Attention: TDR Forum Junkies 
Jonz,
A boost elbow is a little brass elbow that connects directly to the turbo (except the hy-35) that sends air down a little rubber hose to the wastegate. When the air pressure (known as boost) gets so high, then the wastegate opens up and released the excessive pressure, preventing damage to the turbo.
A down pipe is what goes from the turbo to the exhaust pipe. People that are running the HX-35 or HY-35 turbo with a 4 inch exhaust have to have a downpipe. Being that you can't directly connect a 4" pipe to the turbos 3" flange, you have to have a pipe that expands from 3"s out to 4"s.
Hope this helps
Kev
A boost elbow is a little brass elbow that connects directly to the turbo (except the hy-35) that sends air down a little rubber hose to the wastegate. When the air pressure (known as boost) gets so high, then the wastegate opens up and released the excessive pressure, preventing damage to the turbo.
A down pipe is what goes from the turbo to the exhaust pipe. People that are running the HX-35 or HY-35 turbo with a 4 inch exhaust have to have a downpipe. Being that you can't directly connect a 4" pipe to the turbos 3" flange, you have to have a pipe that expands from 3"s out to 4"s.
Hope this helps
Kev
