Have a 2003 R/T which I want to put true duels on. Garage guys say I can't and the best reason is that the truck is set up for only one cat converter. Anyone know of a computer program(er) that can change this situation? As a neighbor says...bound to be some computer wizz out there who can make this happen!

 

I will tell you about my experience with my 2001 QC with 4.7 5sp manual 4x4.

I had true duals put on last summer right from the manifolds back. There were 3 cats on the stock system, 1 right below each manifold and then another after the crossover pipe. Also, there are 4 O2 sensors, 2 on each side being 1 above and 1below each of the 2 pre-cats. My system eliminated all cats and the shop drilled the new pipe and reinstalled the O2 sensors roughly where they used to be. No check engine lights or bad gas mileage have happened as one shop tried to tell me....more like SELL me these simulators for the O2 sensors to the tune of $300 bucks! Needless to say I went elsewhere and found an honest shop where they told me not to worry. The O2 sensors that go ABOVE the cat are the ones the computer uses for fuel mixture etc. Any O2 sensors BELOW cat converters are merely to tell the computer if they're working properly, and don't affect performance. I don't see why you couldn't run your true duals.......phone around, it worked for me. (by the way, the SOUND was worth every penny

 

if im not mistaken, there is only 1 O2 sensor and 1 cat on the R/T. i cant wait to run duals on mine, it already sounds bad *** with the 1 flowmaster dumped down.

 

It depends on the law. IIRC it's federal so it shouldn't matter where you are - if a shop gets caught altering the emissions controls (read: removing cats) they're subject to a $10,000 fine. You as the individual are also liable if memory serves. Which is why some shops refuse to do work as you have experienced. On my 86 Ram, which never had a cat even from the factory, I had trouble getting shops to fix the exhaust. One shop wanted to charge me over $800 to add 2 cats and put it back to "factory". I got a government document showing that my truck didn't require cats (over 8500gvr = HD and no cats for 86) and took my business elsewhere.

All that aside, it depends on the shop. Places out in the county imho would be more apt to do illegal work.

 

ive found places in the past in that would do the work: remove cats and resonators. still know where they are

 

The gains from removing cats all together instead of using a high flow cat are minimal, and the environmental and legal impacts are quite steep. Sure you're only polluting a little more, but your truck was designed to use one. I'm not really one to talk, my 86 has no cats, and my 91 5.0 has none (somebody before me did that, and I'm not keeping the motor in that shell so I'm not replacing them now) but on my other vehicles I've modified I've swapped in high flow cats.

 

oh i definately plan on using high flow cats on mine. the loss of backpressure would result in HP loss[:'(]

 

Well, on examination, I have two "pre-cats" each with two 02 sensors and a third cat between the crossover and the muffler with no 02 sensor. I figure I can either add a fourth cat on second pipe or do away with the OEM cat since it has no sensors?

 

Absolutely. You can run your duals from just behind the O2 sensors and leave those small cats in place. And if you're really worried you could buy 2 hi flow cats and put them in too (not cheap). I would advise not to let the shop talk you into big diameter pipes. Bigger pipe equals less bottom end and a more mellow sound while smaller pipe equals more back pressure and very throaty sound(horny) when on the pedal. I have tru duals on my 4.7 and used 2 1/4 pipe. It sounds good but I wouldn't go any bigger (no bottom end gain but top end seems better). My next move might be headers

 

The R/T Daks made after September of 2000(read 2001 model year) will have 3 cats in the line. 2 pres with 2 O2 sensors apiece and 1 main with 1 O2 sensor. Like what was said before the only ones that matter are the first ones in the manifold. Those are used to regulate fuel mixture and also take temp readings as well.