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Dyno run 4
Quiet option
Knowing that I prefer a quiet exhaust-quiet in this case being relative-Hacker included a traditional reverse cone megaphone that purportedly made less noise and only slightly less power than the open pipe. Replacing the open pipe with the "muffler" took all of three minutes, and they were right-it was noticeably quieter. The bad news was that on the dyno, it folded up like a deerskin wallet.

Compared to the stock pipe (black and red lines), the Hacker (blue and green lines) is behind on both torque and horsepower throughout the entire curve (the only exception being around 2900 where parity is achieved for a few rpm). But from there, it's downhill all the way. Making matters worse is a torque crater at 3500 rpm where the Hacker makes 11 pounds less torque than the stock pipe.

Obviously, any torque loss is cause for concern, but a 12 percent drop is serious business as it negatively affects every aspect of performance. Torque holes like this also make the bike difficult to ride because the power drops off as you accelerate past 3000 rpm, and then it comes back on with a bang at 4000 rpm-which can light up the rear tire if the road is slick. It's entertaining the first time it happens, but after that it's just nerve-wracking.

Initially, we thought fuel mapping might be the problem, but as you can see from the air/fuel chart, the ratios-while not perfect-aren't far off the optimum of 13 to 1. As installed, this combo was unacceptable.

So what's going on?
Neither pipe performed as expected, and in fact the quiet version was downright pitiful. Though we felt we'd honored the test parameters, we also felt that in fairness to HackerPipes we owed them a chance to set things right. So we did the logical thing and removed the airbox lid. The change was dramatic.

Dyno run 5
Quiet Pipe, No AirBox Lid
The green and blue lines represent our first pass with the quiet pipe. Torque and horsepower are down compared to the stock bike, and there's that huge hole at 3500 rpm. The black and red lines show what happens when the airbox cover is removed. With no other changes, power instantly increases, and that gaping hole in the torque curve disappears. Better yet, we pick up torque and horsepower compared to the stock setup and in fact end up making 4.7 more pounds of peak torque-a five percent gain.

With the airbox mod, the HackerPipe isn't bad-there's an overall increase in power and a decent increase in torque. No doubt that if we pursued this tuning avenue we'd see even more of an increase.

Conclusions
So did we learn anything? In truth, no. As we found in our original "Pipe Dreams" test, merely installing an aftermarket pipe isn't going to get you much of a power increase. Understand that modern intake and exhaust systems are extremely well thought out and extensively tested. The OEMs know exactly what they're doing, and any shortcomings are generally the result of EPA meddling. Yes, some extra power may be found by bolting on a new pipe, particularly if you're not overly concerned with current noise and pollution regulations, but don't expect miracles.

Remember the Golden Rule: Changes in either the exhaust or intake affect airflow through the engine, so in most cases a change in one demands a change in the other. Before laying down hard-earned cash, figure out exactly what you hope to gain. If it's simply to make noise or change the way the bike looks, then by all means bolt on a new pipe and cross your fingers; maybe you'll pick up a few ponies, maybe not. However, if your goal is to boost power, chances are you'll need a pipe, fuel module and airbox/air filter modifications before you realize any genuine increases. And even then, you'll be lucky to see a 10 to 15 percent gain.

My last piece of advice: If you really want to know where the bear went in the buckwheat, book some dyno time and quantify your handiwork-anything less is just guessing.