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Originally Posted by craig-444
That's good to hear, I am anxious to get them installed, but all the negatives I heard about the TRD exhaust I was like damn I hope the flow masters work better.
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Nearly all catback dual exhausts (regardless of brand) are going to at least somewhat hurt your low end torque. The problem with dual pipes (unless they're
real small (like 1 and 7/8 inch diameter or smaller) is they let the exhaust gases slow down and cool down much more than the stock single 2 and 3/8 inch pipe. When the exhaust gas cools and becomes stagnant, it gets dense and acts like a plug that has to be
pushed out by incoming gasses from the engine. The net result is that dual pipes actually have
more backpressure than the stock single pipe at low to mid RPM. However, once you get the engine near redline (over about 4500 RPM) the duals begin to help a bit because the gas no longer has a chance to slow down and cool...and wall friction in the single pipe becomes a significant issue. So at very high RPMs the common belief that duals have lower backpressure is true....but at low RPMs it's exactly the opposite, the duals have more backpressure. And the common misperception that the engine "needs" backpressure to make the most power is simply not true...backpressure is bad for torque. The result of all this is you will lose low end torque.
The additional sound from the duals with a louder muffler (and tendancy to use a heavier foot to make that sound) causes a lot of folks to
feel they haven't lost any low end torque. But the torque loss is real and well documented.
The main differences between TRD and Flowmaster exhausts are cost, appearance, and quality/loudness of the exhaust sound. TRDs (which are basically relabeled Borlas) are an absorption (like glasspack) type muffer & resonator; Flowmasters are chambered resonator type mufflers. The TRD muffler actually
might flow a bit better at very high RPM because it's a more straight through design.