How Close Does the O2 Sensor Really Need to Be?

[toddalin]

While a portion of the exhaust system is out of my '64, I thought about having an O2 bung welded into the "H-pipe" crossover. (Obviously no cats.) I figured here, it would see both banks simultaneously without disturbing the exhaust flow so much. On my car this is just infront of the rear axle either just before or after the mufflers. Is this too far from the hot exhaust stream to be an effective point to measure O2? Thanks

[cardo0]

I know you've seen the smog test station sample at the end of your exh pipe. The difference is that some O2 sensors are self heating and some are not. But as a general rule the closer to the exh port the better. And for the serious tuner an O2 sensor in each exh port header pipe right at head is best (yes a sensor for each cyl).

U need to find out if your sensor is self heating or heated by the exh. I think the 3 wire sensors are self heated and location less critical. 2 wire sensors need to at least be in the header collector or closer.

Hope this helps.
cardo0

[No Go]

Is the O2 sensor for the cars fuel injection or to simply monitor the mixture (ie stand alone wide band?)

[toddalin]

Originally Posted by No Go

Is the O2 sensor for the cars fuel injection or to simply monitor the mixture (ie stand alone wide band?)

Just to monitor A/F ratio to best set carb.

Actually, Innovate's web site notes that placing the bung too close to teh engine results in too hot a mixture that cannot be read.

[No Go]

Well the standard for those sensors seem to be in the first 1/3 of after header exhaust. If that is not convenient there doesn't seem to be too many standards...ie I've used the tail pipe probe at the dyno and it worked fine although folks will argue that the 'transitory' time will cause issues with synching the AFR with a particular RPM point.

If it was an EFI control..then putting it at the tail end of the pipe would more than likely cause problems with being too cold and when the engine goes into O2 sensing mode.

I mounted mine in the collector and has no issues-coated headers too.

One other comment is putting it in the h pipe makes sense, but not heard of anyone doing that...wonder if there is enough 'gas passing' to read accurately-I don't know.

[cuisinartvette]

Woudltn put it in the Hpipe, keep it closer to the exhaust manifold, or if you have headers weld it into the collector

[2000BSME]

I have mine at the tail pipe. It measures the same as when its placed in the header bung (hmmm... what does that tell you about the state of my catalytic converters....).

LM-1 unit self heated.

[SBChvy]

Has Anyone installed these on a car that has sidepipes? I was wondering if there was room anywhere that they couldnt be seen?