12/07/2025
Bulletproof 1.9Tdi engine conversion for the T4. T4 engines are good but the 1.9TD engine is an inefficient indirect injection engine which means poor power and mpg as well as having a fatal engineering flaw with only having a single woodruff key securing the end of the crank pulley to the crankshaft which is known to cause the end of the pulley to wobble until it breaks off and blows up your engine! At Retro Rust we like to upgrade our T4 engines to the mk3 golf 1.9tdi 1Z / AHU engine that have direct injection so we can comfortably handle 150-250bhp and get around 48.5mpg running while getting 500k mile engine life, it’s the have your cake and eat it engine!
The Shopping list you need:
1. 1.9tdi AHU / 1Z / AFN engine
2. 1.9 T4 engine mount (additional 15mm spacer needed for Syncro model)
3. 1.9TD T4 turbo, manifold & oil lines
4. 1.9 T4 power steering lines & pump
5. 1.9 t4 dipstick
6. 1.9 rear gearbox mount
7. Mk2 VW LT 2.8TDi injection pump
Or if your running the ecu from the golf you also need:
1. Demobilised mk3 golf ecu
2. Mk3 golf engine bay wiring loom
3. Air Maff sensor
4. 2.5tdi VW T4 throttle pedal.
5. N75 boost controller
Conversion work:
1. Drill 3 engine mount holes to 8.5mm and tap m10x1.5
2. On the rear of engine there’s a light casting mark that you need to drill 10mm wide right through the block then drill the same hole 14mm wide to a depth of 9mm to fit the T4 dipstick tube in.
3. Bolt on T4 turbo and oil lines on
4. Swap over injection pump and time lift by ear or try 0.97-1.2mm if your going MTDi.
If your sticking with the mk3 golf ecu route:
1. Fit the Vw t4 2.5tdi pedal and make a custom loom that extends from pedal to the golf loom.
2. Connect up maff sensor
3. Connect loom to negative
4. Connect loom to fused positive ignition live
5. Connect demobilised ECU
6. Connect loom to the engine (big circular connector)
7. Connect N75 boost controller pipes to turbo
Going the ECU route is the easiest and cheapest way as the LT2 injection pump for MTDI is £600-2500 depending if you go Chinese or quality.
Pic is taken off our 1997 VW T4 Syncro 4WD OG paint panel van that will be for sale soon
Happy Travels 🤙