Thread: Provent 200 outcome after 150,000km

Ahhh, I see what you mean. The 16mm from the rocker cover is not the issue - each of those DR brass fittings reduces the hole size down from the 16mm thin steel outlet tail on the rocker cover (and the 5/8 bore hose) down to about 8mm through the threaded BSP sections of those 5/8 hosetails. Adding in multiple of those fittings in the system is a lot of section where the throughput of vapour has to accelerate and then decelerate to get the volume of gas flow through the fittings. That will add a lot of resistance and flow losses to the system leading to the experience you have had where the relief valve in the filter can do nothing to help you as the restriction is in front of the catch can body.

Plumbing in ahead of the turbo should actually provide a small amount of assistance by reducing the pressure on the outlet side of the catchcan a little below ambient pressure, but it won't be much. Should work to balance out the filter element in the can though...

As Flyblown suggests with the factory supplied connection kit without the step up/down brass fittings, there won't be any of the additional restriction in the setup.