One of the best tools available when doing a performance upgrade is a Dyno run. It is usually best to do a run before a modification. This will allow you to actually gauge the effect on your machine when the modification is done. When you get a run done you will be given a sheet that shows 3 items:
Torque curve
Horse power curve
Air fuel ratio.
Most people look at only 2 things when the get a dyno sheet. The numbers at the top of the readout tell the peak HP, and the peak torque. Unfortunately that is only a little piece of the story. I will be using a sheet from my bike that shows 2 runs, and also exhibits a couple of minor problems.
First the most often ignored, yet most important indicator of how you bike is performing is the Air fuel ratio. In a perfect world the A|F line would be dead straight, and right at 14.7/1. Unfortunately that is rarely the case. Anything above 14.7 is considered to be lean, and below is rich. On a Vic however if you can keep that line straight between 13.5,and 14.5 you are doing pretty good.
Lets take a look at my two runs. The Dyno runs can be viewed at: http://www.kingpincruisers.net/coppermine/albums/userpics/pmrt%20dyno%20run-1.jpg
First the red line
Notice that at first it is about perfect, but as the RPMs go up the bike gets leaner. In fact it is dangerously lean as it crosses 4K. At about 4.5K it starts to go rich. That falling to rich is reflected in the power curves. If you look you can see that both curves mirror the A/F ratio. I believe that I was running out of air because of the stock air box at that point. The red line was done with a stage1 one right out of the box. I had set it a tad lean in the hopes of increasing my MPG. Had I set it up normally my numbers would have been slightly higher.
Now the blue line[what a mess]
Again I start out OK, but from there things go horribly rich. I used a stage 1 map, and just loaded in a bunch of fuel using the TPS. I am sure that if I had not been so heavy handed that it would have been better. At about 3K you will note that it crosses to rich. This set up a cycle that continues throughout the run. Since it stars getting to rich for proper combustion. Extra fuel is left in the cylinder. This keeps on happening getting worse as the run progresses. Until finally I reach a low of 12/1. Again if you look at the power curves you will see that it is mirrored in them. First the HP curve dips below the original until about 4700,and the torque quits going up at about the same time as it goes rich. This run would have looked MUCH better if I had not forgotten the basic rule of little changes, and no wholesale adjustment
This is the link to my dyno sheet readout: http://www.kingpincruisers.net/coppermine/albums/userpics/pmrt%20dyno%20run-1.jpg
Now that we have seen the link between AF ratio, and power curves lets look at the curves them selves.
First torque
A good torque curve ramps up almost immediately. The more that is available right from the start the better the launch from a stoplight. After that the best result is one that solely reaches a peak, and holds a straightest line. One thing to note here is that the number 5252 is part of the mathematical formula. Your Torque, and HP curves should intersect here. If not there is something wrong with the dyno set up. If you look at the two curves on my dyno sheet. You will see that the blue line continues in an almost straight line to the red line. This means that I pull all the way to the limiter. When I get my mixtures cleaned up. It will have more torque, but the line should look about the same.
Now HP
Unlike torque Hp builds across the revs generally peaking, and then falling off fairly rapidly. This is a generality. RPMs=HP. If you look at a diesel you will see that though it produces massive torque the slow spinning nature means that you will see numbers like 175HP600FtLb. on the other end of the spectrum is the sport bike. Its rev happy nature, and light reciprocating mass give you numbers like 160HP65FtLb. This is why the V twin is the engine of choice for cruisers. The HP, and torque are fairly balanced. When looking at HP it should describe a reasonably smooth arc. Jagged sections can mean detonation, and sudden jumps, or drops could mean wheel spin. I believe that pretty much covers it.
Contributing author to Cycle Solutions http://www.cyclesolutions.net
Research performed on the Victory Kingpin technical site: http://www.kingpincruisers.net