I've been thinking...

If I put a wideband sensor in a 914 with a stock exhaust, where is the best place to
put it? Does it matter much whether it is in only one of the exhaust (HE) pipes?
Would it be better in the muffler? If so, where do you put it to get the best
reading? I'm just toying with the idea right now, maybe with the goal of an
aftermarket FI system.

Thanks,

Jeff

well you want a mix representative of all 4 cylinders, so I would put it where ever your collectors are.

But then again, I have NO idea where I would put my O2 sensor if I had one.

hmm,

b

Okay then, what does the inside of a stock muffler look like. I don't have a
collector per se, just four HE pipes into the muffler at opposite ends.
Jeff

thats pretty far out from the engine.

I dunno. Ive seen people just monitoring one cylinder and doing fine

Me, I would be nervous of what the other cylinders were doing.

Simple Answer: Thats too far out, ignore my advice and seek a more experienced person. If it were me, I would monitor #3 and put it before the HE heat shield plenum thing for the air, like 2" before that.

I've only seen the "bung" welded to the exhaust pipe.

the question is where?

I honestly dont know if it should be close to teh engine but measuring only one cylinder, or way far out measuring all 4 but being really far out from the source.

about an inch into the exhaust tiip. I would imagine one cylinder's exhaust would be enough. Most head temp guages read only one cylinde anyway. I suppose you could put a bung on each tip to measure each a/f ratio but how would you adjust each chamber individually anyway? Make sure the injectors are flowing ~ the same and thats about the best you can do.

I'm interested to hear other opinions.

-pt

O2 sensors need heat to function correctly. One or two wire sensors have no heat element and must rely on exhaust gas to bring them up to temp. Three, four and five (Wideband O2 is five) have heaters built in and don't need exhaust to bring them up to temp, so they can be mounted farther away. The stock muffler doesn't have a collector, so you can't mount it there. You can't just put it in the muffler because the quantity of exhaust gas will dilute your readings as you make changes. You have two choices, run an exhaust with a collector (at least just for tuning) or put the O2 sensor in one the the pipes. I don't know for sure if the exhaust pulsing will affect the sensor readings, but my intuition is that it's less than ideal. Based on that (possibly faulty) thinking, I would recommend an exhaust with a collector like a Bursch.

I'm getting one soon, and looked into this. I decided to put it on the hottest running cylinder. That's the one you want to be sure isn't too lean. The others can float.

I think I've heard that the hottest is number 3. Or is it 4? I'm probably going to go to the trouble of checking each cylinder's temp under similar conditions.

I checked with the gauge manufacturer about putting a bung on a small diamater exhaust pipe. I was worried about the restriction the sensor would add to only one pipe. They responded that the sensor only has to be flush with the ID of the pipe, and that you could weld two bungs on top of each other if you want, to get the depth, and still get an accurate reading....