Does anyone have a simple diagram of the different components starting with the headers and going back?

Also, any commentary on which pieces it makes sense to replace if you want improved performance & sound? I've read a couple posts that mention the stock exhaust system being fairly competent and replacing components won't yield much difference besides sound.

Thoughts?

 

I'd say this is pretty simple if you're just looking to see what goes where.

This shows the NPP system. Only difference for non-NPP on this diagram will be the lack of the two rearmost NPP valves.

 

Not to start a major flame-fest on quoting HP numbers but for guidance purposes only....

Upgraded straight through x-pipe - better sound, minor performance from improved flow; i don't remember 2 to 5 hp or something like that.

Upgraded axle back system, better sound, minor performance from improved flow; in the 10 to 12 hp range or less.

Upgraded headers - depends on long tube or midlength, with a tune or without a tune. So, Motor Trend dyno for a stock Z51 was 402 at the wheels - seems about right for a 13% drivetrain loss from the engine being at 465. I've seen some independent dynos for added midlengths that put it close to 428 without tune. Not the best apples-to-apples comparison but is indicative of an improvement opportunity. Long tubes with tune will give you more as would the midlengths with a tune.

CAI upgrade - seen about 10hp increase in presented dyno charts. CAI with a tune in the 18 to 20 hp range given the dyno charts shared here.

Tune alone - 15 to 20 something based on charts shown here, octane used, E85 usage....will impact the number along with a multitude of other variables.

Of course, you can't add all these together to get a net improvement (that's called "ricer math"). All the changes together will be less then the sum of the parts!

 

GM claims 5HP & 5TQ for the NPP over the standard exhaust, so I would not expect much improvement changing stock NPP to an after market exhaust, maybe a few HP. As stated above, an aftermarket intermediate pipe might add a few more. Certainly headers will provide significant gains.

 

I would assume from context there might be a size difference between long tube and mid length, but is that the only difference?

 

I would like my non npp to sound better more like the npp.

I have heard all the after market options.

What would just changing the xpipe do for sound and performance.

Anybody done just the xpipe?

 

Pretty much nothing, your sound is being killed by the mufflers. If you want NPP sound you need the NPP system or aftermarket.

If you don't care about closing and opening and want to run NPP wide open all the time you can find a system for under $500 that someone took off their car.

 

This is no longer the case. Full-function NPP retrofit is now available.