How much horsepower will a Stage 1 air cleaner 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
| RPM | high-flow air cleaner | stock airbox | diff |
|---|---|---|---|
| 2000 | 79 | 76 | -2 |
| 2500 | 84 | 81 | -3 |
| 3000 | 88 | 85 | -3 |
| 3500 | 89 | 87 | -3 |
| 4000 | 86 | 84 | -3 |
| 4500 | 81 | 78 | -2 |
| 5000 | 75 | 73 | -2 |
| 5500 | 70 | 68 | -2 |
Torque, lb-ft, at the rear wheel. Everything except the part named is identical between the two runs.
A high-flow air cleaner on an otherwise stock 103, with the factory map left alone — which is how a great many of them are actually fitted.
The gain is small, and that is the point of the page. The stock airbox is not the biggest restriction on this engine, and adding airflow the calibration does not know about buys very little on its own.
Fitted as part of Stage 1, with a tune, the same part contributes more. On its own it is close to a cosmetic change with a soundtrack.
The build
| Engine | TC103 (2010 CVO / 2012+) 3.875 × 4.375 |
|---|---|
| Crank / balancer | A motor — non-balanced (Dyna / Touring / CVO) |
| Pistons | OEM cast piston (stock dome) |
| Head gasket | STOCK OEM MLS (.030" compressed) |
| Cylinder heads | STOCK 2006+ (-06 casting) · 1.805/1.575 |
| Porting | As-cast / factory (no additional work) |
| Camshaft | Stock TC EFI (B) · 216/220 dur · 0.473" lift |
| Valve springs | Stock springs (as fitted to the heads) |
| Rocker arms | Stock rocker arms — 1.625:1 |
| Pushrods | Stock pushrods |
| Lifters | Stock hydraulic lifters |
| Induction | Stock 50mm Delphi EFI (2008+) |
| Exhaust | STOCK with catalyst |
| Air cleaner | Screamin' Eagle / Stage I high-flow |
| Tune | OEM map (untouched) |
| Power adder | None (naturally aspirated) |
The other one
| Engine | TC103 (2010 CVO / 2012+) 3.875 × 4.375 |
|---|---|
| Crank / balancer | A motor — non-balanced (Dyna / Touring / CVO) |
| Pistons | OEM cast piston (stock dome) |
| Head gasket | STOCK OEM MLS (.030" compressed) |
| Cylinder heads | STOCK 2006+ (-06 casting) · 1.805/1.575 |
| Porting | As-cast / factory (no additional work) |
| Camshaft | Stock TC EFI (B) · 216/220 dur · 0.473" lift |
| Valve springs | Stock springs (as fitted to the heads) |
| Rocker arms | Stock rocker arms — 1.625:1 |
| Pushrods | Stock pushrods |
| Lifters | Stock hydraulic lifters |
| Induction | Stock 50mm Delphi EFI (2008+) |
| Exhaust | STOCK with catalyst |
| Air cleaner | Stock airbox |
| Tune | OEM map (untouched) |
| Power adder | None (naturally aspirated) |