Post Cat O2 Sensor Sampling Rate

[GlassTop09]

Hi All,

I was under my car messing around awhile back just after swapping all my O2 sensors from the "new" Ford OEM O2 sensors (F85F-9G444-BD....which are in reality Bosch #15717 O2 sensors w\ FoMoCo badging) back to NTK 22060/22500 O2 sensors (were FoMoCo OEM std O2 sensors when car was manufactured) & was looking at the post cat O2 sensors (installed using Big Daddies Garage 90* CEL Eliminators....running Kooks 1 5/8" LTH's w\ Kooks Catted X-Pipe using Kooks Hi Flow Race Cats-not the Kooks "Green" Cats due to getting MIL's. Eliminators are mounted in a 25* upward angle to eliminate water collection) & wondering if the readouts would change if I remounted the eliminators to be parallel (in same plane) w\ the O2 sensor bung instead of being angled upwards. Since initial install of these eliminators @ 25* up angle I've had no more issues w\ cat MIL DTC P0420/P0430 codes. So I got my tools & repositioned both eliminators parallel to the O2 sensor bungs to test this out.

After a couple of days driving (mostly in town) seeing all operate as usual I took my car out on an open road run of approx. 60 mi at hiway speeds between 60-70 MPH & during the drive back home the MIL came on. From the car showing no signs of any operational issues I assumed it had to be related to the post cat O2 sensors so when I got back home I hooked up my scan tool, checked & found the following DTC: P0139 Bank 1 Sensor 2 Circuit Slow to Respond. Researched this DTC which indicates that my B1S2 O2 sensor wasn't responding (making current) within a specific amount of time meaning that the O2 sensor readout was at the min end of the scale (or referencing to reference air which is at\close to .000v). Now these O2 sensors are brand new & verified operational before remounting the eliminators in parallel w\ sensor bung so what this told me is that once these eliminators were mounted in parallel w\ the O2 bung there was no more exhaust exchange or circulation occurring within thus trapped mostly O2 inside the eliminators which rendered the O2 sensor out of commission (stopped generating current) long enough to fail the PCM O2 sensor check test.

I then got back under the car, reset both eliminators back to the 25* up angle (as far as I could angle them up & still clear the unibody) then cleared the MIL to see if this MIL would return. After several days of operation since then (includes a 1,752 mi trip over 5 days) I have yet to see any MIL since & all Onboard Monitor Component data (the Mode 6 data) shows all O2 sensors passing all their monitor checks, all cat switch ratio data shows passing (this is the data the PCM is looking at--ratio of the front O2 sensor switching rate vs the rear O2 sensor switching rate--to determine if a cat has passed\failed efficiency) & all misfire monitor checks (1 of these checks is to determine the amount of cat damage associated to misfires) are all passing @ 0% w\ 0 misfires recorded for all 8 cylinders. This determined that these CEL eliminators need to be mounted in a position that would create some thermal exhaust circulation to occur so that the O2 sensors would operate within the expected O2 sensor test parameters as coded within the PCM for the PCM to determine proper operation of the O2 sensor as well as proper operation of any cat thus the amount of exhaust gas sampling volume rate to the O2 sensor is the determining factor...………...

This proved to me that there has to be some exhaust flow/circulation present for the rear O2 sensors to actually operate regardless of where they're mounted & the AMOUNT of exhaust flow volume (oxygen in particular) will determine how often they will switch. Now this isn't new in & of itself, but what is relevant is where they're mounted & the position that they're mounted will determine how much they will react as this controls the amount of exhaust sampling volume they see which determines the switching ratio vs the front pre-cat O2 sensor in addition to the varying amounts of unburnt oxygen present in the exhaust sample. So in essence to ensure that any cat will operate properly on a particular vehicle the cat should be designed to the same dimensions (or as close to it) w\ the same O2 sensor bung placement as the OEM cat that was designed for the vehicle's OEM engine design. The OEM cats for the 05-10 4.6L 3v were a clam shell design w\ the O2 sensor bung welded on the cat's clam shell body after the 1st substrate brick (in the center of the cat clam shell body at a 10 o'clock/2 o'clock position) & not on the 2 1/2" piping. This got me to think that w\ most of the aftermarket cats designed for this platform (w\ a few exceptions) the post O2 sensor bung location is actually in the wrong place which is potentially throwing the exhaust sampling volume rate off (much higher sampling volume) to the O2 sensor than OEM design which is accounting for a LOT of the cat P0420/P0430 codes & not necessarily the cat substrate's inability to process the exhaust volume....especially in conjunction w\ an unaltered OEM long block in NA form which will dictate maximum airflow capacity thus the max volume capacity of an OEM cat design at optimum A/F ratios (which will include the deltaP across the substrate at this max volume) thus NOT necessarily the aftermarket FBO components used w\ it (any FBO part, regardless of how well it is designed, will not allow the full air volume capacity of the OEM long block to be reached in NA form due to it's own operational design restrictions). This also explained to me as to why the only time these Kooks Hi Flow cats would "fail" & set the P0420\P0430 cat codes is when I would lug the engine too long at low speed in 5th gear instead of downshifting.....w\o doing this I never got a cat MIL light. The O2 sensor bung is welded in the post cat 2 1\2" piping & not welded on the cat's 4 1/2" OD outer substrate shell after the substrate brick inside...………..

So I have reached out to a couple of major aftermarket cat manufacturers & asked them both about this (won't reveal any names at this time) w/ 1 of these companies all but alluding to this reasoning of mine being true & stating that all their cat's O2 sensor location bungs are attached according to the OEM cat original design O2 sensor location but the other 1 giving me the std non answer position of stating that the vehicle undercarriage design will determine the O2 sensor placement but not answering to the O2 sensor location placement affecting the perceived cat efficiency by altering the exhaust sampling volume rate to the O2 sensor away from the OEM design...……...

After this I got under my car again & measured the distance 1/2" aft of the 45* bend of the Kooks exhaust pipe off the header collector to the front edge of the trans crossmember....came out to 17". This is more than enough room to accommodate a cat at the EPA Federal OEM dimensions of 4 1/4" OD x 11" L w\ the O2 sensor bung welded in the center of the cat's outer shell w\ 2-2 1/2" extensions added (2 brick substrate design total length of 15") to reattach back to the existing piping (need to be welded) or even a CARB FVN # certified OEM dimensioned cat @ 4" OD x 11" L w\ O2 sensor bung also welded in center of the cat shell housing (2 brick design) w\ 2-1/2" extensions added to reattach back to the existing piping (also welded) w\o interference......so I do not understand why most aftermarket cats don't extend the cat housing shell enough to put the O2 sensor bung on the cat's OD housing after the substrate brick...an extra 1" of shell extension would do it (only found 2 companies that do this across the board on their cats designed for the 05-10 S197 platform which meets the Fed EPA and\or CARB std due to meeting the OEM design std) instead of on the post cat piping which would slow down the exhaust sampling volume rate to the O2 sensor due to the expanded ID area of the cat's outer shell vs the ID area of the 2 1\2" exhaust piping relocating the O2 sensor's element farther away from the center of the exhaust flow so it doesn't get hit w\ too much exhaust volume to sample......just like the OEM cat is designed. There is more than enough room to easily mount the O2 sensor w\o coming into any resemblance of contact w\ the TR3650 transmission (can't say for an automatic as I ain't got 1 to measure).

So I'm gonna look into getting a used Kooks 2 1/2" O\R X-pipe (or H-pipe) that fits w\ my headers then getting a couple of these cats welded in to install on my car to then test them to see if they can handle my engine's exhaust output w\ the current FBO's, cams & tune w\o any eliminators & maintain proper cat efficiency w\o MIL's...…& maintain current HP\TQ levels…….

So I'm wondering how many of y'all are running a FBO & tuned 4.6 L 3V's in NA form w\ OEM exhaust/cats w\ rear O2 sensors active & not getting MIL's...……………….. ?

While I was at it I also looked up the dimensions of the OEM Fed EPA cat for the 07-12 GT500 (5.4L 4V SC V8) & found that it isn't any larger (4 1/4" OD x 9" L w\ total length of 13") than the OEM dimensions for the 05-10 4.6L 3V but the OEM O2 sensor location for these is not on the cat shell itself but is installed on the post cat 2 1\2" exhaust piping (but this car still uses the same NTK 22060/22500 O2 sensors as the GT) so it would seem that the OEM 4.6L 3V cat design should be capable of easily handling an OEM NA 4.6L 3V long block w\ FBO's, cams & tune w\o MIL's & maintain good exhaust flow...………….

The key IMHO is depending on the tune's AF ratio chosen for closed throttle/part throttle/WOT operation not being too far away from the OEM AF ratio used (especially rich) for the same area of operation to not overrun the cat's substrate w\ excessive NOx & unburnt HC's for the amount of unburnt oxygen present from switching pre-cat O2 sensors (how cats are fed oxygen to work instead of using a secondary air pump).

PS--This is another reason why the NTK 22060/22500 O2 sensors are a better design for these 4.6L 3V's is the operational switching voltage range of the sensor. The Bosch 15717 O2 sensor operational voltage switch range is .2v to .8v as opposed to the NTK's @ 0v to 1v. The NTK O2 sensors will allow for a wider operational range w\o going off scale (losing accuracy) which helps especially when FBO's or cams w\ tunes are installed but are especially helpful when cats are being used as the NTK's will do a much better job of feeding cats w\ sufficient O2 levels to facilitate them to maintain their efficiency.

Meant to type this but forgot.

 

[Flapjack]

I actually read all this, and find it very interesting... but I have to ask, where in the hell do you find the time to fuck around with all this? At the very first opportunity, I had my tuner turn off the rear O2s and never,e thought about them again. I most certainly would not consider screwing around with the AF ratio (which will affect VE) to get the lights to go away! If you're environmentally-conscious, you can still have cats in your system, as they operate 100% electrochemically, and require absolutely no input/output from the PCM.

If I had the time to collect/process the data you did just for this post, I would be either a) tearing my front cover off to swap out the cam phaser lockouts I have installed currently for the correct ones, to get my car that has been sitting for years back up and running right, or b) finally starting my PhD, which I've put off for years.

 

[RED09GT]

WallOfText

Just tell us what you want the final outcome to be in 10 words or less and we'll see if we can help.

 

[Flapjack]

WallOfText

Just tell us what you want the final outcome to be in 10 words or less and we'll see if we can help.

I believe the correct term is HWOT (holy wall of text).

But yeah.... I'm pretty sure you lost a lot of people a few paragraphs in. I'm not on the forums much lately, because I've been so busy, but I found a little time to screw around and catch up. Reading this took a while, and I'm still not entirely sure what you're looking for. It is seriously a lot of info for something as insignificant as aftermarket exhaust/cats triggering a CEL. Turn it off in your tune. Problem solved... and you can move onto the next one.

 

[07 Boss]

So wait, you angle them up you get a MIL. You angle them level and you don't. You think because the sampling rate is different when pointed up vs level?

 

[GlassTop09]

So wait, you angle them up you get a MIL. You angle them level and you don't. You think because the sampling rate is different when pointed up vs level?

Yep. When they were angled up at the 25* angle I got no DTC MIL's. When I reset them parallel to the sensor bung (or level w\ the sensor bung if preferred) is when I got the P0139 MIL. This happened due to the fact that the O2 sensor stopped generating current (or voltage if preferred) due to the O2 % sample inside the CEL eliminator being the same % as outside O2 reference sample within the O2 sensor so the sensor stops generating voltage & the .0v signal remained long enough to cross the low volt test time threshold so the PCM failed the B1S2 O2 sensor's lean to rich voltage movement rate thus failing the sensor (this O2 test result data is available in the PCM's Mode 6 stored component test result data as all O2 sensors are continuously monitored by the PCM for proper operation & will show which part of the O2 sensor component failed). This happened due to the sampling volume change to the O2 sensor created by the repositioning of the CEL eliminators, not due to the O2 sensor itself failing so this is not a theory, this is a fact as the recorded O2 sensor test result data backs this up so yes I do know the sampling rate changed. The sample went static due to the loss of thermodynamic circulation due to loss of sufficient vertical air column height inside the eliminator (for thermodynamic circulation to occur there needs to be a certain minimal amount of vertical air column height within a cylinder to allow the heated gasses to rise enough so when they cool the gasses will gain enough mass to force circulation--heavy cool gas condenses, gains mass & falls creating a slight internal deltaP in the upper section of the eliminator into which hot gasses from the exhaust will be drawn into the eliminator thru the upper section of the eliminator's exhaust entry port & rise to fill the void as the heavier, cooler gasses will fall & exit thru the lower section of the same entry port back into the hot exhaust stream creating circulation within the eliminator thus determining the net amount of exhaust gas sampling volume the O2 sensor element will see inside the eliminator at any given engine RPM) when the eliminator was "leveled" to the same plane as the O2 sensor bung. When I reset the eliminator angle back to the 25* up angle the thermodynamic circulation returned due to sufficient air column height above the eliminator entry port which now reestablished circulation to the O2 sensor element which reestablished the O2 sensor's lean to rich voltage signal movement rate so that the PCM now detects a fully, properly working O2 sensor when the PCM now runs the O2 sensor operation tests thus no more P0139 MIL....all noted thru the PCM's recorded Mode 6 stored O2 sensor test results data. This internal sampling volume rate would most likely go even higher if I had the room underneath the car to reset the 90* eliminator to full vertical plane vs sensor bung w\ sensor installed (perpendicular or 90* or a right angle whichever works to help understand).

These Big Daddies Garage 90* CEL eliminators are also initially designed to maintain the O2 sensor switching % ratio of the post cat O2 sensor vs the pre-cat O2 sensor switching rate during STFT around 0% which reps stoich AFR of 14.6/1 (if not changed to a different lower richer AFR number as is usually done to support cams w\ large overlaps to idle correctly...which will kill a catalytic converter) during CL closed throttle operation...normal daily driving...by also controlling the exhaust gas sampling volume rate to the post cat O2 sensor to artificially "maintain" the cat efficiency rate >92% min threshold as set in the PCM during the cat efficiency test cycle as outlined in the OBDII emissions testing procedure (mine stay at 99.21% efficiency which is max cat efficiency for Ford S197 Spanish Oaks PCM's) thus keeping the P0420/P0430 DTC MIL off if the post cat O2 sensors are desired\required to remain active in the PCM tune (you most likely already knew this) using aftermarket performance exhaust systems that aren't designed to original OEM design specs (for off road use only).

The P0139 MIL I got was a side effect of repositioning the 90* CEL eliminators to test for any change in the internal circulation of exhaust gasses inside. The internal sample change inside the eliminator didn't affect the post-cat O2 sensor switching % rate vs the pre-cat O2 sensor switching rate on B1 enough for this to cross the threshold for cat efficiency % < 92% thus no P0420 MIL was set...………….only got the P0139 MIL.

Simple Science 101 application of thermal dynamics concerning properties of a gas when it is heated and then cooled...………..

Hope this helps.

 

[RED09GT]

2 posts, >2700 words over a p0420 code.

The problem is that most people running any performance car only care enough about the post cat O2 sensors to:
1. Turn the fucking light off
2. Show up as "ready" in order to pass emmissions testing.
There are plenty of solutions to make this happen without needing a dissertation in physical chemistry.

Back off the adderall

 

[07 Boss]

All I know is that I have the 90* ones and they are parallel to the ground or even with the bung. I've never had an issue, always pass my OBD smog. Here is what mine look like.

 

[Laga]

2 posts, >2700 words over a p0420 code.

The problem is that most people running any performance car only care enough about the post cat O2 sensors to:
1. Turn the fucking light off
2. Show up as "ready" in order to pass emmissions testing.
There are plenty of solutions to make this happen without needing a dissertation in physical chemistry.

Back off the adderall

Lito also has an emissions tune that helped pass my IL state test.

 

[RED09GT]

My monitor shows up as "ready" even though my post cat O2 sensors are still in my stock H-pipe-which is hanging on the wall in my garage.
This is on my cheap OBD II scanner.
YMMV

 

[GlassTop09]

All I know is that I have the 90* ones and they are parallel to the ground or even with the bung. I've never had an issue, always pass my OBD smog. Here is what mine look like.

Yes I know of your setup from another thread in which we both posted. I am using the same Big Daddies Garage 90* CEL Eliminators as you except that I don't have the Big Daddies Garage Mini Cat CEL Eliminators that you're using in tandem. I have posted pics of my setup below.

Now to clarify, if I were to register my car as it is now in your state it would pass your state's emissions testing just as well as yours has (IM Readiness shows all monitors completed & passed). That is not the point of this thread that I started. The point from my little test result from leveling the 90* eliminator from the up angle position showed that there was a sample volume change that caused the B1S2 O2 sensor to stall switching that was recovered when the 90* eliminator was reset back to the up angle position....on my setup. Outside configuration variables can\will affect how the same part design (in this case the BDG 90* CEL Eliminators & the NTK 22500 O2 sensors) can\will cause an O2 sensor to react differently on even the same platform. The reason why B1 set off the P0139 MIL & B2 did not is due in part to where the O2 sensor bungs are located on the pipe....the bung in the 1st pic is the B1 side, the 2nd pic is B2. That B1 bung is welded in the pipe below the pipe's centerline approx 1/4" vs the B2 side being welded in approx 1/8" above the pipe centerline which put the B1 eliminator low enough into the pipe vertically to have a slightly higher O2% enter it vs B2 side which caused the B1S2 O2 sensor to stall switching before B2S2 O2 sensor did setting off the P0139 MIL, but because this issue actually IMPROVED the B1 cat efficiency switching % rate (took it down to .102% instead of the .227% it tested at prior the leveling, this is due to the B1S2 O2 sensor switching rate slowing due to the sample volume change) the PCM still thinks the cat is good thus no setting of the P0420 MIL even though the PCM also thinks the B1S2 O2 sensor is bad thus sets the P0139 MIL...even though the B1S2 O2 sensor actually operates perfectly fine. So the purpose of the Big Daddies 90* CEL Eliminator preventing a P0420/P0430 MIL (which is what it was designed to do) is not the issue I'm raising...…………...

To give this more context, when both eliminators are reset back to the 25* up angle & PCM has ran the cat efficiency component test B1 comes in at .227 vs B2 at .247 (which is >99.21% max efficiency according to the PCM-passing for both cats) w\ both B1 & B2 pre-cat O2 sensors STFT's switching around 0% (14.64 AFR) in CL using the same 50, 70, 30 actual pre-cat O2 sensor switching count threshold that the PCM uses along w\ the actual PCM counted post-cat O2 sensor switching counts to calculate the cat efficiency % (example: B1 @ .227 using 50 B1S1 switches comes out to B1S2 @ 11.35 switches, B2 @ .247 using 50 B2S1 switches comes out to B2S2 @ 12.35 switches). This cat efficiency % difference between B1 & B2 can easily be attributed to the post-cat's O2 sensor bung clocking position causing the difference & not necessarily the cat's substrate performance, FBO's or tune. Since the min cat efficiency % test passing threshold is <.500 for the fuel content that was used when these cars were manufactured (E10), the difference to fail using this 50 pre-cat O2 sensor switch count example is only 12-13 more S2 switches over the number shown so anything design wise that can\will affect the post cat O2 sensor's operation IMHO shouldn't be overlooked...……………if cats are to be properly & legally used. That is why an OEM cat design spec exists for these cars (or any vehicle driven on Federal hiways & roads since the introduction of OBDII stds).

Now please look at the aftermarket cat design (Kooks Hi Flow Catted X-Pipe) in the pics I posted. Note the cat is using a 4 1\4" OD housing w\ a metal 200 cel substrate inside. Now all this so far is designed according to the Ford S197 OEM cat design spec except for the substrate material (OEM is ceramic @ 100 cel but the overall size & shape is the same as OEM but is thicker to make up for the surface area loss from 100 cel to 200 cel to lower the flowing deltaP) & temp rating (Kooks HFC has a 1500*F operational temp rating which exceeds OEM spec). Where this cat's design is NOT adhering to the OEM spec is where the O2 sensor bungs are welded & positioned (OEM spec calls for O2 sensor bung to be welded on the 4 1/4" housing at 10 o'clock\2 o'clock position behind the 1st substrate which will slow the exhaust gas velocity flow across the O2 sensor element much more vs the 2 1/2" piping as well as space the O2 sensor element higher up the larger OD piping which will lower the amount of O2 % in the exhaust sample that contacts the sensor element much more vs the 2 1/2" piping which will change the exhaust sample volume % rate that contacts the O2 sensor element vs the 2 1/2" piping which in & of itself will contribute to the cat efficiency switching % rate being much better by slowing the number of S2 switches within the same pre-cat S1 test switch count.....this has absolutely nothing to do w/ the cat substrate's ability to clean the exhaust but can affect\alter the PCM cat efficiency switching % rate test result that determines whether a cat is good or not for emissions purposes). My point is if this was corrected on this cat to fully comply w\ the OEM cat design spec this cheaper Kooks HFC could be better able to operate w\ a 4.6L long block in OEM N/A configuration w\ the std array of FBO's AS LONG as any tune changes don't take the CL (closed loop) target AFR outside the AFR target range window for normal cat operational efficiency (somewhere between 13.5 to 15.5 AFR w\ optimum at 14.64/1 stoich AFR...OEM spec) & pass emissions w\o any external aides. When these cats exceed the min operating temp of 900*F to light them off (post cat O2 sensors don't start showing voltage readouts until this happens) once PCM goes into CL operation after cold start is when I stop smelling the heavy fuel odor in the exhaust which tells me that the cats are indeed physically working...……….

Also from looking at these pics now tell me why Kooks couldn't have extended the 4 1/4" cat substrate housing just 1 1/4" longer so that the O2 sensor bung could be welded onto the 4 1/4" cat housing at the 10 o'clock/2 o'clock position as per OEM cat specs instead of on the 2 1/2" piping after the cat's end cap & still fit w\ the O2 sensor installed within the same area of the underbody on both manual & auto trans equipped cars? If this was done according to the OEM spec these Kooks HFC's may very well readily pass emissions w\o using\needing any CEL eliminators at all as the issue may simply be due to the post cat O2 sensor bung location\position being out of OEM cat spec instead of the cat substrate or FBO's or tune as the margin of error to either pass or fail a S197 PCM cat efficiency % test (thus emissions) can be\is a VERY small window.

I can easily understand all this not working properly when applying FI to a 4.6L 3V as FI can easily exceed the OEM cat design specs for the 4.6L 3V as none were developed by Ford for this particular 4.6L engine under FI (which also includes the Spanish Oak's PCM tuning parameters to be in compliance), but for this platform using the unaltered OEM 4.6L 3V NA long block design...….?

Nope...………………. To have to buy a Kooks Green Cat equipped H\X pipe (which is designed specifically for FI applications using the highly expensive GESI High Flow Cats w\ a single cat to handle a 500-800 HP FI 4 cylinder engine at 11.5 AFR at 96% cat efficiency so 2 of these should support approx 800-1,000+ HP FI V8's & pass emissions according to GESI & Kooks) to pass emissions on a 4.6L 3V using cats that has no FI installed & the long block is still OEM bore, stroke & CR is not right IMHO.

But this is my position on this subject...…………………maybe I'm the only 1 in here who cares……. I didn't type this to single out Kooks as other cat manuf's who sell exhaust kits do the same things as well….it just happens that I bought/installed a Kooks Catted X-pipe & have experienced all this before learning of the OEM cat design specs & how the S197's Spanish Oak PCM goes about testing the cats for emissions compliance on these S197's.....which I got from finding Hagman's stickied thread in the 4.6L Tech section on this BBS providing links to download the Ford Workshop Manual .pdf which is a Ford approved wall of text that can be of significant help understanding all aspects of these S197's if 1 takes the time & read thru it...……..

To each their own.

 

[07 Boss]

My monitor shows up as "ready" even though my post cat O2 sensors are still in my stock H-pipe-which is hanging on the wall in my garage.
This is on my cheap OBD II scanner.
YMMV

I used to pass without sensors in but Shelby would not tune my car that way so when I got a dyno tune from them I had to go to the mini cats.

 

[07 Boss]

Yes I know of your setup from another thread in which we both posted. I am using the same Big Daddies Garage 90* CEL Eliminators as you except that I don't have the Big Daddies Garage Mini Cat CEL Eliminators that you're using in tandem. I have posted pics of my setup below.

Now to clarify, if I were to register my car as it is now in your state it would pass your state's emissions testing just as well as yours has (IM Readiness shows all monitors completed & passed). That is not the point of this thread that I started. The point from my little test result from leveling the 90* eliminator from the up angle position showed that there was a sample volume change that caused the B1S2 O2 sensor to stall switching that was recovered when the 90* eliminator was reset back to the up angle position....on my setup. Outside configuration variables can\will affect how the same part design (in this case the BDG 90* CEL Eliminators & the NTK 22500 O2 sensors) can\will cause an O2 sensor to react differently on even the same platform. The reason why B1 set off the P0139 MIL & B2 did not is due in part to where the O2 sensor bungs are located on the pipe....the bung in the 1st pic is the B1 side, the 2nd pic is B2. That B1 bung is welded in the pipe below the pipe's centerline approx 1/4" vs the B2 side being welded in approx 1/8" above the pipe centerline which put the B1 eliminator low enough into the pipe vertically to have a slightly higher O2% enter it vs B2 side which caused the B1S2 O2 sensor to stall switching before B2S2 O2 sensor did setting off the P0139 MIL, but because this issue actually IMPROVED the B1 cat efficiency switching % rate (took it down to .102% instead of the .227% it tested at prior the leveling, this is due to the B1S2 O2 sensor switching rate slowing due to the sample volume change) the PCM still thinks the cat is good thus no setting of the P0420 MIL even though the PCM also thinks the B1S2 O2 sensor is bad thus sets the P0139 MIL...even though the B1S2 O2 sensor actually operates perfectly fine. So the purpose of the Big Daddies 90* CEL Eliminator preventing a P0420/P0430 MIL (which is what it was designed to do) is not the issue I'm raising...…………...

To give this more context, when both eliminators are reset back to the 25* up angle & PCM has ran the cat efficiency component test B1 comes in at .227 vs B2 at .247 (which is >99.21% max efficiency according to the PCM-passing for both cats) w\ both B1 & B2 pre-cat O2 sensors STFT's switching around 0% (14.64 AFR) in CL using the same 50, 70, 30 actual pre-cat O2 sensor switching count threshold that the PCM uses along w\ the actual PCM counted post-cat O2 sensor switching counts to calculate the cat efficiency % (example: B1 @ .227 using 50 B1S1 switches comes out to B1S2 @ 11.35 switches, B2 @ .247 using 50 B2S1 switches comes out to B2S2 @ 12.35 switches). This cat efficiency % difference between B1 & B2 can easily be attributed to the post-cat's O2 sensor bung clocking position causing the difference & not necessarily the cat's substrate performance, FBO's or tune. Since the min cat efficiency % test passing threshold is <.500 for the fuel content that was used when these cars were manufactured (E10), the difference to fail using this 50 pre-cat O2 sensor switch count example is only 12-13 more S2 switches over the number shown so anything design wise that can\will affect the post cat O2 sensor's operation IMHO shouldn't be overlooked...……………if cats are to be properly & legally used. That is why an OEM cat design spec exists for these cars (or any vehicle driven on Federal hiways & roads since the introduction of OBDII stds).

Now please look at the aftermarket cat design (Kooks Hi Flow Catted X-Pipe) in the pics I posted. Note the cat is using a 4 1\4" OD housing w\ a metal 200 cel substrate inside. Now all this so far is designed according to the Ford S197 OEM cat design spec except for the substrate material (OEM is ceramic @ 100 cel but the overall size & shape is the same as OEM but is thicker to make up for the surface area loss from 100 cel to 200 cel to lower the flowing deltaP) & temp rating (Kooks HFC has a 1500*F operational temp rating which exceeds OEM spec). Where this cat's design is NOT adhering to the OEM spec is where the O2 sensor bungs are welded & positioned (OEM spec calls for O2 sensor bung to be welded on the 4 1/4" housing at 10 o'clock\2 o'clock position behind the 1st substrate which will slow the exhaust gas velocity flow across the O2 sensor element much more vs the 2 1/2" piping as well as space the O2 sensor element higher up the larger OD piping which will lower the amount of O2 % in the exhaust sample that contacts the sensor element much more vs the 2 1/2" piping which will change the exhaust sample volume % rate that contacts the O2 sensor element vs the 2 1/2" piping which in & of itself will contribute to the cat efficiency switching % rate being much better by slowing the number of S2 switches within the same pre-cat S1 test switch count.....this has absolutely nothing to do w/ the cat substrate's ability to clean the exhaust but can affect\alter the PCM cat efficiency switching % rate test result that determines whether a cat is good or not for emissions purposes). My point is if this was corrected on this cat to fully comply w\ the OEM cat design spec this cheaper Kooks HFC could be better able to operate w\ a 4.6L long block in OEM N/A configuration w\ the std array of FBO's AS LONG as any tune changes don't take the CL (closed loop) target AFR outside the AFR target range window for normal cat operational efficiency (somewhere between 13.5 to 15.5 AFR w\ optimum at 14.64/1 stoich AFR...OEM spec) & pass emissions w\o any external aides. When these cats exceed the min operating temp of 900*F to light them off (post cat O2 sensors don't start showing voltage readouts until this happens) once PCM goes into CL operation after cold start is when I stop smelling the heavy fuel odor in the exhaust which tells me that the cats are indeed physically working...……….

Also from looking at these pics now tell me why Kooks couldn't have extended the 4 1/4" cat substrate housing just 1 1/4" longer so that the O2 sensor bung could be welded onto the 4 1/4" cat housing at the 10 o'clock/2 o'clock position as per OEM cat specs instead of on the 2 1/2" piping after the cat's end cap & still fit w\ the O2 sensor installed within the same area of the underbody on both manual & auto trans equipped cars? If this was done according to the OEM spec these Kooks HFC's may very well readily pass emissions w\o using\needing any CEL eliminators at all as the issue may simply be due to the post cat O2 sensor bung location\position being out of OEM cat spec instead of the cat substrate or FBO's or tune as the margin of error to either pass or fail a S197 PCM cat efficiency % test (thus emissions) can be\is a VERY small window.

I can easily understand all this not working properly when applying FI to a 4.6L 3V as FI can easily exceed the OEM cat design specs for the 4.6L 3V as none were developed by Ford for this particular 4.6L engine under FI (which also includes the Spanish Oak's PCM tuning parameters to be in compliance), but for this platform using the unaltered OEM 4.6L 3V NA long block design...….?

Nope...………………. To have to buy a Kooks Green Cat equipped H\X pipe (which is designed specifically for FI applications using the highly expensive GESI High Flow Cats w\ a single cat to handle a 500-800 HP FI 4 cylinder engine at 11.5 AFR at 96% cat efficiency so 2 of these should support approx 800-1,000+ HP FI V8's & pass emissions according to GESI & Kooks) to pass emissions on a 4.6L 3V using cats that has no FI installed & the long block is still OEM bore, stroke & CR is not right IMHO.

But this is my position on this subject...…………………maybe I'm the only 1 in here who cares……. I didn't type this to single out Kooks as other cat manuf's who sell exhaust kits do the same things as well….it just happens that I bought/installed a Kooks Catted X-pipe & have experienced all this before learning of the OEM cat design specs & how the S197's Spanish Oak PCM goes about testing the cats for emissions compliance on these S197's.....which I got from finding Hagman's stickied thread in the 4.6L Tech section on this BBS providing links to download the Ford Workshop Manual .pdf which is a Ford approved wall of text that can be of significant help understanding all aspects of these S197's if 1 takes the time & read thru it...……..

To each their own.

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Just seems a lot easier to just go get the mini cats that work, instead of all of the experimentation and the thought process involved in getting them to read properly. But like you said, to each their own.