AFR sensor
Turbo Mini Forums

where should it be fitted on the downpipe?

thanks

mine's half way down the downpipe. Not saying that's right but it does it's job

Instructions for mine are detailed here: http://cdn.shopify.com/s/files/1/0189/1312...Manual.pdf?2057

Although mine is nothing like what it suggests!

Read the sellers instructions - they all vary because of the way the different contollers deal with the cell (sensor) temperature.

The Bosch datasheets are online which state the maximum gas and body temperatures.

As a general rule, further away after a turbo, but plenty on her put them a lot closer and don't appear to have killed them yet despite what Bosch say....


My after turbo one is down by the gear linkage and the internal nearnst (SP?) cell temperauture is exactly what it should be.

My other two also read exactly the right temperature but they are a setup unique to an EFi 5 port.

If the temperature is too hot, the life will be limited and the readings will be skewed as they only read right between 725 and 775 C. The internal heater deals with exhaust gas below 725 but the controller can't stop the temperatures rising above 775 if the sensor is too close. Only a controller that can actually display the cell temperature will tell you this.

All this info is from the 14point7 website, not me, I have just moved to his products and can see the advantage of actually looking at these temperatures.

Schrödinger's cat - so which one am I ???

This is from the latest 14point7 manual

"The bottom row of the LCD displays sensor temperature, SLC Free B displays a sensor temperature range of 740C to 820C, SLC Free C displays a
sensor temperature range of 670C to 828C. The normal operating temperature of the Bosch LSU 4.9 (SLC Free A/B) is 780C, the normal
operating temperature of the Bosch LSU 4.2 (SLC Free C) is 750C. Lambda Accuracy is heavily dependent on sensor temperature, only when the
sensor is at proper temperature is Lambda accurate, -/+ 25C from normal operating temperatures is considered acceptable. If the Lambda
sensor is too cool; readings will tend to look “leaner”, if the sensor is too hot; readings will tend to look “richer”. If you notice that the Lambda
sensor is consistently too hot, then it is a good idea to move the sensor location farther from the engine exhaust port. If you notice that the
Lambda sensor is consistently too cool, it is a good idea to move the sensor location closer to the engine exhaust port, it may also indicate that
your electrical system/wiring is weak. When SLC Free is initially powered on, it will go through a sensor heatup routine to gently bring the
Lambda sensor to proper temperature, this takes approximately 1 minute. It is normal during the heatup routine for the sensor temperature to
exceed normal operating temperature, the temperature should quickly drop to normal operating temperature once the heatup routine is over."

I'm not saying its right but it does make sense.

So beware of possibly overheating the sensor, it might give you wrong readings that you don't know about without knowing the temperature.

I now (thanks to Jean and a bit of new code for his IOx) can see the temperatures and mine are all well within limits.

Schrödinger's cat - so which one am I ???

My sensor is about 6" after the turbo, like lots of others on here nd no problems so far.

Looking at the Saab front pipe that I cut up to use as my front pipe the bosses for the sensors on that are similarly close to the turbo.

A lot of factory fitted sensors will be close to the turbos either because (a) they are narrowband sensors where the cell temperature doesn't have to be closely controlled for accuracy or, (b) they ignore Bosch to gain themselves repair costs later in life (yes, that's me being cynical but it happens, cars are designed to last their warranty period, then reap in the funds from repair costs at the main agents).

At the end of the day, the Bosch datasheet for the 4.2 LSU (which is what most of you will be using) is readily available and the temperature limits stated. If you work outside those limits it's life will be reduced (probably not so much that anyone will see it as the kind of cars on this forum aren't ever going to be 100k miles without a rebuild) but will most likely be reading wrongly.

Just my opinion from all the research I have done and why I can now read the temperatures on mine (thanks to some new code from Jean).

EDIT - just looked up the part numbers for the usual Saab cars where the GT1752s are sourced and they all appear to be 4 wire sensors.
4 wires equals heated narrowband.
A wideband sensor uses 5 or 6 wires (depending on where the calibation resistor is, usually in the plug so 5 wires from the sensor to the plug then 6 wires from the plug to the controller) but never four wires.

Edited by Rod S on 15th May, 2014.

Schrödinger's cat - so which one am I ???

So I am living on the edge again then Rod !!!!

David, I doubt it....

The sensors should outlive both of us, they still last a long time even if outside Bosch's stated range as many on here have proven.

My real point is they won't be accurate once over 775C

Schrödinger's cat - so which one am I ???

That is rather what I meant, especially given the grief I dole out to what is a collection of second hand bits screwed together by an amateur.

Seems to be OK so far as the guy who jumped off the Empire state said as he passed the 27th floor.