I hear, here and there that the Hemis will actually lose low end torque when adding an aftermarket muffler like flowmaster or magnaflow, is this true? any recomendations out there?

 

False. first of all the muffler itself isn't going to effect over-all HP or Torque numbers much unless it's a total POS.

There is some merit to the "too good a flow reduces torque" theory, kinda.

When you have restriction in the exhaust, the engine is forced to work harder to expel gasses, more so at low RPM when there isn't enough airflow built up to carry gasses out efficiently. You feel this as low end torque.

A free flowing exhaust actually not only produces more HP, but more torque as well but the torque curve moves up higher in the RPM band, so you feel more at mid-high RPMs and less down low.

Backpressure is inefficiency, pure and simple. A little is not bad, too much and you lose performance and fuel economy.

The better flowing the muffler (magnaflow, borla, etc.) the higher the gains, but the higher the peak torque rises in the rpm band. The poorer flowing mufflers (Flowmaster & most chambered mufflers) can actually produce lower torque and HP numbers than the stock muffler, but it's perceived as having more power because the resulting torque peak moves lower in the rpm band.

 

My 08 loses a little with a Magnaflow cat-back, but gains more power in the upper rpm's. Not a ton of loss but noticeable. Since you have a variable intake and cam timing, it may not effect your engine as much.

 

well i have the dual "tuned" exhaust sounds really nice for stock, but would like a more aggressive tone without losing any power, i dont really want to spend money on a catback, just more around swapping muffler, and possibly elimating the resonators, but with all this info i dont know if i even want to do that now? lol

 

You should be fine with a Magnaflow replacement muffler.