mixture control

[356-930]

Originally Posted by gogomobil

what happens if the AFR sensor is installed before the turbo? wrong readings? or will the sensor be toasted?

Toast.

[RarlyL8]

I think position sensitivity may depend on the equipment and the engine configuration.
I have my AFR O2 sensor located in the stock J-pipe Lambda location, before the turbo, and it has worked flawlessly for years. I check and tune using the bung right after the turbo and see similar numbers. The response when the throttle is lifted is different as you might expect. The dyno shop that I use runs the typical tube up the tailpipe and gets consistant readings above idle.

[rsrmike]

Originally Posted by Chuck Jones

rsmike: It was the thin gauge of the 304 stainless that made me decide to go to the muffler pipe...but I was close to putting it on the end of the muffler itself...your post makes sense. However with a muffler, the leak is usually easy to spot either thru the sound of the leak or an exhaust stain where it's leaking. It seems to me that as long as the bung was installed correctly, and you check it every so often for leaks, it still might be a good place to put the sensor. I'm sure the experts will chime in...

I agree, that is a good idea I never thought of. I was just curious how a crack in the muffler would actually affect AFR readings, or if it would really matter.

FWIW, most of the mufflers I mentioned were so noisy, the cracks weren't really audible, it's was usually the floppy tail pipes of the borlas that got your attention. They did leave nice black trails though

The point I wanted to make was, if you go that route, and suddenly start getting lean AFR readings, before you freak out and suspect a fuel system issue or try to re-tune, check for cracks in the muffler, that's all

No worries

[hipdoc]

What happens if the O2 sensor is about 6" downstream from the turbo. One of my engines for the track has no muffler and the O2 sensor for my Electromotive just goes into a short exhaust tube. Do I have to make a longer tube?

[x98boardwell]

6" downstream from the turbo is a great location unless the pipe after the turbo is only 7" long. The worry would be that fresh air would enter the pipe and report false readings.

How long is your current pipe? If it is 12 inches long then you are probably ok.

I have heard that 6" after the turbo is ideal. Remember to have the sensor between the 10 and 2 positon from the top of the pipe facing down into the pipe.

Bryan

[NathanUK]

Certainly putting the sensor too near the end of the tailpipe can cause problems at idle and cruise.
Placing the sensor before the turbocharger could be disastrous if it broke up and damaged your expensive turbocharger.

[beepbeep]

Originally Posted by gogomobil

what happens if the AFR sensor is installed before the turbo?
wrong readings? or will the sensor be toasted?

Exhaust backpressure usually leads to wrong readings on-boost to tune of 1 AFR point or more. Sensor will also suffer from the heat and might fail sooner.