EX­PLAINED

TRICKY TECH IN SIM­PLE TERMS

Wheels (Australia) - - Contents -

ECU calls the shots with these valves; the crank has noth­ing to do with it

What is it?

A rev­o­lu­tion­ary form of com­bus­tion en­gine valve ac­tu­a­tion that not only re­moves any phys­i­cal con­nec­tion to the crank­shaft, but also en­ables in­fin­itely vari­able and in­de­pen­dent valve tim­ing. Dubbed In­tel­li­gent Valve Ac­tu­a­tion or IVA, the en­gine in­no­va­tion is the work of Cam­bridge-based tech firm Cam­con.

How does it work?

Un­ortho­dox val­ve­train sys­tems have come and gone in­clud­ing pneu­matic, hy­draulic and so­le­noid types, but the Cam­con so­lu­tion uses the com­pany’s elec­tri­cally op­er­ated ‘bi-sta­ble ac­tu­a­tor’. Un­like a so­le­noid, which has an en­er­gised po­si­tion and a non-en­er­gised po­si­tion, Cam­con’s de­sign fea­tures two nonen­er­gised states. When the unit is en­er­gised it lifts the en­gine valve into the open po­si­tion – when the unit is de-en­er­gised the valve stays open. When the unit is sub­se­quently en­er­gised in the op­po­site di­rec­tion, the valve snaps closed. The point at which the valve opens and closes is gov­erned en­tirely by elec­tri­cal sig­nals, not the po­si­tion of a camshaft, crank­shaft or spring, and power is not re­quired to hold the valve in ei­ther the open or closed po­si­tion.

Why does it mat­ter?

The ad­van­tages of the IVA sys­tem are ex­ten­sive, in­clud­ing the ben­e­fits of re­duced me­chan­i­cal com­plex­ity. Valve springs, camshafts and the chains or belts to con­nect them to the crank­shaft are all re­dun­dant, re­sult­ing in a sim­pler sys­tem, which has the po­ten­tial to be lighter, cheaper and more durable. But the IVA’S real party piece lies in valve tim­ing. The prin­ci­ple al­lows any in­di­vid­ual valve to be opened and closed at any time and in­de­pen­dently of any other cylin­der. That means it’s pos­si­ble to run an en­gine as a high-power per­for­mance unit with huge over­lap and du­ra­tion, and then as a su­per­ef­fi­cient Miller-cy­cle en­gine, or in any vari­a­tion in be­tween. The com­pany says it can even run its pro­to­type four-cylin­der as a con­ven­tional four-stroke or as a two-stroke sim­ply by switch­ing the man­age­ment pro­gram.

While elec­tric propul­sion con­tin­ues to chal­lenge the in­ter­nal com­bus­tion era, Cam­con’s rad­i­cal in­no­va­tion could pre­serve com­bus­tion power into the fu­ture. And it could make the hor­ror show of a snapped cam belt a thing of the past too.

Valve ac­tu­a­tor Com­pact elec­tronic con­trol sys­tem Con­ven­tional pop­pet valve

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