Best/optimum O2 sensor location?

[BigBlockMopar]

What's usually the best location to put an O2-sensor in a non-efi car?
Is there an optimum distance from the motor where it 'should' be put? Should it be near the hottest part in the exhaust-pipe?
I've read some info on this page: http://wbo2.com/lsu/position.htm

We recommend placing the sensor around 1 m (40") from the closest exhaust valve.
Sounds a bit vage, but maybe this is sensor-specific?

I want to install an O2-sensor in my Propane powered Dart, just to see where I'm currently at with AFR's and such. Also, in preparation of the possible 5.7 Hemi installation later on.

If it's of any relevance, the Dart has a dual exhaustsystem with no crossover-tube.

[squirrel]

I've been reading some of the instructions for wideband sensor kits, they suggest anywhere from 30" to the end of the tailpipe. If you're using a heated sensor (wideband sensors are heated) then you don't need to put it very close to keep it warm, and if it's too close it could overheat.

But hopefully someone with real knowledge will chime in

[TheSilverBuick]

DieselGeek would probably know best from raw experience, but on his 8 O2 sensor set up for individual monitoring they aren't very far from the cylinder head.

The only two real issues that concern me about mounting them is condensation and dilution. So you shouldn't mount them at the bottom of a pipe because condensation could puddle around/on the sensor and crack the sensor element when the sensor heater kicks on and mounting too close to the exhaust exit (like open headers, cut outs, end of the exhaust, etc) which reversion can back wash O2 in and give a false reading of what the engine is doing.

[Beagle]

Heated EGO, like Squirrel said.. and put it in the exhaust pipe. That's the best place for it. Wait - not IN it, but in it.

I put mine (2) in the collectors of the long tubes, seems to work fine. I rotated the collector after attaching it and before welding, though, and should have paid better attention to access for removal. I was more concerned with keeping the wires off the pipe and out of harms way.

[TC]

According to some of the reading I've done, 8 inches from the exhaust port is optimum for drag race type motors, for cars with circle track type motors half way between the exhaust port and collector is where you put it....... According to what they said the further away from the exhaust port the cooler the exhaust gasses get and the more skewed your O2 readings will be.........

[CDMBill]

You may have seen the video of our dyno session of the 588" here on Bangshift. In it you'll see the eight individual AFR sensors. Dougans Racing Engine who built the motor loaned me their dyno headers (2.25" primaries/ 4" collectors) so I could weld in the bungs and we went with 12" running length from the flange with the radial location based on ease of installation on the dyno and so we wouldn't burn up the leads. The collector location for each bank is typical for dyno set-ups. For the permanent in car set up I've followed recommended practice as Randall (SilevrBuick) mentions, up on the side of the collector tube in an area that is easy to access on the outside of the bend where the collector extension turns towards the middle of the car. This is because you need about four inches of space for the sensor and harness to extend out and route safely away from heat. I have two sets of bungs there, one pair for the LC-1's and the other pair for use at a chassis dyno shop. With the EFI we saw less than 2% variation from the Virbancic's engine dyno to the Westech chassis dyno to the FAST unit I had on the car for Drag Week.

[CDMBill]

One other note, we don't plan on a particular AFR number going in, we tune for best performance while keeping safe on the leanest cylinders. Then keep that as a bogey while making changes later at the track etc. We don't run closed loop.

[JeffMcKC]

If not running a full exhaust you may need to make a slight turn in the pipe to have enough restriction for it to read, when we take the exhaust off Docs Car we have to put a 45* turn out on the end its all it takes to read still the same 4 inch tube

[BigBlockMopar]

Will an engine which burns some oil because of worn valve seals have any effect on the readings?
The inside of the tailpipes on the Dart are soothy black. Can a sensor 'survive' in a situation like this?
Should the sensor in this be put a little closer to the engine for it to be able to burn off any oil deposits?

So many questions...

[TheSilverBuick]

Hmm, I never thought about it, but my T-bird uses oil like no body's business, a the tail pipes are also sooty black, and the O2 sensor still works on it after a couple years. Don't recall the mileage though.

[BlackGTO]

If not running a full exhaust you may need to make a slight turn in the pipe to have enough restriction for it to read, when we take the exhaust off Docs Car we have to put a 45* turn out on the end its all it takes to read still the same 4 inch tube

So a 45* elbow right off the open header collector would be a fix for false readings from a O2 sensor mounted in the collector?