How we calibrate the Twin Cam simulator
Every tool on the MMM network is held to the same rule: it has to land within a few horsepower of real, published dyno pulls, or it gets changed. We keep a list of anchor tests — bike, parts, dyno, correction factor, peak numbers — and drive the calculator through each one. When it misses, the model changes, not the anchor.
The current Twin Cam anchors
All chassis dyno, rear-wheel, Dynojet. SAE reads a few percent lower than STD on the same pull, so the two are not compared directly.
| Anchor | Configuration | Result |
|---|---|---|
| Cycle Solutions — stock 88 | 2002 Electra Glide Ultra, TC88, all stock (correction not stated) | 56.31 hp / 71.51 lb-ft |
| Cycle World — stock 103 | 2014 Softail Deluxe, stock; peaks ~5,250 against a ~5,500 limiter | 70.9 hp |
| Kane's — 103 Stage 1 | SE Ventilator Elite, V&H Big Radius 2-into-1, tune (SAE, best of 5) | 74.55 / 92.60 |
| Kane's — 103 Stage 2 | Same bike + S&S 583 cams + Heavy Breather (SAE, best of 5) | 78.29 / 100.67 |
| Fuel Moto — 103 cam shootout | One bike, one dyno, twenty-odd cams; Stage 1 baseline | 79.69 hp baseline; cam-by-cam results |
| Laidlaw's — 117 SE Stage IV | 2017 Low Rider S, CNC heads, cam, pistons, intake, Race Tuner, 2-into-1 (SAE, 01/29/2019) | 111.28 @ 5,490 / 117.93 @ 4,180 |
This is the best-fitting site on the network on horsepower: the stock 88 reads 57.0 / 69.8 in the simulator against 56.31 / 71.51 measured; the stock 103 is within a horsepower; Stage 1 reads about five high against Kane's and within a horsepower of Fuel Moto's; the 117 Stage IV is within two. Torque reads 6–14 lb-ft high across the ladder and is on the list to be trimmed.
What the last calibration pass changed
The S&S 583 was added to the cam list — it had been missing, and the nearest name (the 585) is a far bigger cam. Bolt-in cams (up to about .550" lift) no longer drop the rev ceiling to 4,700 on stock springs; they are built to run those springs and rev normally. The compression pop-up on big-bore combinations can still show a ratio the chamber math does not support; it is cosmetic and does not touch the power number.
What is not anchored yet
A stock 96. A 95 or 107 big bore with the sheet on screen. A cam-only swap on a stock, un-piped 103. Anything between Stage 2 and Stage IV, which is where most built 103s actually live. Those pages are modeled from the manufacturers' published cam specifications, the Fuel Moto shootout, and the anchored engines around them, and are labeled as estimates. The Cycle Solutions Stage 1 pull on the same 2002 FLH (the pair to the stock-88 anchor) is queued and not yet run.
What the numbers mean
The simulator reports rear-wheel horsepower and torque, corrected to STD, because that is how every published Harley number is taken. Crank numbers would read roughly 10–15% higher. A sheet marked SAE will read a few percent lower than the simulator for the same bike; that is the correction factor, not the engine.
When the calculator prints "HP at the limit" instead of "Peak HP," the springs or the rev limiter you picked stopped the pull before the cam ran out. On a bolt-in cam with stock springs that should not happen; if it does, the contact page is where to tell us.