Yesterday I took some videos to show how the sound will change after mounting an Akrapovic carbon racing exhaust on your Honda CBR125R motorcycle.
First of all, let me list up the mods that I did on my bike:
- Akrapovic carbon racing exhaust system
- Modified air filters (Daytona 45mm + Kijima 12mm)
- Athena bore-up kit 67mm (166cc)
- DIY ECU additional module
In the following video, you can hear how the sound changes. From 0:53 to 1:05 I recorded the sound of the Akrapovic exhaust (I revved up the engine only up to 8,000rpm because it was still cold). From 1:08 to 1:11 I recorded a little bit the sound of the modified air filter (Daytona 45mm). The motorcycle is equipped with a DIY ECU module which I made and installed under the seat. This ECU is used to increase the injection timings in order to adapt the original fuel injections to the Athena bore-up kit: since the engine volume changed from 125cc to 166cc (32.8% volume increase), the piston "sucks" in the cylinder more air than the original engine did. For this reason, I had to adjust the injection timing (about 30% more) to maintain the proper stoichiometric fuel-air ratio.
In the following video, the engine was at the right temperature, so I revved it up to the red-line of the limiter (10,500-11,000 rpm). I am sorry for the poor quality of the video, but the sound was so noisy that it saturated the microphone of my Iphone. I will try to take a better video in the next days.