Question on my Muffler and 02 sensors - Hemi Truck Club
 
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Old 07-11-2013, 03:18 PM   #1
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Question on my Muffler and 02 sensors

Hi, My truck is a 2003 ram 2500 4x4 hemi that has a flowmaster exhaust system that was put on the truck by the dealership as soon as the truck arrived. It was already installed when i purchased it new in late 2002. Today I took off the cat converters and replaced them with straight pipes i got from autozone, each pipe was approx 18" long. It was a quick bolt on and off job, im keeping the cat conv's in the garage so i can do a swap back when it comes time to do an inspection, good thing everything is just bolted on!

After i got the cats off i disconnected the rear 02 sensors and got them off aswell. After i installed the pipes and was ready to put back the 02 rear sensors i wrapped the sensor tips with hvy duty aluminum foil and secured it with sm small guage wire then screwed them back in place. Everything went together very smooth and looks good so i started the truck and was very surprised on how loud and bad *** it sounds now.

I went on a test run to hear the exhaust and its super loud, i also was watching my dash for any lights that may come on do to not having cats on it and messing with the sensors. No ck engine lt or anything else came on so i guess the foil worked and fooled the rear sensors. I also noticed that my exhaust would occasionaly make a cracking sound after a stop and go. Is this because the age and size of the mufflers? If i replce them with some new bigger flowmasters will the cracking sound go away?

Any opinions would be great! Thanks

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Old 07-11-2013, 05:16 PM   #2
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Originally Posted by capt.raymond View Post
Hi, My truck is a 2003 ram 2500 4x4 hemi that has a flowmaster exhaust system that was put on the truck by the dealership as soon as the truck arrived. It was already installed when i purchased it new in late 2002. Today I took off the cat converters and replaced them with straight pipes i got from autozone, each pipe was approx 18" long. It was a quick bolt on and off job, im keeping the cat conv's in the garage so i can do a swap back when it comes time to do an inspection, good thing everything is just bolted on!

After i got the cats off i disconnected the rear 02 sensors and got them off aswell. After i installed the pipes and was ready to put back the 02 rear sensors i wrapped the sensor tips with hvy duty aluminum foil and secured it with sm small guage wire then screwed them back in place. Everything went together very smooth and looks good so i started the truck and was very surprised on how loud and bad *** it sounds now.

I went on a test run to hear the exhaust and its super loud, i also was watching my dash for any lights that may come on do to not having cats on it and messing with the sensors. No ck engine lt or anything else came on so i guess the foil worked and fooled the rear sensors. I also noticed that my exhaust would occasionaly make a cracking sound after a stop and go. Is this because the age and size of the mufflers? If i replce them with some new bigger flowmasters will the cracking sound go away?

Any opinions would be great! Thanks
First time I have heard of "screwed them back in place". Let's hope that continues to work for you. Usually if you wrap them in tin foil you use a plug for the bung hole and tie sensors safely out of the way. Good luck..
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Old 07-11-2013, 11:06 PM   #3
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To answer the question the noise you are hearing is the exhaust cooling off and shrinking. Its normal to have noises after replacing bits of the exhaust system. I would recommend going with some high flow cats versus no cats on a street vehicle. Your truck will never go closed loop and you will feel it at the pump. Believe it or not you can lose hp and torque with running an open exhaust. The factory spent millions to develop this engine and electronics to operate with some backpressure. Just because it sounds faster doesn't make it faster....
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Old 07-11-2013, 11:40 PM   #4
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Oh yeah before I get berated by some of you on the no cat thing I have done dyno testing and on most vehicles you get better numbers running 8-10 psi of total back pressure and that is especially true of forced induction vehicles whether they are supercharged or turbocharged its called valve overlap. A little back pressure keeps the fresh charge from just blowing out of the combustion chamber and straight into the exhaust.
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Old 07-12-2013, 01:11 AM   #5
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Oh yeah before I get berated by some of you on the no cat thing I have done dyno testing and on most vehicles you get better numbers running 8-10 psi of total back pressure and that is especially true of forced induction vehicles whether they are supercharged or turbocharged its called valve overlap. A little back pressure keeps the fresh charge from just blowing out of the combustion chamber and straight into the exhaust.
Mike, there is going to be a lot of folks on here really disappointed to find out we wasted all those dollars freeing up our exhaust flow. Maybe you can explain how that cam over lap thing works?
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Old 07-12-2013, 01:59 AM   #6
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High flow cats are the way to go "redtruck-va" has done the proper job on his truck (wish I had the dough to do the same too mine) high flow cats and single in muffler. During the combustion cycle at some point both valves are opened at the same time this is called overlap it is at this point when back pressure is a good thing because if there is a small amount of resistance to keep as much of the fresh air/fuel mix in the combustion chamber the more hp and torque the motor will make. The combo I will be using is Doug Thorley tri "Y" headers, magnaflow high flow cats & Y pipe and single 3" in/out magnaflow muffler. This will be the first mod even before a CAI gets done. I know how well this combo worked on my last truck.
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Old 07-12-2013, 04:27 AM   #7
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My muffler is enough back pressure for me don't need catts don't want catts that's just one more thing to plug up and cause a problem

As for closed loop my rears are turned off and I'm in closed loop is less than 30sec on a modus scanner with good mpg on the road guess it all in how it's tuned
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Old 07-12-2013, 10:25 AM   #8
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I expected you to chime in Charged392. You are running an entirely different engine combo than everyone else is that runs at a higher rpm range than the average daily driver. Guess I should have also stated that I live in wonderful (insert sarcasm here) California and smog laws are a huge deal however if we are going to compare apples to oranges remember that you can walk onto a new car lot and buy a 600-1200hp car if you got the dough that has cats on it.......and even you have proven that a little back pressure is good by switching back to a Y pipe instead of the duals.
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Old 07-12-2013, 10:46 AM   #9
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Yeah little is good

I would say if you have emissions where you live run high flows if you don't have emissions and want louder exhaust or run not catts at least have a y pipe and muffler some back pressure is better than none for sure also lack of back pressure has a better chance of burning a valve if tune is off a little
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Old 07-12-2013, 11:18 AM   #10
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Yeah some countys run spot checks on emissions tampering and have fines that starts at $10k automatic! No way is that worth the risk. I'm no tree hugging dirt worshiper but I do care about the air my kid has to breathe. The minimal backpressure that highflow cats produce is worth the increase in hp and torque on the bottem end and midrange power bands when your using the truck for its intended purpose like towing or hauling heavier loads. You'll only see benifits on open systems when you are running above the 4-5000 rpm range. Fuel doesn't plug cats oil does and when you super/turbo charge an engine you inevitably burn more oil.
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