Is a Magnaflow or a Flowmaster muffler the best? We dig deep into the question and get some help from an Engine Masters $40 Muffler Dyno Test.
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Excellent summary of engine exhaust physics, thanks for posting.
My 6.4 Hemi on the 3/4 ton truck has a single, massive exhaust pipe with the school bus muffler. My research led me to do no upgrades. LT headers wrapped was just too much loot and retrofitting for +10% torque. The tow tuner for $600 satisfied me.
Messing with the muffler butterfly valve introduces MDS exhaust drone, so I didn't remove it, leaving MDS on when not towing to prevent Hemi tick. The OEM muffler is so large I fear a Magnaflow might increase back pressure instead of reduce it. Also, the resonator prevents mid rpm drone so I left that alone too.
If I had a half ton truck with dual exhaust I'd for sure add the X crossover pipes. Interestingly, my Harley came with it because the 45 degrees cylinders produce an unbalanced exhaust pulse.