Ridin' the Wedge
Ridin' the Wedge
CW EXCLUSIVE
2008 S&S X-Wedge: Clearing the air for primetime
DON CANET
FOR A PERFORMANCE-MINDED, THIRD-GENERATION, FAMILYowned-and-operated company such as S&S-which has built a name making power and noise for decades-moving ahead
into a brave new world of tighter EPA mandates calling for cleaner and quieter exhaust emissions has presented a formidable challenge. While producing a wide range of hot-rod parts for American V-Twins continues to be a large segment of the Viola, Wisconsinbased company’s daily business, manufacturing complete engines has fed the heart and soul of the custom-bike market.
Forthcoming legislation has provided the handwriting on the wall, spelling the need for a clean-slate emissionscompliant engine. While S&S has enjoyed a lengthy run selling its VSeries Harley-Davidson Evo-style clone engines, the Milwaukee juggernaut’s team of feisty attorneys has made it quite clear that no such liberties shall be taken with its current patent-protected engine designs. This has only fueled S&S’s resolve to forge its own path with an all-new proprietary engine, one that preserves the traditional look, feel and performance its customers desire, while offering closed-loop electronic fuel-injection, reduced mechanical noise, improved performance potential, serviceability and durability.
In June of last year, Cycle World was granted an exclusive inside look at the S&S engine project, revealing the X-Wedge to the world in our January, 2007, issue. While Technical Editor Kevin Cameron toured every corner of the factory and interviewed various engineers charged with bringing X-Wedge to production, I got my feet wet riding the surrounding rural roads aboard an X-Wedge-powered Big Dog chopper and a more sporting S&S-built development mule. Unfortunately, rain washed our plan to conduct acceleration testing during the visit. Now, six months later, S&S has delivered one of its fleet of eight X-Wedge test hacks to the CW editorial offices for further evaluation.
So what makes this air-cooled, pushrod Twin unique? In the finest American tradition, the X-Wedge name is derived from a distinctive physical feature; in this case the wedge-shaped combustion chamber. The advantages of this design allow high compression with an almost flat-topped piston, offering a natural squish area less prone to detonation than traditional dome-piston hemispherical designs. The wedge shape allows the valve stems to run parallel to one another while naturally tilting outboard toward the cam-drive side of the engine.
Strong and simple automotive-style rocker arms actuated by pushrods that also run parallel to one another reach down to hydraulic roller lifters riding atop a clever three-cam configuration. A shared intake cam flanked by dedicated exhaust cams for each cylinder is the key to obtaining ideal pushrod alignment with the rockers above. Ducati lovers may find the X-Wedge’s serpentine belt cam drive old hat but should be envious of its targeted 50,000-mile service life and the knowledge that this free-spin engine design has adequate piston-to-valve clearance to avoid contact should a belt fail.
Use of belt-driven cams-rather than chain or gear-is one of several steps S&S has taken toward reducing mechanical noise. Plain bearings in place of traditional roller bearings have also reduced noise; even the X-Wedge’s 56-degree Vee-spread has played a large role here, doing away with the piston slap that results from the need to trim skirts for BDC clearance when punching out, say, a 45-degree Twin.
The S&S six-speed, Harley-compatible transmission that’s been around for some time uses helical gears throughout, which run quieter than straight-tooth cogs; so the last and perhaps most painful challenge S&S still faces is developing a quieter EPA-legal exhaust that offers the volume to maintain performance without detracting from visual appeal.
With all this talk of a socially conscious powerplant, I wasn’t quite expecting the bellowing exhaust note that assaulted my ears the first time I fired the test mule’s engine. A shout to the boys in very rural Viola provided an answer. “I apologize for not realizing this would present a problem,” offered project leader Scott Sjovall. “We're simply used to riding with loud pipes out here.” While a pair of S&S prototype TUV Euro 3-legal mufflers was headed our way, we proceeded to test the bike in all its offensive outlaw glory.
I found myself riding about town with an apologetic mindset, reluctant to twist the throttle much beyond a quarter-open to avoid unleashing the barking dogs within and risk bringing down the heat. Citizens have become fed up with obnoxiously loud bikes, leading to more and more cities on the West Coast issuing citations for noise violations. Heck, the mile-high city of Denver has recently raised the bar by imposing $500 fines on owners of bikes with non-stock exhausts!
Even idling at a traffic signal disturbed the peace-“Please ’scooze the ruckus ma’am.” Thankfully, with plenty of low-rev torque on tap, pulling away from stops didn’t require but a few hundred revs above the engine’s 1000-rpm idle speed, and I found no need to spin the engine much beyond 2500 rpm between shifts.
Riding in this mannerly fashion revealed a dire need for further refinement in off-idle response and low-rev fuel calibration. Sjovall suspects my conservative riding style had revealed a part of the fuel map that has yet to be fully programmed. While happy under moderate-to-hard acceleration, the engine exhibits the occasional sneeze out its intake when first cracking the throttle, which can result in a stall if the clutch isn’t quickly pulled in to give the engine a chance for recovery. A throatclearing throttle blip before taking off from a stop provided an effective, albeit loud workaround. Worse still, the hiccups often crop up while chugging along at a parking-lot pace.
Out on the open road, the situation improves as the X-Wedge rumbles along contently. Featuring a massive singlepiece crank claimed to damp vibration, the solidly mounted engine vibrates in a way reminiscent of earlier, non-counterbalanced Harley-Davidson Softails. The upper end of its vibration sweet spot is 2400 rpm, yielding 60 mph in sixth gear. At this speed, the pegs are dead-smooth and the moderate amount of vibration coming through the grips is livable. The mirrors buzz a fair amount, but it's still possible to discern what’s in the rear view. Picking the pace up to 70 mph sees 2900 rpm on the clock, fuzz in the mirrors and brings a substantial increase in crotchand finger-tinglin’ vibes. Spinning up near its 5700-rpm rev limit felt like it could register a reading at our local seismic center!
Our testbike’s 114-cubic-inch (I858cc) engine is a shorter-stroke version of the 117and I2l-cube variants slated for production when the XWedge goes on sale in October. There are even larger capacities to come, so it stands to reason vibes will increase, as well. While logic also suggests the chopper crowd doesn’t demand smooth-running refinement, it’s apparent that S&S views the X-Wedge as more than just a driving force for fattire specials.
To that end, S&S is now in the framebuilding business. Because X-Wedge engine mounts are non-compatible with frames designed to accept H-D motors, S&S will be offering this $2700 “hidden-shock” (read: Softail-style) frame, swingarm and oil-tank package to kitbike builders. Everything else needed to complete a build is currently available through the Harley aftermarket. Estimated cost of replicating the bike tested here is $25,000, putting it right in line with a turnkey Harley-Davidson CVO. For that kind of coin, we were anticipating some pretty stout performance out of this otherwise rather plain-Jane-looking platform.
With loud mufflers fitted, the engine produced 98 horsepower at 5500 rpm and 103 foot-pounds of peak torque at 4100 rpm, measured at the rear wheel on our dyno. Torque output comes in strong and early, reaching 100 footpounds by 3000 rpm and doesn’t fall below that mark until beyond 5000 rpm, a pretty generous spread if you can live with the booming exhaust. For comparison, an EPA-legal 103-inch CVO Fat Boy we tested in 2004 made 85 horses and 94 foot-pounds. Although we have yet to test a new 110-inch CVO, we would expect to see about 90 ponies and 100 footpounds.
Thundering through the quarter-mile, the 707-pound (without fuel) tester laid down a respectable 12.54-second/106.49-mph pass while taking 4.2 seconds to reach 60 mph. Its 126mph top speed also puts it in the realm of where a performance cruiser should be. Although we didn’t conduct acceleration tests with a quiet, law-abiding exhaust, we rolled the bike back on the dyno after swapping the free-flowing cans
for the prototype TUV muzzles. Even after logging enough miles to allow the closed-loop EFI time to acclimate to the change, the sneezing persisted and the idle became erratic. Dyno results showed there was now a sizable dip in torque at 2800 rpm, and about 17 horsepower and an equal amount of torque had been lost across the upper rev range. To our ears, the TUV silencers seemed notably quieter than what comes on even a stock Harley, having muted the Wedge’s barroom brawly beat to more of a sorority house pillow fight. What’s needed is something in between, please, S&S.
With the muffled exhaust and removable windshield installed, intake noise and valvetrain clatter were the dominant sounds reflected back to the rider. “We had hoped you wouldn’t take notice,” said Sjovall when I mentioned this. “Once we quieted other areas of the motor, valvetrain noise became more prevalent.” Sjovall’s team is currently running trials with alternate cam grinds featuring gentler ramps to bring the noise level down to their intended target. We were also told that with the final X-Wedge production parts now arriving from various vendors, the EFI programming team will redouble its efforts in the months ahead to sort out the fueling issues we experienced and develop a far more refined map.
What we really learned here was that S&S had provided us with a bike a bit too soon. But who can resist a taste of cookie dough or cake batter when the baker offers? With a little more polish, this admittedly rough pre-production engine holds plenty of promise. Designing an all-new, emissions-minding V-Twin these days is a tough task, be you Honda or Harley. But S&S is close. We expect to see the fully sorted X-Wedge propelling factory customs, speed-shop specials and homebrew hotrods well into the brave new future. U
