Originally Posted by 1984_FXRT
Sorry - but, this is absolute BS. All that any of these pipe inserts do is to break up the reversion wave to minimize part of the negative impact that a poorly timed reversion wave hitting an open intake valve has on cylinder fill.
There've been many papers written more eloquently than I feel like being tonight, complete w/formulae and empirical measurements to help the reader decide for themselves what'll work and what won't.
Aside from tuning for max HP in a very narrow RPM range, DRAG PIPES SUCK.
Your bike - do what you want with it. If you think that the surge you feel when the bike comes off the mostly shitty performance thru the largest part of the machine's overall RPM range into the small and narrow RPM range in which the pipes actually work a little is the feeling of "more power" - then have fun.
All due respect, perhaps you are not familiar with the W version of our Thunder Torque Inserts.
They are Not torque cones, or a bolt or an eye bolt or a bolt with a washer on them. While all those may work in certain instances to certain degrees, the TTI's work much better because of their unique design.
It is correct that drag pipes are typically good only for WOT, but with the TTI's a drag pipe will outperform many of the most popular slip-on that have baffles in them.
They are a patented design and they do work very well, if you look at the link I posted above, down at the bottom of the page there are dyno charts.
While it does not matter if you believe they work or not, I write this so that others are not mislead by your skepticism.
Below is a basic outline of how exhaust works, and why the Thunder Torque Inserts work.
The Thunder Torque Inserts have a proprietary shape that is much better at increasing exhaust gas velocity, thereby reducing reversion, which reduces engine pumping losses, and increasing inertial scavenging. Net result is a significant increase in power & torque in the low and mid range Without sacrificing any top end.
The type of material, shape, size, thickness, & surface coatings all make a difference in how well the Thunder Torque works at increasing exhaust gas velocity.
The TTI's obviously have their genesis in the simple lollipop concept. But they are quite a bit more, especially the W series.
Technically exhaust systems cannot increase or decrease an engines power. However, and this is a BIG however, exhausts systems can have a profound affect on increasing or decreasing engine pumping loss.
You can loosely compare engine pumping loss with adding an extra 200 lbs weight to the bike. The engine still has the same amount of power, but with the extra weight on the bike it will accelerate slower...it will feel like it has less power than it would if the extra 200 lbs was removed.
Every engine will suffer to some degree from engine pumping loss. The goal of many exhaust systems (including the Thunder Torque Inserts) is reduced engine pumping losses, resulting in more felt power at the rear wheel. If efficiency of the engine increases then fuel mileage may also increase because less throttle is needed to move the bike forward at the same speed.
There are Many design factors that can affect whether an exhaust system increases or decreases engine pumping losses, far more than could be put in a post here (by me anyway lol).
Generally most of us that ride Harley's want the most felt (rear wheel) torque in the low to mid rpm range as possible. Inertial scavenging has a major effect on that felt power.
The nuts & bolts of increasing inertial scavenging is the following-
When the exhaust valve opens two thing happen. A pulse (wave) of energy enters the exhaust pipe, generally at 1300-1700 feet per second. This can be understood as a shock wave from an explosion.
At the same time the spent combustion gases enter the exhaust pipe at 150-300 feet per second. (Generally the faster the exhaust gases travel, the better the inertial scavenging and the less engine pumping loss)
The energy wave that is heading toward the end of the pipe will get to a low pressure area faster (low pressure being a bigger area of the pipe OR the end of the pipe) WHEN that happens some of the wave will reverse direction and collide with the slower moving exhaust gases that are still traveling toward the end of the pipe. This will slow down the speed of the exhaust gases. This will produce the result of less felt torque at the rear wheel.
Exhaust systems that are are successful in increasing exhaust gas velocity (resulting in an increase in inertial scavenging and a decrease in engine pumping loss) will make the bike have more felt torque across the RPM band, especially in the low & mid range.
There is much more to how exhaust systems help or hurt the felt power. But the main goal that is achieved by the unique design and combination of materials in TTI's is to increase felt power in most any exhaust system for a low price.