True Duals on my 04: How do I get the o2 sensors to work with dual exhaust?

[JarvisB]

Should I get a XCal3 and a programming as soon as I get the exhaust done?

 

[JarvisB]

James Henson replied and said that the front o2 sensors are required, but the rear sensors are not. But I think I might want to try keep all 4 o2 sensors.

BTW, he recommended a X pipe since it provides equal/constant flow.

I just asked him what if I want to keep all o2 sensors then what are my options.

 

[Rofocowboy84]

The cats are right after the exhaust manifolds, you shouldn't have to even touch them, even if you are doing true duals....

 

[CDW6212R]

I don't agree with you on this point. Yes, absolutely you do need to verify and compensate the a/f ratio if you allow the vehicle to have more flow than the stock tune allows for, but even with the a/f corrected, lower backpressure will rob some low end torque from the motor. This can be corrected by altering the length of the intake runners (by an intake spacer, different intake, etc.). When I opened up the intake and exhaust on my Mach, we did a full dyno tune on the vehicle to ensure that we were running the correct a/f ratios. Even with the ratio corrected, we still had a slight loss of low end torque. The overall numbers were better than stock, but the torque curve was narrower. By going to an intake spacer, we crossed the 300 ft-lb threshold 600 rpms earlier than without the spacer and didn't sacrifice anything on the top end. The peaks in the curve weren't changed, it just fattened the curve up to give you better power over a larger rpm range.

Most of what you write is correct, but that which I highlighted in bold is completely wrong.

Please, anyone, do not allow yourself to believe that any restriction in airflow will produce more power, or more airflow will net you less power.

These engines are all air pumps. Simply, the more air that you can get to flow through them, the more power you will get out. The test is not on a dyno, use a dyno for tuning only. The only true test is in a timed distance. Plus the best tune is done off of a dyno, on the road.

Please go back and test your Mach again, on a track. Put the largest exhaust you can on it, and tune it again. It will go quicker than before.

Back pressure of any kind in the exhaust is lost power, not gained power. the engine has to work harder to push that air through the back pressure. Cut the pipe before that restriction, and the back pressure is gone and the engine accelerates faster. It is that simple, but the fuel has to be enriched to match.

 

[CDW6212R]

Should I get a XCal3 and a programming as soon as I get the exhaust done?

Yes, if you reduce the restriction with better flowing pipes and mufflers. Depending on how much improvement you have, it may or may not change the feel to you. With a better tune, it will be quicker with the better exhaust.

 

[CALDWELL]

serious question ?

on my red explorer i had the exhaust installed, and yes had a drop of low end torque, but gained in the upper end. when i had it installed i disconnected the battery cables to reset the pcm... and then did the same thing again when i installed my K&N intake...

does this help in anyway ? i did notice mpg gains, and power gains...

i never tuned the X, so was i running on an improper A/F even after i reset the pcm by disconnecting the battery ??

i was under the impression that the computer could learn and adapt to the intake and exhaust flowing better...

 

[CDW6212R]

The latest Ford computers have much more ability to learn or adapt to driving conditions etc. Most of that is for the trans though, shift habits etc.

The pre 2002 Fords don't really learn as you think it means. The PCM's store data from the most recent engine run cycles, maybe as many as 50 cycles. That data is used to more quickly find the best idle settings, cold starts, and that's about all the details I know of. They do not have the ability to learn such things as the difference in two air filters, changes to exhaust, cams, heads etc. They have tables like all PCM's do, they are programmed to strive for certain conditions at given rpm's, loads, at certain TPS points.

When you unplug the PCM from power, it loses that data. Then it has to start over with what little OEM data it began with. That may or may not be better than what it had accumulated. If the recent past was full of vastly different engine flow information or conditions, unplugging the battery may be wise.

The bottom line is that the PCM will try to do something for a given known set of conditions, and if airflow has changed significantly enough, it will not achieve the A/F it is shooting for. It will try hard, it will get somewhat close, but the amount that it is off, that is the loss you feel or discover without retuning. With careful tuning, all of the loss you perceive to have, it will turn into a gain there.

99% of the things people "feel" or hear or think they can measure, it's false or can be corrected. People should test before and after with significant changes, that means test with a timing device and not a dyno. Too few people do that, and we end up in conversations like this.

I tested my Lincoln on road about 60 times to compare little changes I made back in 1997. I only gained about a second or so, but most things I thought I felt were almost nothing. I'd have to look at those data sheets, but with the few things I did to it, I gained more from heads, intake, and exhaust. The MAF conversion did nothing, nor did the MAF upgrade, TB, air inlet hose, air filter, silencer, or gearing(.10 second). Now understand, that was a perfect example, my car was a stock 91 PCM, then a stock Mustang 92 MAF PCM. I never got any kind of tune for it, so I surely would have gained a good amount with a new program. That wasn't common back then, as it is now. That was EECIV, and now we have the far better EECV(OBDII).

 

[Limited02]

Now I am not going to get into a debate about what size exhaust will do to the motor and whose right or wrong, but I will tell you my "experience." When I originally did my exhaust, I cut the third cat(resonator?) off and installed a 3" pipe that went into a 40 series flowmaster with dumps. FIRST thing I noticed was the LACK of lowend response. Once it hit around 3500 RPM, it would start pulling like no tomorrow(in other words, much better than stock) But the lack of lowened in town and how freaking loud it was didn't work for me. I had new exhaust(2.5") and a 70 series SI/SO muffler put on and I gained my lowened back and still had a great top end pull(plus it was a lot quieter).

OP- I am trying to find that picture I found on ebay earlier. So give me some more time!

 

[JarvisB]

Yes, if you reduce the restriction with better flowing pipes and mufflers. Depending on how much improvement you have, it may or may not change the feel to you. With a better tune, it will be quicker with the better exhaust.

Actually I do plan on getting a tuner from Henson, but not that soon. But if I have to, then I might be willing to do it.

 

[JarvisB]

The cats are right after the exhaust manifolds, you shouldn't have to even touch them, even if you are doing true duals....

I see, there are the cats and manifolds before the stock y pipe?

 

[CALDWELL]

Jarvis...


the 2 cats are located on the y-pipe... one on each side of the Y...


this is a list of how the factory exhaust runs from the engine to the tailpipe...

Engine - headers ( manifolds ) - Y pipe ( 1 cat on each side ) - ( now a single pipe ) - resonator - muffler - ( pipe goes over driver side rear axle ) - mini muffler - tail pipe exit...

hope this helps fella

 

[JarvisB]

Jarvis...


the 2 cats are located on the y-pipe... one on each side of the Y...


this is a list of how the factory exhaust runs from the engine to the tailpipe...

Engine - headers ( manifolds ) - Y pipe ( 1 cat on each side ) - ( now a single pipe ) - resonator - muffler - ( pipe goes over driver side rear axle ) - mini muffler - tail pipe exit...

hope this helps fella

this helps a lot lol. I have no clue how my exhaust looks, I do not have a jack here.

so there are a cat on each pipe before the y pipe correct?

Now where are the rear o2 sensors?

I suppose that I d like to cut the Y pipe off and then extend the piping towards the X pipe- dual exits- mufflers-tips.. 2.5" piping

 

[morziac]

I also plan on doin complete duals on my V8, the o2 sensors r just behind each cat , so there is plenty of room behind them, before the y piece for u to make ur cut and run them next to each other. this is the way im goin to do it and then have one pipe head over to the opposite side after the diff.

on another note the rear o2 sensors r purely there to tell u whther ur cats r operating properly or not. if ur not fussed about ur cat then u dont need the o2 sensors. i have removed the ceramic out of the inside of my cats which has brought up an engine light, James has informed me that the SCT flash tuner can turn it off and im currently waiting for it arrive so i can do so.

just my 2 cents anyway

Dan

 

[JDraper]

Most of what you write is correct, but that which I highlighted in bold is completely wrong.

Please, anyone, do not allow yourself to believe that any restriction in airflow will produce more power, or more airflow will net you less power.

These engines are all air pumps. Simply, the more air that you can get to flow through them, the more power you will get out. The test is not on a dyno, use a dyno for tuning only. The only true test is in a timed distance. Plus the best tune is done off of a dyno, on the road.

Please go back and test your Mach again, on a track. Put the largest exhaust you can on it, and tune it again. It will go quicker than before.

Back pressure of any kind in the exhaust is lost power, not gained power. the engine has to work harder to push that air through the back pressure. Cut the pipe before that restriction, and the back pressure is gone and the engine accelerates faster. It is that simple, but the fuel has to be enriched to match.

You didn't fully read what I wrote and maybe I didn't fully explain what I wrote. As I said, the overall numbers were better than stock, but there was still room for improvement by better balancing the flow by extending the intake runners. I did gain overall by opening up the exhaust, but narrowed the powerband slightly. By lengthening the intake runners to better balance the system, I gained it back. If you reduce backpressure on the back end without compensating on the front end, the system becomes unbalanced and you are not taking full advantage of the power gains possible. Ever try running a motor hard with no exhaust at all? Runs like crap because the system is so far out of whack.

Yes the motor is an air pump, but it has to be a balanced air pump to get the most efficiency and power. just tuning the a/f ratio isn't enough.

 

[CDW6212R]

I read it all and understood it, really. But you keep coming back to saying that a smaller exhaust at any time is better than the bigger one. That's the myth which needs to die.

Limited02 just gave a perfect example of what I'm pointing to. He installed some amount of larger pipe, and did not correct the program for that higher airflow. Of course he "lost" power, the A/F ratio was no longer close to ideal. If you make an engine run rich or lean at any point, it will be down on power during that period. These computers are not instantaneous, they need to be programmed to keep up with the airflow needs, not react to over rich or lean conditions.

In your case, the intake parts were evidently also not ideal, and those helped. But the answer to the larger exhaust was not to put the smaller parts back on. Evidently you went at the intake side, that's great and helps too. But every single part in the airflow path counts. Each improvement helps.

Now if you take these arguments and points far enough, you will get to one other massive subject. The camshaft has a massive affect on how certain intake manifolds work or do not work. The exhaust also is affected slightly, but not typically enough to notice like an intake. That's where people select smaller intakes due to myths about big intakes hurting low end power. The wrong camshaft will not work worth a damn with a large intake, and the same wrong cam will seem to be better with a smaller intake. I don't think you can have that happen with an exhaust, but I know Jay Allen could say.

I think the point should be to make the exhaust as big as will fit, and that is feasible, and sounds the way the owner wants it. My point is that selecting smaller exhaust parts is usually a waste of money and power. With proper tuning you should always gain power at every rpm, never losing at any rpm. Don't make a judgment without retuning for the change, that's not right.

 

[JarvisB]

I also plan on doin complete duals on my V8, the o2 sensors r just behind each cat , so there is plenty of room behind them, before the y piece for u to make ur cut and run them next to each other. this is the way im goin to do it and then have one pipe head over to the opposite side after the diff.

on another note the rear o2 sensors r purely there to tell u whther ur cats r operating properly or not. if ur not fussed about ur cat then u dont need the o2 sensors. i have removed the ceramic out of the inside of my cats which has brought up an engine light, James has informed me that the SCT flash tuner can turn it off and im currently waiting for it arrive so i can do so.

just my 2 cents anyway

Dan

Cool, yeah apparently I can just cut the rear o2 sensors off, but we cannot remove the front o2 sensors.

When are you going to do the exhaust? FYI I would recommend you to get the exhaust done before you get a tune on your x. I am sure you know that.

 

[JDraper]

I read it all and understood it, really. But you keep coming back to saying that a smaller exhaust at any time is better than the bigger one. That's the myth which needs to die.

Limited02 just gave a perfect example of what I'm pointing to. He installed some amount of larger pipe, and did not correct the program for that higher airflow. Of course he "lost" power, the A/F ratio was no longer close to ideal. If you make an engine run rich or lean at any point, it will be down on power during that period. These computers are not instantaneous, they need to be programmed to keep up with the airflow needs, not react to over rich or lean conditions.

In your case, the intake parts were evidently also not ideal, and those helped. But the answer to the larger exhaust was not to put the smaller parts back on. Evidently you went at the intake side, that's great and helps too. But every single part in the airflow path counts. Each improvement helps.

Now if you take these arguments and points far enough, you will get to one other massive subject. The camshaft has a massive affect on how certain intake manifolds work or do not work. The exhaust also is affected slightly, but not typically enough to notice like an intake. That's where people select smaller intakes due to myths about big intakes hurting low end power. The wrong camshaft will not work worth a damn with a large intake, and the same wrong cam will seem to be better with a smaller intake. I don't think you can have that happen with an exhaust, but I know Jay Allen could say.

I think the point should be to make the exhaust as big as will fit, and that is feasible, and sounds the way the owner wants it. My point is that selecting smaller exhaust parts is usually a waste of money and power. With proper tuning you should always gain power at every rpm, never losing at any rpm. Don't make a judgment without retuning for the change, that's not right.

Where did I say that a small exhaust was better? And where did I say that I went to a smaller exhaust? Please quote me where I made those statements.

On my car, I opened up the exhaust, found that I had not optimized my power curve, so went back and massaged the intake side to help. On the exhaust side, I'm running a Bassani X pipe and Borla Stingers that are both about 1" larger than stock.

I'm not sure what you're reading, but it wasn't part of my statements. What I'm saying is that if you open your exhaust up, you have to work on the intake side too, or you will unbalance your setup and not take full advantage of the improved exhaust.

 

[CDW6212R]

Let's not argue, you said this, "...we still had a slight loss of low end torque." and "...lower backpressure will rob some low end torque from the motor." That is wrong, not in any way correct. I interpreted that to mean that your statements conclude that some smaller exhaust parts are better. That is the only way I can read that.

Don't make conclusions about losing low end power, it did not happen. If you say that without tuning it properly first, that's the worst sin. If it happened after tuning, then the tuning was done wrong. I agree that intake parts need to be great also, but you should not lose any power ever after tuning to compensate for bigger exhaust. If it happened, then something else was wrong, not the exhaust.

We may be agreeing in the end with all said, but I absolutely never will accept that statement that low end power is lost with any bigger exhaust. the point I'm making is, do not say that. People, hundreds of people read this stuff, they take it and spread these myths. We need to try very very hard to never say things like that, novices pick it up and spew it all over the world.

I am not trying to win an argument. I am simply trying to stop such a bad statement from being stated to begin with, and then have it supported uncontested. Your tuner guy may argue with me or hate me, that's fine. But don't tell the World that you did exhaust work, and then lost power. Regards,

 

[morziac]

Cool, yeah apparently I can just cut the rear o2 sensors off, but we cannot remove the front o2 sensors.

When are you going to do the exhaust? FYI I would recommend you to get the exhaust done before you get a tune on your x. I am sure you know that.

My exhaust is already flowing a hell of a lot more than stock so a tune now would benefit wuite well, i probably wont get a round to doing the duals for a few more months as ive got too many other projects on the go at the moment. and i got no problems retuning it again when i do.

if ur goin to keep the cats though theres no need to cut the sensors off, just turn them off. i dont know the rules over there but here in australia u have to have cats by law, hence why i removed the ceramics out of them and put them back as per the factory look

 

[Limited02]

Jarvis- Tried to email these to you but I couldn't send them? So I will post it here instead for the world to see my high quality art work