Wideband o2 Sensor Location on SSI
 

I need to weld an o2 bung on my SSIs for an EFI setup and I’m trying to determine the best location. I’ve searched and found the usual location to be in front of the valve cover to the left of the heater duct in my photo. However, I’m wondering if I can place it to the right of the duct before the flange for the muffler, as noted on my photo. Would that be too far downstream? Any thoughts?

http://forums.pelicanparts.com/uploa...1754059968.jpg

I have a wideband O2 sensor on my 2.7 with CIS and SSI's; I use it to verify CIS is working right. I have the O2 sensor installed right behind the muffler flange. I've found that O2 sensor life isn't very long and I'm suspecting it's because the sensor is cold and not close enough.

If I was doing EFI, I'd install the O2 bung just downstream of where the three flow pipes come together.

You want it much closer to the union of the three individual exhaust pipes- kind of at the left end of the arrow in your photo- right in front of the lower valve cover.


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The sensor needs as much heat as possible from the exhaust flow. On the image above the location is to far away from the heat exchangers merge-collector.

The original bung/thread for the sensor location on SSIs made for the lambda SCs you can see here:
https://nineelevenheaven.wordpress.c...mbda-sonde.jpg

Its from the article in this link, scroll down till the end
https://nineelevenheaven.wordpress.com/the-911-sc-3-0-engine-with-catalyst-and-lambda-control/

The closer to the exhaust ports the better. Also near vertical with the wire harness out to top.

That’s what I figured, but wanted to be sure. Thank you for the responses, everyone!

Are you going to install two sensors so you can alternate reading each bank? Also, it’s been a while, but, it doesn’t have to be vertical, so make sure you can pull the valve cover off without pulling the sensor.

Just one for now. Good call on the valve cover removal. That was one reason I was considering moving it further down, but I suppose the sensor could always be removed to pull the valve cover if the angle is too close.

Yes. I angled my sensors towards the valve cover a little too much, so I have to unscrew the sensor to remove the valve cover. Tilt it away from the valve cover so that the sensor is angled parallel to the valve cover or a little more. A 45 degree angle from vertical works well.

That makes sense, thank you!

The sensor will have a range or degrees which it needs to be oriented. Usually between 10-75


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I agree with a tilt. You just don’t want water to sit on the sensor element.

What does Bosch say?

http://forums.pelicanparts.com/uploa...1754147528.jpg

The location the OP indicated in the first photo is fine.. The change in gas temp between the collector and flange should be minimal

All great info, thanks everyone!

Anyone have tips on wiring a wideband sensor to power on with the fuel pump in our cars, instead of with ignition on? The generic recommendation is to “power it from the fuel pump relay,” but with the wiring of the relay being unlike most vehicles and the safety cutoff from the air metering plate brown/black wire, I’m unsure how exactly to wire the o2 sensor to come on with the fuel pump.

Is your sensor wired to come on when the ignition is “on” or only when the car is running?

I started a new thread with my o2 wiring question. I figured it would be better to have a new title. The other thread is here:

https://forums.pelicanparts.com/porsche-911-technical-forum/1181287-wiring-o2-sensor-powered-only-engine.html