I've read and read about doing porting on my 1.6 td head and some people suggest not porting exhaust because ithe smaller port increases velocity to the turbine .... But cleaning up the casting is beneficial along with taking the hard angle under valve out .and cleaning up around valve guide....... Also I have read that porting the exhaust all the way thru increases flow..... Now this is where I would think that velocity would be better than flow before the turbine.... I'm wondering if there is some of you out there could help point me in the right direction.... I'm wanting to learn what I can on doing it the right way from people that have actually had proven results..... I've read some of David vizards articles on porting and really has some good info just trying to clarify on the route I should take
The David Visard article at the top of the page is very key. What you have said is somewhat accurate. If you open the exhaust a bunch you will have more flow than if you don't, without the tools to measure you will not know if the velocity was improved over stock or not. General rule is to open it up to the size of the gasket and smooth out the bends. This will increase flow and velocity, for all out flow just keep opening. All out flow is best for high rpm engines/race engines/etc...pretty much not what our diesels do. Yes we can rev to 6,000 rpm but that is not where it makes power nor is it close to what gassers do, so we don't need the flow as much. Velocity is king and try to keep all the ports equal. If you need to see pictures look in my thread to get an idea.