CLOSER TO THE PER­FECT EN­GINE

Valve con­trol is set to change with the ar­rival of in­fin­itely vari­able valves

Motor (Australia) - - FRONT END. PACE NOTES -

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 UK-based firm, is work­ing on in­tel­li­gent valve ac­tu­a­tion (IVA), which has big com­po­nent man­u­fac­tur­ers in­ter­ested, and is pre­dicted to reach main­stream pro­duc­tion within five years.

How does it work? IVA em­ploys an in­de­pen­dently driven camshaft for each con­ven­tional en­gine valve via a desmod­romic link­age. All as­pects of the valve tim­ing are in­de­pen­dently and in­fin­itely vari­able, with full feed­back con­trol, al­low­ing valve lift, du­ra­tion, and tim­ing to be adjusted in­de­pen­dently of each other. In other words, a lot more than cur­rently pos­si­ble with crank-driven camshafts.

Be­cause it’s an ac­tive sys­tem, Cam­con’s Roger Stone ex­plains: “It could un­lock ho­mo­ge­neous charge com­pres­sion ig­ni­tion (a very ef­fi­cient, diesel­like com­bus­tion process) and both the Miller and Atkin­son cy­cles re­spond well to IVA.”

Work­ing on the in­let cam side only, it has im­proved a Jaguar In­ge­nium en­gine’s ef­fi­ciency by 7.5 per cent, and a non-VVT en­gine’s by 10.5, with room for fur­ther im­prove­ment in var­ied con­di­tions.

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. Nifty.

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