[Steve in Chicago]

I installed the Innovative Motorsports MTX-L wideband air/fuel ratio gauge about two years ago.

MTX-L Wideband O2 Digital Air/fuel Ratio Gauge

It's been great up till a little while ago. Then I started getting error 08 which is usually a bad O2 sensor. I got a new sensor but not wanting to cook the new sensor, I also got the heat-sink bung extender.

Innovate Motor Sports On-Line Store

The problem is, the bung I've got this installed in is the tall one.

Innovate Motor Sports On-Line Store

The combination of the tall bung and the heat-sink extender leave the sensor pulled too far out of the exhaust stream to take accurate or responsive readings.

In your mind, imagine another inch of bung coming off the threads of the extender and you'll see it doesn't penetrate into the exhaust flow enough.

So I need to remove the sink/extender but I still want some thermal protection if I can to keep from cooking expensive sensors.
I made up a solution I hope will work.

I have thick copper plate to act as a heat sink. This goes between the sensor and the bung like a crush washer but with a bigger outer diameter. Hopefully this will dissipate some of the heat conducting from the bung to the sensor. Copper conducts heat very well.

In addition to this I have a stainless steel plate suspended below the copper heat sink to act as a heat shield. The shield is to protect the sensor from heat radiating off the exhaust pipe. Stainless steel conducts heat poorly.

Here it is installed way down behind everything trying to get in my way of taking a good picture.

The reason for the cut-out in the heat shield is because my #2 sensor is right there and I needed to afford it some clearance.

A test drive showed the gauge readings were back to normal so the sensor is now in the exhaust deep enough to take readings. As far as knowing if this modification will make my sensor last any longer, I guess I'll know in two years.

 

[Tomvw]

Sounds like a good idea.
That should reduce the temperature somewhat, but it would be hard to say by how much.

If you want to reduce it a lot more, you could Silver Solder a heavy braided copper cable to the copper washer, and bolt the other end to the engine block.

 

[rogerius]

I used a 3mm thick aluminum "crush washer" 4inch x 4 inch, as a heat sink. Radiated heat from exhaust , I think is pulled under the car by the airflow from the front.

 

[Steve in Chicago]

I used a 3mm thick aluminum "crush washer" 4inch x 4 inch, as a heat sink.

Did you do this for the same reason I did (failed sensor)?

I was thinking of using aluminum at first. I looked up the thermal conductivity of various metals and found copper conducts about the best of the commonly available metals.

Thermal Conductivity of Metals

 

[rogerius]

it was a note on the Installation Instructions of the Innovate XD16 WB gauge on how to install a heat sink in order to prevent the failure of the sensor. Innitially I looked for computer component heat sink (the one with many fins) then I made my own with fins from a 1mm thick aluminum sheet to finally use a square 3mm thick 4x4 inches plate. It has been there for 4 years now.

 

[Steve in Chicago]

It has been there for 4 years now.

That gives me hope that adding some thermal protection will allow the sensor to live longer.

But here's the thing that gets me... The #1 sensor is right up at the exit of the turbo and it doesn't get cooked to death. Whats up with that?

 

[rogerius]

hahaha, good question.
It must be the heating through the 5th wire that on the OEM sensor is controlled by the ECU while on the gauge sensor is controlled (differently?!) by the "circuitry" in that black box integrated on the cable-sort of controller, I don't know what, that makes the difference. At least on the Innovate XD16 it is like that.
It may be that the gauge sensor is excessivelly heated when compared with the car sensor, in a less controlled manner, therefore it may fail earlier without the heat sink. I think it is not about the exhaust gasses heating the sensors but about the internal wiring heating the sensors.