Hey I have the 99 5.3 ECSB and currently have cats but no muffler. I am going to make it true dual in the near future and had a question about it. Would i get more of a horsepower gain from running true dual with no cats but with mufflers, or with cats and no mufflers. Also what muffler would you reccomend for this if it would be a better hp gain to have mufflers?

 

I would say go with no cats and a muffler. The converters are usually more restrictive than the mufflers. But if you do this, youll lose some low end. I love the hooker aerochamber. I run that with no cats.

 

Mufflers are WAYY more restrictive than cats, cats esp. in the newer trucks 99+ are barely a restriction at all. The older vehicles used pellet style cats which were heavy and horribly restrictive.
The 1996 and up trucks 100% use a monolith style honeycomb style catalyst which barely add a restriction.
Mufflers on the other hand are most of the restriction in an exhaust.

i used to run Hooker long tubes, dual 2.5" headpipes from the headers to the 2.5" cats, when I added mufflers I could actually feel the lessened acceleration.

the dual stock cats on the 1996-99 trucks outflowed the cats on the old style Dodge viper, the new 99+ trucks have even better cats than my truck did.
if flow is your game, keep the cats lose the mufflers, why do you think that cutouts are so popular, its to get rid of the backpresure of the mufflers.


Obviuosly some mufflers are more restrictive than other mufflers, but no muffler would be less resrictive than a NBS truck cat.

You would be best off using dual cats into an x pipe then into 2 low restriction mufflers. I even think you would have the best performance going with dual 2.5" cats into a single 3.5" muffler, having both side join at some point for sure adds torque.

If you dont have enough backpressure, low rpm torque will suffer, with astock cam and tuning anyways. On my setup when I added the mufflers I lost some hp, but the low rpm torque increased due to added back pressure.

peace
Hog

 

you will get mixed reveiws as seen above about this....

from personal experience I lost low end taking my cats off but above 3k it flys! If I was racing 24/7 thats fine... but im idling around town alot and im not WOT all the time so my low end below 2400rpms suks! Any decent stall would fix that. Its all gonna be in your combo and future mods.

I'd say leave the cats and use no muffler, untill you get more mods and then dump the cats

 

You are right you do lose your lowend from taking off the cats. But you just cant beat the sound with no cats!

 

well I had the opposite experience, I felt my truck gained some low end when I removed the cats, cats had about 70kmiles on them if I remember right... oh yeah you'll love the sound of a catless truck..

 

Where do i get o2 sims for my 03 ecsb 4.8 ???

 

If youll give me to summer, ill sell you mine! Gettin a futral tune.

 

Amen on the sound of a truck with no cats. Cant beat it. And as i said before, down low i dont have much w/o cats but at wot i can definitely tell a diff!