Stage 1 and Stage 2 on the Same Twin Cam 103: What Each Was Worth

Most Stage 1 and Stage 2 numbers you will read are from different bikes, different dynos, and different days. This pair is not: Kane's Harley-Davidson ran one 103 Softail through both stages on the same Dynojet, reading SAE, best of five pulls each time. It is the cleanest stage comparison in the calibration set, and it is worth reading slowly.

Stage 1: 74.55 hp / 92.60 lb-ft

Screamin' Eagle Ventilator Elite air cleaner, Vance & Hines Big Radius 2-into-1, tune.

The bike was never dynoed stock, so the Stage 1 gain has to be read against the stock-103 anchor from Cycle World — 70.9 hp on a 2014 Softail Deluxe. Different bike, different day, but the same engine and a plausible baseline: call Stage 1 worth roughly four horsepower and a healthy midrange on a 103. Fuel Moto's own 103 Stage 1 baseline reads 79.69 on their dyno with their pipe and their map, and the difference between those two Stage 1 numbers is a lesson in itself: pipe, map, and dyno day are worth as much as the parts.

Stage 2: 78.29 hp / 100.67 lb-ft

S&S 583 cams and a Heavy Breather air cleaner, on top of the Stage 1 above. Same pipe, same shop, same dyno.

+3.7 hp and +8.1 lb-ft. The horsepower gain is modest and the torque gain is not — and that is exactly what an S&S 583 is for. It is a bolt-in torque grind that runs on stock springs, and what it adds is the 2,500–4,000 rpm pull that a Softail rider actually uses. If you bought it expecting a 10-horsepower peak, you bought the wrong cam; if you bought it to make the bike feel stronger everywhere, you bought the right one. The cam guide covers the rest of the catalog.

Where each number comes from

The map. A Twin Cam's stock ECM is lean and hot by design. Both of Kane's pulls were on a tune; neither would have made its number on the stock map with the airflow changed. The dyno tune page on this site models the map separately from the hardware because the map is worth more than any single part in a Stage 1. Tuner first, then hardware.

The air cleaner. The stock airbox is the choke in the top half of the rev range. A high-flow element in the stock housing (SE Stage 1) fixes most of it; a Heavy Breather or open filter fixes the rest at the cost of weather protection. The air cleaner page runs both. On a stock cam the difference between them is small; it grows when the cam goes in — which is why Kane's added the Heavy Breather with the 583, not before.

The exhaust. Slip-ons on the stock head pipes change the sound and a little of the flow; a 2-into-1 changes the whole system and is the reason a good Stage 1 is worth what it is. Kane's ran a Big Radius 2-into-1 throughout. The slip-ons page and the true duals page show the gap on your build; the short version is that true duals look right on a bagger and a 2-into-1 makes more power, especially once there is a cam.

What Stage 1 and 2 do not do

They do not change the peak rpm much — the stock 103 peaks about 5,250 against its limiter, and a bolt-in cam moves that only a little. They do not get you to 100 horsepower; that is a spring-change cam with compression, or a big bore, and it is the next page. What they do is turn a 103 from a 71-horsepower engine with a soft midrange into an 80-horsepower engine with 100 lb-ft, for the price of a pipe, a filter, a tuner, and a cam that goes in with the rocker boxes on.

Set the calculator to a stock 103, add the air cleaner, the 2-into-1, and a canned map one at a time, then add a bolt-in cam. Watch the torque line on the last step. That is the 583.

Sources: Kane's Harley-Davidson — 103 Stage 1 → Stage 2 with S&S 583 (Tf8IG7IUbTE, Dynojet, SAE, best of five). Cycle World — 2014 Softail Deluxe 103 stock (Dynojet). Fuel Moto — 103 Stage 1 baseline from the published cam shootout.

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