915RUBICON

Well to make a long story short I need a whole new exhaust system, so after a little research I found some OBD-II compliant high flow mini cats, which for my application looked like the way to go. And after a complete custom exhaust with two high flow cats and a flowmaster muffler all running through 2 1/2" pipe .... I ended up with a jeep that sounded wicked.... deep throaty sound damn thing sounds tough...
Well now for the crappy part, I lost a ton of low-end torque, and yes it is so notable that people who know me and my jeep asked what happened at the last off-road session.
Now the question.. What now? Change the whole thing out and pay out the nose again? Anyone else have this problem? Any suggestions to modify what I have to get me back to where I was? well throwing this out there just to see if I can some ideas?

Cunnart

How did you verify you lost TQ? Is it verified via dyno or are you just butt dynoing it? If just butt dyno I would suggest using a real dyno first to make sure it really is losing power.

Cunnart

Yes, suggesting smaller piping was going to be my next suggestion as you probably lost to much back pressure/scavenging. But I would still say verify you lost first.

915RUBICON

Thanks for the advise
Well I could go and pay for dyno pulls and hope I get at least three pulls with constant numbers, but they would be pretty much useless, unless I had some baseline numbers to compare with... but to be honest, it is real bad. You would not need a dyno print out to tell you there is a major loss.

now as far as a change, should I change from cat back, or cat forward, what about options...like mufflers? Or simply changing after muffler tail pipe to slow down the exit? Really would hate the expense of starting over and using smaller pipe thoughtout. Oh well.

RubiRedRider

Auto zone or any other will have a 2.5 to 2.25 reducer/coupling. slap that on the end (after mufflers) and see if any diff. I put a free flow muffler on my H3T and dropped in front of back axle removing quite a few turns. Experienced some of the same issues and then reduced it after the muffler with a reducer. Noticed improvements.

RB

915RUBICON

Thanks, I think I'm going to remove the flowmaster, put a more restrictive muffler and go with your idea of changing the the exit pipe to 2" or 2 1/4"

Thanks again,
If anyone out there has any other ideas? I'm open

TyStick

Stock pipes are 2 1/2. The only difference is how much you opened the cats and muffler? I do not see how you could lose THAT much tq. I run stock pipes and no muffler. You can tell it flows free but loss of tq is minimal. Reducing pipe size, adding restrictive muffler... You are asking to lose mileage by making it tougher for exhaust gases to escape and binding more stuff up.

ZMagic97

I would assume it's due to lack of pack pressure. Have a mototrycle with a shorter, larger piper and it flys and mid to high range, but dead at low range. It can be fixed by adding a smaller and longer pipe. See if you can add an oriface or nozzle to the end, it could help you figure this out more.

f3arn0FJ

Did you replace all 4 cats with two high flow cats? Also did you change out the headers as well?

81ster

x2