One of the most-often asked questions I hear is "What is the best exhaust system?" Easy question; hard answer...

On any bike equipped with both pipes on one side, connected by a crossover pipe, you have a wonderful system. Simply replace the stock slip-on muffler with Screamin Eagle slip-on mufflers. Leave the crossover intact and do not change the SE baffles. These pipes are great. They pull instantly off the bottom, and we have pulled over 100 horsepower on the top with them; they really do work great! Again, do not open the baffles to make them louder. "Loud" does not necessarily mean "better performance" when starting with a free-flowing muffler. Some people simply knock a hole through the stock mufflers to save some money. It will sound louder (but not the deep, throaty sound you want), and it will make some more power. But not as much as the SE slip-ons.

Now for the disclaimer:

OK, so you are determined to trash the stock system. What do you put on?

Drag pipes:

These pipes work best at high RPMs. That's why they are so-named. Usually you will experience a flat acceleration curve below 3000 RPM; this will be worse on higher-horsepower engines. This will also be worse with butterfly carbs and slide carbs with no accelerator pump.

So why is the flat spot there? A brief tutorial: For the sake of 99% of the people reading this, I'm going to use the generic term "back pressure." Everyone has heard of this, but few people understand it, and every Harley needs it. Not enough backpressure causes a torque loss at low RPM. Too much causes a loss at high RPM. Many of my customers have seen me take baffles out of their pipes and increase their performance. Some have seen me add baffles to their pipes, and others still have seen me take them out and replace them with different baffles. Every combination of cam, carb, and pipe needs a different amount of back pressure.

Here are a few rules of thumb to keep in mind:

• Short pipes make horsepower; long pipes make torque.
• Big-inch motors need big-bore pipes; stock motors can use small-bore pipes.
• No manufacturer can make one pipe to bolt on every bike and make the best horsepower. Again, there are too many combinations of carbs, cams, and even "looks"!

2-into-1s:

Generally speaking, a 2-into-1 system will give an excellent midrange with possibly a flat spot at bottom end and/or top.

• My favorite 2-into-1 is the tunable White Brothers E-Series. It pulls sooner and farther than any other I have found.
• The SuperTrapp 2-into-1 is probably next on my list.
• A Thunderheader pulls hard from 3000RPM and up, but has a flat spot below 3000 and will glo flat on top. It is also LOUD.
• A Pro Pipe has a huge flat spot down low and goes flat on top. Unless you use the short six-inch baffle then it works quite well.
• The Vance and Hines Short Shots and Long Shorts can work very well with big-inch motors because they are a large-diameter pipe. Just find me to tune the bottom-end rams for you.
• There are others on the market; Samson, Custom Chrome, S.E., Bubs, but these pipes are mostly found on show bikes because of their looks or sound.

Remember; big motors need big pipes. Don't put a 1 1/2 or 1 3/4 inch pipe on a 96" or bigger motor unless you are willing to sacrifice big numbers on top. We have raised horsepower numbers by 15 to 25 horsepower by removing baffles or going to bigger pipes on big-inch motors.

Torque cones help a little on some combinations. Often I find huge flat spots in bikes with torques cones installed.

Dresser-style Duals:

Now, let's go to dresser-style duals. The stock mufflers are very restrictive and very quiet. Some mufflers can be improved by drilling holes in them but the sound is usually not what you want.

• My favorite slip-on mufflers are the White Brothers E-Series. They have an aggressive sound under acceleration, but the sound drops behind you at a cruise speed. You can talk or listen to your radio with these.
• I also like the performance and sound of the SuperTrapp and Samson pipes.
• Bub slip-ons and 2-into-1s work well on stock bikes, but don't pull the power on built engines.

True Dual systems work well with a free-flow muffler, since stock pipes push 80% of the exhaust out only the right side. You can usually place your hand on the left muffler and feel that it's cool to the touch because not much air goes through it.

A few miscellaneous thoughts:

• You may have a ThunderHeader with no flat spot or a Bub that pulls 100 horsepower. Great! You have an engine combination that works well for your setup.
• In general, fuel-injected bikes do not run well with Thunder Cone slip-ons. They really screw up the injection pulses.
• If you run drag pipes, or even Python pipes with built-in baffles, you need more backpressure. But just enough; not too much. Come see me...
• Cycle Shack is probably the best choice for the older Shovels, Pans, Knucks, and Flatheads. They are about the only company who seems to have pipes for about any of the older models.
• There are some rather exotic and expensive pipes out there; Borla, AR Racing, and others, that offer some performance. But you really need the right combination or you can be way off.
• Buels: The S.E. pipes seems to be about as good as any. The stock pipe usually is not; Yoshimura and 2 Brothers seem to work OK in some combinations.
• Oh yeah; the late-model S.E. slip-ons (with the donut sticking out of the end of the muffler) really suck on a built motor. They are really not as good as the early S.E. mufflers.
• It seems to come down to how serious you want to get. The best pipes I've seen were step headers. They pull the most top-end but also have the flattest bottom end.

It's really hard to have it all; all the top end and all the bottom end, and the sound and the quiet. You just can't have it all...

Come and see me and I'll get you all I can.

- The Dynoguy