...haven't quite got around to studying up on this topic yet. Anyways, I'm starting to plan out my exhaust and want to build it around a Spintech muffler. Some people have said they only lost a few HP over a cutout or TD's w/X-pipe on these things, while some have said they're a huge flow restriction.

I've found some flow numbers for the muffler I want, but the problem is they're at 5" of water. My question is if flow numbers scale somewhat linearly with pressure, meaning will a muffler that flows 175cfm @ 5" flow somewhere around 980cfm @ the industry standard of 28"? It seems really high for a split-case muffler, but who knows?

Also, how well do flow numbers scale across muffler sizes assuming the design and construction remains unchanged? For example, the cross sectional area of a 4" muffler is 78% larger than that of a 3" muffler. Does this mean it flows about 78% more cfm at the same pressure?

 

Do a search, there are flow numbers around for many of the mufflers and cats. The flow changes are not linear with pressure.

 

I've looked through the flow numbers floating around here and they don't include the Mufflex mufflers.

About the numbers, I guess what i should ask is if they scale predictably (i.e. linearly, quadraticaly, cubicly, inversely, etc.)? I'm trying to figure out how well the mufflex flows in comparison to other mufflers.