Downpipes Open V Closed ?
#3
Scooby Regular
Join Date: Jun 2002
Location: From Kent to Gloucestershire to Berkshire
Posts: 2,905
Likes: 0
Received 0 Likes
on
0 Posts
Closed neck - cheaper and easier to make. Blocks off wastegate flow, causing turbulence which spoils turbo spool up (ie turbo needs more revs to start working), also limits total flow and hence reduces peak power.
Open neck - tend to be a little pricier. Almost always much superior for power, spool up etc. Open tends to mean "bellmouth" (one big oval pipe), but also good is twin dump (separate pipe for the wastegate flow). Lately it's getting common to see a splitter in the downpipes which further reduces turbulence between exhaust gas coming out of the turbo and gas coming out of the wastegate.
Which is better out of twin dump & bellmouth? The debate has caused interesting disucssions, but either is going to be a big improvement on the closed type.
Open neck - tend to be a little pricier. Almost always much superior for power, spool up etc. Open tends to mean "bellmouth" (one big oval pipe), but also good is twin dump (separate pipe for the wastegate flow). Lately it's getting common to see a splitter in the downpipes which further reduces turbulence between exhaust gas coming out of the turbo and gas coming out of the wastegate.
Which is better out of twin dump & bellmouth? The debate has caused interesting disucssions, but either is going to be a big improvement on the closed type.
#7
Scooby Regular
Join Date: Jun 2002
Location: From Kent to Gloucestershire to Berkshire
Posts: 2,905
Likes: 0
Received 0 Likes
on
0 Posts
It blocks it after about 20mm, so the gas has to go round a right angel bend, into the turbo flow and then round another right angle bend down the downpipe. It is where it crosses the flow coming out of the turbo that you get the real turbulence problems.
Closed neck is cheap as it's easy to make. It is just a bent piece of pipe and a flange, as opposed to a taper or other more complex shape.
Closed neck is cheap as it's easy to make. It is just a bent piece of pipe and a flange, as opposed to a taper or other more complex shape.
Trending Topics
Thread
Thread Starter
Forum
Replies
Last Post