Trying to figure this out. I'm currently running a Bursch exhaust on SSI exchangers on my '76. Stock FI. I want to install the O2 sensor and my AFR gauge kit, but I also want to switch to a better exhaust than the Bursch. My research tells me that the stock is hard to beat, except for price... Bursch is too raspy for my taste. When I wind it up it sounds like my 2 cycle leaf blower...

Depending on the internal layout of the stock (or Dansk?), I suppose it would be possible to weld the bung onto the body of the muffler at the first stage where the left /right mixing and initial expansion takes place. What do you guys think about that? And does anyone have a diagram of the 4 cylinder Dansk or OEM (if different) internals? I found cut away views of the early 911 Dansk. Is that similar?

Thanks,
Jim

911 Dansk diagram
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Although my application is a six, I think that all systems would be the same. I put the O2 sensor bung at the very end of the header right before where the muffler attaches. My system came with one input, but I added another O2 sensor and a dual input switch to the meter so I can switch between the two exhausts.....mounting it to the muffler may not be the best location.....others will chime in with their input......

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At the end of the header is the right spot

The stock setup for the 4 cylinder has four separate exhaust pipes bolting up to the muffler. So if I do it pre-banana, one cylinder would predominate. There would be some influence from the adjacent cylinder, I suppose, because of reversal between pulses, but the one would predominate.

Anyone have a picture or drawing or sketch of the internals of the 914-4 2.0 stock or Dansk muffler (or both, it they're different)?

Someone here must have done what I'm contemplating! Namely, installing an AFR (or Lambda) gauge with stock FI and stock exhaust.

Thanks,
Jim

If it's stock FI, does it really matter where you put it? It's just for reference in your situation. The further back you go, the more you will need a 4 wire heated O2 btw. Mine is right after the header collector, and I still use a heated one.

I think the closest to the junction of the four ports. You do realize though that one cylinder can be lean and the other three can hide it. Especially if the ecu has any learning charistics.

I'm going to plumb one into my Six and I'm gonna put it dead center of the muffler ... right or wrong.

I believe he said stock FI.

For my 3.2 conversion I put it on the left header right before the muffler.

Car runs great. Not using it for an AF meter, just part of the motronic

I install the o2 bung at the "TEE"section of the stock TRIAD system. both sides mix at this point and is before the mufflers.results are true

It matters. I want to use it to tune the D-Jet. MPS, fuel pressure, ballast resistor, they're all adjustable to some degree. I'll be using a wide band sensor, which is heated and should be about 40" back from the nearest exhaust valve anyway.

Anyone know where I can get a pic of the internals of the stock banana muffler? Or does anyone have a heavily used one I can buy for cheap? I'll share the pics of the internals.

Thanks,
Jim

That's really a cold location, a couple of inches behind the merging point of the collector is the best to average 3 cylinders which should be adequate. I understand the desire to average all 6 but the muffler is so cold it might be problematic.

Here is where I located my six and even it's too far back for my comfort. When I converted to fuel injection in my truck I drilled a hole in the exhaust manifold, the most appropriate spot for an O2 sensor.

If you do mount it in the muffler please report back the results and if you had any tuning issues.
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on the 76 the HE 's end in 2 single outlets to the muffler?
Is yours backdated to the 73-74 HE's?

If so what I did on my 73 2.0 w/factory d-jet was weld up a bung on my Bursch at the union before the muffler, we used the LM1 to tune & tweek the MPS then reinstalled the Banana

Sorry, I should have said that my '76 has the 73-74 type SSI heat exchangers.

My original plan was to just run with the Bursch, and install the sensor on or just downstream from the collector. Then when I decided I didn't like the Bursch, I thought I'd do as you're suggesting- get it tuned in and then switch over to the stock banana. Then I heard that the Bursch will run leaner than the stock set up, meaning that to tuning it on the Bursch wouldn't be the same as tuning it on the stock. Unless I come up with a way to so this with the stock muffler, I'm going back to plan A. At least I'll get some experience in tuning the FI while I try and figure this out.

Jim