Straight Flow Catalytic Converters

Straight Flow’s catalytic converters are universal parts for building a catalyst into an exhaust or replacing one, from bare substrates to complete units.

Metal substrates are the bare catalyst element, a metal honeycomb with 200 cells per square inch, sold by diameter from 80 mm to 130 mm for your own housing. Sport catalytic converters are complete units with pipe stubs from 50 mm to 90 mm, also at 200 cpsi, each marked with its Euro emissions level, from Euro 3 to Euro 5. The universal ceramic converters have a denser 400 cpsi core, are listed for Euro 4, 5 or 6, and are sized by body diameter, inlet and length. Some have a lambda sensor boss, shown as ‘zond’ in the title, and some a centre-to-offset layout.

Cell density is the main trade-off: a 200 cpsi core leaves the exhaust a more open path, while a 400 cpsi core gives the catalyst more surface. Match the emissions level to the car’s original standard and the pipe size to the system around it.

A new catalyst position may need a second lambda sensor boss, and the engine management should be checked after fitting.