he dubs ‘roaming’ cylinder deactivation. “It varies with the engine configuration, but you can avoid individual cylinders cooling down and giving you a hydrocarbon spike when you restart by running all cylinders, but skipping cycles as necessary, depending on power and torque demands.” Imagine, also, the potential of
linking the valve control unit (VCU) into topographical navigation system, so the power and torque demands to maintain a given vehicle speed can be predicted and precisely tailored for the local terrain and traffic conditions, to
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www.automotivedesign.eu.com May/June 2013
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