Delta time explained

Every delta needs a reference lap, usually your best lap of the session or the day. The timer stores how long that lap took to reach each point around the track.

A reference delta is simple: at this point, how much time have you gained or lost compared with the reference? If the reference reached Turn 5 at 42.3 seconds and you got there at 42.1, your delta is −0.2.

A predictive delta goes one step further and adds the current delta to the reference lap time. If your best is 1:32.40 and you’re 0.2 ahead, it predicts 1:32.20. The prediction assumes you drive the rest of the lap exactly like the reference, which you won’t, so treat it as an estimate.

Most displays show the number and a bar that grows left or right, or changes colour. The value tells you the running total; the movement tells you what’s happening now.

If the delta drops through a corner, you made time there. If it climbs on the following straight, your exit was slower and the straight is costing you, even if the corner felt quick.

This is the most useful thing delta does. It turns a vague feeling ("that felt fast") into evidence ("that was 0.15 better, but I gave 0.2 back by the next brake zone").

To compare two laps, the timer must match points on one lap with the same points on the other. Matching by elapsed time doesn’t work, because you’re in different places at the same second. Matching by distance does.

There’s a catch: different lines cover slightly different distances. A wider line through a long corner adds a few metres. Good systems project your position onto the reference path, or re-align at sector boundaries, so a different line doesn’t show up as false time.

The quality of the delta depends on position data. Low GPS sample rates and poor reception make it jumpy or slightly late, especially in tight sections.

Delta is a feedback tool, not a target to chase at any cost. If chasing green numbers makes you overdrive, stop looking at it for a session.