How much horsepower will true duals add?

Simulated rear‑wheel horsepower and torque — measured after the primary drive, clutch and transmission, the same way a chassis dyno reads a bike. These are not flywheel numbers, and they are not directly comparable to a manufacturer’s crank rating. Rev ceiling for this combination: 5500 rpm, limited by engine.

Where each one wins

Torque, lb-ft, at the rear wheel. Everything except the part named is identical between the two runs.

True duals give each cylinder its own path out. Compared with the stock catalysed system on an otherwise untouched 103, the change is larger than a slip-on and lands slightly higher in the rev range.

Look at where the torque peak moves. A freer exhaust shifts the curve up the rpm scale — helpful if you rev the bike, less helpful if you ride it at 2,500 in top gear on a highway.

Exhaust choice on a Twin Cam is as much about where you want the power as how much. The delta table above is the useful part: read the rpm you actually ride in, not the peak.

The build

The other one

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