i just bought a magnaflow exhaust for my cherokee. First of all I am very satisfied with the sound and it stays quiet when i want it and loud when i get on the throttle. It's a straight through muffler with an offset.

I was wondering as far as intake and exhaust is concerned. My exhaust goes 2 precats for each bank of 3 headers and a cat before the muffler. I'm trying to word this i can't really explain it good. Does the muffler even matter as car as flow. If the highest resistance is the main cat whatever beyond that (as long as it lets more flow) doesn't even matter.

For example say you have pipe in sections and different sizes letting air through. I'll designate cfm. Each number is a section. lets assume the

ex 1 300cfm, 300cfm, 300cfm, 100cfm (cat), 300cfm, 300cfm (stock muffler), 300cfm

ex 2 300cfm, 300cfm, 300cfm, 100cfm (cat), 300cfm, 400cfm(larger muffler), 300cfm

The smallest pipe in 1 is 100cfm, and i assume the max flow is 100cfm

In 2 the "exhaust" lets more air through, but the smallest pipe is still 100cfm

I don't know how much exhaust flows that why i used easy numbers. Do they flow the same, or does it flow slightly better.

http://www.team-integra.net/sections/articles/showArticle.asp?ArticleID=2

http://www.burnsstainless.com/TechArticles/Theory/theory.html

http://www.nsxprime.com/FAQ/Miscellaneous/exhausttheory.htm

Do your readinz.

When someone says something flows 500 cfm, it doesn't mean that the maximum you can get it to flow is 500 cfm.

It just means that at the pressure drop they chose between the in side and the out side, 500 cfm was flowing. The pressure drop they chose for these measurements is somewhat standardised, but redundant.

If you increase the pressure drop, then you will increase flow. They are proportional. There is no limit to flow (except if the pressure gets so high something breaks).

The reason you want high CFM items is not because low CFMs will not flow enough - it's because the engine will need to push like it's giving birth to actually get that much air out, and that causes a loss of power.

If your engine is pushing out 500 CFM, and has a 501 CFM exhaust on it, and you replace that with a 499 CFM exhaust, the difference will be negligible. You have not crossed any invisible threshold.

Do you have a basic knowledge of electricity? The resistance of a resistor is analogous to the inverse of the rated CFM (what is written on the box) of a fluid flow part, the voltage is analogous to pressure drop, the amps analogous to the actual CFM (what is actually flowing through it). More volts = more current. More resistance = less.

Do you have a basic knowledge of electricity? The resistance of a resistor is analogous to the inverse of the rated CFM (what is written on the box) of a fluid flow part, the voltage is analogous to pressure drop, the amps analogous to the actual CFM (what is actually flowing through it). More volts = more current. More resistance = less.That's just what I was about to say...
Along with that, just like with electricity, all "resistances" in a series configuration are additive.