I am wanting a new cat back system for my 4.0 and like a relatively quiet exhaust on my Jeep. Never have enjoyed a loud 6 banger, love V-8 muscle though. Who makes a good quiet yet efficient system? And how can you tell if your cat is plugged, without tearing it apart?
Thanks. Sounds like the Dynomax cat back is what I want. Don't mind a little extra sound.
So, does anyone know how to tell it the cat is plugged, short of replacing? I have 97K miles, if that makes any difference.
Couple different ways of looking for a plugged cat. The easiest, though least conclusive is the vaccuum guage. Find a good manifold vac port, hook it up and start the engine. Slowly raise engine speed and watch the vac. If it starts to drop drastically at higher speed its a candidate. Another option if your hardware isn't solid rust is to pull the cat and look into it with a bright light on the other end. Today's cats are "monolithic" meaning one piece. Its like a brick with hundreds of holes straight through it, and you should see light through the holes.
What about Magnaflow? Would you put this in the same class as the Dynamax? As opposed to the Flowmaster. I'm in a similar situation.
I went to a muff shop and the guy had a CJ with a 4.0 and a flowmaster on it. He said from his experiance the Magna was too quiet for the Jeep. He said the Flow 40 was even too quiet for his liking on his Jeep. He started it up and I tended to agree, it was weak. For a 40 seires. I was interested in Magna and he showed me a Flow that didn't impress me.
The reason I was wanting to go with the Magna is the said 'growl' as opposed to roar of the Flow. Besides, I think a 6cy just doesn't work for a 'roar'.
So, back to my question. Do you think the Magnaflow is in the same class as the Dyna, as far as low growl, as opposed to loud roar...(if you could call it that on a 4 liter)?
Couple different ways of looking for a plugged cat. The easiest, though least conclusive is the vaccuum guage. Find a good manifold vac port, hook it up and start the engine. Slowly raise engine speed and watch the vac. If it starts to drop drastically at higher speed its a candidate.
That is a tricky test because vac is proportional to load. Higher rpms and no load = high vacuum. You could use a scangauge to watch the MAP. The best test would be at WOT where vacuum should be close to 0. I'm still not sure it would show if your cats were clogged. The best test would be to install a pressure gauge in the front o2 port and watch it at WOT.
I was working for GM in the early to mid 80's and we had many issues with the old bead type cats. The vaccuum guage is indeed an effective means of diagnosing a restricted exhaust. Have to use your brain a little to interpret the results.