Indian’s “Challenger” went 180 mph at Daytona this 12 months. That’s 10–12 mph quicker than a 12 months in the past. Issues are heating up quick on this class, which has turn out to be American manufacturing unit racing. At MotoAmerica’s Laguna Seca nationwide on the weekend of July 10, the highest Bagger lapped faster than Eddie Lawson did on Yamaha’s fearsome two-stroke YZR500 within the 1988 US Grand Prix.
This stuns and surprises us, making this MotoAmerica’s hottest class. It’s the very last thing we count on from heavy, long-wheelbase bikes designed for comfortable interstate touring or chugging to Sunday membership breakfasts. However we like to be stunned.
Early this spring I attended Harley-Davidson’s pre-Daytona baggers race team test at Podium Membership raceway, southeast of Phoenix, Arizona, to see the brand new racing class. Then I used to be invited by its nice rival, Indian, to MotoAmerica’s Laguna Seca nationwide close to Monterey, California.
There, in Baggers Race 1 on Saturday, I noticed O’Hara and H-D’s Kyle Wyman carve one another up in shut quarters, flicking (Sure! Flicking!) down Laguna’s well-known Corkscrew, then each dropping the entrance coming into flip 11, giving the win to Hayden Gillim on a Vance & Hines H-D. O’Hara one way or the other righted his 620-pound machine and restarted shortly sufficient to complete fourth!
The 2 constructing blocks of that 180 mph Daytona velocity are mighty acceleration off the chicane and the facility to drive the obligatory 29-inch-wide entrance fairing by way of the resisting air (sportbike fairings are 19–21 inches large). Acceleration? As a result of these bikes have big V-twin engines (Indian’s liquid-cooled PowerPlus 60-degree V-twin is 108ci/1,825cc) and long wheelbases over 65 inches, they’re like 2022 MotoGP bikes with their variable ride height systems on minimal. Being lengthy and low turns each into dragsters. I used to be instructed that on sure tracks the Baggers obtain faster sector accelerations than Superbikes.
Why the 60-degree vee angle, when conventional Indians had 42 levels? As such large-bore pistons strategy backside heart (BDC) the vee angle should be giant sufficient to stop skirt-to-skirt clashing.
I had a protracted dialog with S&S Chief Engineer Jeff Bailey, who’s supervising engine growth (and as I’d quickly see, pitching in as a line mechanic when wanted). After I repeated what’s typically stated concerning the class, that horsepower is someplace between 155 and 165, he stated, “Extra.”
Extra To Come
If we think about that “extra” is 170, we will mix that with the 7,700 rpm rev restrict MotoAmerica provides Indian to search out that this modified engine breathes and burns properly sufficient to attain a 162 psi stroke-averaged internet combustion strain (aka “BMEP,” for brake imply efficient strain). That quantity, about 80 % of what’s achieved in MotoGP or World Supers, signifies that this engine is at a good however average degree of growth, implying extra to return.
Working this engine to 7,700 rpm with its practically 4-inch stroke (96.5mm) leads to a median piston velocity of 4,880 ft per minute and a peak piston acceleration of 4,020 G. Evaluate the latter determine with the 7,000 G commonly achieved in redlined 600 Supersport engines, or with the 11,000 G in MotoGP engines at 18,000 rpm.
Harley-Davidson’s bigger 131-inch engine is given a rev restrict of seven,000. Earlier than higher rpm limits have been set, engines have been wrecked by over-revving however reliability now appears strong. Though inventory Challenger bore is 108mm, for this class it’s 110mm, giving a 112ci displacement.
Sitting to at least one aspect in Indian’s work space was a 9-foot-long wheeled engine cupboard containing two fresh-off-the-dyno engines, totally dressed and prepared to be used. At one finish of the cupboard was a set of handlebars with a hand brake.
Evaluate Indian’s engine with Chevy’s famed 427 V-8, whose dimensions have been a near-identical 108 x 95.5mm. If the KOTB-modified Indian makes 170 hp, 4 of them mixed right into a V-8 would make a perky 680 hp.
On inventory Challenger engines there are two vertical consumption pipes whose oval cross part is equal to 2 52mm spherical holes. Consumption space was restricted by the part of the solid principal body beam instantly above the cylinder heads however the modified engine wanted extra air. The group elected to bypass the body beam by making a CNC-ported and additive-manufactured proper angle bend served by a large 78mm throttle physique on the fitting aspect. Regardless of losses doubtless related to the bend, this gained 10 or extra horsepower.
Growth is all the time “triaged”: Early within the course of, it’s the massive objects providing giant good points that get tackled first. Because the undertaking matures, the main target can shift to smaller issues. That is an thrilling time, because the expertise is visibly altering from race to race.
Cam lift and timings aren’t regulated on this class, so when these engines are began they sound like V-8s with lengthy cams. They ka-thump ka-thump till warmup evaporates extra of the injected gasoline, bringing within the second “voice.”
As a result of this can be a trendy all-plain-bearing engine, its life relies upon upon dependable supply of air-free strong oil 100% of the time (dangerous issues occur when air will get into plain bearings). However being initially designed for the low mounting place of a touring engine, it was not designed with a deep sump as discovered on Superbikes. Bailey instructed me there’s a cavity behind the crankshaft into which the scavenge oil is pumped, assuring that the strain pump’s consumption will stay submerged.
As in sportbike engines, Challenger’s crankshaft is a one-piece forging having a single crankpin carrying the 2 connecting rods aspect by aspect somewhat than in a single airplane in fork-and-blade style. For that reason its separate Nikasil-plated cylinders are offset by the thickness of 1 rod.
Primary drive from crank to gearbox is by gear, and drive to the rear wheel is by an S&S chain conversion.
In early growth it was discovered that the crankshaft flung off too little oil to ensure gearbox lubrication, so oil jets are supplied (there are additionally piston-cooling oil jets). Just like the two-speed Indians that completed 1-2-3 on the 1911 Isle of Man TT, this six-speed gearbox is shifted by mild dog-rings somewhat than by sliding the substantial gears themselves (one key to fast shifting is to cut back the overall mass that the rider should transfer when altering gear).
Chains drive single overhead cams in every head, initially working four valves per cylinder by forked rockers carrying compact hydraulic clearance adjusters. S&S present billet rockers with mechanical lash adjustment, eliminating the mass (and a potential “pump-up” rpm restrict) of the hydraulics.
Shaping the Torque Curve
When this engine was initially conceived its torque curve was deliberate to be “rainbow-shaped”—emphasizing midrange acceleration important for on-ramps and passing. That is in distinction to what was lengthy conventional for such bikes—the “lean-to” torque curve of older two-valve big-inchers—with peak torque on the backside, reducing as engine velocity climbs, and at last wheezing out approaching 5,000 rpm.
As with every trendy engine, PowerPlus torque curve shaping is achieved by a mixture of port and valve sizes (in what rpm vary will the consumption velocity finest for cylinder filling happen?) plus intake port downdraft angle (how will the kinetic vitality of the consumption circulation be divided between the 2 duties of cylinder filling and the era of combustion-accelerating tumble motion?).
Compression and Head Temperature
Cylinder heads on Indian’s KOTB engines are CNC-ported. Inventory compression ratio of 11-to-1 displays the worth of liquid-cooling, however as a result of the competing 131-inch pushrod Harley circulates cooled oil between its paired exhaust valves, it most likely doesn’t undergo as a lot from excessive head temperature as a pure air-cooled. Compression ratio might due to this fact not be that completely different between the rivals. Most torque is achieved by operating the very best compression ratio potential with out knock on the gasoline supplied.
The gasoline on this case is VP’s T4, characterised as a pour-in substitute for pump gasoline. It’s lead-and-ethanol-free however does include the oxygenate MTBE.
The exhaust headers start with additive-manufactured stainless items becoming a member of the top ports to cut-and-welded head pipes that merge into a big high-mounted and horizontal collector. Every cylinder has its personal oxygen sensor, permitting it to be tuned as a “separate engine,” with its personal fuel and spark maps. The big exhaust collector introduced vital good points. As a result of the engine is large and initially mounted fairly low, it’s tough to rearrange for equal-length header tubes and nonetheless stow the collector underneath the right-hand footpeg. Once more, as a result of this engine was born to tour, it was designed “backward”—with the compromise falling on the exhaust system (within the type of sharply curved exhaust ports) somewhat than on the chassis.
On Friday I realized that the engines had just a few new components on them not tried earlier than, however they have been solely an ignition rotor cowl and first cowl, each in low profile for cornering clearance.
Tyler O’Hara’s crew chief Al Ludington (who was at American Honda Racing within the Miguel Duhamel years) stated the riders sometimes use 5 of the six transmission speeds: when you ignore first, the ratio of second to sixth resembles a correct roadrace trans. However from first to second there’s a whopping 47 % drop in engine rpm!
The weekend confirmed that Indian definitely has aggressive energy however that Harley might in the meanwhile have extra refined management over theirs. Ludington summed up by saying, “On a transparent observe we will do the lap occasions, however in a race there will be one other bike blocking you.” He famous that nook exit and acceleration are already good. The current issues are in braking and nook entry. He additionally stated, “The bike responds in a different way to the rider in right- and left-handed corners.”
When a motorcycle is capably ridden close to its grip limits, small enhancements in engine throttle connection and smoothness can have giant results. Riders on the 2023 MotoGP Ducati communicate of such enhancements over the earlier 12 months’s software program. In racing, time, funding, and assets are all the time in disaster. All the pieces is a race—winter growth, spring testing, and each apply in season.
Take note of this racing class as a result of it has the complete consideration of main American firms. It’s a fast-advancing demo of all of the methods of racing growth and rider versatility being utilized to a category of motorbike nobody ever imagined on a racetrack.