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Old 08-25-2009, 10:55 AM   #1
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Default EGR bund for custom manifold?

I'm going to have a jgs manifold welded by a machinist friend for my t3 flange turbo and don't want to remove egr system because it seems to make tuning more complicated(going to be running ms) so I'm wondering where i could find a egr bung for a 94-97 miata - also does the placement of the bung have to match up 100% with the stock one?
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Old 08-25-2009, 11:39 AM   #2
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Im not sure MS has provisions to control EGR. Secondly high boost may have enough exhaust pressure to open the EGR valve and reintroduce exhaust back into the intake when you don't want it there = major stumbling:( GL tuning through that.
The most accessable bung is to cut the stock one off the oem manifold. Or find/buy a steel -12 AN fitting if memory serves me right. Should have others check if that is the correct fitting.
placement can go anywhere, but matching it to the existing EGR pipe would be ideal. no need to make it more complicated then it already is.
GL on your project.
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Old 08-25-2009, 12:06 PM   #3
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Well since im going to be running ms i guess the egr won't work then. Would i run into problems just capping off the egr pipe and leaving the system(valve) in place?
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Old 08-25-2009, 01:16 PM   #4
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I hacked an 01 EGR bung off a stock manifold and welded it to my turbo manifold. it wasn't perfect, but you can bend the EGR pipe some.
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Old 08-26-2009, 12:23 AM   #5
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On the '99, the EGR tube is 1/2-in, or a very close metric equivalent.

I have a 316SS -8 AN male fitting from McMaster that I will weld to #4 runner of my DIY manifold and figure out a customization of the EGR tube to connect it. My 9:00 coolant reroute using a 1.6L thermostat housing blocks the normal approach of the EGR tube to the manifold, so I have to route the tube below all that and approach the manifold from an angle.

If I remember right, the EGR valve on the NBs is a spool valve. Unlike a poppet valve, the pressure across it doesn't really translate into opening force, so I wouldn't expect it to leak under turbo backpressure.

I've never held '01+ fittings in my hands and measured them, but from the research I did, I'm deducing they are JIS flare, which is a goofy angle (30 degrees?) and thread size, with diameter and pitch that likely match British Standard Pipe (straight, not taper) sizes. Good luck finding that stuff in this country. Get a stock manifold and EGR tube from someone who replaced them with an Ebay header over at if you want to try that way.

I believe the NAs are completely different and come in more under the middle of the manifold. BEGI has some pics and stuff on the web site.
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