Oxygen Sensor Location

[3yearplan]

Doing research on an upcoming build. I have a DOHC 32V out of a 2004 Mach 1 and I am wondering where the oxygen sensors go when using the the FFR long tube headers. I know it says to delete (or bypass) two of them but that still leaves two. Any advice or information would be greatly appreciated.


Mike

[MPTech]

I'm not crazy about it, but planning to install the O2 sensor on the side-pipes just behind the 4-into-1 collector. I understand this to be the best location.

[3yearplan]

That's what I was thinking. Out of site, but still functional. Just thought I would gather ideas.

[efnfast]

Don't forget you want your o2 sensor positioned in a place where moitsure won't accumulate. For example, on a piece of straight pipe, you ideally want it between 9 o'clock and 3 o'clock. The worst place would be 6 o'clock

[markesmith]

Installed mine on my 5.0 340 hp crate motor roughly 12 " from the exhaust port on the two rear cylinders, welded bung that i removed from the stock exhaust headres onto my FFR long tube headers. I was told you want it pretty close so the heat does not dispate and change the quality of the sensor reading.

[3yearplan]

Does it matter that the 5.0 motors only used two (I believe) and the DOHC motors use four sensors, eventhough only two are used on this install. Does anyone know which two are actually used, the upstream sensors, or the downstream sensors ?

[AC Bill]

Installed mine on my 5.0 340 hp crate motor roughly 12 " from the exhaust port on the two rear cylinders, welded bung that i removed from the stock exhaust headres onto my FFR long tube headers. I was told you want it pretty close so the heat does not dispate and change the quality of the sensor reading.

I did likewise, and the car runs great. I think it may depend on the sensor used, as some apparently had self heaters so you could run them further away from the engine, and still get an accurate reading.

3YearPlan, good question on which to use, upstream or downstream..I imagine you may need both if you are running cats?

[3yearplan]

AC Bill, no cats here. So I still need to figure out which two to use. I have time on my side. This is my first time working with Ford engines and such. Up until now I have been working on Mopars. Ford parts are a LOT cheaper thats for sure.

[AC Bill]

I'm thinking the 02's before the cats would be the ones to use. They should be able to give the needed feedback to the computer, as to the actual rich/lean running conditions.
The ones after the cats I would think, would be giving confused signals, since your exhaust hasn't passed through any cat. They may continue to try to lean out the engine, as they would be reading an overly rich mixture, compared to what it normally would be, after having passed through the cats.

Purely speculative on my part, and I would get some confirmation on what's best, before installing them.

[dyno7351]

I'm thinking the 02's before the cats would be the ones to use. They should be able to give the needed feedback to the computer, as to the actual rich/lean running conditions.
The ones after the cats I would think, would be giving confused signals, since your exhaust hasn't passed through any cat. They may continue to try to lean out the engine, as they would be reading an overly rich mixture, compared to what it normally would be, after having passed through the cats.

Purely speculative on my part, and I would get some confirmation on what's best, before installing them.

The rear O2 sensors are used for OBD-II catalyst monitoring. Without active catalysts, the rear sensors should be deleted and the EEC strategy modified to omitted that function.

[3yearplan]

Thanks for the info dyno7351, I have taken down notes so I don't screw it up. Dyno7351 do you have a completed car ? If so, which engine are you running ? I am over here in Dearborn and wouldn't mind seeing a completed car in person sometime in the future. I have seen a few in the past, but didn't look to closely because I never thought I would be building one myself, but the stars they are aligning...

[Richard Oben]

Just make sure the O2 sensor does not hang down too far or is too far up so as to hit the body. We put them in the collector and point them straight in but at about the 4 O'Clock position. No issues with moisture and they are far enough down that they so not not hit the body and paralell to the bottom of the pipe so as not to be knocked off easily. Sorry no pic, Richard.