I am usualy the last to post asking "how much does this make or how much power does that make" but, here we go..
I had a hacked up exhuast on my truck, a 98 1500 5.9 automatic. I told teh exhaust shop, I want 3" cat back (since its 3" already from the cat) and a flowmaster....
Well I pick it upa few months back and its got 2.5" crimp bend pipe from the muffler back which is also 2.5"
how much did I lose in power and ecomnomy for flow? It had rusted out duals under it.. felt a lot better with it.... and (hate ot ask) when taxes come in,would it be worth getting a real 3" mandrel bent flowmaster kit(not a muffler and handbent pipe) ? I like the small rumble, bu tI think that half inchof pipe really hurt the air flow, especially with the AFE Magnum air filtersystem...
thanks inadvance.

 

no it shouldnt... stock exhuast is 2 1/2' and all of the cat backs i seen (kits) are also 2 1/2' the duals will flow a lot better than a single

 

No, the 2.5 is fine. I put a custom 3" all the way back on a custom Toyota Carmry. It ended up being to much flow. I believe the guys a Flow Master said .5-1.0psi back pressure is a good thing. I had to put a bottle neck in the exhuast, so it would run good. Bottom line: there is such thing as to much flow, and call the guys at Flow Master. They have always help me with my toys.

 

Well, they offer a 3" kit for the truck, so assuming it wouldnt be a bad thing.. I understand that duals are 2.25 or 2.5 " but I have a SINGLE crimped bend 2.5 " outlet..... thats what I meant to ask,if there will be a marked improvement

 

yes there will be. the dual 2.5's would work for a lighter truck (I dont rmemeber what your truck is...) but a std cab 4x4 short bed would probably be ok with dual 2.5" outs. anything lighter too would be ok... anything heavier and you might conside reducing the duals to a smaller diameter.

oh yeah, do the math on the flow area if your between 2.25" or 2.5" to figure how it compares to a single 3" out. If I remember correctly, the dual 2.25's were just slightly bigger than the single 3" in flow area. dual 2.5's were way bigger.

 

Ok, so are we in agreeance that a 3" single outlet woudl be marked improve ment over a crimp bend style 2.5" pipe and flowmaster?? Trying to figure this out BEFORE I take off the 7 month old exhuast and buy new..

 

when you say crimped bend... r u talkin about the at the bends theres little ripples on the short side of the beds? i was confused on that

but yea... if you think about it... a 3" exhaust system for these rams are all single pipe and the 2.25" inch exhaust systems for these rams are all duals... (coming from flowmaster systems..they know what there tlakin about)

and all you have is 2.5 on a single pipe... bad news boss

 

yep, it crimps down narrows AND has flow disturbing ripples in the short side. was wondering how much I'm gonna feel a 3" kit being added

 

yeah, get rid of that garbage... if you dont already have it... get a 50mm (5.2 motor) or 52mm (5.9 motor) a good intake kit, I recommend the K&N and headers.

if your cat is a 3" out, make sure the plumbing between the cat & muffler match and are 3" or whatever it is. I just found out mine was wrong after a year and it made a big difference in low end.

 

yeah,its 3" tillthe muffler,then they opened upa 2.5" muffler to fit, how ghey is that?? I asked for 3" paid cash got hoem measured and it wasnt, guy said " too bad" I was pissed..for that he got a OSHA inspection 2 weeks later... I am looking at the flowmaster kit on summit racings page... $199...the summit version is only 129,but, I love the soundof my flow, I jsut think its bottlenecked
it has a AFE MAgnum stage 2 intake kit... no bigger tb yet though...