Mandrel bending versus regular

this is some good info that i just found to consider as well......

Consider a straight plastic straw that you might use to drink a soft drink.
If the straw is completely straight, it's very easy to blow air through the
straw, as there are no restrictions. However, lets say you decide to
bend the straw 90 degrees into an "L" shape. Now, blowing air through
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 "compression 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. Exhaust gas
follows fluid dynamics. You want to eliminate backpressure while
maintaining exhaust gas velocity. Mandrel bending allows the hot exhaust
gases to flow with less turbulence.

2. Myth-You don't need mandrel bending unless you have a nascar running
800+ horsepower.

Truth-Mandrel bending alone will add 3-5% more horsepower and torque.

3. Myth-Your motor is to small for mandrel bending to make any difference.

Truth-It doesn't matter what size your motor is you will still get a
3-5% gain in horsepower & torque. Obviously the bigger the motor, and
the more horsepower you have, the larger the gains.

4. Myth-We will only be making a few small bends so you don't need
mandrel bending.

Truth-(We will be using 3" tubing as our example) It doesn't matter if
you bend a pipe 1 degree or 180 degrees you will still smash the pipe
1/2 inch. A press bender will crush the pipe before it starts bending.

5. Myth-We will only be putting 1 bend in the pipe so you don't need
mandrel bending.

Truth-If you have 3" tubing that is press bent it will smash 1/2 inch at
the center of the bend. At that point you have 2 1/2" flow instead of
3". It doesn't matter if you have one bend or five bends you still have
2 1/2" flow.