psu_Crash Posted May 21, 2009 Report Share Posted May 21, 2009 OK so I am sure this has been covered several times but the search is failing me. I am going to port my exhaust manifold and turbo sometime in the near future and I'm just looking for some pointers and/or pics of what others have done. So the plan is to port to match the gasket on the exhaust side of the head and the manifold runners. Then port the mani to match the housing on my 18G since the manifold opening is a good bit smaller than the turbine inlet. Should the turbine housing side from the mani just be ported staight or should it be done with a cone shape narrowong as it nears the turbine for higher velocity? The same for where the housing meets the 3" DP? I know I can't port the housing to match the 3" DP perfectly but I think I can do a much better job than the current configuration. Right now it's a huge step from the turbo to DP. No intentions of porting the intake side, since it seemed to match pretty well. And last but not least how much do i stand to gain by doing this? Mods in my sig. Link to comment Share on other sites More sharing options...
Technology Posted May 21, 2009 Report Share Posted May 21, 2009 Have you had it on a dyno? The only way to really tell if something happens is to look on a dyno, or maybe datalogging will be good enough. You should get it all warmed up and go log several 4th gear pulls starting at 1500rpm or so all the way up. Then after the porting, do the same thing and compare spool times and how boost tapers off up top. I think spool up will be the main difference you will see. As for the shape; the turbine housing is basically a cone anyway, you are just smoothing it out and matching the gasket. When i did my 12a, I went pretty far into the housing, but the further you go, the less and less you can take out. On the outlet side, I gave it a little bit of a cone shape and I rounded off the outlet edge so maybe the air wouldn't tumble over it so much. Link to comment Share on other sites More sharing options...
Whiplash Posted May 21, 2009 Report Share Posted May 21, 2009 (edited) You want the port on the head to be smaller than the exhaust manifold. It give a ledge to keep the exhaust gases from backflowing. Edited May 21, 2009 by Whiplash Link to comment Share on other sites More sharing options...
Indiana Posted May 21, 2009 Report Share Posted May 21, 2009 You can port the head and manifold to match then just leave the gasket alone or you can port it out too. I've seen the effects of porting it out and not porting it out. When its not ported out you do have turbulence in that area evidenced by soot in the manifold just behind the gasket but you'd have to pull each and inspect to see this and then they all match there is no soot deposits in there at all. How does the air know where the head stops and the manifold begins? Enlarge that outlet on the manifold all the way out to remove that step where the ring was laying then back bevel grind it so that makes the collector path for the turbine begin sooner. Its not just open, opening, housing its should all taper in and don't worry that the WG path is a big step into the side of that. The turbine housing you can port the crap out of it. You need to pay attention to the wastegate path, that path needs ported as much or more than the rest. When you are at high rpms and you have your boost level reached then WHERE do you suppose the gases are to go? They are to go out the WG path so do not forget this. When the WG can react quicker that's a benefit. If its small and you don't touch it then you'll have boost creep because its easier for the air to flow out the turbine blade than out the WG opening on larger turbos. Its more likely to happen when using a header. You don't have to do anything to the DP side. Link to comment Share on other sites More sharing options...
psu_Crash Posted May 22, 2009 Author Report Share Posted May 22, 2009 Thanks Guys! I run an external tial wastegate so that area is taken care of. Link to comment Share on other sites More sharing options...
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