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VintageWatercooleds.com Technotes :: 1.8T Shopping List and Information

Big thanks to The Nothing for this techtip!

Volkswagen’s venerable 1.8L watercooled iron block, dating back to the late seventies and remaining in the same basic form, has recently spawned an exiting new generation of multivalve engines. Although in Europe they are found in such 20V variants as normally aspirated 125HP and turbo 150HP, 180HP, 210HP and 225HP versions, here in America we have only the 150HP and 180HP turbo fours. These are found under the hood of the VW Passat and Audi A4 1.8t and TT Coupe in longitudinal form and in the VW New Beetle Turbo in transverse layout. One would think, therefore, that finding a motor from a donor New Beetle or Passat would offer some interesting conversion possibilities, especially when an early A1 platform is used for it’s light weight. However, the Audi longitudinal layout (Passat included, as it’s a shared Audi platform) creates troubles, in that the intake, exhaust and accessory systems won’t properly line up for transverse swap applications. The TT Coupe (for now only 180HP in front or Quattro drive with 225HP version slated for early 2000 US release) and New Beetle 1.8t motors have an additional twist, in that they employ a Motronic 7.5 throttle by wire management system, making retrofit into earlier platforms troublesome at best. However, several tuners have begun the task of stuffing these high-output fours into early Golf chassis and details are beginning to emerge. Here then are as many details as I have been able to gather for what SHOULD be involved in a 1.8t to A1 motor swap. The information presented is based upon the work of Berkeley Auto Service’s Tim Tomas, who is at writing performing a 1.8T swap into an A1 Convertible customer car. There are still items to be worked out, such as radiator/intercooler type and placement and some electrical harness details, so as the conversion progresses I will update this document.

Shopping List:

• 1.8T motor from Passat 1.8T (Audi 1.8T should work as well)
• Audi A3 intake/exhaust manifolds w/Passat throttle body
• Golf/Jetta Mk III oil filter output flange
• Golf/Jetta Mk III accessory brackets
• Golf/Jetta Mk III accessories
• Golf/Jetta Mk III crank pulley
• A1 passenger’s side motor mount bracket/mount
  

OK so you found yourself a good used Audi 1.8t motor, but guess what – the intakes don’t line up with your A1 car! And even if they do, the long runners of the intake manifold means the throttle body will end up somewhere in the middle of the radiator. That’s where the Audi A3 manifolds come into play. In Europe, the Audi A3 uses a transverse layout for their turbo four, so procuring these components from Ron’s Parts or other out of country source is a must. The Passat throttle body will fit the A3 intake perfectly, and also take care of the need for a throttle-by-wire system conversion if a New Beetle or TT motor was used. The good news is that an 020 transmission can be mated to the 1.8t block, along with the three motor mounts familiar to the A1 chassis. The fourth mount that is on the passenger’s side requires some trickery to work as the 1.8t motor features a hydraulic timing belt tensioner that will interfere with an A1 mount and bracket. By removing the hydraulic assembly and using a 16V belt and tensioner you have room to fit the A1 style mount. Further clearancing is required at the oil return line for the turbo, which runs from the rear of the oil pan to the turbo housing, as it must be cut and routed to clear the A1 axle shafts. Also, the A3 oil filter output flange must be drilled and tapped to accept the turbo’s oil feed line. The A3 accessory brackets (and accessories) will bolt to the 1.8t block, thank god for the VW Lego system! The wide 1.8t crank pulley is exchanged for an A3 version, as the A3 accessories use a narrower belt setup. The A3 pulley must be machined down to line up properly with the A3 bits, but no difficult task.

Well, that’s the physical part except for the actual turbo and intercooler plumbing and what to do for a radiator. The idea for now is to fit an as yet undetermined intercooler (likely custom and yes much larger and more efficient than stock) below the lower radiator support, perhaps mounted in the air dam. A standard A1 radiator should work, but the A3 accessory ‘bundle’ may require some custom (or oddball) hoses and driver’s side fitment bias. We also haven’t discussed the airbox but the mass airflow sensor and a conical filter with heat shield plan is in the works. Next comes the wiring harness, the current plan is to use a Garrett 1.8t chip that should remove the vehicle speed sensor requirement as well as add some welcome boost. There may be need to use some of the dash harness, but for the most part the management harness adaptation should be similar to a 16V A1 swap in that it is thinned of systems not needed and spliced into the A1 power ‘grid’.

Big thanks to polov8 on the VWVortex forums for these pictures...

This Picture shows the A1 mount on the side of an ADR 1.8T engine

 

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