VTC cam angle and VTEC engagement on a K20 or K24

• A 2007–2008 car is the donor generation and runs FlashPro on its supported ECU. Buying for a 2004 as if it were a 2008 is the mix-up. The older KPro test on a 2005 TSX used an RSX ECU and adapter for dyno work. The cluster, air conditioning and stability assist did not work. It is not a street route beside FlashPro.
• The 25 degree stock travel can stay on a 2004–2008 K24A2. A 50 degree table target on a stock 25 degree actuator does not create travel. A 50 degree target on a modified engine still needs the physical stop and clearance check.
• The JDM note is a calibration instruction. KManager's VTEC page says to disable the VTEC oil pressure sensor for JDM engines and JDM ECUs. That is not a psi threshold and does not make the pressure switch a tuning target.

The feedback loop is the important part of the diagram. CAMCMD comes from the target table and the running conditions. CAM is the measured result. The phaser has to move the cam, the sensor has to report it, and the ECU has to correct the solenoid.

A target that the stop cannot reach will show as a flat ceiling. A target that the phaser can reach will show as a short lag and then a settle.

The angle-indexed MAP fuel and ignition tables are split by lobe and by cam angle. KManager's help describes six fuel and six ignition maps per lobe. The breakpoints are 0, 10, 20, 30, 40 and 50 degrees, and the ECU interpolates between them.

The current FlashPro VTC page describes five copies at 0, 15, 30, 40 and 50 degrees. It gives an allowed range of 0 to 45 or 0 to 50. Both descriptions are real for their software and calibration. FlashPro's tuning overview also lists a 0, 10, 20, 30, 40 layout.

Read the calibration rather than assuming either layout applies.

On FlashPro, confirm Fuel Table Type first: AFM-based fueling does not use the MAP fuel tables. The angle-blend examples below apply to angle-indexed tables. At a steady 24 degrees on a KPro layout, the angle blend is 60% from the 20 degree table and 40% from 30.

On a FlashPro layout with 15 and 30 degree breakpoints, the weights are 40% and 60%. Read the actual CAM value from the log, then find the tables that bracket it. These weights describe only the angle axis at matching rpm and load.

The ECU also interpolates across the rpm and load axes.

Part throttle is part of the target map, not a separate economy map. KManager's guidance puts idle below 1,000 rpm at 0 or 5 degrees. Cruise at 1,500–4,500 rpm sits near 30 degrees.

Above normal cruise rpm, the guidance uses the full-load angle to avoid a phase drop during a shift. The FlashPro VTC help gives 15 to 30 degrees for the cruise region at columns 2 to 7.

Overlap at cruise is deliberate, and the cam should not swing back to zero every time the throttle closes.

The help topic is still titled CAMCMD. Use the pair the open calibration actually logs; a missing CAM channel does not mean the phaser is not logging. Add coolant temperature, intake temperature, vehicle speed, oil pressure if available, and the VTEC pressure switch if the calibration exposes it. The logging guide covers the export and channel setup. This page covers the cam and switch traces.

CAM is the measured intake cam position in crank degrees; FlashPro calls it VTC Actual. CAMCMD is the desired position; FlashPro calls it VTC Cmd. Hondata's KManager help states that the actual cam can lag the command by 0.1 to 0.5 seconds.

The mechanism is a closed loop, so a short lag during a step is normal. A permanent offset, a flat ceiling or an oscillation is not.

The first 10 seconds after a start are a lock, not a fault. KManager's CAM channel definition says the intake cam is held in the zero, fully retarded position for the first 10 seconds after startup. The FlashPro VTC page words it as a hot start.

Let the engine run past that window before you diagnose a zero trace. If CAM stays at zero after 10 seconds at a warm idle, check the solenoid, oil supply, actuator and sensor. The target must be above zero.

VTEC is not an rpm-only switch. The FlashPro VTEC parameters page describes a window based on rpm and manifold pressure, plus coolant temperature and vehicle speed. High load can occur below full throttle, so a part-throttle log can still show the switch. The command bit records the ECU request to the solenoid.

The pressure switch is a second signal. Neither proves the rocker pin moved.

Compare low-cam and high-cam runs with fuel, spark and phase already checked on each lobe. Move the switch within the applicable limits and record only the rpm range needed to bracket the expected intersection. Do not hold the low cam to redline to finish the comparison.

Overlay the two curves at the same rpm and load. The crossing is the starting point. Bracket it in 100 rpm steps and keep the most torque through the transition. A small dip is normal. A large dip means the point or the cam blend is wrong.

The bounds are separate from the optimum. KManager gives 2,000 rpm as the low guide and 6,500 rpm as the high guide. The FlashPro VTEC parameters page gives 2,500 rpm for a twin-cam engine and 6,500 rpm as the ceiling.

For this procedure, stay between 2,500 and 6,500 rpm unless the build requires a narrower range. These guide values do not certify an aftermarket valvetrain. Below the floor the oil pressure may not support the rest of the engine.

Above the ceiling the high-speed rocker can float and damage the valve train. These are warnings, not targets.

The VTEC window uses rpm and manifold pressure. The lower boundary is the point you found at high load. The upper boundary is a higher rpm for lighter load. It does not switch VTEC off above that rpm; the main rev limiter remains separate.

Hondata's setting steps use 6,000–6,500 rpm at the top. The naturally aspirated example uses 80 kPa up to the lower rpm, falling to 40 kPa at the upper rpm. These are absolute manifold pressures, not boost-gauge readings. Smooth the pressure between the points.

The boost guidance on that help page gives two different starting ranges. Its numbered steps specify 110–120 kPa at the lower rpm. Its separate forced-induction paragraph specifies 120–150 kPa there, falling to 70–80 kPa at the upper rpm. Those are separate examples, not one combined prescription.

Choose the window from the engine's load-dependent crossover and verify it in the log.

The cam cannot jump at the switch. Hondata's crossover page gives the worked example. The switch is at 4,350 rpm, the low-cam target is about 12 degrees, and the high-cam target is about 37 degrees. The move is 25 crank degrees.

At 10 degrees per 0.1 second it takes about 0.25 second. The help rounds the theoretical move to about 0.3 second. Its separate pictured log moves from 26 to 50 degrees in about 0.3 second.

During that time the engine is on the high lobe at the wrong angle.

The fix is to start moving the cam on the low-cam table before the switch. Set the low-cam target at the higher row to the high-cam angle at the same rpm. The phaser is then near the new position when the lobe changes.

The car gives up a little low-cam torque before the switch and gains it back after. Hondata's example uses 4,200, 4,300 and 4,400 rpm rows for a 4,350 rpm switch. Those rows are an example, not a required axis.

Re-index the rows around the switch so the move happens over a short interval. Do not let the high-cam angle drop toward zero across the switch rows, or the cam retards during a shift. Remove rows the high cam never uses and put the resolution where the cam moves.

Check that the resulting torque curve improves through the switch. Re-indexing alone does not prove the cam arrived in time.

For a separate timing example, suppose the targets step from 30 to 48 crank degrees. The nominal travel time is 18 ÷ 10 × 0.1 = 0.18 second. At 1,000 rpm per second, the engine gains 180 rpm during that move. At 2,000 rpm per second it gains 360 rpm.

These are illustrative rates, not measured K-series results. A ramp spanning 150 rpm would allow only 0.15 or 0.075 second at those rates. Check elapsed time and actual phase before choosing how early the ramp starts.

A brief full-advance spike after a cold start can be the ECU's VTC cleaning cycle. FlashPro help describes overrun pulses near 2,000–3,000 rpm, about five seconds after throttle release, with logged spikes to 45 or 50 degrees. Match that pattern before calling it a control fault.

It also explains why a limited target map cannot replace a mechanical stop on an engine that cannot clear full gear travel.

If the trace oscillates or sits permanently offset, check the mechanical timing, oil supply, solenoid, filter, actuator and sensor wiring before you change the controller. A cam phase code is a clue, not an obstacle to delete.

KManager's VTEC page describes P0341 as an intake-to-exhaust phase error of more than about 5 degrees. That is a fault description, not a 5 degree VTC target limit. It also states that some aftermarket cams will set it.

The answer is to verify the mechanical timing and the actual phase, not to switch the check off.

If VTEC does not engage, check the conditions before the calibration. Oil level and temperature, coolant temperature, vehicle speed and manifold pressure all affect the switch. The solenoid and spool valve can seize, and the screen can clog. The pressure switch circuit can set a code.

A car that pulls cleanly to redline with no switch may have a hardware or condition fault, not a table that needs a lower number.