Ok does anyone know an actual mathematical way to choose the size piping for a cat-back exhaust system? Anyone know how to determine what flow (CFM) muffler to get?

I've searched all over the internet and all I've been able to find are confusing articles and no formulas...

 

they make it easy know a days Gibson cat back is the way to go for the Blazer.

 

The soul purpose of the exhaust system is to take the spent gases and move them past the passenger compartment. The cat cleans up the environment, and the muffler mufflers the sound.

The most noticable gain in performance is with headers. Then get exhaust pipes in the same diameter. All modern cats are free flowing. Teh most free flowing muffler is a glasspack.

Long tube headers will give you the best performance at lower rpms, while short headers will give the best perfromance at higher rpms. Which ever you choose will give better performance compared to the factory exhaust manifolds. The trouble your going to run into is finding headers for the S-series. Hedmann is one supplier and I hear great things about them. Give em a call and ask them what they recommend for your application.

If you just want to change the exhuast sound, get a different muffler.

 

So to pick exhaust tube sizes I should match them up to what I plan to use as a header in the future? Who makes headers for 2003 LS models?

 

I saw a chart ONCE. Cannot place where anymore. It was based on cubic inches, modifications, number of cylinders and number of exhausts, one or two, (REAL)

I gatherred from that the information I had already assumed (dangerous). It showed the 4.3 at the lower end of the need for a 2.5 exhaust if true dual, and some performance improvements. If stock, it would move to the 2.25 catagory. About 383 to 400 was the top end of that 2.5 range.

All that aside, the better sound is normally the 2.5 and the best advice was already posted. Base it on the headers and the collector you get, if they come together. The manufacturer knows and sells the right parts. If you arent sure, do like that poster said, call them.