what difference performance wise is there between a downpipe with two pipes coming off the flange and joining further down or the open neck style? has there been a proven difference (rr) or is it just peoples opinions or views? this is for a classic.

jason

 

not sure if any performance gains occur. The purpose of the two pipes is to stop exhaust gases bypassing the Turbo through the wastegate from interfeering with the gasses leaving the exhaust turbine. I suppose it could help the turbo spool up slightly sooner. That's just a guess I am sure someone will kick my comments out to the Vultures.