Ported Exhaust Manifold

[Catbox_95]

Has anyone ported or had ported their stock exhaust manifold? It is extremely clear that port-matching it to the head is dead-necessary since the casting looks like it was cast from a diagram draw with a crayon, but is there any other cutting necessary? There is a flange that appears to separate the 2 inner cylinders from the 2 outer cylinders, but this flange, while obtrusive in appearance, looks like it might be necessary.

Any suggestions?

 

[Stapl3]

I'd port it a bit larger than the size off the head.

 

[ruf_round_edges]

I ported mine, but did not port the runners. I just ported the inlet into the turbo.

Will

 

[91TSi FWD]

Though many people port out the piece that directs air into the turbo, I would highly go against the idea. By porting that out, you will get a lot of turbulance in the turbine housing. Its thier to direct air straight into the turbo. Polishing it would be ok though.

 

[Catbox_95]

That was my thinking on it, and since someone else feels the same way, it must be the way to go!

 

[joeym4130]

When I port cast Mani's , I leave most of the divider that directs the airflow downward. I remove a bit of it, because it allows me to get into the runners easier at the turbo side of the mani. I Also remove the stock step in the turbo side of the mani. Most places don't port the runners themselves, although on my mani i did a mild port/polish of the runners a few inches in, just cause i have fun porting things

 

[ruf_round_edges]

Though many people port out the piece that directs air into the turbo, I would highly go against the idea. By porting that out, you will get a lot of turbulance in the turbine housing. Its thier to direct air straight into the turbo. Polishing it would be ok though.

I didn't grind away the divider, just smoothed it out a little and removed the step down so that the inlet to the turbo is one diameter. Also, if your exhaust housing is ported, it wouldn't make sense not to port the manifold. That's my reasoning.

Will

 

[91TSi FWD]

For the turbine housing, extrude honing is the only way to go IMHO. When you port the turbine housing, you lose the original overall shape(you could have gone deeper in some areas than others). Because of this, air is not flowing in the path that it was made to, making the turbo less reliable. It is hard to get a perfect port job.

Extrude honing is more expensive, but worth every penny as it gets more horsepower gains from better flow, and retains the stock internal design of the housing.

Remember, you want your turbo to spin like it was made to, by re-designing the inside improporly, a lot of turbulance can be going through. Turbo's spin EXTREMELY fast, if anything goes wrong, you are going to have a very bad day.

Don't get me wrong, I know porting helps and I agree that porting the intake manifold, head, exhaust mani and 02 housing is benifitial, I'm just against porting the turbo.

 

[fate86]

if you port that lil step ont he side of the manifold that goes to the turbo, do i have to put that lil ring back in?

 

[siceclipse]

Oh GOD no. Dont put that back in once you've ported out the exhaust housing.

 

[fate86]

the exhaust houseing is on the turbo?

my manifold has a crack in it, so im just foolin around with it, im going to get it welded for now. so i used soem medium grit honein stones and seom grinding stones and i grinded away that ring inside the manifold and then polished it up ( unfortunatley that toungue lookin thing that directs airflow ####ed up my honer)

 

[Spln_Hrd]

the exhaust houseing is on the turbo?

that is the large peice of cast iron that the turbine and wastegate sit in.

i would use a carbibe bit for porting then sand stone ones to "clean" up the flaws

 

[Geezus_Aach]

porting, yes...but is polishing necessary? like buffing the insides to a shiny finish? I figured it would coat over with exhaust cra p anyways...

 

[fate86]

polishing is good because it smoths it out so the exhaust can flow more freely

 

[psychlow]

polishing is good because it smoths it out so the exhaust can flow more freely

It aids in reducing air turbulence due to friction against the imperfections in the housing's surface, more specifically...

If you're not getting oil into the combustion chamber, you shouldn't have much of an issue of the exhaust carbon-coating your polish job. Personally, I plan on running water injection, which helps steam-clean that area anyway.