911 3.2 '87 Oxygen sensor

[ggraaf]

Hello, I just bought a 3.2L engine from a '87 Carrera, complete with ECU and wires. There is a small device fixed at the wire with a support to be placed onto something, together with a connector. After much searching, it seems to be an Oxygen sensor that is positioned in the engine compartment, just under the fuel filter (O2 sensor?/84 Carrera). The connector is for a separate heater element to make the sensor function properly.

I am wondering what sense does it make to place a O2 sensor in the engine compartment instead of in the exhaust tube?

As I do not have the heater element for this O2 sensor I would like to know what to do with it:
1) Shopping for a heater element and place it in the engine compartment in the way as it should be.

2) Leaving it unheated in the engine compartment. This would mean the sensor would not work properly or not at all.

3) Cutting off the sensor. Leaving the wire open or make a short circuit with the wire shield (=Mass?).

4) Substituting the O2 sensor with an integrated heater and placing it in the exhaust.

What are the consequences for these options?

BTW I am living and driving in the EU and the motor will be placed in my 914 without catalytic converter.

[ischmitz]

Let's be really clear. An O2 sensor is to be placed into the exhaust stream before the catalytic converter to measure the residual partial pressure of oxygen. It needs to be at a certain operating temperature (~600 degree Fahrenheit) to function properly. They are heated from the exhaust gasses. However, during engine cold start it takes a while for the manifold and other things to heat up. For a faster startup of the sensor they have a resistive heater circuit that gets them functional quicker.

Whatever the previous owner has done here is plain nonsense. Maybe he wanted to fake an O2 input but this will not work. You might as well loose this thing. A muffler shop can weld in a proper threaded fitting into the collector tube past the headers where an O2 sensor needs to live.

Then, you need to get the correct connectors. From the images it looks the original Porsche style connector has been removed (they break over time) and replaced with something different. As long as you equip the narrow-band sensor you'll install with the mating connectors all should be well.

Ingo

[pavegeno]

When I purchased my 88 in 2005 there was a bypass pipe and no cat along with a no-name performance chip. The car ran a little rough, smelled a bit, and the mileage wasn't that great. I had a shop weld in a port to insert an O2 sensor and thankfully found the plug-in for the sensor lying quietly in the engine compartment. Thankfully in the box of parts the previous owner gave me, I found the stock DME chip and replaced it. Through a combination of the chip and oxygen sensor, the smell was better, the car idled and ran more smoothly, and my gas mileage improved. Later I installed a cat and the smell went away. Porsche knew what they were doing. I spent several years un-modifying the car in several areas and returning to stock and things keep getting better. I am literally down to replacing a few stickers that are trashed out in my quest for perfection.

[76FJ55]

The connections you have are as delivered from the factory. If you get an OEM O2 sensor it will connect directly to the connectors on your harness. The bracket attached to the o2 sensor wire is mounted near the bottom of the fuel filter as shown in the thread you linked. The single wire connector is for the sensor wire and has a boot attached to the wire on the O2 sensor that slips over the white plastic on the harness connector to create a seal. The 2 wire connector in for the heating element. The heating element is built into the O2 sensor itself so no separate part is needed. The O2 sensor is mounted into the exhaust after the Y and before the Cat (or pre-muffler if non-cat). Since the connections are in the engine bay, the wire has to pass through the engine tin to get to the exhaust, which again you can see in the first photo photos from the linked thread.

[ggraaf]

Originally Posted by 76FJ55

The connections you have are as delivered from the factory. If you get an OEM O2 sensor it will connect directly to the connectors on your harness. The bracket attached to the o2 sensor wire is mounted near the bottom of the fuel filter as shown in the thread you linked. The single wire connector is for the sensor wire and has a boot attached to the wire on the O2 sensor that slips over the white plastic on the harness connector to create a seal. The 2 wire connector in for the heating element. The heating element is built into the O2 sensor itself so no separate part is needed. The O2 sensor is mounted into the exhaust after the Y and before the Cat (or pre-muffler if non-cat). Since the connections are in the engine bay, the wire has to pass through the engine tin to get to the exhaust, which again you can see in the first photo photos from the linked thread.

Now I got it: the small device fixed to the cable is just one of the connectors to O2 sensor. Thanks very much!