The evaporative emission (evap) system in your Volkswagen/Audi relies on a complex network of vacuum lines. When tuning out the Secondary Air Injection (SAI) system using VCDS, it’s crucial to understand these connections to ensure proper evap system function. This article outlines the original equipment manufacturer (OEM) vacuum line routing for a clear understanding of how to reroute or plug lines after an SAI delete.
The evap system’s vacuum originates from the intake manifold, specifically below and behind the throttle body. A plastic “T” connector distributes this vacuum source. One branch of the “T” connects directly to the intake manifold. This branch provides vacuum to the system.
The second branch of the “T” incorporates a check valve and a line leading to the N80 valve. This line is typically a hard line and connects to a “Y” connector downstream of the N80. The N80 valve controls the purge process of the evap system.
The base of the “T” connector also has a check valve within its line. Following this hose reveals a quick connect fitting attached to a hard plastic line running under the driver’s side front fender. This line continues along the vehicle’s undercarriage, ultimately reaching the Leak Detection Pump (LDP) positioned beneath the left rear wheel well.
Finally, the open check valve in a tuned-out SAI system requires attention. This line, branching from the “Y” connector, originally connects to the Turbo Inlet Pipe (TIP). In the OEM configuration, the TIP connection provides vacuum to the N80 valve when the engine is under boost and manifold vacuum is absent. After an SAI delete, it might be possible to plug this line and rely solely on the intake manifold vacuum. However, this could potentially affect the N80 valve’s performance under boost conditions.
Understanding these OEM vacuum connections is crucial for properly managing the evap system after tuning out the SAI system with VCDS. While plugging the TIP line might seem like a simple solution, it’s important to consider its potential impact on the N80 valve and the overall functionality of the evap system. Careful consideration of these connections will ensure optimal performance and prevent potential issues.
