The 20VT engine swap into a Vw Mk2 is a popular modification, offering a significant performance boost. This guide provides a detailed overview of the process, drawing from personal experience and research. While not claiming to be the definitive guide, it aims to equip enthusiasts with the necessary knowledge to undertake this ambitious project.
Choosing Your MK2
A 90 spec 16v MK2 is the ideal starting point for this conversion. Its CE2 fusebox and wiring simplify integration with the donor engine. The front brakes can be easily upgraded to G60 specifications, and the 5-bar fueling system is compatible with the 20v’s 4-bar fuel pressure regulator. Avoid pre-GTI models due to potential complications with rear drum brakes and inadequate fueling systems.
Selecting the 20VT Engine
Numerous 20VT engine options exist, ranging from early MK4 AGU units to those found in modern Polos. While all offer performance advantages, certain choices can streamline the conversion process. Avoid longitudinally mounted engines from Passats or Audis, as they require swapping manifolds and oil filter housings.
Consider the engine’s age and mileage. Opting for a complete donor car allows for pre-purchase inspection and potential part reclamation. A 5-speed donor car is preferable, as its gearbox is directly compatible with the MK2. 6-speed gearboxes require significant modifications to engine mounts.
Gearbox and Pedal Box Considerations
If your donor car doesn’t have a 5-speed gearbox, sourcing an 02A/02J gearbox from a MK3/4 Golf is recommended. These gearboxes bolt directly to the engine and utilize the MK2 GTI’s driveshafts. However, they necessitate a cable-change, hydraulic-clutch setup and an 02A starter motor. This requires replacing the shifter and potentially the pedal box. A G60/ABF flywheel and VR6 clutch are recommended for this setup.
Shifter options include the readily available MK3/Corrado 02A shifter or the more refined MK4 02J shifter with its corresponding tower.
For the clutch, either a Seat cable clutch mechanism with the MK2 clutch pedal or a Corrado/Passat hydraulic clutch pedal box setup can be used. The latter offers a more reliable and responsive feel.
Engine Management Systems
Engine management options include aftermarket systems like Qpeng or Emerald, or retaining the OEM system. Aftermarket systems offer plug-and-play simplicity, while OEM systems, once integrated, provide comprehensive diagnostics and reliability. Using the OEM system requires immobilizer defeat and splicing the engine loom into the MK2’s fusebox. A tach adapter is necessary for proper rev counter function. You’ll also need a cable throttle body or a custom bracket for the 20v accelerator pedal.
Exhaust System
A 2.5″ exhaust system is the minimum recommended size for a 20VT in a MK2. MK2 16v systems often meet this requirement. For the downpipe, specialized options from Qpeng or TrackSlag are recommended.
Brake Upgrades
Upgrading the brakes is crucial for handling the increased power. Consider potential master cylinder clearance issues. A Seat ‘stubby’ master cylinder is an option, but its reservoirs can be difficult to source. Using the standard 22mm master cylinder might require slightly lowering the engine.
Engine Installation
The 20VT engine requires specific mounts for proper installation in the MK2. A Corrado 4-pot engine mount bracket is needed for the front, while the rear mount can be addressed with a Corrado or Passat bracket. G60 rear and gearbox mounts are compatible. The choice of front mount depends on the master cylinder used. A VR6 T-mount might require modification but provides clearance for a standard 16v master cylinder.
Cooling and Induction
A 16v radiator and minor pipe modifications are generally sufficient for cooling. The header tank can be relocated using a modified MK2 bracket. For induction, choose an air filter that won’t damage the MAF sensor. Numerous intercooler options exist, with the choice depending on the specific engine and desired performance.
This guide provides a solid foundation for embarking on a VW MK2 20VT conversion. Remember that this is a complex project requiring thorough planning, mechanical aptitude, and a realistic budget. With careful preparation and execution, the rewards of a powerful and unique MK2 are well worth the effort.
