Solid File vs Hollow File — How to Evaluate a Purchased Calibration

ThomasPirowski
Mon, 09 Mar 2026 10:25:00 +0000
Knowledge Base

Not all purchased calibration files are equal. Some are solid — real engineering work on the right maps, consistent across the ECU’s torque model. Others are hollow — a few numbers changed to make the dyno graph look different, while the core logic is untouched.

Here’s how I evaluate a file before I trust it.

What a solid file looks like:

Open it in WinOLS. Look at the maps that should have changed for the claimed modification level (Stage 1, Stage 2, etc.).

For a diesel Stage 1, I expect to see changes in:

Driver Wish (torque request shaped, not just scaled up)

Smoke limiter (raised in proportion to available air mass)

Injection duration (adjusted in the load/RPM areas that matter)

Rail pressure (raised selectively, not uniformly)

SOI (advanced slightly in the upper load range)

Torque limiters (raised to match — otherwise the rest is theater)

If I see only duration and rail pressure changed, I’m suspicious. If duration is raised uniformly across the entire map — same percentage everywhere — that’s not calibration, that’s guessing.

What a hollow file looks like:

One or two maps changed by a flat percentage. Everything else identical to stock. The maps that should have changed — smoke limit, torque coordinator, injection timing — are untouched. The file will produce a different dyno number. It will not produce consistent real-world performance.

The quick check:

In WinOLS, use the comparison function against the original file. Look at which maps have changed and by how much. Spot patterns. A real calibration shows surgical changes in specific load/RPM cells. A hollow file shows either nothing, or a brute-force scaling of one or two maps.

Why does this matter?

If you’re reselling someone else’s calibration, you’re responsible for what it does. If you’re a shop buying wholesale files, you need to know what you’re selling. And if you’re learning calibration from purchased files, hollow files teach you nothing — or worse, teach you the wrong lessons.

Learning to read what a file says — not just what the seller claims — is a core skill. We cover the comparison methodology in Diesel Practice and WinOLS from Zero as part of real-file analysis. Once you can do this, you’ll never buy a file blindly again.

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