| Message |
100% Mandrel Bent Tubing - Mandrel bending is a process in which the inside of the tubing is supported by a "Mandrel" during the bending operation. The "Mandrel" is pulled through the tubing during the bending process, which causes the tubing to stretch on the outside of the bend, and allows it to bend/compress on the inside of the bend. Unlike typical "Muffler Shop" compression bending (or those found in your stock exhaust system) which reduces the inside diameter by as much as 35% through the bend, Mandrel bending maintains a constant inside diameter throughout the bend resulting in no loss of flow capacity. As there seems to be some confusion as to why mandrel bending of
a pipe is a good thing, we offer the following explanation. Consider a straight plastic straw that you might use to drink soda out of a bottle. If the straw is completely straight, it's very easy to draw the liquid out of the bottle, as there are no
restrictions to the flow of soda. However, lets say you decide to bend the straw 90 degrees into an "L" shape. Now, drinking from the straw will be very difficult, as the opening at the straw's elbow
will have changed from a circle to a very narrow slit. This is exactly how the pipes in your car's intake and exhaust system work. Air is drawn through pipes, which, when "press bent," become very restrictive to the flow of air.
Mandrel bending is the solution to this problem. Mandrel bending works much like the flexible straws that you can buy in a grocery store. When the straw is bent, a flexible section of the straw expands to maintain the round opening no matter how much of an angle
the straw is bent at. When an exhaust or downpipe is manufactured with mandrel bends, the steel is allowed to stretch on the outside of the bend and compress on the inside of the bend, maintaining the
nominal pipe diameter. To see how much of an improvement mandrel bending can make, take a look at the chart below, which shows the effective cross-sectional areas for press bent and mandrel bent pipes. In the press bent
column, two numbers are shown, corresponding to a 20% and 30% reduction. 20% is typical for a slight bend, 30% for a larger bend. | Nominal Pipe Diameter
| Press Bent Area (Square Inches) | Mandrel Bent Area (Square Inches) | | 2.25" | 2.74 / 3.13 | 3.92 |
| 2.5" | 3.43 / 3.92 | 4.90 | | 3" | 4.94 / 5.65 | 7.06 |
As can be seen from the table, a 2.5" press bent downpipe is actually smaller in cross-sectional area at the bend than a 2.25" mandrel bent downpipe! Why doesn't everyone use mandrel bending when fabricating pipes?
It's simple... cost. It's much more expensive to bend pipes using mandrel bending than to bend them using press bending. So, when shopping around for downpipes, exhaust systems or other piping for your car, insist on mandrel bending. And if someone
tells you it's just as good to use press bent pipes, ask them what kind of pipes they run on their car.
 |
 |
