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

[JarvisB]

Hello,

It is more likely that I am going to get dual exhaust done next week since my brother knows a friend that can do a deal for me. So I am positive that I will get it done.

Before I proceed, I wanted to find out how am I going to get the o2 sensors to work? or at least bypass it? because I dont want to have the check engine light being on all the time.

Also my best bet is to run 2.5" pipes correct?

It is going to be installed on my 2004 V8 4.6L RWD

Input would be appreciated! Thanks

 

[Limited02]

Unless you plan on removing the two cats that come right off the manifold, you will not have any problems. The only real way to bypass the 02 sensors if you remove them, is to purchase a tuner from hensonperformance.com and you should be able to turn them off. There is also a MIL eiliminator you can buy, but I have heard they can short out and cause fires.

You are not at a power level to worry about taking the cats off(just take the third one off) so there won't be any real benefit in doing so. I am looking forward to hearing your exhaust after you finish it up. If you want to make it LOUD, get some FM Super 44's with 2.5" exhaust and 3" tips Take LOTS of pictures!!!

 

[JarvisB]

So it is ok to remove the o2 sensors? wont it throw a code after I remove them?

You mean if I leave 2 cats and remove the 3rd one, then I wont have any problem??

P.S. I am not going for a "loud" set up. I just want some nice sounding mufflers that makes some noise when I push it hard but other than that I dont want it making too much noise. I got audio system so might not want to mix that with some loud exahust lol.

 

[CALDWELL]

there a ( 2 ) 02 sensors on your exhaust. both are located on the Y-pipe after the cat's...

DO NOT REMOVE THEM... because there is no reason to remove them...

you can start running 2.5'' pipe at the END of the Y-pipe. There are no other sensors after that point.

the RESONATOR ( 3rd CAT ) as ppl call it... can be removed without any negative effects to the vehicle. from this point you can now remove the factory keg of a muffler, and replace it with flowmaster or magnaflow of your choice, then dual 2.5'' pipe the rest of the way back...


if you dont want nasty loud sound... i would suggest a FM 50 series or FM 70 series... 50 is on the mid range of the loudness scale, and 70 is on the quieter side of the scale...

 

[JarvisB]

there a ( 2 ) 02 sensors on your exhaust. both are located on the Y-pipe after the cat's...

DO NOT REMOVE THEM... because there is no reason to remove them...

you can start running 2.5'' pipe at the END of the Y-pipe. There are no other sensors after that point.

the RESONATOR ( 3rd CAT ) as ppl call it... can be removed without any negative effects to the vehicle. from this point you can now remove the factory keg of a muffler, and replace it with flowmaster or magnaflow of your choice, then dual 2.5'' pipe the rest of the way back...


if you dont want nasty loud sound... i would suggest a FM 50 series or FM 70 series... 50 is on the mid range of the loudness scale, and 70 is on the quieter side of the scale...

I do not want to start after the Y pipe because then it would just be like a single exit exhaust. I dont see any point in redoing my single exhaust set up because my exhaust is fine really, I would only change the tip if I have to.

I want to see what are my options when it comes to running true duals.

Some have suggested that James from Henson Performance would be able to make it work with a tuner. I might have to deal with the CEL being on until I get a scanner from James. But I am not sure if this is for real. I need someone to confirm this.

Anyone running true duals around here?

 

[CALDWELL]

i sure with a little modification you could work off your stock y-pipe, if the exhaust shop is good...

or if worse comes to worse then you again with modification turn your y-pipe into a custom x-pipe, which actually would make your exhaust flow nice and even through both pipes

 

[JarvisB]

i sure with a little modification you could work off your stock y-pipe, if the exhaust shop is good...

or if worse comes to worse then you again with modification turn your y-pipe into a custom x-pipe, which actually would make your exhaust flow nice and even through both pipes

No thanks to the Y pipe idea. Defeats the purpose of doing this modification at first place.

I am in this only if I can get the duals to work. I want to see performance gains.

Right now it seems like X pipe is the only way, but I am not sure if it is as good as running 2 separate pipes.

Or I might have to deal with the CEL until I get a tuner from James. I emailed him this morning about this to see if he knows anything about this. So as of now, I am waiting on James' response then hopefully proceed to do the right thing.

 

[JDraper]

Your 02 sensors will work fine if you put them on a true dual setup. You'll just have to weld sensor bungs into the exhaust pipes at a similar location (relative to the engine and the cat converters) that they are now. The sensors measure the ratio of air to fuel, they don't care about the volume going by them.

BTW, an X or an H pipe is better than running true duals because it helps balance the flow better.

 

[Limited02]

I am a fan of H-pipes because I had one on my mustang and loved the balanced rumble. But if you like the way true duals sound, then go for it. After rereading your first post, you have 2wd only correct? If so, then you have a much better chance of getting true duals ran because you're not fighting the t-case like us 4wd guys would.

Also, legally a shop cannot remove any cats off a vehicle, they can only replace them. If there is any problem with them removing the third cat(resonator) then just chop it off yourself and have them finish the work. That's what I did and there wasn't any problems. As I said before, I wouldn't bother removing the two cats that come off the manifold because you're not at the power level to remove them and it will be pointless(and more $$$).

Now go to the shop and get your exhaust finished! I'm waiting for a before and after sound clip Before I forget, if you want to set alarms off, get the 40 or super 44 series(possibly dumped for extra loudness). If you want good rumble that will maybe be annoying when the mother-in-law rides with you, get the 50 series. If you want to hear your exhaust without drone or annoying mom, get the 70.

 

[JarvisB]

Your 02 sensors will work fine if you put them on a true dual setup. You'll just have to weld sensor bungs into the exhaust pipes at a similar location (relative to the engine and the cat converters) that they are now. The sensors measure the ratio of air to fuel, they don't care about the volume going by them.

BTW, an X or an H pipe is better than running true duals because it helps balance the flow better.

can you give me an example of which location would be the best, and what is a sensor bung? sorry lol.

 

[JarvisB]

I am a fan of H-pipes because I had one on my mustang and loved the balanced rumble. But if you like the way true duals sound, then go for it. After rereading your first post, you have 2wd only correct? If so, then you have a much better chance of getting true duals ran because you're not fighting the t-case like us 4wd guys would.

Also, legally a shop cannot remove any cats off a vehicle, they can only replace them. If there is any problem with them removing the third cat(resonator) then just chop it off yourself and have them finish the work. That's what I did and there wasn't any problems. As I said before, I wouldn't bother removing the two cats that come off the manifold because you're not at the power level to remove them and it will be pointless(and more $$$).

Now go to the shop and get your exhaust finished! I'm waiting for a before and after sound clip Before I forget, if you want to set alarms off, get the 40 or super 44 series(possibly dumped for extra loudness). If you want good rumble that will maybe be annoying when the mother-in-law rides with you, get the 50 series. If you want to hear your exhaust without drone or annoying mom, get the 70.

Yes I have 2wd, not 4wd. And I have V8 4.6L, just to clarify as some ppl thought I had a 4.0- I wouldnt do this if I had a 4.0 lol.

I am considering the following set up: 2.5" piping after o2 sensors on each pipe, X pipe, upgrade to 2 high flow cats, cut off 3rd one, dual exits, not sure what muffler, 3" tip

Am I going in the right direction here?

For the mufflers, to be honest I was thinking about 70 series lol, but now I am thinking about 50 series. how loud is 50 series really?

 

[JDraper]

can you give me an example of which location would be the best, and what is a sensor bung? sorry lol.

A sensor bung is a fitting that you weld to your exhaust pipe that has a thread to accept an 02 sensor. You drill a hole in the pipe at the location you choose, then weld the sensor bung over the hole. the 02 sensor then plugs into that sensor bung.

As far as 02 sensor location, if you have one between the exhaust manifold and the 1st converters on the old system, put it in the same place on the new system. If there is also one downstream of the converters in the old exhaust, put one there in the new exhaust too.

 

[JarvisB]

I am not sure if this guy my brother knows got a lot of experience in modifying the o2 sensors. But he works at the exhaust shop I think.

How hard is it really? I think I just got to talk to the guy myself and see what he can do for me.

I am trying to understand, I suppose that there are 2 pipes coming from the engine, the headers, correct? then they turn into single pipe after the manifold?

 

[Limited02]

I am going to post up some pictures I just took to show you what's underneath. I'm 4x4 so you'll have more room to play with. Give me a min or two

EDIT: Cell phone pics-

Looking from the back towards the front on the drivers side. This is where the Y forms a single pipe(3") and there should be a cat(resonator) where the new exhaust is attached, but a sawzall made it dissappear

This is from the passenger side looking towards the back/drivers side. You can see the cat on the drivers side and how the Y meets. It will be tight, but the muffler guy should be able to cut the Y pipe off exposing two single pipes and go from there. Also, don't bother with high flow cats because once again, you are not at the power level to need them.(In other words, they will be a waste of money)

 

[CALDWELL]

plus the cats that our X's have are very small to begin with in the 1st place...

just like Limited said... dont waste the money, cause your no where close in power to really need to swap CATs for hi flows...

if you went blown, then sure go ahead...

 

[JarvisB]

well I would like to do it right at first time. If I can upgrade the cats later down the road, then I ll wait. But if it is suggested to be replaced at same time with the pipes and set up, I will do it.

02limited, thanks for the pics! they were helpful, thanks!

 

[CDW6212R]

Nice, the 02's have more space to work with. The crossover pipe is in the space behind the transmission, much better than in front of the trans.

Jarvis, if your mileage isn't high and you still don't plan to boost, the stock front cats are okay. Those and the 2.25" pipes are restricting 5-10hp, but nothing major.

 

[Rofocowboy84]

My plan, when I eventually get the money to do it, is to use the "Y" as a sort of "X". For instance, the pipes come from the manifolds to the "Y", and then it's a single pipe from there. If I branch off to two pipes from there, it essentially serves as an "X", correct? I personally don't see the point of "TRUE" duals, but if you are going to do it, just run them from right behind the cats, there's no reason to remove them...

 

[CDW6212R]

Any exhaust restriction costs horsepower. Each small pipe, each cat, each curve, each tailpipe, each joint in the system, they all cost HP. All stock exhausts are terrible for making the most power.

The best exhaust is one with zero restrictions past the collectors. That's why cutouts are popular at race tracks, and drag cars generally have no exhaust unless required to.

If power is the highest priority, then anything to open up the exhaust helps.

Now... do not radically open up an exhaust without enriching the A/F ratio. Any large changes will cause a leaner air/fuel mixture, that hurts power. There have been thousands of people point to power losses after opening up the exhaust. That is entirely due to the leaner A/F, it is not "a loss of low end torque because of big pipes." The answer is to correct the A/F ratio, not to complain about the exhaust.

These vehicles we drive now all have computers controlling the A/F. Those PCM's cannot adjust for large air flow changes, automatically. They can be told how to do it with new programming.

Do what you can with your vehicle to improve the exhaust, and then immediately richen the mixture with a new program for the PCM. The magic is in the PCM, but the PCM is not magic.

 

[JDraper]

....There have been thousands of people point to power losses after opening up the exhaust. That is entirely due to the leaner A/F, it is not "a loss of low end torque because of big pipes...."

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.