En­gine man­age­ment

Motor Equipment News - - CONTENTS -

There’s life in the old dog yet. That’s the news from a Bri­tish com­pany called Cam­con Au­to­mo­tive, which has de­vel­oped a sys­tem with the po­ten­tial to take the con­tin­u­ally ma­ligned in­ter­nal com­bus­tion en­gine (ICE) to new heights of ef­fi­ciency, both in terms of fuel con­sump­tion and emis­sions.

Cam­con’s In­tel­li­gent Valve Ac­tu­a­tion (IVA uses elec­tric ac­tu­a­tors to di­rectly trig­ger each valve in­di­vid­u­ally, and in do­ing so, can cre­ate dif­fer­ent sce­nar­ios within the en­gine de­pend­ing on the driver’s needs.

Roger Stone, Cam­con Au­to­mo­tive’s chief en­gi­neer, says the sys­tem is equally ap­pli­ca­ble to petrol and diesel, and can be used to, in ef­fect, turn the en­gine into not one, but a mul­ti­tude of dif­fer­ent en­gines, all within one crank­case and cylin­der head.

For in­stance, the lat­est buzz is HCCI (Homeoge­nous Charge Com­pres­sion Ig­ni­tion) which ef­fec­tively com­bines the ben­e­fits of both diesel and petrol en­gines by com­press­ing petrol to the point where it ig­nites with­out a spark.

This re­sults in a much more ef­fi­cient en­gine, with low NOx, and Mazda has just re­leased its lat­est Skyactiv-X en­gine which em­braces this tech­nol­ogy, us­ing vari­able spark ig­ni­tion for control.

“Po­ten­tially it’s (IVA) an en­abler for HCCI, for ex­am­ple, at lower speeds, we are fast enough to get more than one valve cy­cle in dur­ing a 720 de­gree pe­riod so we could have the nor­mal ex­haust event fol­lowed by an ad­di­tional, much smaller, event dur­ing the in­duc­tion stroke to in­duce the vol­ume of ex­haust rad­i­cals re­quired,” Stone told Au­to­mo­tiveDe­sign Magazine.

The same en­gine could also be run as a two-stroke be­cause there’s no link be­tween the valves and the crank, mak­ing it pos­si­ble to open the valves ev­ery stroke be­low 3,000rpm. In­stead of the fir­ing or­der be­ing 1, 3, 4, 2 as in a nor­mal Otto four-stroke cy­cle, cylin­ders 1 and 3 could be on a power stroke while 2 and 4 are on ex­haust (and vice versa), re­sult­ing in more power and torque for short pe­ri­ods.

An­other as­pect which can be pur­sued within an IVA en­gine is the Miller Cy­cle. A Miller Cy­cle en­gine, patented in 1957 by Ralph Miller, is a su­per­charged ver­sion of the Atkin­son Cy­cle en­gine used by Toyota in its hy­brids, and which de­lays the clos­ing of the in­take valves dur­ing the com­bus­tion stroke.

How­ever, there has been some jux­ta­po­si­tion of the names “Miller Cy­cle” and “Atkin­son Cy­cle” by some man­u­fac­tur­ers; suf­fice to say that when de­scrib­ing the Miller Cy­cle and IVA, Stone is re­fer­ring to the abil­ity of IVA to keep the in­take valve open longer than it would be in an Otto cy­cle en­gine.

At the same time there’s the pos­si­bil­ity of what he de­scribes as “roam­ing” cylin­der de­ac­ti­va­tion – de­ac­ti­va­tion on de­mand.

He says this 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 de­pend­ing on power and torque de­mands. Again, be­cause the valves are not linked to the en­gine all valves can re­main open dur­ing de­ac­ti­va­tion, which elim­i­nates pump­ing losses.

So far Cam­con’s work on IVA has been de­vel­oped in col­lab­o­ra­tion with Jaguar Land Rover, with 1,000 hours of test­ing on a mod­i­fied four-cylin­der twolitre In­ge­nium en­gine; it showed 7.5 per­cent bet­ter econ­omy than the stan­dard In­ge­nium en­gine. So how does it work? The ba­sis for Cam­con’s IVA is a de­vel­op­ment of its pro­pri­etary Bi­nary Ac­tu­a­tion Tech­nol­ogy (BAT) in­vented in the late 1990s by Wla­dys­law Wyg­nan­ski.

The IVA em­ploys a Des­mod­romic pos­i­tive open­ing and clos­ing mech­a­nism for the valves, but the break­through for IVA was the Cam­con bi-sta­ble ac­tu­a­tor, a very low en­ergy and fast 12V elec­tric ac­tu­a­tor.

Un­like a so­le­noid, it has two zero-power sta­ble states whereas a con­ven­tional so­le­noid has only one, re­quir­ing power all the time and an ex­tra latch­ing mech­a­nism at the ex­treme of move­ment.

The Cam­con Bi­nary sys­tem is fired from one end to the other with no sep­a­rate latch­ing and no power ex­cept dur­ing the switch­ing op­er­a­tion.

Nat­u­rally, be­cause it’s more com­plex than a con­ven­tional OHC sys­tem, IVA is more ex­pen­sive, but Cam­cor is con­fi­dent ramp­ing up man­u­fac­ture will re­sult in prices sim­i­lar to the cost of a diesel injection sys­tem. And us­ing just some of its fea­tures could cut th­ese costs fur­ther.

“You could have one per valve or just run IVA on the in­lets only with a con­ven­tional ex­haust camshaft. Al­ter­na­tively you could use a tan­dem ar­range­ment so there’s one IVA ac­tu­a­tor shared be­tween a pair of in­let valves,” says Stone. “Or, maybe go the whole hog on the in­lets with in­di­vid­ual valve ac­tu­a­tion and use a tan­dem ar­range­ment on the ex­hausts.”

And, nat­u­rally, there are sav­ings to be made in the parts you no longer need, such as the tim­ing gear and camshaft drive.

So when is it all go­ing to see the light of day – or more im­por­tant, the show­room?

At the moment Cam­con is look­ing for in­ter­ested par­ties, par­tic­u­larly in the East, where there is not the pres­sure to­wards elim­i­na­tion of the ICE as there is in Europe.

“It would be nice to think that we could move it for­ward quickly enough to be in ser­vice, with some rea­son­able ex­pe­ri­ence, be­fore the 2020 reg­u­la­tions come in, maybe 2018. It all de­pends on what goes on from here,” says Stone.

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