Re: Making a muffler
Posted: Thu Sep 05, 2019 8:04 am
Here’s a quick summary of what worked for us for low rpm sound suppression and high rpm flow capacity in a twin-turbo V8 intended for street use.
Make the wastegate pipe large enough diameter and then set the length such that with the wastegate closed the wastegate pipe functions as a closed side branch resonator suppressing certain frequencies.
Use a slim resonator on each side to trap any supersonic blast waves after the wastegate dump pipe merge. This really mostly helps at high loads with high rpms when the wastegate is open. In my case, the resonators can be swapped for catalytic converters.
Combine both sides into a single pipe, which then combines the pulses into a more even rhythm, cancelling some sound frequencies and equalizing pressure. (Equalized pressure allows for smaller pipes downstream with additional losses.)
Divorce the single pipe again into two smaller pipes. Add the largest case volume straight thru packed muffler that fits on each side. The smaller pipes (dual 3” in my case) with large case mufflers allow for good noise suppression.
Run unequal pipe lengths from those muffler into another merge on one side of the car. Unequal pipes lengths again cancel some frequencies.
Add a single large straight thru packed muffler to the end. This will get rid of any flow induced noise etc.
This is not a cheap exhaust if made from stainless steel and with inconel bellows in multiple spots to allow for compliance and prevent cranking, but it works in my car.
Make the wastegate pipe large enough diameter and then set the length such that with the wastegate closed the wastegate pipe functions as a closed side branch resonator suppressing certain frequencies.
Use a slim resonator on each side to trap any supersonic blast waves after the wastegate dump pipe merge. This really mostly helps at high loads with high rpms when the wastegate is open. In my case, the resonators can be swapped for catalytic converters.
Combine both sides into a single pipe, which then combines the pulses into a more even rhythm, cancelling some sound frequencies and equalizing pressure. (Equalized pressure allows for smaller pipes downstream with additional losses.)
Divorce the single pipe again into two smaller pipes. Add the largest case volume straight thru packed muffler that fits on each side. The smaller pipes (dual 3” in my case) with large case mufflers allow for good noise suppression.
Run unequal pipe lengths from those muffler into another merge on one side of the car. Unequal pipes lengths again cancel some frequencies.
Add a single large straight thru packed muffler to the end. This will get rid of any flow induced noise etc.
This is not a cheap exhaust if made from stainless steel and with inconel bellows in multiple spots to allow for compliance and prevent cranking, but it works in my car.