That got my attention. In August 2003, we ran an article titled "Pipe Dreams," wherein we dyno-tested some of the more popular aftermarket exhausts. The results were interesting to say the least; the majority of pipes delivered less than stellar results. I'd long wanted to do a follow-up.
So I made the guys at Hacker a proposal: If they'd supply the pipe and one of their Anger Management Fuel Modules, I'd install it and do all the tuning-mimicking what an over-the-counter purchaser would do. The catch was that the pipe and fuel module would be the only changes. There'd be no airbox or ignition modifications, and win, lose or draw, we'd report the unvarnished results. To their credit, Hacker agreed.
Baseline
Step One
To establish baseline numbers, the bone-stock KingPin was delivered to John Tavolacci at Dyno Solutions in Danbury, Connecticut. I chose Dyno Solutions because its only business is dyno testing. John doesn't sell parts, he doesn't build engines and he doesn't offer any sort of tuning services beyond some custom mapping; he simply runs a dyno, and as such, could be counted on to be completely unbiased.
After three pulls we had our numbers and there were no surprises. As you can see from the readout, the KingPin's best run produced 72.95 horsepower and 93.45 lbs.-ft. of torque. While not outstanding, the numbers are healthy and right in the ballpark for a big-inch cruiser. We also sent a copy of the chart to Polaris; they confirmed our King was hale and hearty and our numbers right on the mark.
Baseline
The torque curve (represented by the upper line) is fairly smooth, with just a few hiccups in the delivery. Just above idle we're making over 80 lbs.-ft. of torque, which rises quickly to the maximum of 93.45 lbs.-ft. and, despite some peaks and valleys, stays fairly constant up to 4200 rpm. After that, cylinder filling becomes less efficient and torque starts to drop off. As an aside, the horsepower continues to rise slightly because horsepower is torque multiplied by rpm, and the extra rpm more than compensates for the reduced torque. Similarly, the bottom line representing horsepower shows a nice steady climb toward its maximum of 4500 rpm before leveling off.
Dyno Run 2Black line HackerPipe, blue line stock. The bottom graph illustrates the fuel/air ratio.
With the baseline established, the OEM system was replaced with the HackerPipes Track-Tuned Header and open megaphone, along with the Anger Management Fuel Module. The module was dialed in per the instructions and the bike test-ridden on a 10-mile loop. During the ride, two things became apparent: First, the noise level-while loud by my standards-wasn't totally obnoxious as long as some right-hand restraint was used, and second, the bike was running way too rich at the bottom, but that was something we'd sort out on the dyno.
Dyno run 2
Track-Tuned Header Open Muffler Anger Management Fuel Module (base settings) For the sake of illustration, we made our first dyno pull using my seat-of-the-pants fuel module settings. Surprisingly, things don't look too bad. We picked up 2.58 extra lbs.-ft. of peak torque, and the curve is almost identical to that of the stock pipes. Toward the end of the run there's a drop in horsepower as the bike starts to run rich.
With the air/fuel ratios resolved, the power curve begins to look better. Although there's a small loss at the bottom of the scale and the curve is a little shaky compared to the OEM pipes (black and red lines), it's not too bad. We lost a little bit of torque at the bottom of the curve, but we picked up horsepower at the far end, and the peak numbers are slightly better than stock.
Dyno Run 3
Open Header Corrected Fuel SettingsIn essence, this was a breakeven situation, and with no other modifications the Hacker wasn't going to set the world on fire. But at least it hadn't cost us any real performance; it in fact offered measurable gains in horsepower and torque.
What we have here is a bolt-on pipe that changes the look and sound of the bike and provides a modest performance increase at some points of the powerband. Since it's lighter than the industrial-strength OEM unit, you can also argue that some performance is gained through weight reduction.