Pipe Analysis & Redesign A pipe design (shown below) was emailed to me for analysis. It is an aftermarket pipe on a Aprilia RS125 although it was designed for a different bike. The engine is bored out to 138cc and used for drag racing. Here is the return waves graph for it (leaving off the secondary waves). Diffuser wave is lacking the optimal shape of increasing strength to the right. Here is the dyno for this pipe : After finding a web site listing the gear ratios I was able to figure out the spread of RPM between each upshift happening at 11,000 RPM. 2nd gear has a ridiculous spread of 3430 RPM but usually on a race track 2nd isn't used. 3rd is the lowest gear used except for at the start. (I'm not sure what gear is used to start in for a drag race bike.) 3rd gear needs to use the top 2620 RPM. Motocross bikes are usually designed for the same RPM spread for each gear above 2nd. This bike was designed so the two top gears only use the most powerful part of the powerband. But the lower gears have to pay for that luxury. Anyway this bike needs a powerband of at least 2600 RPM. This is a good example of the importance of knowing the RPM spread between gears (above 2nd). Here is the graph of this pipes power. It agrees with the real horsepower dyno of the beginning and end of the powerband and the beginning hump. Keep in mind that ECcalc doesn't show the final complete horsepower graph but rather the extra power that the pipe adds to the raw engine power. (Click here for a graphic example.) Here is the power graph after changing the pipe design using ECcalc. It made the power higher and the powerband shorter which is what you want for racing. Here's its new pipe design: HOME