O2 Sensor Placement on Uel, pls help
 

I have a JDL UEL header coming in this week, and I am confused on where to put the primary (upstream) sensor on the header, as I will be using ecutek I can prob eliminate the secondary catalyst monitoring O2 sensor. So as we have all seen on most uel headers there are 2 sensor placement positions, one by its self on a runner to the collector and one just past the collector exiting to the overpipe. in theory it would be best to monitor what all 4 cylinders are doing so would it be better to have the sensor at the collector or on that lonely runner ?? I see everyone putting it on that lone runner but then your only monitoring that one cylinder which makes no sense. has anyone had experience with tuning these headers and the O2 sensor placement ?? thanks a lot :)

I agree with you. I have a revworks header and want to place it in the secondary O2 port. Ive read the harness doesn't really allow for it though. Id like to be wrong.

@FRS_Jack

well I would be willing to extend the harness for the pre-cat to take the place of the post cat and just cancel out the post cat.... if you look at the oem header it picks up exhaust gas from all 4 just before entering the cat, Id like to keep it that way and not just have it read off one cylinder, maybe Bob@driftoffice can help us out with this

Since there is no cat, you can really put the sensor in any which port you'd like. On the JDL UEL though, the wire length will be best if you put the primary sensor closest to the drivers side.

Thanks for the reply, that's good to know, yes I am ready to hack and extend my o2 sensor wires or just but a male and female connector splice and put them together too gain the needed length because im just not a fan of having the wideband which is used for open loop a/f ratio management right ? on that single runner, gives me the impression im only monitoring on one cylinder and not all 4

Thanks for opening this thread, I also have the JDL UEL header -not installed yet. Awaiting the answer on whether the first sensor needs to be moved. If it does, I'll be ordering one of these...

http://www.casperselectronics.com/st...oducts_id=1395

to extend it slightly (12") so I dont have to hack the stock sensor, and it'll allow me put everything back to stock if I need to at a later date.

I've already ordered a 36" one to move the second sensor back behind my JDL catted front pipe - I'm adding a bung behind it. Will be anxious to see if the computer is OK with it. Once again, everything can go back to stock if need be.

Thanks again! :thumbsup:

Once you change the exhaust manifold and placement of the front o2 sensor, your monitoring of the exhaust is screwed up anyway. Putting the front sensor in a collected area should be better than putting it in a single runner, but who can say how much better? You need computational fluid dynamics modeling to know that. That's how the original sensor placement was decided in the first place. You can put the sensor in a collector but that doesn't automatically mean it's reading all the cylinders, or even part of them. This is because of pulsation effects and turbulent flow in the exhaust stream.

And the rear o2 sensor, in stock configuration behind a cat, compensates for drift in the front o2 sensor. It's there for more than just monitoring the catalyst. Once you take the cat out and the rear o2 sensor's position changes (or is deleted), you're also affecting the front o2 sensor reading, under lower loads at the very least.

TL;DR I wouldn't be too concerned about front o2 sensor accuracy once you drastically change the exhaust configuration because it's going to be bad anyway.

Yes I have many points of view on this as well, even down to the leaching of heat tru the pipe due to restriction/insulation/type of steel, only way to know and give a accurate answer to this is to monitor the sensor on the factory tru running logs and leaning the afr/then enriching the afr at given load and rpm, then finding a place on the aftermarket header which is a mirror image to these findings, this would be a lot of r&d and not sure if its worth it, I will just trust Bob@Drift-Office and let him work his magic on my tune, i think for now until i get a master tuner licence and a dyno that is the best option :P