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Hi Guys

I live in South Africa so emissions are not a problem. I have a WK2 5.7 Overland 2011. 160 000kms. I assume my cats are blocked. Sulphur smell under acceleration. Down on power. Alot of hesitation. And a rattling sound which I'm told is the cat. I want to decat and at the same time perhaps put in x pipe in place of suitcase muffler. Any advise appreciated. Thanks
 

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Muffler stuff is pretty simple so not much advice to give on my part. However, if you delete or get hi-flow cats you'll most likely get a check engine light that won't go away due to the absence of the O2 sensors.
 

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Discussion Starter #3
Thanks MDK. Not quite that simple though. Yeah i will have to tune away the engine light, but my worries are as follows:
1) If i delete the cats and then add an X Pipe, will there be enough back pressure
2) Will there be that tinny rattle sound from the exhaust under revs
3) Will there be drone?

Is it advisable to decat and then do the following:
1) Remove suitcase muffler and install an x pipe
2) Leave suitcase muffler and change resonators
3) Remove suitcase muffler and install x pipe and change resonators
4) Remove suitcase muffler and install x pipe and remove resonators

I do not want it too loud, i want a nice V8 sound without a tinny/metal vibration (Heard on some of the x-pipe videos)
 

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Those really into the Engine mods can tell you better....
The lack of back pressure in exhaust reducing power is something from carburetors, modern fuel injected engine usually don't have any side-effects from reducing back pressure....
Power is made by increasing the airflow through the engine.... ....you can't flow out more air than you flow in, nor can you flow in more air than you can flow out..... ....most modern vehicles have low restriction exhaust and the choke point is the intake system, not the exhaust....

I'm happy with HEMI in stock form, I have not been reading up on performance mods for it....
Perhaps these aren't true for the WK2, but judging from the posts I've read it does seem to be true for the HEMI....
Catalytic convertor removal and exhaust mods only, will likely produce a different sound, not any noticeable performance gain....

If I had to guess, since the Catalytic Converters are closest to the engine and do a lot to attenuate noise, removing the Catalytic Converters might be likely to make the exhaust note more raspy......

Check Engine Light (CEL).....
Since you're in South Africa, I'm assuming your WK2 is an export model, so the emissions systems may be set up differently, but I think Europe has pretty much modeled their Emission approach after the U.S. so there may not much difference (assuming your South Africa WK2 came from Europe)....
There is no way to Tune Away a CEL from a failed Catalytic in U.S. based emissions system....
There is an upstream O2 sensor that provides feedback to the PCM for adjusting the engine........after the Catalytic Converter there is a downstream O2 sensor, that is only used for checking the operation of the Catalytic Converter.... ....when the engine controller performs this check on the Catalytic Converter it compares the O2 sensor signals before and after the Catalytic Converter, if they are the same, and they will be without a Catalytic Converter, it lights a warning the CAT has failed..... ....there is no way to tune the engine so that exhaust composition somehow changes over a foot of pipe length, without a catalytic converter....
You have to trick the system or disable the part of the PCM software that sets the CEL warning.... ...perhaps there is a tuner device that is capable of changing the software or some of sort of cheater device that spoof the Downstream O2 sensor signal.....
 

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there is not a ton of information on exhausts on here, other than a few popular catback options. use something with resonators, otherwise, you will have rasp.
the need for backpressure is a myth for these types of engines.
 

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Discussion Starter #6
Thanks for your comprehensive reply. There is a tuner or two that can change the software and either trick or disable the downstream O2 sensor. SA Jeeps are more than likely Europe Models as you say. a Jeep Mechanic / Shop here has totally swapped his exhaust system with headers too on his HEMI and removed cats, sounds great and no CELafter tuning. but... this system was a full replacement and rather expensive. I just want to remove my faulty CATS without making it sound terrible. So would the answer be to remove open CATS, scrape out the innards and then weld back up, leaving sensors in place or to cut it out and replace with straight pipe.
 

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Discussion Starter #7
Yeah have seen most of the videos, all have done either an X Pipe with stock mufflers / resonators and with out, but not many that have decatted
 

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removing the innards of a catalyst and welding it back up would probably be worse than anything. the catalysts do help with keeping noise in check. straight pipe it, but use two sets (four total) of resonators, plus mufflers. you won't restrict flow, and the rasp will likely be gone.
 

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Thanks! just to check. cut out cats, and straight pipe it, that way cats can be put back if ever required and if i cant manage to get rid of CEL light. But again, the cats are badly blocked anyways.
Where would you install the resonators and mufflers? Should i just leave suitcase muffler in and stock resonators at the end, or replace both? Should i replace suitcase muffler with an Xpipe?
Also, what will happen to the sensors if the cats are cut out and straight piped? removed and disconnected?
 

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let me ask you this... what is your goal? to make the most horsepower possible, or to be happy with the sound? because once you start hacking and welding is going to add lips and weird bends in the tubing that could hinder flow. you would put resonators where you can fit them in straight sections of the exhaust.
you are going to want to keep bungs in the piping for the o2 sensors, even if you don't have cats. the engine still uses them.

do you have the ability to buy this system?
it will likely yield the most gains, and probably sound good since they somewhat tune for sound.
 

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Discussion Starter #11
I came from a 2.8 Diesel Wrangler, and then a 3.8 Wrangler and then a 3.6 Wrangler. The power in the Hemi is more than enough for me. This isn't about horesepower. The CATS on my WK2 are severely blocked. I have had it checked by exhaust shops, but the local shops are clueless on what to do. There are some performance shops that understand the system but are way way overpriced. When accelerating there is a very very sharp strong sulphur smell from the CATS. Airflow is also very very restricted and at times the Jeep is as sluggish as my wifes Hyundai 1.4 low down in the rev range. You can hear it flow thru again and then the power is available. The CAT is now also rattling under load.

I just want to decat, and at the same time not have a tinny raspy sound, and at the same time, make it sound like a V8 :)
 

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you likely have a problem other than the catalysts based on what you're describing. either they are clogged, or they aren't, there wouldn't be any intermittent flow problems. you would also already have a check engine light.
exhaust doesn't smell like sulphur, either. if i had to guess, you have something wrong that is lubricated with gear oil, like your rear diff is shot or something and the truck is trying to manage torque.
 

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Rear diff has recently been replaced, thanks for your help. Wish i could find a specialist here that could offer solutions.
 

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why was it replaced? i'm starting to think you have a differential problem and that what you're smelling. have you ever smelled hot gear oil? it has a sulfur smell.
 

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i kept on getting serv 4wd light. a Jeep specialist a friend of mine, swapped diff actuator with another Jeeps and it went away, the motor and control box was burnt out. Claimed from my aftermarket warranty and replaced rear diff actuator and control box and its been fine ever since. The sulphur smell was there when i bought the Jeep 2nd hand before the diff issues. its still there now. Exhaust shop has stated that it is the cats. diff works correctly.
 

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...Yeah i will have to tune away the engine light, but my worries are as follows....
Thanks for your comprehensive reply. There is a tuner or two that can change the software and either trick or disable the downstream O2 sensor....
Tuning is a process of making adjustments to optimize the performance of an engine....
A Tuner Device is an electronic device that hacks the software/hardware of a modern vehicle, to allow changes that you normally can't make....
There is a difference, but since you have to hack the vehicles computers to "Tune" it, using a Tuner Device, they add extra features into that tuner device to do some additional hacking that enthusiasts buying the device might want to do....

So no amount of tuning, as in making adjustments to the engine, will change the results of a test of the Catalytic Converter....
But using a Tuner Device to hack the vehicle computers, if it has the features, could be used to turn off or disable the test of the Catalytic Converter....

BTW, adding to the confusion, most modern vehicles use a Speed-Density System that utilizes Experimentally Derived Data from a test engine as reference for values (or adjustments) to operate the engine, but still correct for variances and wear between engines.... ....so the makers of a Tuning Device could "Tune" a test motor and develop that experimental data to just load into your PCM....

People doing real "Tuning" are taking their vehicle to a speed shop with a rolling dyno, spending a week there "Tuning" their engine by making fine adjustments to operating parameters to get every bit of power possible out of the engine....

But people are also using "Tuner Devices" to hack the vehicle computers to load data into their vehicles for a more optimized engine profile, they call this tuning, it's a stretch but not wrong either.... ...using computers to control the engine allows you to transfer the adjustments from one engine to another via the computers...

They also refer to these Data Sets that are loaded as "Tunes", stretching it a little more, but it's not wrong......

If you didn't know what tuning was, you'd get the misconception any kind or hacking or modifying the vehicle was "Tuning" it....

In the old days, as an engine wore, you periodically had make measurements and adjustments (i.e. tune) to compensate for the wear and keep it performing optimally... ...the old Tune-Up... ...this was done when spark plugs and filters were changed, because eroded away spark plugs and dirty filters throw off the performance and adjustments of the vehicles.... ....modern engines with computers and sensors tune themselves (different than performance tuning).... ...so a tune up is no longer necessary, but they still need spark plugs and filters changed, so Dealerships will pray upon people's ignorance and charge twice as much for a spark plug and filter change, telling them its a "Tune-Up" when they is no tuning they do, the engine computer is doing the tuning several times a second as you drive...

And finally, if you're changing the engine operating parameters with a Tuner Device, keep in mind, if the OEM could make the engine more powerful by changing the data in the computers they would have done so.... ...there are three reasons the OEM's have the engines power reduced below their full potential....
  • Emissions - the engine has to pass emissions and that emissions equipment has to last, at least 85k miles, so operating engine at different parameters that might make more power would cause it to produce to much pollution, or burn up its emissions equipment, like burn up or clog your Catalytic Converters... ...but you don't have to worry about emissions in South Africa, and you're removing your Catalytic Converters, so no worry in that regard for you....
  • Safety/Reliability - most vehicle owners and drivers are idiots that don't understand the first thing about how their engine works, they will not recognize problems with the engine and even knowing their is a problem, will continue to drive with the problem.... ....the OEM's build in a safety factor in the operating parameter of the engine, so the engine is not operating right at the edge of envelope so that inattention or neglectfulness from the owner doesn't result in the engine melting down....
  • Longevity/Reliability - the OEM tests these engines thoroughly, fully instrumented and torn down and all parts inspected with each change in operating parameters.... ...so the OEM's already know that the 25 extra HP you can get from a little tweak to a certain parameter actually results in a rise in temps of the exhaust valves that result in halving the life of those exhaust valves..... ....the candle that burns brightest is also the candle that burns the shortest.... ...the motor makes a much power as it can safely for hundreds of thousands of miles....
No, upping power a bit with a Tuner Device is not inviting disaster, but just keep in mind race cars have their engines tuned to extract every bit of power they can make, and every other race you see one of those motor explode.... ....so you don't want to go too crazy changing your motors operating parameters, and you need to be vigilant on watching that motor and catching any malfunction...
 

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You can also throw in a 4th, mileage, in the U.S. and some European countries, the Manufacturers have regulations to meet certain fuel economy standards for the vehicles they sell.... ....so they have lots of pressure to keep the fuel economy of their engines up as well.....
 

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i kept on getting serv 4wd light. a Jeep specialist a friend of mine, swapped diff actuator with another Jeeps and it went away, the motor and control box was burnt out. Claimed from my aftermarket warranty and replaced rear diff actuator and control box and its been fine ever since. The sulphur smell was there when i bought the Jeep 2nd hand before the diff issues. its still there now. Exhaust shop has stated that it is the cats. diff works correctly.
Since you WK2 is an Export Model, there could be differences from the U.S. models, because the regulations differ from country to country. But the WK2 runs a test on the Catalytic Converter, if they were bad, you would have a CEL and code that means the Catalytic Converters have failed their tests. This is assuming your export version of the WK2 has the same Cat test feature as the U.S. model. At the same time, if you have Catalytic Converters, even if its not required, I'd think they still include the feature on any WK2 with Catalytic Converters simply to help identify problems.....

And bad Catalytic Converts do emit excessive Sulphur Dioxide gas, but that is not a Sulphur Smell, it's the smell of rotten eggs and you should be able to smell it at the exhaust pipe while the engine is idling...... ...the smell of Sulphur is minorly annoying, the smell of Sulphur Dioxide, Rotten Eggs, is outright revolting, it causes people to wrech if the smell is strong enough.....

Do they still have leaded fuel in South Africa? Leaded fuel will destroy Catalytic Converters, but many impurities in fuel can damage the Catalytic Converters, as well as engine malfunctions or changes in their tune, like running rich or too lean, misfires that result in raw fuel being released into the exhaust.....
 

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Discussion Starter #19
Tuning is a process of making adjustments to optimize the performance of an engine....
A Tuner Device is an electronic device that hacks the software/hardware of a modern vehicle, to allow changes that you normally can't make....
There is a difference, but since you have to hack the vehicles computers to "Tune" it, using a Tuner Device, they add extra features into that tuner device to do some additional hacking that enthusiasts buying the device might want to do....

So no amount of tuning, as in making adjustments to the engine, will change the results of a test of the Catalytic Converter....
But using a Tuner Device to hack the vehicle computers, if it has the features, could be used to turn off or disable the test of the Catalytic Converter....

BTW, adding to the confusion, most modern vehicles use a Speed-Density System that utilizes Experimentally Derived Data from a test engine as reference for values (or adjustments) to operate the engine, but still correct for variances and wear between engines.... ....so the makers of a Tuning Device could "Tune" a test motor and develop that experimental data to just load into your PCM....

People doing real "Tuning" are taking their vehicle to a speed shop with a rolling dyno, spending a week there "Tuning" their engine by making fine adjustments to operating parameters to get every bit of power possible out of the engine....

But people are also using "Tuner Devices" to hack the vehicle computers to load data into their vehicles for a more optimized engine profile, they call this tuning, it's a stretch but not wrong either.... ...using computers to control the engine allows you to transfer the adjustments from one engine to another via the computers...

They also refer to these Data Sets that are loaded as "Tunes", stretching it a little more, but it's not wrong......

If you didn't know what tuning was, you'd get the misconception any kind or hacking or modifying the vehicle was "Tuning" it....

In the old days, as an engine wore, you periodically had make measurements and adjustments (i.e. tune) to compensate for the wear and keep it performing optimally... ...the old Tune-Up... ...this was done when spark plugs and filters were changed, because eroded away spark plugs and dirty filters throw off the performance and adjustments of the vehicles.... ....modern engines with computers and sensors tune themselves (different than performance tuning).... ...so a tune up is no longer necessary, but they still need spark plugs and filters changed, so Dealerships will pray upon people's ignorance and charge twice as much for a spark plug and filter change, telling them its a "Tune-Up" when they is no tuning they do, the engine computer is doing the tuning several times a second as you drive...

And finally, if you're changing the engine operating parameters with a Tuner Device, keep in mind, if the OEM could make the engine more powerful by changing the data in the computers they would have done so.... ...there are three reasons the OEM's have the engines power reduced below their full potential....
  • Emissions - the engine has to pass emissions and that emissions equipment has to last, at least 85k miles, so operating engine at different parameters that might make more power would cause it to produce to much pollution, or burn up its emissions equipment, like burn up or clog your Catalytic Converters... ...but you don't have to worry about emissions in South Africa, and you're removing your Catalytic Converters, so no worry in that regard for you....
  • Safety/Reliability - most vehicle owners and drivers are idiots that don't understand the first thing about how their engine works, they will not recognize problems with the engine and even knowing their is a problem, will continue to drive with the problem.... ....the OEM's build in a safety factor in the operating parameter of the engine, so the engine is not operating right at the edge of envelope so that inattention or neglectfulness from the owner doesn't result in the engine melting down....
  • Longevity/Reliability - the OEM tests these engines thoroughly, fully instrumented and torn down and all parts inspected with each change in operating parameters.... ...so the OEM's already know that the 25 extra HP you can get from a little tweak to a certain parameter actually results in a rise in temps of the exhaust valves that result in halving the life of those exhaust valves..... ....the candle that burns brightest is also the candle that burns the shortest.... ...the motor makes a much power as it can safely for hundreds of thousands of miles....
No, upping power a bit with a Tuner Device is not inviting disaster, but just keep in mind race cars have their engines tuned to extract every bit of power they can make, and every other race you see one of those motor explode.... ....so you don't want to go too crazy changing your motors operating parameters, and you need to be vigilant on watching that motor and catching any malfunction...
Thanks for all of your info. I guess in this case i would be using a tuner to just disable the downstream 02 sensor or another attribute related to this. Tuners that can do this dont really hack the vehicle system. The tuner or manufacturer of the tuner has figured out a way to hack through the ODBII encryption and thus is now able to change certain parameters or settings.
 

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Discussion Starter #20
Since you WK2 is an Export Model, there could be differences from the U.S. models, because the regulations differ from country to country. But the WK2 runs a test on the Catalytic Converter, if they were bad, you would have a CEL and code that means the Catalytic Converters have failed their tests. This is assuming your export version of the WK2 has the same Cat test feature as the U.S. model. At the same time, if you have Catalytic Converters, even if its not required, I'd think they still include the feature on any WK2 with Catalytic Converters simply to help identify problems.....

And bad Catalytic Converts do emit excessive Sulphur Dioxide gas, but that is not a Sulphur Smell, it's the smell of rotten eggs and you should be able to smell it at the exhaust pipe while the engine is idling...... ...the smell of Sulphur is minorly annoying, the smell of Sulphur Dioxide, Rotten Eggs, is outright revolting, it causes people to wrech if the smell is strong enough.....

Do they still have leaded fuel in South Africa? Leaded fuel will destroy Catalytic Converters, but many impurities in fuel can damage the Catalytic Converters, as well as engine malfunctions or changes in their tune, like running rich or too lean, misfires that result in raw fuel being released into the exhaust.....
Yes that does make sense, im sure i would get an error code. So instead of me trying to diagnose my own problem, let me rather explain the symptoms and see if there is another angle.
At idle, there is no issue. Only under load and under acceleration is there a sulphur kind of smell, its not massively rotten, but its not fuel or oil either. After some time on the highway the smell goes away. When you drive the vehicle again and accelerate the smell returns.
 
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