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OEM exhaust manifold porting
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OEM exhaust manifold porting
OEM exhaust manifold porting
OEM exhaust manifold porting
OEM exhaust manifold porting
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Old 01-25-11, 06:12 AM   #11
stinkfinger
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Default Re: OEM exhaust manifold porting

Quote:
Originally Posted by gamma_man View Post
How did the x-pipe "outlet" diameter compare to the inlet diameter of the manifold section (the one with 3 inlets and connected to the up-pipe). Was there an appreciable step-down? If so, this would presumably cause more back pressure than the step-up from the other manifold into the x-pipe.

i hope that made sense...
The inner diameter of the Grimmspeed x-pipe was quite a bit larger (~1/4" going from memory) than the manifolds to which it attaches. This mismatch is the same at both ends. I'd agree with your assumption that such a large step change in diameter would negatively affect flow. I wouldn't bother installing a larger x-pipe without port matching the cast iron manifolds.

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Old 01-27-11, 06:37 AM   #12
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Default Re: OEM exhaust manifold porting

I Just finished porting my cast iron manifolds and got the Grimmspeed Xpipe. I am doing a turbo upgrade so no dyno #s compared to the STG2 tune. I just gasket matched each flange and smoothed everything over. I also went and ground off the exterior flash casting as to not cut the wrap and I read somewhere it helps. I am going to wrap them with some DEI Ti wrap and spray them with heat treatment. I have some Prosport EL headers and they are not compatable as they come 3 flange and the turbo kit is set up for 2.(P&L 3076R .62) So they are for sale now. My car did really well (302whp,358wtq stg2 Dan Mach V) with the EL I will be curious how switching will affect it. I am sure once I get it tuned after the install I wont notice the change over!
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Old 08-18-11, 04:40 PM   #13
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Default Re: OEM exhaust manifold porting

Quote:
Originally Posted by stinkfinger View Post
The inner diameter of the Grimmspeed x-pipe was quite a bit larger (~1/4" going from memory) than the manifolds to which it attaches. This mismatch is the same at both ends. I'd agree with your assumption that such a large step change in diameter would negatively affect flow. I wouldn't bother installing a larger x-pipe without port matching the cast iron manifolds.
how many carbide burrs did you use for the exhaust manifold porting?
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Old 08-31-11, 09:31 PM   #14
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Default Re: OEM exhaust manifold porting

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Originally Posted by fatbastard View Post
how many carbide burrs did you use for the exhaust manifold porting?
Just one, it held up fine and is still going strong.
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Old 09-02-11, 09:36 PM   #15
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Default Re: OEM exhaust manifold porting

I have an 04 with a 35r, heads, and cams. I am running the perrin EL header, primaries are less then 1.5" so I think its choking, and there are bad transitions from ports. I want to get an UEL header or port out an oem manifold myself. I was thinking the oem route and porting it all the way through to match the grimmspeed x-pipe, 1.9" and port matching. Thoughts? I guess anything would be better than what I got now...
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Old 09-09-11, 11:43 AM   #16
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Default Re: OEM exhaust manifold porting

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Originally Posted by 04ssti View Post
I have an 04 with a 35r, heads, and cams. I am running the perrin EL header, primaries are less then 1.5" so I think its choking, and there are bad transitions from ports. I want to get an UEL header or port out an oem manifold myself. I was thinking the oem route and porting it all the way through to match the grimmspeed x-pipe, 1.9" and port matching. Thoughts? I guess anything would be better than what I got now...
I guess I would have assumed (based on the classic "Rainmaker" header dyno comparison thread over on nasioc) that Perrin ELs flow better than P&P stockers w/crosspipe.

Why specifically UEL, out of curiosity? If I had a big turbo car, I'd probably look for an EL alternative with larger primaries.
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Old 03-19-17, 09:55 PM   #17
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Default Re: OEM exhaust manifold porting

I recently bought a porting tool and carbide bit to port the stock header. Also will wrap it in titanium wrap when I'm done.

But based on what I'm reading the head and the manifold are already the same diameter. hmm. So the claims of spool increases are mainly due to smoothing out the bend in the manifold or what?

EDIT: Ported my manifold. I thnk there is an advantage in porting it. Why? Because hot exhaust gases leaving the ex valve needs some space to go, but not too much. This is why the ex port on the head is significantly larger than the valve itself. I'm guessing the sweet spot diameter is closer to what we reach when porting the stock manifold.

Last edited by jmlegacy; 03-31-17 at 08:21 PM.
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