Hi, 

I am at a loss over my newly built subie.

I have rebuilt an EJ20G Turbo engine with some WRX Sti heads, race spec bearings and timing belt, bigger turbo, 3" exhaust, sti injectors and other goodies.
It is running like a dream with one exception - 200kms per tank and low power. 
It is running an after market ECU (Link G1) off a 96 WRX with a road tune. 

The ECU obviously requires an o2 sensor to be fitted on the vehicle to adjust the mixture.

After looking for the bloody connector to an o2 sensor in the engine bay, I looked at the old down pipe and realised there is an exhaust temp. sensor but no o2 sensor on it.

I have never heard of a subie without an o2 sensor, and there is no information available online. (as far as I can tell)

Can someone please tell me, am I going insane or do they really did not have an o2 sensor??

Thanks in advance! 

Welcome to the USMB.

 

On the first gen Legacies (89-93 in Japan) the O2 sensor in the turbo downpipe. Is this where you're seeing the temp sensor? If so, that was probably modified by the previous owner. The O2 sensor should be at the top of the downpipe right after the turbocharger.

 

Can you confirm your engine is the single turbocharger setup.

Yes, it is the single turbocharger setup.

It has a 2 wire plug in the loom that looks stock that connects to a temperature sensor after the cat. No other bungs for other sensors and I can't find any other plugs for an o2 sensor.

 

Is there a way to maybe wire in a plug?

Could you perhaps take a picture of the wire/plug and temp sensor?

Sure. 

Yup, that's definitely an EGT sensor.

 

I would recommend having an exhaust shop weld on an O2 sensor bung so you can install an O2 sensor. The O2 sensor should be just downstream of the turbo at an angle to prevent moisture build up.

 

You can see in this picture where the stock location is just after the turbo on the downpipe.

 

I have got a 3" down pipe with the bung after the cat. I can weld another one where you said if necessary but I still don't know what to do with the wiring.

 

According to the ecu pinout diagram there is a shielding wire that connects to the ECU as well as the signal wire from the o2 sensor. The shielding wire is shown as if it goes around the signal wire as a dotted line but doesn't connect anywhere else.

 

How do I wire an o2 plug with that shielding wire? (Where does it go to after the ECU? Maybe there is a way to avoid connecting the shied and just wire in the signal wire?)

No matter, iv gone to the wrecking yard, pulled the wiring from the ecu connector and out of the loom. Going to wire that into my car and be done with it.

Update: I found the wiring for the o2 sensor at the ecu and traced them into the engine bay. It appears the plug was cut off. Possibly by the previous owner when he installed the exhaust temperature sensor.

 

Thanks for the help anyway!

The shielding on the sheilded wire keeps out interference. It needs to be grounded with the shielding for the crank and camshaft position sensors or you can get goofy signals going to the ECU.

O2 sensors operate at less than 1v so any interference in the O2 circuit will cause the ECU to alter fuel trim. Not a good thing on a turbo engine.