By far the most common question regarding engine software is "How accurate are these programs?"
This is a tricky question because of the nature of engines and dynamometers. Engine power is not something you can measure exactly with a micrometer. The measurements from the same engine on the same dyno can be different for three consecutive "pulls" as shown in the graph below.
Unscrupulous dyno operators can make the numbers higher or lower. So, the accuracy of a program can depend on whose dyno you use as a baseline.
It is important to understand that while engine output at a single RPM can vary, the overall power curve identifies a specific trend. Notice that the three dyno power curves above do not follow the exact same path, but they do have the same trend. As such, you want an engine software program that properly identifies power trends, not just a horsepower number at a single RPM.
Due to the fact that the engine itself won't repeat the same power curve on the dyno, how closely a computer program predicts the little wiggles in the "power" curve depends on how complex the software is and how much information you must enter for the program to work properly. It is best to choose a program based on the level of detail you want to get from it and how much data you are willing to enter to get that level of detail.
For example, the graph below is a comparison of our Engine Shop software to that of an actual dyno run. This graph shows the trend to be very similar and close in position to the dyno run. Engine Shop is the easiest program to run that we stock. The software's predictions are very useful because they are accurate enough to help the average weekend racer find an advantage over the competition.
On the other end of the spectrum, however, you find the Engine Analyzer Pro. It requires much more detailed input such as intake runner length piston skirt area and bearing surface area. This along with other additional information will result in a "tighter" prediction as shown below. This level of precision is very helpful if you are a professional racer or engine builder.
So, no matter what or where you race, you can count on the programs at this web site to be sufficiently accurate to satisfy your specific racing needs.