How To Determine Exhaust Pipe Flow

This is one way that you can determine how well your exhaust pipe flows and how to determine where the torque will peak with different cams and exhausts.

First, look at this Super Tuner VE map comparison.
This map is of a Touring bike and has a stock engine with a SE air cleaner and slip on exhaust.

The left graph is the front cylinder and the right graph is the rear cylinder

Look at the 100% throttle position and you can tell where the engine's peak torque is by finding where the highest numbers are located. The area that peak TQ occurs will be where the engine will scavenge the best (has the highest volumetric effiency). This area can be determined by finding the highest numbers in that column. In this graph, the peak TQ occurs between 2200 - 2700 RPM.
Looking at both graphs, you can compare the numbers in each RPM row at 100% throttle. This graph shows that the numbers are very even which means that the front and rear cylinders scavenge very evenly wit the stock header. Even though the stock header flows evenly, it does not flow well. This is indicated by the low numbers on the graph. Remember that the higher the numbers are, the better the pipe is flowing.

This graph shows that the TQ location of the SE 255 cams peaks in the 3,000 RPM area.

This next graph is a Power Commander map using SE 255 cams and Rinehart True Duals.
You can compare the 100% throttle positions and see how that the numbers in two cylinders are not very even. This means that one cylinder has a better volumetric effiency than the other in some areas.

The numbers in a Power Commander map is considered to be in percent. In other words, the 2500 RPM at 100% throttle on the lower graph shows to have been increased by 10% vs the same area of the upper graph with 27 %. This means that the cylinder in the upper graph at that location requires 17% more fuel which also means that in that cylinder in the same area in the upper graph's flows (scavenge) better.

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Nine Time Undefeated Dyno Shootout Winner 2008 - 2009