Meet the per­fect en­gine

Valve con­trol is fun­da­men­tally com­pro­mised on con­ven­tional en­gines. But that’s all chang­ing with the ar­rival of in initely vari­able valves. By Ian Ad­cock

CAR (UK) - - Tech -

IMAG­INE A VALVE con­trol sys­tem with­out com­pro­mises, one that isn’t crank-driven and doesn’t play by con­ven­tional rules. Such an en­gine would al­low in­fin­itely vari­able tim­ing on all its valves, in­de­pen­dent of one an­other, mean­ing it could ef­fec­tively tune it­self on the move, boost­ing power and ef­fi­ciency. It could also of­fer cylin­der de­ac­ti­va­tion, elim­i­nate a tur­bocharger’s waste­gate, switch be­tween four- and two-stroke cy­cles and even run as an in­ge­nious, very ef­fi­cient 12-stroke.

Cam­con, a Mid­lands-based firm, is work­ing on in­tel­li­gent valve ac­tu­a­tion (IVA), which is now at­tract­ing the at­ten­tion of big com­po­nent man­u­fac­tur­ers, and is pre­dicted to be in pro­duc­tion for main­stream cars within the next five years. Pro­to­types are show­ing a fuel con­sump­tion im­prove­ment of up to 7.5 per cent.

IVA em­ploys a four-phase ro­tary ac­tu­a­tor driv­ing a sep­a­rate camshaft for each con­ven­tional pop­pet valve. A desmod­romic link­age con­nects this camshaft to the valves. All as­pects of the valve tim­ing are in­de­pen­dently and in­fin­itely vari­able, with full feed­back con­trol, al­low­ing fea­tures such as max­i­mum open­ing po­si­tion shift­ing, lift-dwell re­turn, dou­ble and missed events, roam­ing cylin­der de­ac­ti­va­tion and con­trol of both com­bus­tion cham­ber swirl and tum­ble.

Be­cause it’s an ac­tive sys­tem, Cam­con is still dis­cov­er­ing the sys­tem’s po­ten­tial, as Cam­con’s Roger Stone ex­plains: ‘It could un­lock ho­moge­nous charge com­pres­sion ig­ni­tion [a very ef­fi­cient, diesel-like com­bus­tion process], and both the Miller and Atkin­son cy­cles re­spond well to IVA.’

And that 12-stroke sys­tem we men­tioned? In mo­tor­way cruis­ing, ev­ery cylin­der fires only ev­ery third stroke, which is po­ten­tially cleaner than cylin­der de­ac­ti­va­tion since there are no CO2 spikes as cylin­ders are re­ac­ti­vated.

DESMOD­ROMIC, SO VALVE ARE POS­I­TIVELY CLOSED AS WELL AS OPENED  NOSPRINGS ACTUATORS KEY TO IN­DE­PEN­DENT VALVE CON­TROL

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