legacycentral bbs

So i've located a stock STI downpipe from a friend that is gonna sell it to me for next to nothing. I searched the downpipes, and it seems that most people use the wrx downpipe, but is it the same as an STI downpipe? Also, are these 3inch in diameter all the way through? ANd will the STI downpipe bolt directly on to my stock ej22t turbo?

Will there be a bung i can install my stock 02 sensor back in? so i wont be tripping CEL codes.

And another thing, if i buy one of those 40 dollar ebay fart cannons, will they really sound that bad. Im not lookin into a world class sound here, just somethin to give me that good boxer rumble.

The DP will bolt up to the turbo fine. I don't know about after the DP. There won't be an O2 bung at the top. I think they're only like 2.5" at the most. And the ebay coffee cans sound just fine.

awesome, so hopefully i can plug off the bung at the back of the downpipe and weld a new one near the top stock location. haha, that sounds so dirty doesnt it. oh im an idiot.

If I recall... You need to add spot for the second 02 sensor that these ECUs need...

smh0101 wrote:If I recall... You need to add spot for the second 02 sensor that these ECUs need...

Our cars only have one O2...as they are OBD1

STis have 2...as they are OBD2...

So...you could either plug the bottom sensor bung or just extend the wires on your sensor...with the latter being easier in my book.

555BCTurbo wrote:

smh0101 wrote:If I recall... You need to add spot for the second 02 sensor that these ECUs need...

Our cars only have one O2...as they are OBD1

STis have 2...as they are OBD2...

So...you could either plug the bottom sensor bung or just extend the wires on your sensor...with the latter being easier in my book.

Huh, cool...

I thought it was the other way... Thanks for correcting me (That isnt sarcastic).

smh0101 wrote:


I thought it was the other way... Thanks for correcting me (That isnt sarcastic).

No problem...


The second sensor on the OBD2 cars is simply for measuring cat efficiency...it's really quite rediculous...

The primary one still does the open loop fuel trimming, just like the one in the Legacy Turbo

Alright, thats for clearing that up fellas. looks like i'll just extend the wires down to fit the bung on the wrx dp. Im assuming they are the same size bungs right?

courtjesterclown wrote:Alright, thats for clearing that up fellas. looks like i'll just extend the wires down to fit the bung on the wrx dp. Im assuming they are the same size bungs right?

Yeah, it's generally an industry standard size

Where do you run the wires and what do you wrap them in running down next to the hot pipe?

Or do I have that all wrong?...

Generally, the O2 sensor is run along the tranny in various hooks and stuff.

555BCTurbo wrote:

smh0101 wrote:


I thought it was the other way... Thanks for correcting me (That isnt sarcastic).

No problem...


The second sensor on the OBD2 cars is simply for measuring cat efficiency...it's really quite rediculous...

The primary one still does the open loop fuel trimming, just like the one in the Legacy Turbo

It was my impression for the Subaru manual that the O2 sensor was for closed loop fueling. Just because they are a narrow band O2 so they look specifically for 14.7:1 and and It can only read very little in either direction rich or lean.

and as far as extending the wires, I was talking with one of the GM techs at work and as far as GM is concerned, splicing in wire to an O2 sensor opens up the wire itself to reading more oxygen. With subaru you can get around this if you have the 4 pin O2 sensor. I think it is 96-99 outbacks have a 3.5-4 foot extension harness for the O2 sensor. No gaurantee that it works, but I am pretty sure. I have one sitting in my bay at work.

But before I knew that...I extended the wires myself as well....

Yes, you're right; closed loop is the one that uses the sensor.

The idea that extending the wires opens up the wire to reading more oxygen doesn't make any sense. Don't worry about it. Just make sure you don't get any solder or anything else on the sensor itself. That's not a big worry, because most sensors these days have wires made of an alloy that you can't really solder to, so you have to crimp instead.

ok. Thanks vrg3. I didn't understand the oxygen on the wire thing myself...

Does the STI DP have a cat in it? If so it wouldnt make any sense to extend your O2 sensor to it, the car would run EXTREMELY rich that way.

As far as splicing wires,,, most manufacturers of O2 sensors sell "universal" replacements which include splicing aids. The Bosch universals are best, both because they are OE parts and also the splicing block they provide is very high quality and waterproof!

So im thinking just splicing into the wires and extending them is far easier that welding up the old 02 bung and cutting and welding in a new one. When i splice it, should i be using any particular type of wire? same size, same material. will the basic wire crimps work to splice?

Regular automotive hookup wire will be fine.

You'll need a very good crimper; the sensor's wires are made of a very tough alloy. Use waterproof crimp connectors.

ok. another thing, since the sensor is going to be in a new area and the new downpipe has no cat, this combo will still throw a CEL wont it? Also, if i install the downpipe and get the sensor hooked up properly, would it be ok to run it with just a downpipe for a day or two till i can get the rest of the system fabbed up. Or should i see if the exhaust place will put the downpipe on at the same time that they fab the system up?

courtjesterclown wrote:ok. another thing, since the sensor is going to be in a new area and the new downpipe has no cat, this combo will still throw a CEL wont it?

No. Our ECUs don't monitor catalytic converters at all.

Also, if i install the downpipe and get the sensor hooked up properly, would it be ok to run it with just a downpipe for a day or two till i can get the rest of the system fabbed up.

If you're confident the hot, loud, poisonous exhaust coming out that part of the car won't hurt anything.

yea, i kno there are some definite dangers in running it with just a downpipe. Im sorta thinking that im gonna have alot of trouble getting the old downpipe off because the nuts will be stuck. So should i attempt it myself or let the shop fool with it.

It might overheat the transmission or melt the rubber on the buttom of the car but otherwise it should be fine.

bmxpunk wrote:

555BCTurbo wrote:

smh0101 wrote:


I thought it was the other way... Thanks for correcting me (That isnt sarcastic).

No problem...


The second sensor on the OBD2 cars is simply for measuring cat efficiency...it's really quite rediculous...

The primary one still does the open loop fuel trimming, just like the one in the Legacy Turbo

It was my impression for the Subaru manual that the O2 sensor was for closed loop fueling. Just because they are a narrow band O2 so they look specifically for 14.7:1 and and It can only read very little in either direction rich or lean.

Yeah, you are totally right...I'm such a doofus...

Another fine instance of my brain thinking one thing and my fingers typing another


And Vikash...do you know what the specific alloy is that the wiring is made out of on the O2 sensors?

No, I don't. With the sensors I've dealt with, the metal in the wires kinda feels like stainless steel; it's very springy and you can't solder to it with rosin flux.

So is it difficult to block off the WRX sensor bung and cut and weld a new bung in the top of the WRX downpipe? OR is it just gonna be easier to extend the O2 sensor wires.

Depends; what are you better with? Metalworking or electrical work?

Another option you have is to extend the wires on the car's harness rather than the sensor's harness. Those are plain old copper wires. It does mean cutting factory wires on your car though.