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Discussion Starter #1
Hi-
I have debating for awhile between running a Catco Y-pipe or Bassani Y-pipe. But, now im thinking it is much cheaper if I build one myself. I have read a couple of build threads in the technical writeups. I am running a stock 5.0, but plan on doing the six litre tuneup. I plan on doing 3" single exhaust in the stock location. Now, I need to pass emissions, so im need to run a cat. I plan on getting a Catco High Flow Cat. I am also going to run the stock exhaust manifolds also. So, what size pipes should I run for the "Y" part of the pipe? I don't want to loose torque due to not enough back pressure. I still need to run a air tube and have a place for the oxygen sensor. I know alot of people use the Flowmaster Y-collector, but where do I put the Oxygen Sensor? I plan on hooking up to a Hooker Aerochamber and out a 3" tailpipe, so everything will be 3" past the converter.
Thanks-
 

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im curious about this too:scratchhe. someone said to use 2.5" pipes for the y pipe but apparently almost no one sees any improvement changing the exhaust from the muffler back. i want to do the y pipe with a flowmaster collector 2.5" to 3" then run it through the stock 2.4 inch exhaust from the muffler back. do these measurements sound right? please someone help our poor souls.:rolleyes:
 

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Discussion Starter #3
Well, also what size socket tube fits the stock headers? But, the oxygen sensor is my biggest question. I want to use that flowmaster y collector. It is said to be better than the bassani to fab your own. And it sounds about half the price to go this route. I have to run a Catalytic converter though to pass emissions.
 

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Well, also what size socket tube fits the stock headers? But, the oxygen sensor is my biggest question. I want to use that flowmaster y collector. It is said to be better than the bassani to fab your own. And it sounds about half the price to go this route. I have to run a Catalytic converter though to pass emissions.
i beleive i measured them at 2 1/4 inches. i heard theyre different sizes and i measured the driver side one. im going to just use some stock ones since aftermarket ones wont allow more flow from the manifolds. im going to use a small pipe between the primary header pipes right before they enter the collector as a place for the oxygen sensor. if you wanted to you could cut it off your old cat.
 

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Satyr of the Midwest
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Man you guys really love to overkill things. :rofl:

asdaven: your oxygen sensor should be located as close to the original place as possible, and by that, I mean with regard to the distance between the manifold and the sensor. This is one thing no one seems to pay attention to here (not directing this at anyone, it's just overlooked by virtually everyone), so I'm very happy to see you're at least having some concern about it. :thumbup

The delay between an exhaust pulse, and when the oxygen sensor signal is considered representative of the oxygen content in the exhaust stream, is called Transport Delay. It is a critical table in the PCM's programming, and Ford's own internal documentation says so, in addition to my own tuning experience.

System transport lag time; time delay from when a fuel change is made until
the HEGO sensor indicates this change; varies with engine speed, units are
REVs.

***********************
***** WARNING *****
***************​
It is imperative that an accurate value for the system transport lag be
entered. An incorrect value will result in greatly reduced catalyst
efficiencies due to excessively fast or slow ramp rates, incorrect jumpback
amounts, etc.


***************
***** WARNING *****
***********************​
After an HEGO switch, a finite amount of time (equal to the transport lag)
should pass before the HEGO can switch. Noise in the HEGO system could be
interpreted by the computer as HEGO switches. These phantom switches could
occur at a faster rate than dictated by the system transport lag time. Since
the jumpback is made from the lambda when the HEGO switches, phantom switches
could make the jumpback go beyond the average Air/Fuel ratio. A high rate of
phantom switches would create a high rate of jumps. A special feature of the
closed loop strategy prevents this problem.

A full jumpback is done only if the proper transport lag time has elapsed.
If not, the jumpback distance is reduced to match the reduction in transport
lag time
. The actual strategy uses PIP signal counts to control this
feature.
These are the reasons I always advocate sticking with factory exhaust tube sizes, at least until you're past the oxygen sensor(s). This way, your table's values won't be as nearly as inaccurate as they would be with larger tubes and/or an incorrectly-located sensor.

I'm using 2.25-inch tubes (actually it's that size from the collectors to the tips of the tailpipes, but I digress), and located both HO2S six inches below the collector flange, which is the factory sensor bung distance -- I'll admit it's an educated guess since I never had the factory Y-pipe from a BIO0-equipped Bronco, but I've performed meticulous measurements upon detailed photographs of the proper Y-pipe. I also have the ability to change the transport delay table in the PCM's program since I have a Quarter Horse, so it's just a matter of tuning it if I've gotten it wrong. Being the lazy-ass that I am though, I'd rather get it right the first time.

For everyone else, it's best you avoid this type of problem by not using large tubes and not altering the sensor location; go with 2.0- or 2.25-inch head pipes, locate the oxygen sensor properly by measuring the approximate distance to the old one, and you should be fine. The Bassani is HUGE compared to the factory Y-pipe, but you guys with single oxygen sensors would probably not notice as large a difference in driveability using one, as I would. That said, I still think the Bassani pipe is way overrated and overpriced. I just finished building my own FULL dual exhaust complete with flex joints and an H-pipe, and really, it's not terribly hard to do. Those of you with the factory collector exit locations won't have nearly the amount of fun that I did with my GT40P-compatible Ford Racing headers.
 

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Man you guys really love to overkill things. :rofl:

asdaven: your oxygen sensor should be located as close to the original place as possible, and by that, I mean with regard to the distance between the manifold and the sensor. This is one thing no one seems to pay attention to here (not directing this at anyone, it's just overlooked by virtually everyone), so I'm very happy to see you're at least having some concern about it. :thumbup

The delay between an exhaust pulse, and when the oxygen sensor signal is considered representative of the oxygen content in the exhaust stream, is called Transport Delay. It is a critical table in the PCM's programming, and Ford's own internal documentation says so, in addition to my own tuning experience.


These are the reasons I always advocate sticking with factory exhaust tube sizes, at least until you're past the oxygen sensor(s). This way, your table's values won't be as nearly as inaccurate as they would be with larger tubes and/or an incorrectly-located sensor.

I'm using 2.25-inch tubes (actually it's that size from the collectors to the tips of the tailpipes, but I digress), and located both HO2S six inches below the collector flange, which is the factory sensor bung distance -- I'll admit it's an educated guess since I never had the factory Y-pipe from a BIO0-equipped Bronco, but I've performed meticulous measurements upon detailed photographs of the proper Y-pipe. I also have the ability to change the transport delay table in the PCM's program since I have a Quarter Horse, so it's just a matter of tuning it if I've gotten it wrong. Being the lazy-ass that I am though, I'd rather get it right the first time.

For everyone else, it's best you avoid this type of problem by not using large tubes and not altering the sensor location. The Bassani is HUGE compared to the factory Y-pipe, but you guys with single oxygen sensors would probably not notice as large a difference in driveability using one, as I would. That said, I still think the Bassani pipe is way overrated and overpriced. I just finished building my own FULL dual exhaust complete with flex joints and an H-pipe, and really, it's not terribly hard to do. Those of you with the factory collector exit locations won't have nearly the amount of fun that I did with my GT40P-compatible Ford Racing headers.
that one guy used 2.5 inch pipes on his. i cant remember his username, it has a bunch of 2s and 1s in it. i thought a slightly larger y pipe was where the extra power and mpg (my main motivation) came from. could the difference between mandrel bends and non mandrel bends really be that much? i was just gonna put the o2 sensor there cause thats where it was factory.i figure if no one sees and improvement with the exhaust from the muffler back then theres no point doing it.

btw, i have a ngk 02 sensor i got like a few weeks ago. im still wondering if i should keep it or go to a bosch like the original.
 

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Satyr of the Midwest
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I wouldn't buy the same part twice unless it was defective. NGK's oxygen sensors are fine.

You can go slightly larger, just don't go nuts and know how augmenting the system can affect other things. Knowledge is the one true power, man. :thumbup

Power and mileage come from a combination of things, not a single component or system. With the exhaust, your goal is to make it more free-flowing without disrupting important characteristics under which the PCM was programmed. Larger pipes do NOT always mean more flow, especially with the factory catalyst setup behind 'em and/or factory cylinder heads. These engines just don't flow that much air in stock form.*

If the factory two-catalyst [TWC-COC] setup is replaced with a single catalyst, with mandrel bends leading up to it, and a good muffler (NOT a Blowmaster) and tailpipe, then you'll have accomplished something. Don't expect a miracle unless the catalyst was clogged or the system has been in disrepair for some time.


*The maximum my current setup can measure accurately is 960 kg/hr incoming air mass, which translates to 454 ft³/min @ 50°F, 29.92 inHg, 60% R.H. I come very close to pegging the MAF on occasion, but considering that I have an optimized system (heads, cam, intake, exhaust, etc.), many would expect it to regularly do so. That's why so many guys blow money unnecessarily on larger MAF sensors, injectors, exhaust systems, yada yada. The fact is, our engines just don't eat as much air as people think they do, even under heavy acceleration. Of course, considering the mass of the very air you and I breathe is sort of an abstract concept to begin with: how much does your breath weigh? :rofl:
 

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You have an 02 sensor?

I don't... (I think)
1991? yes you do

I wouldn't buy the same part twice unless it was defective. NGK's oxygen sensors are fine.

You can go slightly larger, just don't go nuts and know how augmenting the system can affect other things. Knowledge is the one true power, man. :thumbup

Power and mileage come from a combination of things, not a single component or system. With the exhaust, your goal is to make it more free-flowing without disrupting important characteristics under which the PCM was programmed. Larger pipes do NOT always mean more flow, especially with the factory catalyst setup behind 'em and/or factory cylinder heads. These engines just don't flow that much air in stock form. If the factory two-catalyst [TWC-COC] setup is replaced with a single catalyst, with mandrel bends leading up to it, and a good muffler (NOT a Blowmaster) and tailpipe, then you'll have accomplished something. Don't expect a miracle unless the catalyst was clogged or the system has been in disrepair for some time.
are 2.5 too big? i just did seafoam and it didnt seem to make that big of a difference but i think it may have clogged the cat (it could have been clogged before:whiteflag). i was planning on keeping the stock muffler since most people dont experience a gain replacing it. i was gonna run a 2.5 to 3 inch flowmaster collector and run without a cat for now.(no emissions testing) im not expecting enormous gains from this one mod, im doing multiple small mods to get to a goal and this is one of them. i just dont want to miss out on possible mpg gains.
 

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Satyr of the Midwest
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You're gonna kill mileage without a catalyst. 2½-inch is too large IMO.

You can test the system for a clogged converter with a vacuum gauge attached to the intake manifold. Google it, or search FSB, and you should be able to find a full diagnostic procedure (animated too, IIRC).
 

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You could also talk to hefty on here we just did his exhaust a week or so ago ... hes running a 5.8 but he used the stock y pipe cut off right in front of the cat and btw the stock y is 2.5 inch on one side and 2.25 on the other im guessing to equalize velocity of exhaust gasses and he used a 2 into 1 that he got from summit and modded it a little and it looked and seemed to work great... a catco cat 3" out the back and a thrush welded muffler it worked and sounded great.. and im sure he would tell ya he couldnt be happier with the new setup he did run some pace setter headers but not necissarily needed he just wanted it all done at once...
i plan on running same setup on my stock5.0 but ill swap on some gt-40 heads at same time
 

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You could also talk to hefty on here we just did his exhaust a week or so ago ... hes running a 5.8 but he used the stock y pipe cut off right in front of the cat and btw the stock y is 2.5 inch on one side and 2.25 on the other im guessing to equalize velocity of exhaust gasses and he used a 2 into 1 that he got from summit and modded it a little and it looked and seemed to work great... a catco cat 3" out the back and a thrush welded muffler it worked and sounded great.. and im sure he would tell ya he couldnt be happier with the new setup he did run some pace setter headers but not necissarily needed he just wanted it all done at once...
i plan on running same setup on my stock5.0 but ill swap on some gt-40 heads at same time
You're gonna kill mileage without a catalyst. 2½-inch is too large IMO.

You can test the system for a clogged converter with a vacuum gauge attached to the intake manifold. Google it, or search FSB, and you should be able to find a full diagnostic procedure (animated too, IIRC).
i measure the driver side one at 2.25 and thats the one id expect to be larger. so what im gathering here is that i need to do stock sized pipes with mandrel bends, flowmaster 2.5/2.25 to 3" collector and high flow cat? why do i need a cat? wouldnt no cat just make it better? i only have one oxygen sensor.
 

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Satyr of the Midwest
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You need a catalyst because of the things I mentioned earlier. Also, it's MY air too, as well as everyone else's, and I don't want it stunk up.
 

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You need a catalyst because of the things I mentioned earlier. Also, it's MY air too, as well as everyone else's, and I don't want it stunk up.
it wouldnt have been perminant, just until i felt comfortable dumping another $40 into my truck.
 

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Discussion Starter #15
I was thinking 2.25" for the headpipes, which will be alright because that will be duals. Then, I ll go up to 3". Yeah I was worried about that oxygen sensor. Really my main goal here is to gain gas mileage and replace an aging cat. I like the sound of that flowmaster y-collector thing. I was thinking of getting one with 2.25" duals into 3" single. Then, put the cat on after that. But, still where do I put the oxygen sensor on a setup like this? How well does Catco or Bassani's y pipe place the oxygen sensor? I think im either going to go with Catco or custom now and forget Bassani. Does the placement of the Cat affect the oxygen sensor readings or is it mostly just distance from the manifolds? Will the 3" after the y-collector hurt anything?
Thanks-
 

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I was thinking 2.25" for the headpipes, which will be alright because that will be duals. Then, I ll go up to 3". Yeah I was worried about that oxygen sensor. Really my main goal here is to gain gas mileage and replace an aging cat. I like the sound of that flowmaster y-collector thing. I was thinking of getting one with 2.25" duals into 3" single. Then, put the cat on after that. But, still where do I put the oxygen sensor on a setup like this? How well does Catco or Bassani's y pipe place the oxygen sensor? I think im either going to go with Catco or custom now and forget Bassani. Does the placement of the Cat affect the oxygen sensor readings or is it mostly just distance from the manifolds? Will the 3" after the y-collector hurt anything?
Thanks-
i said where it should go like 3 times:duh
 

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Age. Fac ut gaudeam
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1991? yes you do



are 2.5 too big? i just did seafoam and it didnt seem to make that big of a difference but i think it may have clogged the cat (it could have been clogged before:whiteflag). i was planning on keeping the stock muffler since most people dont experience a gain replacing it. i was gonna run a 2.5 to 3 inch flowmaster collector and run without a cat for now.(no emissions testing) im not expecting enormous gains from this one mod, im doing multiple small mods to get to a goal and this is one of them. i just dont want to miss out on possible mpg gains.
My catalytic converter is aftermarket, what would my sensor look like?
 

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Satyr of the Midwest
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My catalytic converter is aftermarket, what would my sensor look like?
I think you meant, "where would I locate my sensor," in which case I'd say probably somewhere in the area immediately after the Y connection.



Maybe two to three inches downstream of that little I.D. tag on the body.
 

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...somewhere in the area immediately after the Y connection.
Maybe two to three inches downstream of that little I.D. tag on the body.
x2
Right at the end of the flat-part, since welding it to the flat-part will be easier. ;) LOL

And screw a junk O2 sensor into it so the welding can't warp it enough to mess with you.

Alvin in AZ
 
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