AFR sender position

[ian65]

Before I put the turbo system into my silver car, I'm going to weld a lambda type plug into my downpipe so that I can fit a AFR gauge....
this is the type of plug...



I could do with a bit of advice.... this is the stainless downpipe... where is the best position for the plug, bearing in mind the heat from the turbo? ( the smaller branch off goes to the wastegate as the Elford dumps any excess boost down the exhaust.)



any ideas?

[TOOL]

Just after the turbo should be fine, like any O2 sensor.

On an NA engine you want it after the collector to measure thwhen tire engine (so you have to run it all the way down to the diff)

[Steve-A]

You want the lambda bung post turbo and before the first silencer/cat. The normal trade off is closer to the turbo means better response time but the sensor is exposed to more heat. You also want to weld the sensor bung on on the top half, preferably top quarter, of the pipe as it sits on the car. This reduces the amount of condensation thats likely to build up on the sensor which can damage it.

With your set-up Ian I'd be mounting the bung just before the first silencer, so you get minimum. A few milliseconds difference in response time wont matter to you watching the numbers while you drive like it would to an ECU making changes to the fuelling on the fly. Some manufactures recommend making a heatsink/shield to go between the sensor and the mounting face on the bung you weld on to help protect the sensor from heat in turbo rotary cars.

This probably preaching to the choir but it's only worth bothering if you go for the wide band sensor, controller and gauge. A narrow band can essentially only say <14.7 AFR or >14.7AFR. The narrow band can't say whether you're cruising at 14.6 AFR which is fine or 10 AFR which is power sapping and fuel guzzligly rich.

[Lucky]

I've received loads of dire warnings about the location of the sensor for my wideband on the FD. They're supposed to be like a minimum of 36 inches from the turbo, or the farther away the better. To be fair, even Bosch recommend locating it a loooong way from the ports on a rotary due to the zillion degrees of righteous rotary exhuast gas washing over it three times more often than a piston engine. Innovate recommend distant mounting as well, and even offer a special copper heatsink to recess the probe end and take away some of the excess heat. Apparently they burn out within weeks otherwise.

With that said, I completely ignored all theses warnings and mounted the sensor about eight inches from the hotwheel of the turbo (slightly bigger than T04R size on a big street port) mostly because that's where the boss was already welded in . It works perfectly, hasn't fried itself yet in two years of tempearatures close to those at the heart of the sun, and that includes two engines exploding and spraying it with neat fuel/apex seals

Now I've said that the little smegger'll eat it's own head next time I drive it, you watch...

[ian65]

thank's for the advice...

sounds like here is about right then?...



.

[Lucky]

Looks like a good compromise to me

[Steve-A]

Yup looks good to me.

I thought I'd heard 36" from turbo banded about somewhere too but couldn't find where when I put the other post up. Like Nik I've ignored the advice and my sensor was fine after a year of being about 20" from the ports on my n/a 13b with no extra heat shield.

[BO0557]

I've always put mine around 8-10" away from the rear of the exhaust housing and never had an issue..

On my car I run a AEM wideband and it performs well..