Exhaust: Yamaha Genesis 80FI

[FSAE_MTU]

My team and I are working on the Yamaha Genesis 80FI exhaust system for our current car, we are mainly focusing on the muffler design because we are using the same engine in multiple cars. We are in the research and design phase right now and are wondering if anyone has made any mufflers for this engine or have any generalized information about the two cylinder exhaust system? Any information would be greatly appreciated.

[Mbirt]

It will be a challenge meeting the draconian new noise rules with a CVT drivetrain contributing extra clatter at idle and at test speed. Snowmobiles use lots sound absorbing material around the CVT to get the noise down. I would suggest running your muffler forward along the opposite side of the car from the clutches to get the mic away from the mechanical noise.

Teams using the Phazer engine were passing sound under the old rules with off-the-shelf performance mufflers, so the muffler design itself won't be terribly complicated. Avoid sharp internal edges for grazing flow throughout the entire exhaust system to minimize high-frequency flow noise. More silencer volume equals more noise attenuation. If it's an absorptive design, follow the material's spec for packing density (packing the silencer as tight as you can with fiberglass is going to decrease the effective volume of the silencer and will hurt its attenuation capabilities). Experiment on the dyno with how small you can go with diameters inside the silencer and for the tailpipe while keeping the torque curve you need. Being a CVT application, I'm thinking you can go smaller than you expect because peak torque will be the first thing affected by the backpressure, not peak power.