Photography by Dean Groover...
Photography by Dean Groover (www.DeanGroover.com)
Picking an exhaust system for your motorcycle involves science, art, and luck, at least if you are shopping for a pipe for a Yamaha Road Star.
Bikers are a funny breed. We like to gather in groups, then try to be individuals within the flock. Yet for all our attempts to forsake the herd mentality, we tend to follow preordained patterns when in a crowd. For a quick lesson in group dynamics, go to any cruiser watering hole and observe the activities. In a ritual not too different from the dog greeting of sniffing each other's butts, riders circle strangers' motorcycles to see if they are friend or foe. If they find something that puts them at ease, hackles relax and much tongue wagging ensues: "Hey, nice pipe. I was thinking about getting one. What does it sound like?"
After a week in Daytona Beach repeatedly watching the above exchange -- one usually followed by the throttling of some poor unsuspecting engine -- we felt we were well prepared to conduct an exhaust-pipe comparison. What we weren't prepared for, however, was the difficulty we'd have acquiring pipes for our long-term Yamaha Road Star. Since adding an aftermarket pipe is the single most popular modification cruiser riders make to their machines, we should have -- in retrospect -- been prepared for the incredible appetite for exhausts generated by Yamaha's fast-selling large displacement cruiser.
When we contacted pipe manufacturers, we told them we were using a Road Star to conduct an aftermarket exhaust test that would be judged on looks, performance and street-reasonable sound. Based on those considerations, manufacturers were free to send us anything they wanted. Surprisingly, a few of the major players in the aftermarket were unable to supply systems by our deadline since consumer demand had outstripped their supply. Notably, Cobra and Vance & Hines are absent from this test -- a pill that is doubly difficult to swallow since Vance & Hines just announced a new 2-into-1 Pro Pipe that could be a performance leader based on the buzz we've heard in the industry. Other manufacturers that were able to actually deliver pipes also had to go through great lengths to deliver them by our deadline. Bub (which also has a cool 2-into-1 Road Star pipe), after originally saying there wasn't a pipe available for our test, was able to participate because a pipe due to be shipped to a paying customer was slightly dented and, therefore, failed quality control shortly before our test date. Hard-Krome pulled a pipe and slip-on off its assembly line for an overnight, rush chrome job in order to hand-deliver them to our test site. It sounds like Road Star owners are really shaking up the aftermarket!
Testing One, Two, Three...
Our testing procedures were based on those we used in our last exhaust pipe comparison (February 1997). We enlisted the services of Craig Erion of Two Brothers Racing and his Factory EC997a eddy-current rear-wheel dynamometer. Each pipe would be mounted, run on the dyno, ridden on the street, and measured with a decibel meter. Our long-term Road Star was equipped with a Baron's Big Air Kit and revised jetting (175 main jet, 35 pilot jet, and clip position of four). Although Baron also had a slip-on system in the comparison, we felt that having the proper jetting for the intake kit was important. (No changes to the jetting were allowed for any pipe once this off-the-rack jet kit was installed.) A Dynatek Dyna 2000 ignition module set at curve three and a 5250 rev limit (to facilitate getting dyno readings at 5000 rpm) completed the modifications. All tests were run with Chevron Super Unleaded gasoline.
The sound tests were conducted in two stages. The static test incorporated the AMA sound standard of holding the sound meter 20 inches away (measured at a 45 degree angle from the exhaust exit) with the microphone facing away from the pipe. As with all previous exhaust tests conducted by both Motorcycle Cruiser and our sister magazine Sport Rider, 104 decibels on the A scale (dbA) were set as the street-reasonable limit for noise. For the drive-by test, we rode the bike past the sound meter at a distance of 12 feet at 45 mph in second gear. Three passes were made and the value recorded was the average of the three runs.
A Dyno is a dyno, right? Wrong.
Dyno testing at Two Brothers...
Dyno testing at Two Brothers Racing. See the charts below.
Every time we list dyno numbers in an article, we get e-mail saying something like: "You guys don't know what you're doing. My Honzukamasaki VSX-1700 puts out 154 horsepower on my buddy's dyno..." Similarly, every time we post dyno numbers we say something to the effect of: "The horsepower figures generated by a dyno are valid for that bike on that dyno on that day. Different brands of dynos will generate different numbers. So, when considering the results of this test, look at the percentage of change instead of directly comparing these numbers to another company's dynos."
Craig Erion of Two Brothers Racing has been working closely with Factory Pro Tuning -- the developer of the Factory Eddy Current Dyno's software -- to arrive at a conversion factor to allow a semi-direct comparison between the Factory dyno's numbers and those of the Dynojet dyno commonly seen in shops around the country. The Factory dyno's current generation software reads about 11 percent lower than Dynojet models.
To test this theory, take our Road Star's peak output of 55.4 horsepower in this test (with the Roadhouse pipe, Baron's Big Air Kit with slightly altered jetting and Dyna 2000), add 11 percent, and compare the result to the numbers in April's "Playing with Fire" Road Star hop-up. Our trusty calculator reads 61.5 horsepower. Our previous article reported 61.0 horsepower -- a minor difference considering the new jetting. So, if you must compare the numbers generated in this test, don't forget the conversion of 11 percent. And stop complaining.
We've divided the testing into two categories. Slip-on systems often cost less and are easier to install than complete exhaust systems. Full systems offer the advantage of having the header matched to the breathing capacity of the canister(s). Either system will usually be lighter than stock and produce more power. Unfortunately, many systems resort to excessive noise to produce the extra power. Part of the problem is in cruiser styling constraints. Drag style pipes do not give exhaust developers much room to include effective baffling. In these situations, most manufacturers resort to louvered-core baffles -- which are less effective than the more current technology of perforated core. However, perforated core baffles require large canisters -- such as those seen on many sportbike systems -- to reduce noise while still delivering good power. But, some pipe manufacturers have more success at reducing excessive noise than others while staying within cruiser fashion requirements.
Baron Big Nasty Slip-On
This uniquely styled 2-into-1 megaphone slip-on features a 1.75-inch baffle. An optional inversion kit allows one of three baffles ranging from 1.50 inches to 2.00 to be inserted into the slip-on for tuning of noise and power. This straightforward, easy installation only took 25 minutes. The slip-on produces a deep, throaty note at idle that is arguably the nicest of the slip-ons. However, in the static test the decibel meter registered 106.1 -- way above our 104.0 limit -- and was the loudest of the slip-ons we tested. The drive-by test ranked the volume in the middle on the street, at 84.1 dbA. The Big Nasty churned out 54.1 horsepower and 87.5 foot-pounds (ft-lbs) on the dyno -- that's best and second best of the slip-ons, respectively. The street ride highlighted the slip-on's improved throttle response over stock. The engine pulled cleanly at all throttle openings and throughout the rev range. Deceleration with closed throttle produced some backfiring that may be able to be tuned out with some more jetting work. The junction of the two headers yellowed slightly during the extreme loads of the dyno testing. We did not drag the slip-on while cornering in our street test. With the exception of the excessive noise, the $295 Big Nasty slip-on worked well and was the lightest of the three we tested, weighing in at 9.7 pounds. The smaller baffle included in the $60 inversion kit might reduce the noise to a more socially conscious level.
Hard-Krome Drag Slip-Ons
These drag style slip-ons installed easily in 15 minutes -- although we did have to fiddle with the lower canister to get it to match up with the stock header's heat shield. The resulting look of the pipe is true to drag-pipe styling with a flawless chrome surface. Unfortunately, this type of canister doesn't allow much room for baffles of any kind. At 105.9 dbA, the sound, though not the loudest, had a harsh raspy sound that neither of the other slip-ons exhibited. On deceleration with a closed throttle the top canister sounded like something was loose and rattling in it. After inspecting the canister, we determined that the noise was reverberation within the rear cylinder's pipe. Compared to the other slip-ons, the Hard-Krome drags were down on power, delivering a peak of 50.8 horsepower -- 1.0 horsepower lower than stock -- and a 6.0 ft-lb increase to 86.7 ft-lbs. In the street portion of the test, the lack of power was apparent in the upper portion of the rev range, while response off the line was improved slightly. Ground clearance was not impeded in any way. The chrome did not yellow or blue during our test, thanks to Hard-Krome's double-walled construction. Tipping the scales at 10.6 pounds, Hard-Krome's Drag Slip-ons retail for $200.
Samson Rolled Edge Slash Cut Slip-Ons
Bolting on in only 10 minutes, the 10.6-pound Samson 2-into-2 canisters have three-inch openings that give the impression of wide-open pipes. Hidden inside the mufflers, a louvered core keeps the sound level down to a reasonable 103.1 dbA while allowing the engine to churn out 54.0 horsepower. Although the slip-ons missed the top horsepower number by 0.1 horsepower, the Samsons brought home the big torque numbers with 88.0 ft-lbs. The rolled-edge exhaust outlets from which the canisters get their name have a unique look. The finish is good, but a slight discoloration of the chrome appeared at the front of the canisters after the dyno runs -- no doubt due to the extra heat generated while strapped to the dynamometer. In the street course, power delivery was hiccup-free. The lower canister touched down in corners after the floorboard dragged -- slightly later than the OE system. The exhaust note is deep with a slight high pitched "attack" at the onset of each pulse. Closed-throttle deceleration didn't result in backfires. The best combination of power and neighborly sound levels in this slip-on trio can be purchased for approximately $349.
Bub Enterprises 2-2 Billet Cone System
We were struck by the style of Bub's 2-into-2 cone exhaust when it began cropping up on custom bikes. Other cruiser enthusiasts must feel the same way, since the only example of the two systems the company makes for the Road Star (the other one is a slick 2-into-1) available was blemished and didn't have a heat shield. For the record, Bub pipes feature Guard Dog 220 degree (as in degrees of a circle) chrome heat shields that should keep the blues away. Bolting on the 2-into-2 system took 30 minutes, but heat shields will add time to that total. The conical canisters and their billet end caps give the pipes a different look and were chosen as the best looking in our survey. The exhaust note has a less bassy tone than the others with more high-frequency overtones. Although the system didn't sound as loud as some of the others, the decibel meter registered 105.1 in the static test and the highest reading of all the pipes (92.0 dbA) in the rolling test. The 18.4-pound pipes trotted out 52.4 peak horsepower and 86.6 ft-lbs of torque. During street testing, the power delivery was strong at most throttle positions except full throttle at low rpm. We suspect that this pipe would have benefited from slightly leaner jetting due to its narrow head pipes. In right-hand turns, the pipe drags front and rear just after the floorboards. The Bub pipes carry a $495 retail price.
Hard-Krome Double D Straights System
These are the biggest, fattest pipes we've ever seen. Hard-Krome's double-walled construction wraps a 2.75-inch-diameter outer pipe around a 1.75-inch inner, effectively isolating the pretty dual nickel chrome exterior from the hot interior. Since the two pipes are single-piece construction, bolting the pipes to the headers and their proprietary bracket only takes 30 minutes. We knew the sound meter was going to have a field day the moment we thumbed the starter. Registering 107.1 dbA in the static test and 87.9 dbA rolling -- for the loudest and second-loudest measurements respectively of this comparison -- the Straights still surprised us. When strapped to the dyno, the Double Ds generated some more big numbers with the number two horsepower score at 54.5 horsepower. Torque anted up with 87.0 ft-lbs, the best of the full systems. From the get-go, the power was apparent on the street without the backfiring of some of the other pipes. However, ground clearance was limited to the point where the floorboard cannot touch the ground. Riders should be careful until they learn their bike's reduced cornering limits. The Straights weigh 29.0pounds, which was expected, given their beefy appearance. Rustle up a set of Double D Straights for $400.
Jardine Slash Cut System
Cruiser pipe designs don't get much more classic than Jardine's Slash Cuts. The 2-into-2 pipes feature 1.75-inch, single-walled head pipes feeding into mufflers with 1.5-inch louvered baffles. Our system arrived with optional full-length heat shields (approximately $95) already affixed. The standard system incorporates two partial clamp-on heat shields. Installation took 25 minutes from picking up the wrenches to turning the ignition key. Our only complaint about the process was having to dust off our SAE wrenches to tighten down Jardine's hardware. Metric-bike systems should ship with metric fasteners. The pipes issue a deep rumble with just a hint of the attack and backfiring that a couple other systems exhibited. Street riding revealed what the dyno numbers had already told us. The Slash Cuts made the least power of the comparison with only a 0.2 horsepower increase in peak horsepower. The torque numbers, at 85.0 ft-lbs, were better, which explains why the engine felt strong in the bottom end. When cornering comes into play, the Jardine system was tops among the full systems, touching down right at the Road Star's maximum lean. The pipe registered 104.0 dbA in the static test, qualifying it for street-reasonable status. The rolling test delivered the quietest of the full systems by almost 5 dbA. Tipping the scales at 16.2 pounds, the Jardine Slash Cuts can be ordered for $294.
Roadhouse Classic Exhaust System
Retro is the only word necessary to describe Roadhouse's entry in this test. Although no current riders should be able to remember when pipes of this style were cutting edge technology, Roadhouse has packaged a modern 2-into-1 exhaust into a vintage package. The multiple-step installation takes approximately 45 minutes once the final tweaking has been finished. The unique serrated header covers are made of stainless steel and are less likely to blue than chrome. The collector hides under a chrome cover, and the canister also features a chrome finish. The leading edge of the muffler exhibited some yellowing after multiple dyno runs (this pipe was also used in "Playing with Fire," Motorcycle Cruiser, April 2000). The deep exhaust note sounds great and generated the lowest sound levels in the static test. The 102.8 dbA static reading was followed up with an 87.7 dbA rolling test. Spinning out 55.4 horsepower, Roadhouse proved neighborly sound doesn't have to come at the expense of big power. Besides winning the horsepower war, the Classic Exhaust tied for second with an 86.6 ft-lb torque reading. The Roadhouse exhaust exhibited crisp throttle response, pulling strongly at most engine speeds -- including wide open at moderate rpm. Backfiring on deceleration was a nuisance that can probably be tuned out, possibly with the removal of the Road Star's air induction system. Ground clearance is the only real fly in the Classic Exhaust's ointment, with the canister becoming intimately acquainted with the pavement way before the floorboard touches down. The pipe weighs in at 20.6 pounds. The Classic Exhaust retails for $570.
Click on the images to see...
Click on the images to see larger dyno charts.
The Motorcycle Industry Council...
The Motorcycle Industry Council was kind enough to loan us its decibel meter. The nylon cord attached to the meter is our 20-inch standard for consistent distances from of all the pipes. To verify the meter's accuracy, a calibration tone generator (cylindrical device) was included in the package. DG Performance (HArd-krome)
(800) 854-9134, (714) 630-5471
www.dgperf.com
Evans Brasfield, Motorcycle Cruiser magazine's Feature Editor at the time this was written, is currently freelancing. He may be reached through his website.
For additional evaluations of, comparisons of, and shopping advice for motorcycle gear and accessories, see the Accessories and Gear section of MotorcycleCruiser.com.