⏲️ Lap Time Delta

Written and maintained by the PhDino author · Last reviewed 21 September 2026 · Checked against 1 independent reference calculation · how PhDino checks its numbers

Estimating how much a lap time changes from a change in average speed around a fixed-length track.

A lap time is simply the track's length divided by the average speed maintained around it — which means any change that raises average speed (more power, less drag, more grip, a better line) directly and predictably shortens lap time, and the relationship isn't linear: the same absolute speed gain matters more at a track already being driven slowly than at one already driven very fast.

This is a useful way to sanity-check a claimed lap time improvement against a claimed average speed gain (or vice versa) — a setup change that's claimed to gain "2 mph average" should produce a specific, calculable lap time gain for a given track length, and if the numbers don't roughly agree, something about one of the claims deserves a second look.

Key formula

Lap time (s) = (track length ÷ average speed) × 3600
Lap time delta = new lap time − baseline lap time

Notes & limitations

• This treats the whole lap as a single average speed, which is a simplification — a real lap is really a sequence of corners and straights each with very different speeds, and a change that helps one section (say, a high-speed corner) doesn't necessarily translate proportionally across the whole lap the way this single-average model assumes.
• A negative delta means the new average speed is faster (a lap time improvement); a positive delta means it's slower — worth double-checking which direction a specific change actually pushes average speed before reading too much into the sign.