Mk1 ABA Swap How To

Here's a basic how to for swapping an ABA into a Mk1.  I've condensed the material as much as I could.

Electrical

There basically two choices when you decide to install the entire ABA with the stock fuel injection.

• Keep your stock wiring and merge the ABA's engine harness with your stock fuse panel. This is fairly straight forward, you're looking at 10-15 splices. 
• More info can be found here:
• CE2 Connector List 
• ECU Pin Outs
• Mk3 Harness Pictures
• Convert the entire car to the CE2 fusebox and wiring harness, which involves having the entire donor car's harness and literally rewiring the entire car from front to back.  
• More info can be found here: Mk1 CE2 Conversion

I converted my car to CE2 for several reasons. I had a bad stock fusebox, the CE2 wiring harness is a much better design than the stock Mk1, and it made my corrado dash swap a plug in affair.

VERY IMPORTANT: You will not be able to accomplish the swap unless you have both the Mk1 and Mk3 Bentley Manuals. The wiring is straight forward but there will always be some random wires that you will have to spend time bonding with your Bentley to identify.

Engine Mounts

• ABA Swaps in using existing Mk1 mounts.

Gauges

Gauge options dependent the wire harness used.

• Mk1 Harness
• Wire existing gauge cluster into the appropriate inputs from the ABA's engine harness.  You'll need to run over to the negative side of the coil for the tach input which is under a plastic cover on the Mk3 coil.
• CE2 Harness
• Wire existing gauge cluster into the CE2 dash harness.
• Use a Mk2\Mk3 CE2 Gauge Cluster (You will need to have a Mk3 VSS sensor for the speedo to work, but this solves the VSS cut off issue)

VSS Cut Off

OBDI ABA's require that the ECU recieve a VSS signal for prolonged usage over 4500rpm.  If you're converting to CE2 and using a CE2 gauge cluster then just install the Mk3 VSS sensor.

If you are using a Mk1 gauge cluster with a cable driven speedo you don't have a source for the VSS signal. To get a signal for the VSS you need to install an MFA/Cruise Control module from a Mk2 gauge cluster.  This installs on the back of the gauge cluster and has three pin connector which outputs a pulsed speedo signal that can be used by the ECU.

Fuel Lines

• Carefully cut fuel lines just below the brake booster with a small tubing cutter.
• Either by hand or with a tubing bender carefully rebend the lines to come up on the passenger side of the firewall.
• To connect to the hardlines I used 6’ of 5/16” Fuel Injection Hose from Napa (Roughly $7 a foot but required to take the pressure).  Also from Napa I purchased special rounded edge fuel injection clamps and clamped the fuel line to the hardlines.
• The return line can be ran straight from the Mk1 hard lines to the ABA fuel rail.
• The feed line requires a fuel filter to be put inline since CIS cars have their filters in the engine bay not back by the pump like an Mk3.  I used an Mk2/Mk3 Fuel filter which can simply be clamped inline with the feed line hose running to the fuel rail.

Transmission

You have a lot of choices, any 020 will bolt up with the right clutch and if you're going for serious power there's the 02A and 02J tranmissions that require some fabrication of mounts.

Coolant system

One key item I found after driving my swap was that the Mk3 is setup to always be circulating coolant through the heater core where as the Mk1 is setup with a valve that turns on and off the coolant flow.  This means you must build a coolant bypass with two 2 T fittings to ensure coolant can still circulate when the Mk1 heater core valve is closed.  Other wise the pressure of the coolant will destroy the Mk1 heater valve.  I have removed my heater core and looped the line since my car is mostly used for the track now.

This is a list of the hoses you will need to hook everything up to a non-AC Mk1 Radiator. Larger and different radiators may required custom hoses. Side Note: The mk3 radiator does not fit in the mk1, it's about 3 inches too tall.

• Mk1 Lower Radiator Hose
• Waterpump Thermostat Flange to Lower Radiator Flange
• Mk3  Waterpump to Oil Cooler Hose
• Middle cooling hose goes from waterpump to the oil cooler and to the hard line running across block.
• Mk3 Upper Radiator Hose
• Upper Radiator Flange to side of cylinder head and splits and goes to waterpump and oil cooler. (Shortened to fit application, you will have to play with this depending on the length of your radiator.)
• Mk1 Heater Core Hose
• Coolant Flange on side of Cylinder Head to Heater Core (Shortened to fit application)
• 5/8” Universal Heater Core Hose
• Hardline to Heater Core Pipe
• Also used for hooking up Coolant Reservoir feed
• ¼” Universal Coolant Hose
• Used for the Coolant Reservoir return line, can be tee’d to both the radiator and the back of the cylinder head or you can block off the radiator return and only use the cylinder head return.

Serpentine Belt Setup

If you're not running AC and power steering there will be just 3 pulleys.

• You'll need to swap to the VR6 or 2.0 Non-AC waterpump pulley (It isn't ribbed but it works)
• 40.5" (1033mm)  6 rib Serpentine belt available at any auto parts store

Throttle Cable

There are a couple of choices for the throttle cable.  The easiest cable to use is a 16V Scirocco throttle cable. 

On my car I modified the Mk3 cable by removing a rubber and plastic spacers which could be cut off easily on the pedal end of the cable.  The Mk1 cable has a 90 degree bent at the end to be fed through the accelerator pedal bushing where as the Mk3 cable end is straight.  So I used some pliers and bent the Mk3 cable to match the  Mk1 cable end.  It’s a little tougher to get through the bushing but mine is working great.

Ignition Coil

The ignition coil from Mk3 bolts straight to the rain tray using the existing holes from the  Mk1 coil.  The bolts are a little short but I was able to use them.  I did have to enlarge the hole in the rain tray slightly to get the Mk3 connector through.

Timing Belt Cover

I used both the Mk3 upper and lower timing belt covers.  The job is pretty easy to do just by lining up the mount while test fitting the covers.  On the inside of the upper and lower covers there is a casting line that if you trim along you will have a perfectly clearanced set of covers.

Exhaust

There are a few choices for the exhaust

• Early Mk1 dual outlet manifold w/ a Techtonics Dual Downpipe
• Mk3/Mk4 Exhaust Manifold w/ a Techtonics Stainless ABA Conversion Downpipe
• Pacesetter/Brospeed Header/Etc with a 15mm spacer (May not require spacer depending on brand)

Intake

• 2.75" ID cone filter mounted to the MAF.