Chapter 49 · Emissions Systems, Diagnostics & Deletes

Tank Ventilation (N80)

Purge valve dynamics, the FTE vapour observer, and deleting it for track use.

Calibration symbols

ESKONF KRKTE TVUB N80

ECUs covered

06A906032LP

Size

4 symbols · 1 diagram · ~841 words

Purge valve dynamics, the FTE vapour observer, and deleting it for track use.

To satisfy strict global evaporative emissions regulations (EPA Tier 1 / Tier 2 and Euro 4), gasoline vapors evaporating inside the fuel tank cannot be vented to atmosphere. On the VAG 1.8T platform, fuel vapors are routed into an activated carbon canister (Aktivkohlebehälter - AKF) mounted in the right rear wheelhouse or engine bay.

The Bosch ME7.5 ECU purges this stored fuel vapor into the engine during closed-loop operation by pulse-width modulating the Evaporative Canister Purge Solenoid Valve (N80) (ECU Pin 64). Because the desorbed vapor contains variable concentrations of raw hydrocarbons, introducing it into the intake manifold introduces a major disturbance to the fuel-air mixture. ME7.5 incorporates an active **Tank Evaporation Fuel Compensation Subsystem (Tankentlüftungsregelung - TE)** that dynamically learns vapor concentration and subtracts fuel mass from the fuel injector pulsewidths to maintain \lambda = 1.000.

┌──────────────────────────────────────────────────────────────────────────────────────────────────┐
│                    EVAP PURGE (N80) DYNAMIC FUEL ESTIMATION ARCHITECTURE                         │
├──────────────────────────────────────────────────────────────────────────────────────────────────┤
│                                                                                                  │
│   [ Fuel Tank Fuel Vapor ] ──► [ Activated Charcoal Canister (AKF) ]                             │
│                                                   │                                              │
│                                                   ▼ Hydrocarbon Vapor Flow                       │
│                                     ┌───────────────────────────┐                                │
│                                     │ EVAP Purge Solenoid (N80) │                                │
│                                     │ (Pulsed by ME7.5 Pin 64)  │                                │
│                                     └─────────────┬─────────────┘                                │
│                                                   │ Variable Vapor Stream                        │
│                                                   ▼                                              │
│                                     ┌───────────────────────────┐                                │
│                                     │ Intake Manifold Chamber   │                                │
│                                     └─────────────┬─────────────┘                                │
│                                                   │ Cylinder Intake Charge                       │
│                                                   ▼                                              │
│   ┌─────────────────────────────────────────────────────────────────────────┐                    │
│   │ Wideband O2 Sensor (LSU 4.2 / CJ125): Measures Mixture Deviation        │                    │
│   └──────────────────────────────────────┬──────────────────────────────────┘                    │
│                                          │                                                       │
│                                          ▼                                                       │
│   ┌─────────────────────────────────────────────────────────────────────────┐                    │
│   │ Vapor Hydrocarbon Concentration Observer: FTE                           │                    │
│   │ - FTE = 0.0: Pure ambient air through canister (Lean disturbance)       │                    │
│   │ - FTE = 1.0: Saturated rich fuel vapor (Massive rich disturbance)       │                    │
│   └──────────────────────────────────────┬──────────────────────────────────┘                    │
│                                          │                                                       │
│                                          ▼ Dynamic Subtraction                                   │
│   ┌─────────────────────────────────────────────────────────────────────────┐                    │
│   │ Final Injector Base Fuel Mass: rk_final = rk_air * (1.0 - delta_rk_te)  │                    │
│   │ Prevents rich stumbling, surging, and catalytic converter damage!       │                    │
│   └─────────────────────────────────────────────────────────────────────────┘                    │
└──────────────────────────────────────────────────────────────────────────────────────────────────┘

49.1. Hydrocarbon Vapor Dynamics & Real-Time Observer (`FTE`)#

When the engine enters steady-state part-load or closed-loop idle, ME7.5 initiates canister purge by modulating the low-side driver for N80 at frequencies between 10\text{ Hz} and 30\text{ Hz}.

The mass flow rate of gas inducted through N80 is calculated from the manifold vacuum pressure differential:

$\Delta p = p_{\text{ambient}} - p_{\text{manifold}}$ $\dot{m}_{\text{te}} = f(\Delta p, \text{duty\_cycle}_{N80})$

However, the chemical composition of this gas is completely unknown upfront:

On a cold morning with an empty canister, \dot{m}_{\text{te}} is pure ambient air, leaning out the engine.
On a 38\text{°C} (100\text{°F}) summer afternoon with a full tank of summer-blend fuel, \dot{m}_{\text{te}} is saturated gaseous butane/pentane vapor, capable of supplying up to 30\% of the engine's entire fueling requirement!

The Bosch Adaptive Learning Routine#

ME7.5 initiates a short pulse train on N80.
The closed-loop lambda controller (LSU 4.2) registers the instantaneous mixture deviation (\Delta \lambda).
The ECU updates the internal fuel vapor concentration factor FTE (Faktor für Tankentlüftungs-Kraftstoffkonzentration): $\text{FTE}_{k+1} = \text{FTE}_k + K_{\text{adapt}} \cdot (1.0 - \lambda)$
The learned value of FTE scales an active fueling subtraction parameter (\Delta r_{k,\text{te}}). Injected fuel pulsewidth t_i from the primary port injectors is proportionally trimmed down before the fuel ever leaves the injector tip: $t_i = (r_k - \Delta r_{k,\text{te}}) \cdot \text{KRKTE} + \text{TVUB}$

49.2. Common Failure Modes & Diagnostic Troubleshooting#

A mechanical or electrical fault in the EVAP purge subsystem creates severe drivability anomalies:

Diagnostic Trouble Code (DTC)	Failure Mechanism	Operational Symptoms on 1.8T Engine
`P0441` / `16825`	Incorrect Purge Flow	Canister purge flow detected during diagnostic sealing phase does not match expected manifold vacuum drop. Usually caused by seized N80 valve or blocked carbon line.
`P0444` / `16828`	N80 Circuit Open	Electrical disconnection or wire break on ECU Pin 64. Output driver load check fails.
`P0445` / `16829`	N80 Short to Ground	Solenoid winding shorted. Transistor driver over-temperature shutdown.
Mechanical Leak / Stuck Open	N80 Seated Leakage	Solenoid valve mechanically stuck in the open position due to carbon granule debris: <br>• Massive vacuum leak at idle (LTFT trims swing to -25\% rich at idle as vapor is sucked in). <br>• Severe hard start / long crank immediately after refueling (fuel tank vapor floods the intake manifold).

49.3. Core Calibration Maps & Relocation Table in `06A906032LP`#

Map / Symbol	Flash Offset (032LP)	Dimensions	Units	Description
`CDTE`	`0x018240`	1 \times 1	Hex	Codewort für Diagnose Tankentlüftung (Master EVAP Purge Diagnostic Switch)
`CWTE`	`0x018241`	1 \times 1	Hex	Codewort Konfiguration Tankentlüftung (Operating configuration switch)
`TVTE`	`0x018264`	8 \times 1	\%	Tastverhältnis Tankentlüftungsventil (Base purge valve PWM duty cycle map)
`FTE`	RAM `0x382A14`	1 \times 1	Factor	Internal RAM variable: Learned hydrocarbon vapor concentration (0.0\dots 1.0)

49.4. Software Deletion for Fuel-Cell & Track Applications#

When building a track car, drag car, or installing an aftermarket fuel cell lacking carbon canister plumbing:

Disable Diagnostic Testing: Set master diagnostic codeword CDTE = 0x00.
Zero Purge Duty Cycle: Set all cells in TVTE (Tastverhältnis Tankentlüftungsventil) to 0.0% duty cycle.
Hardware Driver Masking (ESKONF): Locate the ESKONF bitmask entry for ECU Pin 64 (N80 purge solenoid) and set it to 11b (0x03 = Unused / Diagnostic Masked) to suppress electrical open-circuit faults (P0444).
Physical Sealing: Disconnect the purge line from the intake manifold and seal the brass vacuum barb with a reinforced silicone plug to eliminate vacuum leaks.