AFR/Wideband bung position

Started by bikewiz, September 21, 2021, 01:31:29 PM

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I think I know the answer, but figured I would ask.
My LCB header has a bung in the "V" of the outer two pipes which is really close to the exhaust port (circled in red), I believe this was factory for SPI cars. Most of what I've read says it needs to be further away from the exhaust ports probably in the 2 into 1 collector (marked with an X)
So can I run it in the existing hole or do I need to weld in a bung at the "X"?

John Gervais

I put mine (Maniflow Freeflow) on the left-hand side of where the 'X' is -
- Pave the Bay -


I agree, it should be in the collector.....but I do wonder why the factory would put it there? IIRC the SPi was a cast iron manifold, so maybe that had something to do with the location?
Complete failure at retirement

1989 Cooper Racing Green
2009 Clubman S
2014 Audi Allroad


Here is a picture from when I converted "Flur" from SPI to Carb.  I circled and labeled the factory O2 sensor.  The factory SPI manifold is cast iron like Dave said and all three "branches" converge where the factory sensor is and a single down-pipe goes from there.

John Gervais

The biggest problem with mine is that the bung is positioned slightly wrong - I can't get the manifold out because it interferes with the left pot joint, so I've got to pop it out to remove it.  If I'd have moved it up at a slightly higher upward angle, it would have been fine.  Next time...
- Pave the Bay -


I ran our cars with the injection LCB for quite awhile. I did not really seem to have issues.
I wonder if there is a difference between wideband and narrowband acceptable locations.
The cast manifold has the sensor even closer to the head.

With the wideband in the injection car using the cast manifold, I do see some pulsing. That may be normal with the charge robbing going on. The injection LCB only sees two cylinders.


OK cool. Looks like X marks the spot.