In a typical scenario, you install an aftermarket exhaust that (ideally) increases the volume of air being pumped every combustion cycle. Meanwhile, the ECM is still utilizing VE numbers based on that factory test mule with the stock exhaust and air cleaner. It thinks it’s pumping less air than it actually is. Your engine is running lean somewhere –maybe everywhere. It might ping under hard acceleration or surge at cruising speed. Your mileage hasn’t suffered, but the engine runs noticeably hotter. Because of this, even a stock bike can benefit from a dyno tune.

Perhaps you then install a Power Commander and download a map from the Dynojet web site. The helpful map index might list your bike and even the exact exhaust system you installed. It has to work, right? Not necessarily, let me explain why.

The Dynojet Power Commander is a piggyback product that simply intercepts signals sent from the ECM to the fuel injectors and modifies these signals based on its own map. It doesn’t care about VE tables or anything else the ECM is “thinking” about.

The Power Commander map is relatively easy to read using its proprietary software interface. Not unlike the VE tables, it utilizes columns and rows representing throttle position and RPM, respectively. Everywhere a column and row intersect represents a given load condition and is an opportunity to offset (increase or decrease) the amount of fuel delivered that is indicated by the stock ECM signal. A negative offset directs the PC module to lean-out the stock signal and a positive offset directs the module to enrichen the stock signal. This offset may or may not be what your engine needs to deliver optimum power under the given load condition.

The map is a collection of offsets, ostensibly for a given configuration; i.e. model, year, exhaust, air cleaner, etc. However, the fundamental fact that no two configurations are exactly the same, even with the same list of components, has not changed. Therefore, your internet “map” won’t be the optimum for your motorcycle.