Cut away of a Dyno Max muffler #18381

For best performance, you certainly want ZERO back pressure. To larger or an exhaust pipe can hurt. Just like my above example on race parts on a stock engine. While it is on the extreme side of an example, it is still true.

What you (the new guys to this) needs to know is how much power your engine is making and how much a simple exhaust tube will flow . Or how much power can be made through an open pipe at 2-1/4, 2-1/2, 3... etc... Then how much the muffler will flow. According to David Vizard, the flow rate of a muffler should be 2.2 cfm per HP.

Street bound guys looking for a reasonably quite ride can error on the size smaller while drag racers go larger for the max HP. A place street guys visit once in a while and drag racers see every time.

The hardest part of D Vizards exhaust calculation method is having the engine on the dyno and finding the exact length of straight pipe off the collector/reducer without a muffler that makes best power. There is your pressure termination box.

Then comes the task of making one, and then connecting the exhaust via H or X pipe of the proper size into the rest of the exhaust. Followed by the mufflers of the appropriate size for the power on hand.

The muffler I cut up with above would be just fine for a ever so slightly modified engine with the traditional dual exhaust that is a low powered engine. Considering the internal pipe size restriction, these mufflers would be good at I’d guess the basic stock low compression mill that could barley wheeze out 275hp.

These would be fine for the guy that just wants the dual tail pipes on his ride. And maybe a 2-4 bbl. upgrade. Nothing else. Being there the “Sound XF” line of mufflers, the ever so quite rumble can be heard at the tail pipe. And I really mean “ever so slight rumble.”