Most club racers have data they don't fully use. The logger is fitted, the laps are recorded, the files are saved - and then the session debrief happens based on driver feel and gut instinct, the same way it always did. This guide changes that. It covers the structured workflow used at SupaTune Motorsport in Porsche Club GB: starting from a blank screen, finding where time is being lost, and translating that into a coaching point or a setup change. AiM EVO4S and Motorsport VBOX Video HD2 are the tools used here, but the methodology applies to any data system.
The Lap Analysis Workflow
This is the process used after every session. It is deliberately structured - each step feeds the next, and you do not skip ahead. The most common mistake in data analysis is diving straight to the detailed speed trace before establishing what the sector picture actually says.
Pick your reference lap
Before anything else, establish what you are comparing against. This is either the driver's fastest clean lap from the session, or - better - a reference lap from a faster driver in the same car and conditions. Do not use a lap where a yellow flag was shown, traffic was encountered, or a kerb was hit that isn't part of the normal line. Dirty reference laps corrupt every comparison that follows.
In AiM Race Studio, set the reference lap using the lap picker in the top toolbar. In Circuit Tools, open the run comparison and select your reference run first. Every channel overlay and delta will now be calculated against this baseline.
Read the sector summary - find the problem corner
Look at the sector time delta before you open a single channel trace. The sector split tells you where on the circuit the time is being lost. If sector 2 is 0.4 s slower than the reference and sectors 1 and 3 are within 0.05 s, everything that follows is focused on sector 2. This keeps the analysis scoped - you are not trying to explain the whole lap.
If all three sectors are equally slow, you are likely dealing with a systemic issue - tyre warm-up, braking confidence, or a setup problem - rather than a specific corner fault. The approach for a systemic issue is different: look at early-lap vs late-lap sector splits to identify whether the gap closes as tyres come in.
Open the speed trace overlay - find the braking point
With the problem sector identified, open the speed trace for both laps overlaid. The first thing to look for is the braking point. Where does each trace begin to decelerate, and at what speed? A braking point that appears earlier in the reference lap does not automatically mean the reference driver is braking earlier by technique - they may be carrying higher minimum speed from the previous corner and arriving faster, which requires them to begin braking sooner from a greater distance.
This is the single most misread trace in club racing data. Always check the speed at the point of brake application, not just the distance marker. Two drivers braking at the same distance marker but from different entry speeds are doing categorically different things - the one arriving faster is braking from a much higher energy state. Conversely, a reference lap that shows an earlier braking point is not necessarily braking earlier by technique - they may simply be carrying more speed and need the additional distance to scrub it off.
Identify entry, apex, or exit - where is the speed delta?
Once the braking trace is understood, locate the minimum speed point (apex speed) and the point of full throttle application. These three markers - braking, apex, throttle - define whether the problem is a corner entry issue, a mid-corner issue, or a traction zone issue.
Entry issue: the reference lap carries more speed into the corner but arrives
at a similar apex speed. The reference driver is managing the braking zone more efficiently —
most likely with a more progressive trail brake release that keeps the front tyres loaded
and maintains rotation into the apex. Note that simply braking later without the corresponding
technique to control the additional energy typically produces a lower apex speed,
not a similar one — so if the apex speeds are equal despite the entry speed difference, the
efficiency of the braking zone is what differs, not just its starting point.
Mid-corner issue: apex speeds are similar but the reference exits faster - the
driver is getting to throttle earlier and using more of the road on exit.
Exit issue: apex speeds are similar, throttle point is similar, but the reference
pulls away on the straight - usually a traction problem, either the car (rear setup) or the driver
(over-rotating on exit before getting on throttle).
Cross-reference with lateral G
Lateral G tells you how hard the car is being pushed in the corner and how balanced the cornering load is. A driver with a lower apex speed but similar lateral G is either running a tighter line (smaller radius, same grip level) or carrying understeer (less lateral G for the speed being used means the car is not rotating cleanly).
The shape of the lateral G trace matters as much as the peak. A clean smooth arc peaking at apex and decaying symmetrically on exit is a driver using all the grip, all the time. A trace that peaks early, drops mid-corner, then spikes again on exit is a driver who has disturbed the car - either with mid-corner braking, a steering input change, or an early throttle application that caused understeer before the car was fully pointed.
Check longitudinal G at the braking and acceleration zones
Longitudinal G under braking should build quickly and hold, then release progressively as the driver begins trail braking toward the apex. A longitudinal G trace that shows a sharp spike and then an abrupt release indicates hard braking followed by a complete release - the driver is using the brakes as an on/off switch rather than as a tool for rotation and balance. This is one of the most common coaching findings in club racing.
Under acceleration, the longitudinal G should build smoothly as throttle is added. A trace that oscillates - multiple peaks and troughs - indicates wheelspin being corrected, traction control hunting, or a driver who is stabbing and lifting rather than committing to a progressive application.
Build the coaching point or setup action
Every analysis session should end with one primary finding per corner. Not a list of ten things - one clear, actionable conclusion. Either the driver has a specific technique to work on (trail braking confidence, earlier throttle on corner exit) or there is a setup change to investigate (rear ARB too stiff causing exit oversteer, front spring too soft causing poor turn-in response).
If the data shows an entry problem and a setup change is proposed, the coaching point for the next session is to drive to the proposed new line - not to wait and see whether the setup change fixes it. Data, coaching, and setup work together. Separating them produces slower progress than running all three in parallel.
SupaTune Motorsport - Porsche Club GB 2026
This workflow is used across the SupaTune Motorsport Porsche Club GB programme. Data is acquired via AiM EVO4S loggers for vehicle dynamics and channel logging, and Motorsport VBOX Video HD2 systems for synchronised video, GPS-based speed logging, and overlay review. Post-session analysis follows this seven-step process for every driver, every session. The sector-first discipline prevents the common trap of spending 45 minutes analysing the wrong corner. For hardware-specific detail on GPS logging rates and what differs between VBOX variants, see the Data Channel Reference.
SupaTune Motorsport →What Each Channel Actually Tells You
The channels logged by an AiM EVO4S or VBOX system cover more ground than most club racers ever use. This table covers the channels that matter for lap analysis - what the number means, what good looks like, and what anomalies to watch for.
| Channel | Unit | What it measures | What good looks like | Watch for |
|---|---|---|---|---|
| GPS Speed | km/h or mph | Vehicle speed derived from GPS position changes. Update rate depends on the device and configuration. | Smooth trace, no step changes or noise spikes. Consistent with wheel speed where both logged. | Dropout under trees or in stadium sections. High-frequency noise on low-quality GPS. Higher GPS logging rates give better resolution for braking-point analysis — the rate available depends on your device variant. Check your logger configuration before the season, not just before the session. |
| Lateral G (Ay) | g | Sideways acceleration - how hard the car is cornering. Positive = left turn, negative = right on most AiM setups. | Smooth arc peaking at apex, decaying progressively on exit. No mid-corner steps or spikes. | Mid-corner spike usually means a driver correction. Flat plateau with no peak often means understeer - the car stopped rotating at that G level. Asymmetric decay on exit can indicate traction imbalance. |
| Longitudinal G (Ax) | g | Forward and rearward acceleration - braking (negative) and acceleration (positive). | Braking: builds quickly, holds, releases progressively with trail braking into apex. Acceleration: builds smoothly without oscillation. | Abrupt release in the braking zone (on/off braking style). Oscillation under acceleration (wheelspin or traction control hunting). Positive G spike during cornering (throttle burst to correct understeer). |
| Yaw Rate | deg/s | Rate of rotation about the vertical axis - how fast the car is turning. Logged by AiM EVO4S internal IMU. | Proportional to steering input and speed. Matches the expected rotation for the corner radius being driven. | Yaw rate spike mid-corner with no corresponding steering input often indicates the rear stepping out. Yaw rate lower than expected for the corner and speed indicates understeer - front is not generating rotation. |
| Heading | degrees | Compass direction of travel from GPS. Useful for circuit mapping and comparing lines. | Smooth arc through corners. Rate of change proportional to corner radius. | Less useful for moment-by-moment analysis than Ay or yaw rate - primarily used for track map generation and line comparison overlays. |
| Throttle Position (TPS) | % | Throttle opening - 0% closed, 100% wide open. Requires external connection to ECU or a TPS sensor channel. | Clean transition from 0% to 100% on corner exit with no hesitation or reversal. Zero throttle maintained through the braking and mid-corner phase. | Throttle application and release in the braking zone (lift-off oversteer management or balance seeking). Multiple partial applications on exit (driver not committing). TPS not reaching 100% on long straights (mechanical issue or driver). |
| RPM | rev/min | Engine speed. Cross-reference with TPS and speed to identify gear selection and engine response. | Consistent gear selection at the same points each lap. RPM at corner exit matching the expected point in the powerband for the gear being used. | Gear changes mid-corner (driver unsettling the car unnecessarily). RPM drop under braking inconsistent with expected gear (wrong gear into the corner). RPM rising faster than GPS speed = wheelspin — the wheels are turning faster than the car is moving. Flat RPM with rising speed indicates the opposite: the car is accelerating in a gear the engine is no longer driving — check for a missed upshift or a false neutral. |
| GPS Lap Time | s | Lap time derived from GPS position crossing a defined start/finish line. Resolution depends on the GPS logging rate of the device in use. | Consistent with timing system. Cross-check first 3 laps to confirm the GPS line is placed correctly - a badly placed GPS line gives incorrect splits without affecting total lap time. | GPS lap time differing from transponder by more than 0.1 s usually means the GPS line is placed on the wrong GPS point. This also corrupts sector splits. Verify gate placement at a new circuit before trusting split data. |
| Sector Delta | s | Time gained or lost vs the reference lap within a defined circuit sector. The primary diagnostic channel. | Time gain versus reference in all sectors. Consistent across multiple laps - variance of more than 0.1 s sector-to-sector on a clean lap indicates technique inconsistency. | A sector that is slower than the reference by more than 3x the other sectors is almost always a specific corner or braking fault - not a diffuse issue. Investigate that sector in isolation. |
Questions from the Paddock
The questions that come up at every debrief, at every circuit. Straight answers - no padding.
Start with sector times. Open your session in AiM Race Studio or Circuit Tools, pick your fastest lap, and compare the sector split against your second fastest. Find the sector where the biggest time was lost. That is the only thing you are trying to understand in your first session with the data.
Do not start with channel traces. Do not try to analyse braking points or G traces until you know which corner you are looking at. The most common beginner error is spending an hour looking at everything - and concluding nothing.
One question. One corner. One conclusion. Build from there.
Compare the speed trace at the point of brake application for both laps. If the reference lap begins braking from a higher speed and from a point further down the circuit - and arrives at the same apex speed - the reference driver is carrying more momentum into the braking zone and also braking more efficiently. That is a genuine braking point advantage.
But if the reference lap is braking from a higher entry speed because they carried more exit speed from the previous corner, an earlier braking point from greater distance is a consequence of that extra speed - not an independent technique advantage. Always trace the speed delta back to where it originates - it is 0 frequently not where the sector time shows the loss.
Practically: look at the speed trace at the very beginning of the lap. If the reference is already faster at the first corner exit, the time loss is there - not at the later corner where the sector split shows the gap.
Minimum corner speed. Not peak lateral G, not braking point distance, not sector time. Minimum speed through the apex is the number that single-handedly predicts lap time better than any other channel for a mechanically equal car.
A driver who consistently carries 5 km/h more through each apex than their competitor will be faster by the end of the lap even if their braking points are identical and their outright straight line speed is the same. The reason is compounding: higher apex speed means a shorter acceleration phase to reach the next braking point, and a higher minimum speed to brake from into the following corner.
When coaching a driver, minimum corner speed is the first number we look at for every corner on every session. Everything else - braking technique, throttle application, line - is in service of that number.
Because braking point distance is the least important of the three braking zone variables. The other two are entry speed and braking efficiency.
If you are braking from the same distance marker but from a lower speed (because you carried less exit speed from the previous corner), your braking zone is shorter in time and covers less road. The reference driver braking from the same marker but 15 km/h faster is doing something categorically different even though the distance looks identical on the trace.
Braking efficiency is the other variable. Look at the longitudinal G trace under braking. A driver who builds 1.2 g of braking force instantly and holds it is stopping faster than a driver who builds to 0.9 g and trails off early. Same braking point, same entry speed - but the efficient braker arrives at the apex with more time budget remaining and with the car better placed for rotation.
The primary channel is the relationship between yaw rate and lateral G. In a neutral car, the yaw rate at any given lateral G and speed is predictable from the corner geometry. Understeer shows as lower yaw rate than expected for the lateral G being generated - the car is not rotating enough for the grip it is using. Oversteer shows as higher yaw rate than expected - the car is rotating faster than the lateral G and speed combination would predict.
In practice at club level, without a model to calculate the neutral reference, use the video. Overlay the lateral G trace against the video channel and watch for the nose pushing wide mid-corner while lateral G flattens - that is understeer. Watch for the rear stepping before the driver has unwound the steering - that is oversteer. The data confirms what you see; the video tells you where to look in the data.
If you have steering angle logged, the picture becomes clearer. Increasing steering angle mid-corner with no increase in yaw rate is a textbook understeer signature. Steering angle reducing while yaw rate increases is the car rotating without the front helping - oversteer building.
Three clean laps minimum to identify a consistent pattern. One lap proves nothing - the driver might have been on a good lap, the traffic might have been clear at the right moment, the tyre temperature might have been perfect. Three consistent laps showing the same sector structure gives you something to work with.
For setup correlation, you need pairs: a run before the change and a run after. Minimum 3 laps per condition, same track state, same tyre age. Anything less and the natural variation in lap times - typically ±0.3 to ±0.5 s at club level - will mask whether the setup change made a real difference. If the change is worth less than 0.3 s, you need 5+ laps per condition to detect it reliably.
This is why test days are structured the way they are. Each run should be long enough to produce a minimum of 3 clean representative laps. Pit before the tyres fall off the cliff — the degraded laps at the end of a long run contaminate your dataset if you are trying to extract setup information.
The full structured test day methodology - including how to sequence runs, manage track state, and avoid the most common test day failures - is covered in Part 3: Setup Correlation.
A theoretical fastest lap (TFL) is constructed by taking your best sector time from each sector across all laps in the session and adding them together. It is the lap time you would have achieved if you had driven your best sector 1, then your best sector 2, then your best sector 3, all on the same lap.
AiM Race Studio calculates this automatically. In Circuit Tools you calculate it manually by adding your fastest sector splits.
The TFL is useful for two things. First, it tells you the gap between your fastest actual lap and what was achievable in that session - the difference is the consistency deficit. A driver 0.8 s off their TFL has a significant consistency problem; a driver 0.15 s off it is close to the limit of what the setup and conditions allow.
Second, it tells you where to focus. If sector 2 is never your best sector on your fastest laps, that is where the lap time is hiding. Improving consistency in that sector will convert a TFL gain into a real lap time improvement.
Yes - if the test is structured correctly. The requirements are: same driver, same circuit, similar track and tyre temperature, same tyre age at the start of each run, minimum 3 clean laps per condition, and changes made one at a time.
The mistake most teams make is changing two things between runs and then trying to attribute the lap time improvement to one of them. You cannot. Change one thing. Drive the same laps. Compare the data.
The channels to look at for a setup change confirmation: lateral G at the affected corner (did the grip level change?), minimum corner speed (did the driver carry more speed?), and the sector delta vs baseline (did the sector time improve?). If the lateral G went up, the minimum speed went up, and the sector time dropped — the setup change worked and the driver was able to use the improvement. If only the sector time dropped but lateral G and minimum speed are the same, the driver found something on their own — the setup change may have had no effect at all.
For the complete adjustment matrix - what each permitted change looks like in the data channels, with Porsche Club GB regulation references and factory alignment specs for 986 and 987 — see Part 3: Setup Correlation.