2-port with the right sized restrictor pill works fine.
3-ports just give your mapper a slighty easier time but both achieve the same result.
Standard cat up-pipe restricts the boost to 1bar at high rpm on a VF35. The gasses cannot exit fast enough. Any more boost causes pre-ignition regardless of timing advance.
I call it pre-ignition and not detonation as it's not the timing/spark igniting but the exhaust gas backlog due to the cat.
|