i have a magnaflow cat back on my car now and was curious as to how restrictive it actually is with my set up? The dyno #s are from when i had 2.5" true duals with an x-pipe. I have not dynoed with this catback on, however i was wondering if it would be beneficial to put on cut outs?

 

A cut-out would probably release about another 10hp

 

The Magnaflow is a very good flowing catback so I'm sure its not choking up your setup too badly. I have a cutout on my Magnaflow as well, but its mainly for added noise. I doubt by having it open, I'm gaining a full 10hp, but I'm sure there is a few extra ponies being had.

 

Do Magnaflow catbacks flow better than Flowmaster? The only comparisons I've ever seen did not include the Magnaflow.

 

And completely off topic, I used to live in Atlanta and bought my current daily driver, a 2001 Jeep Grand Cherokee, at Nalley Jeep.

 

I'm pretty sure the Magnaflow is going to have the upper hand. There is alot mentioned of the Flowmaster being poor in terms of flow.

 

does anyone know where i can find this article im am really interested in to see how everyone did.

 

flowmaster flows very bad. Pretty much any exhaust company can produce something better than them

 

how can you beat something that has no baffles and no chambers just striaght through.. cant beat that!

 

Hard to believe that a 3" catback is going to provide adequate breathing to a 383 that is capable of making 457rwHP. Its got to be costing you HP. If you want a catback, and not duals, look at a 3.5" or 4" Mufflex. They will support huge HP. I saw the 4" with the single in/single out Flowmaster make 1,125 flywheelHP. Taking the 4" Mufflex/Flowmaster off, and running Borla XR1's on the collectors did not produce any HP increase - verified on a chassis dyno... just a 50# weight reduction.

Its sort of pointless to make a gneeral statement like "flowmaster flows bad".... they make a huge range of mufflers, and many of them flow very well. Sure... some comparison test run 15 years ago by a magazine on a low-end Flowmaster did not produce impressive numbers.... but that's a single data point.

 

I thought my 3 1/2" Mufflex would support a 383 - D1, but, I was wrong. I selected a Spintech muffler, but, was running a dual cat Random 2 1/2" cat system. After much work re_working the blower suction and pressure side indiction system, I actually blew the cat elements into the exhaust pipe. I have since cut the converters out and installed straight pipe (I also had a QTP cut-out after the cats as well). I found that the Spintech 3 1/2 chambered muffer was flowing alot more. Well, it was alot of noise and resonated very bad @ 2K rpm. I installed a CarChem 3_plate insert after the Qtp cut-out. That helped alot. That's where I'm at. The best way to learn is on your own. I had to re-yune the fuel map and engine dur to the change in exhaust flow. I still run the open 3 1/2 QTP when I need to. B