A buddy of mine just threw a couple of these into the wife's softail with fish tail exhausts and was crowing about the increase in low end power. After a little reading, I found out that the basic premise works the same was the lollipops that used to be put into short drag pipes to build low end power. All of this is bad around the management of the reversion of exhaust gases, of course, but I was wondering if anyone here actually has any experience with this particular product here?
If I can get them to nail down a couple of specifics, I may go in and be the test monkey myself on this one. They're only $30.
or any other techs have experience w/these?
The washers in the drag pipes were to kill off reversion. And by taking up space, they also caused some increased back pressure. Think of a reversion wave as a flat disk running back up the pipe. it has X amount of energy. If you cut the center out of it, it will reform to fill the pipe, but expend some of that X energy in so doing. A baffle that makes the wave run into a dead end will kill it. A perforated tube will constantly shave the out edge off, cause the wave to expand to fill the pipe, loosing energy as it does. Steps inside the muffler will cut the outer edge off at each step. And cones wil cut the outer section of the wave off. A cone with a 2 inch center hole in a 4 inch opening can reduce the wave energy by more the 60%.
The cones at the pipe inlets work a little differently. They force the gas to move faster, this causes a low pressure area in the system and almost unlimited energy in the exhaust pulse. Depending on where the cone is placed, it can create some extra scavenge. And they cause back pressure by reducing the flow capacity of the system right from the start. What they are mostly doing depends on size and placement in the system. They also help with reversion by reducing the energy of each pulse by cutting the outer edge off and causing it to thin as it expands to fill the pipe again.
Now, with all of that said, it only works until you run out of flow at higher RPM's. The little spigot step baffles are for Evo's and Twin-cam's and deal with reversion and velocity at the port. M8's use a large cone baffles in the right can, that's about building the back pressure for low end torque. Some aftermarket head pipes come with a cone baffle right where cat was in the oem pipe. And that size of that baffle has a huge effect on what the torque curve looks like on the dyno. Many tuners have a poor understanding of this, and toss the baffles. Preferring to get that extra 2 horse power at wfo.
And there is an even better way of doing it, but for some reason it has never fount its way to Harley. Spiral baffles in a perforated pipe kill reversion and noise, without killing flow. Harley bagger cans would be the perfect place for spiral baffles.