In the MY01, the 02 sensor in the exhaust system has been relocated to be further away from the engine (in the centre section of the exhaust).

Does anyone know why, and whether this change is a problem for exhaust upgrades?

I have a STI VII (MY01) and I will be removing the cats, installing a downpipe, cat free centre section and free flowing back box. (no cats, as they are not required in NZ)

Most aftermarket exhaust parts seem simply to provide a mount for the 02 sensor in the centre section location, as per factory.

My concern is that without the cats, the ECU will run the mixture rich to try and adjust the 02 levels at the sensor to what they would have been with the cats in place.

This wasn't a problem pre-MY01, as the o2 sensor was pre-cat, in the first bend of the system post-turbo.

Does anyone know if this is an issue to be concerned about, or does the ECU compensate and correct for the missing cats.

Should the o2 sensor be removed/bypassed, (if so how?), or are there any advantages in relocated it to the position it resided in pre-MY01?

Any ideas appreciated...

 

There are two O2 sensors fitted to the MY01, first is in the UP pipe after the pre-cat (before the turbo) and the second is at the bottom of the downpipe, when you decat this can cause the check engine light to come on as the reading from the second becomes too high with respect to the first, contact Scoobysport who have (or will have) a fix for this

 

If it is an STi7 you are talking about there is no sensor in the up pipe pre turbo fitted on them, A scoobysport up/pipe needs a blank fitting or EGT gauge sensor if fitting a gauge my STi7 has had no problems with engine lights been fitted a few weeks now cheers Barry

 

Barry

That's an interesting post. So your MY01 STi has only one O2 sensor, unlike the Euro MY01 WRX that has two. Is this because yours is a JDM spec car? Do you know what the new UK STi will have?

Duncan

 

Thanks for the info.

So what you are saying is that to avoid any problems, I will have to remove the pre-turbo cat?

Is this just a pipe, or does the whole header system need replacing?

I assume that my concerns about mixture are not really a problem then?

Cheers...

 

Yes thats what I have done, it is only a short section of pipe from the headers but a pig to fit either lift engine up as per scoobysport or I did mine by dropping the rack but a real fiddle, you have to remove headers complete to do this do not try splitting it as bolts lock up a treat, The header lamba can also be a pig behind the heat shield as for the uk version I would think its the same as the Japan model cheers Barry

 

Thanks for the info again!

In summary then, could I just fit a downpipe (e.g. Scoobysport) without the uppipe without problems/risk of overboosting on a STI VII?

 

In my car (MY01) I have a catless up-pipe(replacing the pre turbo cat) there is a factory EGT sensor there (top part of the pipe). I also had another bung welded in low on the pipe for an aftermarket EGT sensor(Greddy). The First O2 is in the header, right before the up-pipe. The second is in the mid pipe. If you remove cats you are going to have a steady CEL, unless you go with aftermarket management. I have one cat in the mid pipe, I had the bung for the second O2 put in just after the cat. No CEL for catalyst inefficiancy. I used the bung in the down pipe for tunning using a wideband O2 sensor. Under normal driving there is a bolt there.

Ken

 

Thats a lot of bungs !!!!

Jza

 

Ken got it right.

There are two O2 sensors on all New Age Imprezas. One in the centre section, just in front of the last cat and one in the headers where they collect into one.

The sensor in the up pipe is an EGT sensor, which the STi does not have.

There have been numerous problems with the tips burning off the EGT sensors. This sensor sits just after a cat and the temp of the gas leaving this cat is incredible. So incredible, in fact, that several people have burnt the end off the sensor. I also know of two EGT failures from from cat less up pipes.

The O2 sensor in the headers is a wideband Lambda sensor. This controls the main fuelling balance for the engine. The rear O2 sensor is there primarily to monitor the quality of the cat treated gas. Hence the CEL lights up if the rear O2 sensor sees non treated, or poorly treated, exhaust gas.

The in line ECU that we developed modifies the signal from the rear O2 sensor so that the OBD system thinks the cats are still there and working properly. Our "0420 Delete" ECU is only available to existing and future Scoobysport downpipe customers.

The OBD cat checking system is a requirement on all modern cars and some cars (eg Mercedes) will not even start if it has previously detected a fault.

On a Subaru, although the CEL lights up if the OBD has detected two driving cycles with poorly catted gas, it does not affect any of the operating parameters of the car. The only operating condition that OBD monitors is when the car is used on a light throttle cruise, eg 55-70 mph.

 

Thanks Pete, for that detailed reply.

It sounds like you guys at Scoobysport are the only guys that are on top of the mods needed for the new model.

I'll drop you an email to sort out prices and so on!

 

Pete

If I'm reading this correctly now - if I come to you for say, the downpipe, centre sections and backbox, for my new MY01, you would also fit the 'inline ECU' to remove the CEL problem?

If so, I'll be visiting soon

Cheers
Chris

 

BretMan,

There is a company in the US that sells rear O2 simulators ( http://www.casperselectronics.com/gp/O2SIM/index.htm ). I installed this sim. 6 month ago and since then have had no problems with the cat efficiency CEL nor with the fuelling in my Euro WRX. It’s about $40 plus H&S, so you can give it a try.

L015