Cycle News - Archive Issues - 1990's

The cast-aluminum crankcases of the 9O-degree V-twin wet-sump engine - the cylinders of which are rotated backwards about 30 degrees on the ~rankcase, to reduce the. wheelbase, yet 'provide space for front wheel deflection under braking (the new TLlOOO Suzuki has the same idea) - are vertically split, but with a third section removable at the rear, similar to. the new GSXR 600/750 Suzuki design. This permits rapid access to the gear-. box (six-speed on the XIR, five-speed on the Boss, with a wet clutch on both but with the option for a dry-clutch conversion for the racer): Hallam reckons that it should be possible to swap internal ratios inside 45 minutes at the race tracJe Great attention has been paid to minimizing crankshaft flex, as part of an overall objective of reducing power losses and vibration, which also sees an innovative torsional vibration damping system fitted to the engine, using a secondary crank-driven oil pump which feeds oil to a mechanical damper. The crank has two main roller bear.ings, with side-by-side paired conrods (titanium on the XIR road and race versions, steel on the Boss) running on slipper-type plain bearings - the only nonroller or ball bearings in the engine. The three-ring pistons are lighter than compatible slipper"type ones (e.g. Ducati), but are able to have a quite long skirt thanks to the choice of cOlmecting-rod length, to give good ring stability and minimize rocking and scuffing under extreme load. The innovative oil system sees the primary oil pump submerged in the wet sump, sitting below the oil level so there's no problem with priming, where it also acts as a low pressure scavenger. But the crankshaft also acts as a secondary oil pump, in turn reducing the necessary size of the primary one, a direct means of saving horsepower. The engine is primarily oil-cooled but partially air-cooled as well, via the finned cylinders which help lower temperatures enough that none of the prototypes, not even the racer, needs an oil cooler. Indeed, Hallam says oil temp is too cold at present. A set of three timing ge~s driven directly off the crank fulfill another of his objectives, which is to get a single set of components to do more than one job, if possible. "Simple is everything," he asserts. "I've tried very hard to keep thinking about the poor guy at the end of the line Jwho has to work on one of my engines. You ought not to have to be a rocket scientist to work on a motorcycle, so I've tried to reduce the number of parts as much as possible, also thereby saving weight, friction, power and manufacturing costs." So the timing gears both provide a trigger for the ignition function of the Motec/HH engine management system, and also drive the tWin toothed belts for the dohc camshaft drive. The 38mm . inlet/34mm exhaust valves (same sizes on all engines - titanium on the XIR, .steel on the Boss, operated by twin-lobe camshafts via 26mm buckets and shims) sit at a total included angle to each other of just 26 degrees, (12 'degrees on the inlets, 14-degree exhausts), with a single 10mm plug sitting centrally in the tricked-out combustion chamber design, which incorporates not only a full radial squish but also what Hallam calls Axial Targeted Combustion (ACT). 'This is a process I've developed over the past few years in superbike racing," he says. "It allows you to obtain large quantities of midrange and top-end torque, via a very small lens-type com- bustion chamber that delivers a very controlled burn and similar efficiencies to what you get on racing two-stroke engines, only in a four-stroke context." Valve guides also benefit from Hallam's expertise, this time in the area of metallurgy. "We've developed our own specification of titanium for t!)e valve guides," he says. "Our superbike customers get two seasons of racing out of a single set of titanium valves - material, and keeping the heat out of it are the answers." The bore and stroke of the XIR motor is 97 x 67.5mm, for a capacity of 997.6cc. "This is a little more stroke that most would expect," Hallam says. "But the conrod ratio allows this, without the usual cost of piston acceleration and deceleration rates becoming unaccept- able, but with the ad vantage of the torque increase." The Boss Power Cruiser motor originally started out 'with 105 x 80mm dimensions, for a capacity of 1385cc in the form in which 1 rode it. In this guise it ran as high as 10,000 rpm wifhout problems on the HH dyno, but slight bore distortion led Hallam to reduce the capacity slightly to 1353mm in preproduction form, with 102.5 x 82 mm dimensions, which offered extra cylinder-wall thickness and improved combustion efficiency. Indeed, compression ra tios are very Iowan all the bikes except the racer, indicating the efficiency of the top-end design. Though the XlR racer can run as high as 13:1, depending on the circuit, the Boss runs an 8.6:1 ratio and delivers 108.8 bhp at 7000 rpm at the rear wheel in 1385cc form as I rode it, while the XIR streetbike runs an 8.8:1 compression ratio, and is presently producing an almost unbelievable 140.6 bhp at 9500 rpm, again at the wheel, Hallam claims. "1 know this will seem improbable to many people," he says, "especially compared to what we currently know other bikes produce. But that's an honest power reading from a pretty stingy dyno, using a single induction 50mm throttle body with a very, trick manifold, no air cleaner, but a baffled street silencer, whieh was actually a stock Honda VFR750 unit. There's 'no real point in exaggerating, because once the bikes are out in public, people will ,be able to compare and contrast, anyway. We're just very, very pleased with the results of our development." As they might be - because, amazingly enough, that claimed figure is achieved with the 1000cc XIR engine stilL running with conventional valve springs, not the revolufionary pneumat- (Right) While outside parts sources are kept to a minimum on the Hunwick Hallam, the 41mm Inverted fork comes from WP and the brakes are by Brembo. (Below) Sport and speed: The engine on the left is the 1385cc used in the Power Cruiser, the one on the right the 1000cc superblke engine to be used in the X1 R. Both are 90degree V-twins with four valves per cylinder. ie-valve operation Paul Hallam has designed for the ra£e version, which will also be available on the street bike - thus meeting the new FIM superbike regulation introduced this season, requiring just that. Today's three-liter Formula 1 racing cars revving to 17,000 rpm and more all have pneumatic valve systems, which are nothing more than an alternative, non-mechanical method of desmodromie (meaning positive operation) valve closing as well as opening. Ducati already has proved the benefits of this in clinching six World Super~ bike titles in the past seven years, but it's taken Hunwick Hallam to finally introduce a more-modern, equally advantageous non-mechanical method of achieving the same thing, namely the ability to chase more horsepower further up the rev scale without suffering valve float, as well as to eliminate the mechanical'losses delivered by valve springs at low rpm. But Hallam's gone one step further: he's actually incorporated the chambers for the nitrogen gas which operates the system into the cylinder head castings, and has made it a fully sealed system, so that gas is not discharged into the atmosphere. This means there's no need to strap on a heavy nitrogen tank somewhere on the bike, and worry about when it'll tun out. Moreover, Hallam's pneumatic valve operation is a variable-pressure system, delivering improved horsepower at all rpm levels, not only at the top end. The first time a Hunwick Hallam XIR races with the pneumatic system in public, a new chapter in motorcycle performance engi,neering will have been opened - one that'manufacturers in Japan and, perhaps, especially Europe will find hard to ignore. The XIR's pneumatic valve system will be controlled by the Motec/HH multi-sensor computerized engine management system, a 100 percent Australian-developed package which incorporates full sequential fuel injection. On the Boss (and Rage), a single 45mm throttle body feeds both cylinders via a siamesed intake, with a single injector per cylinder: on all engines, the 45degree inlet angle delivers a substantial degree of downdraft, when combined with the 90-degree V-twin cylinder configuration. , On the X1R Superbike in both road and race forms (as required under superbike regulations), the same twostage injector system is used, with overhead injectors variably phased relative to engine load and speed. Mapping this must not have been the work of a moment. The race version will, however, have an extra dimension to the ems, namely the provision of a multi-channel teleme-, try system incorporating a data-logger. Ignition comes via spark plug-top coils of a type seen so far only in car racing, with each cylinder's coil incorporated in the plug cap. ' This incredibly avant-garde engine doesn't really sit in any kind of chassis: it just has everything else hung on it. The front end is attached to it via an adjustable steering head cartridge, which allows the head angle' to be varied from the Boss' kicked-out 300 to the XIR's stock 23.50 Simply by using different attachment points. Altering tlle steering geometry in the race paddock will be quickly done; and same thing for'the wheelbase, which on the XIR at present is 1410mm, but can be brought as sh'ort .as 1320rnm if you really insist. An WP upside-down fork is used on all the bikes, and the innovative rear suspension design, too. This has overtones of'another Australian bike, the Ducati-powered VeeTwo Alchemy, as well as the Britten, in terms of the forward, offset shock location and the long rod used to operate it via a rising rate link from the swingarm. In prototype form without street equipment, the XIR weighs 356 pounds halfdry, Hallam says. Since that's the current superbike minimum weight limit, sounds like they have no weigM problems. To top off this remarkable engineer-

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