moving o2 sensors downstream

[sikhabib]

I bought a second hand set of 1 5/8 pacemaker tri ys and under car cats that bolt between the extractors and catback system . i currently have the cats in the engine bay and o2 sensors very close to stock exhaust manifolds. With the tri ys im going to have to move my o2 sensors to the end of the extractor which will be approx 60cm downstream from the stock location. What i want to know is will my stock o2 sensors work that far down and will i have to play with the o2 sensor settings in the tune like switch point etc

Thanks Ronny

Car is a 2004 VY2 SS Holden Commodore

[S2H]

I dont know for sure on teh commodores if what sensor they are using stock...but I know on F-body's and several other US vehicles we upgrade the stock ones to Bosch #13111's whenever headers are added or whenevre the o2's move further downstream as they need a better heater when moved...and teh 13111's have a much better heating element in them...

but like I said...dont know about the comodores

[possum22]

Ronny,

This is the reply I got from SSBaby on ls1-australia when I asked the same question.

Since the extractors will extract the heat a bit better and increase power slightly, the effect might be slightly leaner running. You might need to richen up your VEs a little and your PEs might need an adjustment to your top end rpms.

I hope this helps, it didn't make much difference to my tune, I did richen up my PE by .005 in some areas after fitting the extractors, my O2's were only moved 6" 150mm. cats still in same place on my VY2 Adventra.
Rob

[sikhabib]

hey rob did you get the 4>1 short extractors put on??(just guessing cause your cats are in same place) how much difference did it make to the power/tourqe of car?

SE what happens if you dont upgrade the o2s when there moved? do they not switch fast enough of just dont give readings at all??

i was pretty sure i would have to adjust the pe and ve tables as the engine will be breathing easier with the extractors but i wounder it my stock o2s will still be giving an accurate readings in closed loop when moved.
If you tune your ve table and fuel trims with o2 sensors in the stock positions and all you do is move them further downstream with the same exhuast (around 60cm) will that generally affect fuel trim readings??
Im thinking that it shouldnt as the fuel requirements of the car havent changed but if it does make a difference dont you run the risk of running the car lean as the o2s will be giving false readings??

[possum22]

No, mine are 1 1/2" Pacemaker try-y's made for the Crewman Cross8 & Adventra AWD, I did notice did it had more power down low, where I wanted it.
I fitted a SureFlow 2 1/2" SS catback system about two weeks earlier, that did make difference all over.
As I said my o2's were moved 5" for the drivers side & 7" on the other side just before the cats, going by HPT's trends the o2's are switching. My WBo2 says 14.5-14.7 when driving normally.

[S2H]

sikhabib... to answer your question....
with any o2 sensor they are basically calibrated to switch properly in your vehicle for the stock locations...
since they are heat dependent, moving them down stream can cause them to not switch proprly resulting in poor fueling and sometimes some very odd LTFT/STFT's
I have a buddy that his longtubes made one o2 read lean and the other rich.....not exactly ideal..LOL
he changed to an o2 that has a better heating element(the bosch #13111's) per my recommendation and his fueling was back to consistent and very even between banks.
usually when colder the read lean...
the 14.7 switchpoint is supposed to be accurate at a wide variety of temperature ranges.... but exhaust dependent could allow for too much of the heat being dissipated before it gets to teh o2's
I have also found that headers with high temp coatings on them do drastically better than headers that do not have any coating..
here in the US one of the cheapest and easiest to get is JET HOT...they make coatings ranging from basic to ready to handle solid rocket booster heat....
I tell most perople while they say that their basic coating is designed for all N/A applications..its smarter and better to step up ione step from recommended basic to their 2000 series coating which they claim is designed for small to medium turbo applications...
its amazing how much difference the coating makes...
helps keep the heat on the inside of the pipes..and teh heat makes teh exhaust scavenge faster...allowing for more potential horsepower and torque.

[sikhabib]

That for the help guys

im gonna be installing the extractors this weekend so ill see how i go with the stock senors in the new positions. Extractors arnt heat coated so if the o2s give me any trouble ill just run the car in open loop until i get my hands on some new o2s with better elements.

Ill post up my results

Rob did the try ys make much difference to the note of the exhaust??

[possum22]

They made the note sound deeper, not as loud & not just all noise as Greg the SureFlow exhaust maker said they would, I still got a section of 2" after the cats cause the local exhaust shop couldn't bend the pipe to fit over the transfer case cross member.
My extractors have the HPC cermic heat coating. My catback are the quietest sport system SureFlow make, they seem to drone at 60 kph before fitting the extractors, any droning is gone now.