mine sucks off the line it doesnt really pick up until 35 or so.
i think the biggest you should go on a N/A motor would be 3" unless you go duals then id go down to 2.5". if that makes sense. turboed mmmm 4"-5"

 

Is that with TM removed?

 

dunno. it was tuned the way the guy wanted to do it. im in the process of retuning just works keeping me away from the tuning session. if i dont like the new tune ill just buy the blackbear tune that way i know its done right and i know id love the tune

 

I don't necessarily buy into the whole backpressure thing. I don't believe that the newer engines need near as much backpressure as older one, however you do IMO need to try and keep the exhaust velocity as high as possible. Thats why you hear so much about headers scavengine ability.

That being said, your exhaust doesn't sound over the top at all IMO. You may be able to benefit a little on the low end by adding some high flow cats and/or a little more restrictive muffler, however, you will be taking it away from another part of the power band. You may also benefit from going down to a 2.5 inch exhaust. But being a NNBS owner myself, my 4.8 RCSB is a dog off the line. I'm running stock manifold and cats, with SLP loudmouth 3" all the way dumped, and I felt a bit of power loss of the line too, been thinking about going with a magnaflow or something that has some type of restriction, the SLP is just an open tube.

I think you'd benefit most from a 2600-3000 torque converter or something.

Spoolin, yes even with the TM on the NNBS trucks turned off, they still suck off the line. In 07 they went to a computer controlled Throttle control, and to my knowledge it cannot be changed by the tuner, it slowly opens the TB blade. I've got all my TM off on my 4.8, which isnt a power house by any means, but still it should hit alot harder than it does. Anything other than a dead stop - start and it runs extremely well.

 

Didn't know that...kinda sucks!

 

There actually is a way to fix that with HP Tuners but on the nnbs the opening rate is already set to 100%. There is however a tip-in torque management that can be deactivated but you need a beta version of hp tuners. Mine has all this removed and even like that it doesn't launch very hard.

 

Mine is still sluggish off the line also even with mods. Guess it's just the nature of the beast.

 

plz don't take this as a dumb question guy, but all this back pressure has got me wondering how exactly the h pipes exactly work. you know equalizing the pressure on both sides of the motor to make it run better. fill me in spoolin if you think the h-pipe is worth the hype or not?