2G 2G exhaust manifold porting, how much to remove?

[Thecarfixerguy]

How far should I go with this? Obviously the baffles were engineered for a reason. I’m planning on bolting this to an FP6851S(68HTA V3).

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[Justin DuBois]

When I did mine, before switching to an E3 manifold, I removed the step that would hold the stock fire ring. match the dimeter to the SS gasket on both the exhaust manifold and the turbine housing.

It is typical to remove the fire ring step in an e3 manifold as well.

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This is a unported 7cm D2 turbine housing, notice, it makes little sense to use a gasket match port on the manifold if it does not smoothly transition to the turbine housing.

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[CrackedDSM]

Might just be my anecdotal “evidence” but I’ve always seemed to have better luck with leaving the divider in the middle and just sharpening it. Port either side so it become a blade basically. I remove the step ring like Justin did, and then I’ll hog out the runners as far deep as my bit will allow. Always really seemed to work well but don’t port the runners out TOO much. Basically just gasket match. Too much and it’ll crack like an SOB.


No numbers or evidence to back it up, but there was a noticeable difference afterwords. Not much but noticeable.

 

[jdxnc]

You're not supposed to remove the divider, it helps keeps exhaust pulses from going back into other ports. You're just supposed to enlarge the opening to match the compressor housing.

 

[MorrisonFab]

Our miscellaneous thoughts-
Agree to preferably keep the divider in there since it helps the exhaust turn into the turbine housing and a little less into other runners. The opening area itself isn't undersized at all for the flow, but a larger opening would seem to give more opportunity to exit/make the turn since it relies on a pressure difference to move things along vs aiming it where it needs to go. The actual size is likely less important than the transition itself, thinking of the manifold and turbine housing as one combined/matched piece. Probably beneficial to pay attention to the inside radius/short side radius at the outlet when you feel around the inner "edge" to make sure its rounded and smooth rather than squared off.

 

[Thecarfixerguy]

You're not supposed to remove the divider,

Well that ship has sailed haha. I saw a pic somewhere of one ported like this. Now I’m kicking myself for not looking in to it a little deeper before I started grinding. The divider did have some decent cracks in it so I figured I’d just yeet it. I’m just doing this since the manifold is off already.

Anyone with experience have any suggestions if I should just run it with the divider out or is it bad enough that I should get another manifold? I’m not looking to break records, just have a fun street car.

 

[CrackedDSM]

Well that ship has sailed haha. I saw a pic somewhere of one ported like this. Now I’m kicking myself for not looking in to it a little deeper before I started grinding. The divider did have some decent cracks in it so I figured I’d just yeet it. I’m just doing this since the manifold is off already.

Anyone with experience have any suggestions if I should just run it with the divider out or is it bad enough that I should get another manifold? I’m not looking to break records, just have a fun street car.

You’ll be fine. It’s not gonna kill your setup. It’s just more optimal to keep it.

 

[4wsaddict]

Good base for in any porting is when in doubt just smooth it out. Take out the casting marks with out changing the shape will not hurt but if you change the size/shape with out purpose or reason your just flying blind.