Exhaust Fabrication

The design of my exhaust system was largely inspired by David Vizard's article on "zero loss" exhaust systems in Popular Hotrodding some time back.  A link to that full article can be seen here:  http://www.superchevy.com/how-to/exhaust/0505phr-exh/

The basic idea of this is to end up with a complete exhaust system that preserves open-header performance while achieving reasonable levels of sound reduction for street driving.  Several important general concepts come from that article:

1. Primary pipe diameter is more important than length.  For example, there is not much benefit to be realized in pursuing equal length headers on a 90 degree V8 like the LS - the exhaust pulse spacing does not lend itself well towards realizing any significant benefit from the additional effort, material costs, and packaging constraints in an already cramped engine bay.
2. Secondary length (collector extensions or other components where the cross section undergoes significant areal changes) has a big impact on the characteristics of power delivery.
3. 2.2 CFM / HP is required to approach open pipe performance while still achieving a reasonable amount of overall sound reduction.

 

Full Length Headers

Since I can't do CFD involving compressible gases flowing through complex geometries in my head, I relied mainly on dyno results from similar engine setups, recommendations from builders, and a program called Pipemax to try and figure out what sizing would be best to use.  

I knew I wanted to do a long tube design, and I saw that there were an awful lot of mild to high performance built LS1's that seemed to realize benefits and minimal downsides from utilizing a 1-7/8" header vs. the much more commonly used 1-3/4".  So I decided to try the 1-7/8" for a few reasons:

• My car is going to weigh 3000 lbs max soaking wet - I'm not going to miss 10 ft-lbs at 3k rpm to get the thing moving, since I will be spending pretty much all of my (performance) driving time in the upper registers where the extra breathing capacity will be more beneficial.  I think the induction and valvetrain work I have done with the engine warrants this - the parts combination should be good to a 7200 rpm redline - we'll see if it actually pulls all the way there.
• I am running 3.73 gears and a T56 magnum short ratio gearbox - I am going to have plenty of torque multiplication.
• Going with the larger header gives me the freedom to swap in a larger engine in the future should I choose to without leaving power on the table.
• There is no current offering for 1-7/8" headers on the market - would be filling a niche in the market if I'm every able to get reproductions going.
• Most guys said it couldn't be done.

Pipemax seemed to recommend it as well, but first a word on how I used this.  Since I didn't have my own dyno data to base any of this off of, I plugged in as much data as I did know and then tweaked the VE until the theoretical output was in the ballpark of very similar engine builds.

Since I was targeting mid-range torque and high RPM hp (high average power / area under the curve), 1.875" tubing seemed to be a good fit.

 

 

Passenger side:

 

 

Driver's Side:

 

 

Merge Collectors

Harmonics Termination Box

The basic idea of this device is to provide an enclosed volume ranging between 11-16x the displacement of 1 cylinder - it tricks the engine into thinking that the headers are open to atmosphere, thus insulating the wave tuning of the headers / collector from any potential effects caused by the secondary exhaust piping, mufflers, etc.

 

Exhaust Hangers